Saltwater concrete compositions comprising activator admixtures

Abstract

The present disclosure relates to saltwater concrete compositions comprising activator admixtures, and methods for their production and use. In particular, although not exclusively, the invention relates to concrete compositions comprising activator admixtures with distinct chemical compositions and / or particle size distributions and their use in augmenting the performance of concrete compositions made using saltwater. The uses, methods and admixtures of the invention have broad application to saltwater concrete compositions used in buildings, roading, footpaths, marine structures, bridges, dams, and standard or high-performance concrete for precast elements.

Description

SALTWATER CONCRETE COMPOSITIONS COMPRISING ACTIVATOR ADMIXTURES TECHNICAL FIELD

[0001] The present disclosure relates to activator admixtures for preparing concrete compositions incorporating saltwater. These activators are formulated for use in minimal dosages within a concrete mix, yet they elicit substantial improvements in the resulting concrete's properties. In particular embodiments, the activator admixture has an electrostatic charge and comprises at least two pozzolan portions each with distinct chemical compositions and particle size distributions.BACKGROUND

[0002] Cement is a widely used construction material, which is produced by grinding clinker, gypsum, and other mineral additives. While cement production is a vital component of the construction industry, it comes with significant environmental challenges, in particular related to carbon emissions. Cement production is a major contributor to global CO2 emissions. The primary source of CO2 emissions in cement production is the chemical reaction involved in converting limestone (calcium carbonate) into lime (calcium oxide) during the process known as calcination. This process releases CO2 as a byproduct, accounting for around 50% of the total emissions associated with cement production. As well as direct emissions, cement manufacturing also requires substantial energy inputs. The processes involved demand a significant amount of energy, primarily derived from fossil fuels. For example, quarrying raw materials, crushing, grinding, and heating them to high temperatures.

[0003] There is a growing desire to replace at least a portion of the cement used in concrete production with alternative materials that maintain concrete properties while reducing its carbon footprint. Pozzolans, both natural and synthetic, are widely used for this purpose. Pozzolans react with calcium hydroxide and water to form cementitious materials, enhancing the strength and durability of concrete.

[0004] The pozzolanic reaction involves the combination of silicon and aluminium from the pozzolan with available calcium to produce calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH). These compounds improve the mechanical properties of concrete by continuously developing reaction products, resulting in enhanced compressive strength, reduced permeability, and improved chemical resistance.

[0005] Despite their benefits, pozzolanic materials have limitations, including delayed strength development and reduced workability of fresh concrete, which create challenges for their widespread use. Additionally, certain environmental and performance factors, such as the interaction of seawater with concrete, further complicate their adoption in specific applications.

[0006] Seawater offers a potential alternative to freshwater in concrete production, particularly in regions where freshwater resources are scarce. However, the use of seawater introduces several challenges that must be addressed to ensure durable and high-performance concrete. These challenges include:• Corrosion of Reinforcement Steel: The high chloride content in seawater accelerates corrosion in steel reinforcements, limiting the durability and lifespan of reinforced concrete structures.• Reduction in Concrete Strength: Salts present in seawater, such as sodium chloride (NaCI) and magnesium chloride (MgCh), interfere with the hydration process of Portland cement, causing a reduction in compressive strength over time.• Inconsistent Performance: The effects of seawater on different types of cement can vary significantly, leading to inconsistent results depending on the specific mix and environmental conditions.

[0007] Natural and synthetic pozzolans can mitigate some of these issues by enhancing the chemical and mechanical properties of concrete. However, the use of seawater exacerbates challenges such as corrosion, reduced strength, and inconsistent performance, highlighting the need for innovative solutions.

[0008] In light of the above, there is a need for activator admixtures tailored to address the specific issues posed by seawater in concrete production. The present invention at least partially addresses this need by providing activators and methods that mitigate corrosion, enhance strength, and ensure consistent performance. These advancements enable the production of high-quality, durable concrete with a lower environmental impact, paving the way for wider adoption of sustainable construction practices.

[0009] In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

[0010] It is an object of the invention to provide activators for concrete to enable enhanced strength, workability and / or durability, concrete compositions comprising the activators, and related methods of use and production, that overcome or ameliorate at least one of the disadvantages of the prior art. Alternatively, it is an object of the invention to provide the public with a useful choice.SUMMARY OF THE INVENTION

[0011] The present invention provides activator admixtures suitable for use with saltwater in concrete production. In some examples these admixtures enable the use of saltwater without compromising the mechanical properties, durability, or environmental sustainability of the resulting concrete. By accelerating pozzolanic reactions and stabilising the interaction of saltwater salts with cementitious materials, the invention seeks to overcome the key challenges associated with saltwater-based concrete.

[0012] In one example, there is provided a concrete composition comprising an activator admixture, cementitious material, and saltwater, the activator admixture comprising a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions. In some examples, the saltwater comprises dissolved salts between about 5 and 45g / L.

[0013] In some examples the water comprises dissolved salts of at least about 5g / L. In some examples 5-45g / L. In other examples between about 5 to about 25 g / L, about 25 to about 45 g / L, about 30 to about 40 g / L, about 32 to about 38 g / L, about 35 to about 40 g / L, or about 35 to about 45 g / L.

[0014] In one example the water comprises dissolved salts in a range from about 25 to about 45 g / L.

[0015] In one example the dissolved salts comprises sodium chloride (NaCI) and magnesium chloride. In some examples the dissolved salts comprises from about 70% to 85% of sodium chloride. In some examples the dissolved salts comprises from about 5% to about 15% magnesium chloride.

[0016] In some examples, the composition further comprises fibre reinforcement selected from polymeric, basalt, or glass fibres.

[0017] In some examples, the activator pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.

[0018] In some examples, the activator comprises an electrostatic charge. The electrostatic charge may have been applied to the activator by any suitable method. In some examples, the electrostatic charge has been applied by way of external electrical or electrostatic fields generated by electrodes, electrostatic spraying techniques, triboelectric charging in a fluidised bed, corona discharge methods, electrostatic fluidisation, and mechanical mixing-induced friction.

[0019] In some examples, the activator first pozzolan portion comprises an intermediate median particle size in a range of 0.5-1.5pm, and the activator second pozzolan portion comprises a coarse median particle size in a range of 10-80pm.

[0020] In some examples, the composition further comprises a reinforcing material and a corrosion inhibitor selected from the group consisting of passivating agents, chloridescavengers, cathodic inhibitors, anodic inhibitors, oxidation inhibitors, electrochemical inhibitors, nitrite-based inhibitors, organic inhibitors, silane / siloxane treatments, galvanic protection systems, and polymeric barrier coatings.

[0021] In some examples, the activator pozzolan component exhibits a first volume density peak of between 0.3 and 1.5% for particles at between 0.5pm and 1.5pm and a second volume density peak of greater than 3% between 10pm and 80pm. In some examples, a volume density ratio of the first pozzolan portion peak to the second pozzolan portion peak comprises 1:3 to 1:6.

[0022] In some examples, one or more natural or synthetic pozzolans comprise at least about 60% by weight of the activator.

[0023] In some examples, the activator comprises a plasticiser, and the ratio between the activator pozzolan component and the plasticiser comprises from about 11:1 pozzolan: plasticiser to about 1.5:1 pozzolan: plasticiser.

[0024] In some examples, the activator comprises a plasticiser at between about 8% and 40% w / w.

[0025] In some examples, the activator is present in an amount of from 0.25-10% by weight of cementitious materials in the concrete composition. In other examples, the activator is present in an amount of from 0.5-8% by weight of cementitious materials in the concrete composition. In other examples, the activator is present in an amount of from 1-4% by weight of cementitious materials in the concrete composition.

[0026] In some examples, the cementitious materials comprise Portland cement and at least one pozzolanic supplementary cementitious material (SCM) selected from the group consisting of fly ash, slag, silica fume, metakaolin, rice husk ash, synthetic pozzolan, natural pozzolan and pumice.

[0027] In some examples, the pozzolanic SCM is present in an amount of 10 to 50% w / w of cementitious material.

[0028] In some examples, the pozzolanic SCM is substituted by limestone in an amount of 10 to 100% w / w of pozzolanic SCM.

[0029] In some examples, the supplementary cementitious material comprises limestone in an amount of 10 to 100% by weight of the total supplementary cementitious material.

[0030] In some examples, the composition comprises cementitious material comprising Portland cement at a quantity selected from the group consisting of less than 50%, less than 60%, less than 70%, less than 80%, or less than 90% cement.

[0031] In one example, the composition comprises cementitious material comprising Portland cement at quantity of less than about 80%, and a supplementary cementitiousmaterial comprising fly ash at a quantity of between about 10% to about 50%, optionally about 20% to about 40%.

[0032] In one example, the composition comprises cementitious material comprising: a. a supplementary cementitious material comprising fly ash at a quantity of between about 10% to about 50%, optionally about 20% to about 40%; andb. the balance made up of Portland Cement.

[0033] In some examples, the compressive strength determined in accordance with NZS3112 part 2 at day 28 is greater than 20MPa, optionally greater than 25MPa or 30MPa.

[0034] In some examples, the activator further comprises a plasticiser component, preferably a powdered plasticiser component.

[0035] In a further example, there is provided an activator admixture for producing saltwater concrete, the activator comprising a pozzolan component and a plasticiser component, wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide, and 5-40% w / w aluminium oxide.

[0036] In a further example, there is provided an activator admixture for producing saltwater concrete, the activator comprising a pozzolan component and a plasticiser component, wherein the pozzolan component comprises a chemical composition comprising 40-80% w / w silicon dioxide, and 10-40% w / w aluminium oxide.

[0037] In some examples, the activator comprises a Dv50 of less than 40pm. In some examples, the activator comprises a Dv50 of less than 50pm. In some examples, the Dv50 comprises 10-50pm.

[0038] In some examples, the activator comprises a powdered activator admixture.

[0039] In some examples, the plasticiser comprises a particle size from 50-500pm. In one example, the plasticiser comprises a Dv50 of from 50-500pm, or preferably, from 100-200pm.

[0040] In some examples the pozzolan component and plasticiser have been mixed for over 5 minutes.

[0041] In some examples, the activator comprises a plasticiser at a percentage (w / w) of from about 10% to about 25%.

[0042] The plasticiser may comprise at least one of:a) a polycarboxylate plasticiser;b) a naphthalene-based plasticiser;c) a lignosulphonate plasticiser;d) a dry powder plasticiser; ande) a dry powder polycarboxylate plasticiser.

[0043] In other examples, the plasticiser may be applied at a higher proportion, for example from 10-35%. This is preferred when a significant increase in workability is needed, such as in highly reinforced sections where the concrete needs to flow easily around the reinforcement, or in complex formwork, or where a significant reduction in water-cement ratio is needed to achieve high strength or enhanced durability.

[0044] The activator may comprise from about 9:1 pozzolan: plasticiser to about 3:1 pozzolan: plasticiser.

[0045] In some examples, the activator comprises a ratio of pozzolan component to plasticiser at a ratio of from 9:1 pozzolan : plasticiser to about 3: 1 pozzola plasticiser.

[0046] In one example the plasticiser present in the activator has a Dv50 of from about 50-500pm. In another example, the plasticiser present in the activator has a Dv50 of from about 100-200pm.

[0047] In one example the plasticiser is added to the other activator components as a powdered plasticiser.

[0048] In some examples, the activator admixture comprises a particle size distribution defined by:• 15-55% of particles are less than 15 pm;• 50-80% of particles are less than 40 pm; and• 70-100% of particles are less than 90 pm.

[0049] In some examples, the activator admixture comprises a particle size distribution defined by:• 30-40% of particles are less than 15 pm;• 50-65% of particles are less than 40 pm; and• 75-90% of particles are less than 90 pm.

[0050] In some examples, the specific surface area (SSA) of the activator admixture comprises between 350-1000m2 / kg.

[0051] In some examples, the Dv50 of the activator admixture comprises 10-40pm.

[0052] In one example, there is provided a concrete structure, product, or element comprising the concrete composition as described in any of the examples. The concrete composition may be used in the formation of one or more of a building, bridge, roadway, pavement, foundation, wall, slab, column, beam, panel, or pre-cast concrete element, including but not limited to pre-cast beams, panels, pipes, culverts, barriers, sleepers, or modular construction components, or other structural or non-structural concrete applications. The concrete structure may be formed using a concrete composition according to any one of the preceding paragraphs.

[0053] In one example, there is provided a method of producing an activator for use as an admixture for concrete comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a first particle size Dv50,b. obtaining a second pozzolan portion with a second chemical composition and a second particle size Dv50;c. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;d. mixing the pozzolan component with a plasticiser to produce an activator composition.

[0054] In one example, the method of producing an activator further comprises the application of an electrical or electrostatic charge according to methods described herein.

[0055] In one example the plasticiser comprises a powdered plasticiser.

[0056] In one example, the mixing step is carried out for a period of at least five minutes.

[0057] In one example, the activator comprises an intermediate particle size distribution and a coarse particle size distribution. In one example the intermediate median particle size is in a range of 0.5-1.5 pm and the coarse median particle size is in a range between 10-80 pm.

[0058] In one example, the plasticiser is present at 8-40% w / w of activator.

[0059] In one example, the activator comprises a Dv50 of less than 40pm. In some examples, the activator comprises a Dv50 of between 10 and 50.

[0060] In some examples, the method further comprises the steps of:a. identifying a chemical composition of a first pozzolan as the first pozzolan portion; b. identifying a chemical composition of a second pozzolan as the second pozzolan portion; andc. calculating an amount of the first pozzolan and an amount of the second pozzolan required to achieve the chemical composition of the pozzolan component.

[0061] In one example, there is provided a method of producing a saltwater concrete composition comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a second pozzolan portion with a second chemical composition;b. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c. mixing the pozzolan component with a plasticiser to produce an activator admixture; d. combining the activator admixture with cementitious material and saltwater; wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% aluminium oxide. The activator admixture may be as previously described.

[0062] In one example, there is provided a method of producing a saltwater concrete composition comprising the steps of:a. obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;b. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c. providing a plasticiser;d. forming an activator admixture comprising the pozzolan component and the plasticiser;e. combining the activator admixture with cementitious material and saltwater to form the saltwater concrete composition,wherein the activator admixture may be formed prior to addition of saltwater or may be formed in situ during mixing of the cementitious material and saltwater, wherein the pozzolan component may be combined with the cementitious material prior to addition of saltwater, and the plasticiser may be added to the cementitious material either before or after addition of the pozzolan component and prior to addition of saltwater,wherein the pozzolan component comprises a chemical composition comprising 20- 80% w / w silicon dioxide and 5-40% w / w aluminium oxide, andwherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

[0063] In some examples, the activator admixture comprises an electrostatic charge. The electrostatic charge may have been applied to the activator by any suitable method step. In some examples, the method further comprises the application of an electrostatic charge by way of external electrical or electrostatic fields generated by electrodes, electrostatic spraying techniques, triboelectric charging in a fluidised bed, corona discharge methods, electrostatic fluidisation, and mechanical mixing-induced friction. The application of electrostatic charge may be incorporated into methods of production of the activator admixture.

[0064] In one example, the pozzolan component comprises a chemical composition comprising 40-80% w / w silicon dioxide, and 10-40% aluminium oxide.

[0065] In some examples the water comprises dissolved salts between about 5 to about 25 g / L, about 25 to about 45 g / L, about 30 to about 40 g / L, about 32 to about 38 g / L, about 35 to about 40 g / L, or about 35 to about 45 g / L.

[0066] In one example the water comprises dissolved salts in a range from about 25 to about 45 g / L.

[0067] In one example the dissolved salts comprises sodium chloride (NaCI) and magnesium chloride. In some examples the dissolved salts comprises from about 70% to 85% of sodium chloride. In some examples the dissolved salts comprises from about 5% to about 15% magnesium chloride.

[0068] In some examples, the concrete composition comprises no reinforcement material.

[0069] In some examples, the concrete composition further comprises a corrosion inhibitor, optionally selected from calcium nitrite or organic-based corrosion inhibitors.

[0070] In some examples, the concrete composition further comprises a salt-neutralising or stabilising agent, optionally selected from reactive silicates or chelating agents.

[0071] In some examples, the concrete composition further comprises surface sealing agents to reduce permeability and minimise chloride ingress.

[0072] In some examples, the concrete composition further comprises alkali-silica reaction (ASR) inhibitors to mitigate reactions exacerbated by the alkalis in seawater.

[0073] In some examples, the activator is present in an amount of from 0.25-10% by weight of cementitious materials in the concrete composition. In other examples, the activator is present in an amount of from 0.5-8% by weight of cementitious materials in the concrete composition. In other examples, the activator is present in an amount of from 1-4% by weight of cementitious materials in the concrete composition.

[0074] In some examples, the activator admixture comprises a particle size distribution defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm.

[0075] In some examples, the activator comprises 20-80% w / w silicon dioxide, 5-40% w / w aluminium oxide, and the concrete composition develops a compressive strength of at least 20MPa, 25MPa, or 30MPa at 28 days, and wherein the composition comprises at least 10% by weight of natural or synthetic pozzolan SCM based on the total cementitious material.

[0076] In one example, the activator comprises 20-80% w / w silicon dioxide, 5-40% w / w aluminium oxide, and the concrete composition develops a compressive strength of at least20MPa, 25MPa, or 30MPa at 28 days. Additionally, the composition may comprise at least 10% by weight of natural or synthetic pozzolan SCM based on the total cementitious material.

[0077] In some examples, the method comprises using a powdered activator comprising 20-80% w / w silicon dioxide, 5-40% w / w aluminium oxide, a particle size distribution defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm;wherein the concrete composition develops a compressive strength of at least 50MPa at 28 days, and wherein the composition comprises at least 25% by weight of natural or synthetic pozzolan SCM based on the total cementitious material.

[0078] In some examples, the method comprises using a concrete composition comprising a powdered activator described herein comprising 20-80% w / w silicon dioxide, 5-40% w / w aluminium oxide, a particle size distribution defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm;wherein the concrete composition develops a compressive strength of at least 25MPa at 28 days, and wherein the composition comprises at least 10% by weight of natural or synthetic pozzolan SCM based on the total cementitious material.

[0079] In a further example, there is provided a concrete composition comprising:a. an activator as described in any of the previous examples,b. cementitious material, andc. aggregate.

[0080] In some examples the concrete composition further comprises saltwater.

[0081] In one example, there is provided a method of reducing the overall cementitious material in a saltwater concrete composition by up to about 30%, while maintaining or increasing the strength of the concrete, and reducing the embodied carbon of the concrete. In some examples, the reduction in cementitious material is up to about 10%, up to about 20%, up to about 40% or up to about 50%.

[0082] In one example, there is provided a method of reducing the overall cementitious material in a saltwater concrete composition by amounts described above, for example up to about 50%, while maintaining or increasing the strength of the concrete, and reducing the embodied carbon of the concrete.

[0083] In one example, there is provided a method of inhibiting the detrimental effect of chloride ions in a concrete composition comprising adding an activator admixture composition as described in any of the examples above.

[0084] In one example, the invention provides a construction material comprising the activator of any of the previous examples, and saltwater.

[0085] In one example, there is provided a method of reducing chloride ion mobility and / or chloride ingress in a saltwater concrete composition comprising an activator admixture, cementitious material and saltwater, the method comprising adding the activator admixture to the cementitious material and saltwater, wherein the activator admixture comprises an activator admixture as described in any of the foregoing examples. In one example the activator admixture comprises a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

[0086] In one example, there is provided a method of increasing bound chloride fraction in a saltwater concrete composition comprising an activator admixture, cementitious material and saltwater, the method comprising adding the activator admixture to the cementitious material and saltwater, wherein the activator admixture comprises an activator admixture as described in any of the foregoing examples. In one example the activator admixture comprises a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

[0087] In one example, there is provided a method of improving chloride resistance of a saltwater concrete composition comprising an activator admixture, cementitious material and saltwater, the method comprising adding the activator admixture to the cementitious material and saltwater, wherein the activator admixture comprises an activator admixture as described in any of the foregoing examples. In one example the activator admixture comprises a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

[0088] Those of skill in the art will appreciate that the examples, features, variations and embodiments described in relation to any of the aspects herein are intended to be read in combination with the features of any other aspect or example provided herein, regardless of whether such examples, features, variations and embodiments are specifically appended to said aspects or examples.

[0089] Aspects of the invention may also be said broadly to consist in the examples, parts, elements and features referred to or indicated in this specification, individually or collectively, in any or all combinations of two or more of said parts, elements or features, and where specific integers are mentioned herein that have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0090] Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Embodiments will now be described by way of example only and with reference to the figures:Figure l.a.i - Comparison of strength over time for activator versus control concrete.Figure l.a.ii - Particle size and volume density of particles for activator gamma.Figure l.a.iii - Particle size and volume density of particles for activator omicron.Figure l.b.i - Slump loss of concrete over time for control and activator-containing concrete.Figure l.b.ii - Comparison of strength over time for activator versus control concrete showing that the activators produced concrete with higher compressive strength at all time points. Data for day 28 still to come.Figure l.b.iii - Particle size and volume density of particles for activator Tau.Figure l.b.iv - Particle size and volume density of particles for activator Omega2.Figure l.c.i - Slump loss of concrete over time showing that workability of control 2 and activator retained workability to a similar extent.Figure l.c.ii - Comparison of strength over time for 25MPa concrete, 40MPa concrete, and activator-containing concrete using 25MPa concrete's cement volume with strength at 1, 3, 7 and 28 days post-pour.Figure l.c.iii - Particle size and volume density of particles for activator Pi.Figure 2.a.i - Slump loss of concrete over time showing good workability for all activatorcontaining concrete mixtures.Figure 2.a.ii - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete at all cement-reduction levels had compressive strength substantially equal to or greater than control at 1, 3, 7 and 28 days post-pour.Figure 2. a . iii - Particle size and volume density of particles for activator Pi.Figure 2.a.iv - Particle size and volume density of particles for activator Tau.Figure 2.b.i - Slump loss of activator-containing concrete over time showing significant improvement in workability vs. both controls.Figure 2. b. ii - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete with 50% less cement produced compressive strength greater than controls 1 and 2 at all tested ages - 1, 3, 7 and 28 days post-pour. Figure 2. b. iii - Particle size and volume density of particles for activator Tau.Figure 3 - Comparison of strength over time for KNP activated natural pozzolans vs control and Activator activated pozzolans vs. control, both at 20% cement replacement levels. Figure 4 - Particle size and volume density of particles for activator Pi.Figures 5A-5C show volume density of particle size classes of activators of the invention in example 5.Figure 5D shows compressive strength over time for mortar mixes from example 5.Figures 6A shows volume density of particle size classes of an activator of the invention according to example 6.Figure 6B shows compressive strength over time for mortar mixes of example 6.Figure 7 shows compressive strength over time for mortar mixes of example 7.Figure 8 shows compressive strength over time for mortar mixes of example 8.Figure 9A and 9B show exemplary concrete compositions prepared using 9A ordinary Portland cement and 9B activator admixtures of the invention.Figure 10 shows compressive strength over time for activators of the invention.Figure 11 shows compressive strength over time for saltwater samples containing activators of the invention.Figure 12 - Particle size distribution curve showing cumulative % volume under versus particle size (pm) for activators K4e, A+, PT1 and PT2.Figure 13 - Compressive strength development at 1, 3, 7 and 28 days for freshwater control, saltwater control with water reducer, and saltwater plus activator K4e concrete. Figure 14 - Compressive strength development at 1, 3, 7, 28 and 56 days for freshwater control, saltwater control, and saltwater plus activator A+ concrete.Figure 15 - Compressive strength development at 1, 3, 7, 28 and 56 days for saltwater concrete with 30% fly ash replacement, with and without activator A+.Figure 16 - Compressive strength development at 1, 3, 7, 28 and 56 days for saltwater concrete with 30% natural pozzolan (Pl) replacement, with and without activator A+.Figure 17 - Compressive strength development at 1, 3, 7, 28 and 56 days for seawater concrete comprising 30% fly ash and different activators (A+, PT1, PT2).Figure 18 - Chloride migration coefficient (Dnssm) for freshwater control, saltwater control, and saltwater plus activator concrete samples.Figure 19 - Comparison of acid-soluble and water-soluble chloride content for saltwater concrete mixes with and without activator.Figure 20 - Comparison of acid-soluble and water-soluble chloride content for saltwater concrete mixes with pozzolanic replacement, with and without activator.Figure 21 - Percentage of bound chloride calculated from total and water-soluble chloride measurements for pumicite-containing concrete with and without activator.DETAILED DESCRIPTION OF THE INVENTION

[0092] Unless the context clearly indicates otherwise, terms used herein are defined as follows:

[0093] "Comprising" means "consisting at least in part of". When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise", include", "including" and "comprises" are to be interpreted in the same manner.

[0094] "A" or "an" does not exclude a plurality.

[0095] "About" as used herein means a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, when applied to a value, the term should be construed as including a deviation of + / - 5% of the value.

[0096] It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

[0097] Whenever a range is given in the specification, for example, a dimensional range, a time range, or a composition range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure.

[0098] "And / or" means additionally or alternatively. Moreover, any use of a term in the singular also encompasses plural forms.

[0099] "Particle(s)" refers to particles having a well-defined physical shape as well as those with irregular geometries, including any particles having the physical shape of platelets, shavings, fibers, flakes, ribbons, rods, strips, spheroids, toroids, pellets, tablets, or any other physical shape.

[0100] "Cement" includes Portland cement and similar materials that contain one or more of the four clinker materials: C3S (tricalcium silicate), C2S (dicalcium silicate), C3A (tricalcium aluminate), and C4AF (tetracalcium aluminoferrite).

[0101] "Concrete activator", "activator", or "activator admixture" means a mixture of components for adding to concrete mixtures which modifies the reaction speed or curing process when the activator is added to a concrete mix.

[0102] "Cementitious material" means the total quantity of hydraulically reactive binder material in the composition and comprises Portland cement and optionally one or more supplementary cementitious materials (SCMs), but does not include aggregate, filler, water, or activator unless expressly stated.

[0103] "Natural pozzolan" means a non-calcined natural silified shale mineral that is a Class N Pozzolan is under the chemical and physical requirements of ASTM C-618.

[0104] "Binder" means the cementitious materials and any admixture or activator components for use in the preparation of a concrete composition. In some examples, the binder comprises activator plus at least one of Portland cement and Supplementary cementitious materials (SCMs).

[0105] "Mortar" designates a mixture of cementitious materials, fillers, sands, water and optionally additives or activator.

[0106] "Admixture" means a chemical substance added to a binder, concrete or mortar mix, in minor proportions compared to the primary components, with the purpose of modifying and enhancing specific properties of the final material (e.g. concrete or mortar). These properties include, but are not limited to, workability, setting time, strength, durability, and resistance to environmental factors. Admixtures may be chemical and / or mineral in nature and are employed to achieve characteristics in the concrete that cannot be attained by the primary components alone (cement, water, and aggregates). Activators of the invention are admixtures and references to activator is intended to be read as a reference to an activator admixture.

[0107] Concrete admixtures are mixtures that are added to the concrete mixture to enhance its properties and improve its performance. They can be in dry or liquid form. They are typically prepared and sold independently of the concrete and are tailored for different concrete applications. There are many different types of admixtures available, each with its own specific function. Generally, concrete admixtures comprise the following components:

[0108] Plasticisers: also known as water reducers, or superplasticisers, reduce the amount of water required to achieve the desired workability of the concrete mixture. They are typically made from sulfonated melamine, lignosulfonates, sulfonated naphthalene, or polycarboxylate-based polymers.

[0109] Retarders: Retarders slow down the setting time of concrete, allowing more time for placement, finishing, and transportation. Commonly used retarders include lignosulfonates, carbohydrates, and citric acid. Retarders and natural pozzolans can also work synergistically in concrete, particularly when it comes to controlling the setting time of the mixture. When used together, retarders and natural pozzolans can help to provide greater control over the setting time of the concrete, particularly in situations where a longer setting time is desirable. For example, in hot weather, the addition of a retarder can help to slow down the rate of hydration and prevent the mixture from setting too quickly. Similarly, in situations where longer transport times are required, the use of a combination of retarders and natural pozzolans can help to ensure that the concrete remains workable and does not set before it can be properly placed.

[0110] Accelerators: Accelerators are admixture components that speed up the setting and hardening of concrete, allowing it to gain strength more quickly. Calcium chloride is a commonly used accelerator, but other types of accelerators, such as triethanolamine or sodium thiocyanate, can also be used.

[0111] Air-Entraining Agents: Air-entraining agents are admixture components that create microscopic bubbles in concrete, which help to improve its durability and workability. They are typically made from natural or synthetic surfactants.

[0112] Corrosion Inhibitors: Corrosion inhibitors are admixture components that are added to concrete to prevent the corrosion of reinforcing steel. They work by forming a protective layer around the steel, which prevents the penetration of corrosive agents.

[0113] Colorants: Added to concrete to give it a specific colour or hue. They are typically made from pigments or dyes.

[0114] The activators of the invention described herein are admixtures in that they are added as a minor component of a mixture which also comprises cementitious materials to achieve a binder, mortar and / or concrete with modified properties. In certain examples, the dosage of the activator admixture may be varied depending on the composition of thecementitious system and the intended performance characteristics of the concrete. Operable ranges include 0.25-10% by weight of cementitious materials, and in certain examples 0.5-8% by weight of cementitious materials. In certain examples, the activator admixture may be present at between 1-4% by weight of cementitious materials.

[0115] The lower end of the range, including dosages of approximately 0.25-1.5%, may be suitable where the activator is dry-blended directly with Portland cement prior to addition of aggregates and water. In such configurations, intimate particle-to-particle contact between the activator pozzolan fractions and cement grains may enhance dispersion efficiency. Intimate contact may increase surface interaction between reactive phases. Lower total activator quantities may therefore be sufficient to activate supplementary cementitious materials. Lower dosages may also be appropriate where the concrete composition contains relatively high-reactivity supplementary cementitious materials, including finely divided natural pozzolans, silica fume, or metakaolin.

[0116] Intermediate dosages, including for example 0.5-8% by weight of cementitious materials, may be appropriate for blended systems containing moderate-reactivity supplementary cementitious materials such as fly ash, slag, pumicites, volcanic ash, or limestone-containing binders. In certain examples, the activator may enhance dissolution kinetics of reactive phases. In certain examples, the activator may promote formation of carboaluminate phases. In certain examples, the activator may accelerate nucleation of calcium-silicate-hydrate (C-S-H). In certain examples, the activator may improve interfacial bonding within the binder matrix. The dosage within this range may be selected according to the total SCM loading, the specific surface area of the SCM, the particle size distribution of the SCM, and the desired rate of strength development.

[0117] Higher dosages within the range of approximately 5-10% by weight of cementitious materials may be employed in applications requiring enhanced rheological performance in addition to chemical activation. In self-compacting concrete or highly flowable concrete systems, increased activator content may contribute to improved particle packing. Increased activator content may improve dispersion of binder particles. Increased activator content may enhance flowability without segregation. The multi-modal particle size distribution of the activator, particularly where intermediate particles fill interstitial voids between coarser particles, may improve flow characteristics. In certain examples, this packing effect may reduce bleeding. In certain examples, this packing effect may improve stability of the fresh concrete mixture.

[0118] The appropriate dosage may therefore depend on multiple parameters including: (i) the type and proportion of supplementary cementitious materials; (ii) the reactivity of the SCM; (iii) the particle size distribution of the SCM; (iv) whether the activator is preblended in dry form with cement or introduced during mixing; (v) the desired compressive strength development profile; and (vi) the rheological requirements of the concrete,including whether the composition is intended to function as conventional vibrated concrete or self-compacting concrete.

[0119] The examples described herein demonstrate that the activator is effective within the ranges recited above. The underlying activation mechanism may involve increased surface reactivity. In certain examples, electrostatic interactions may contribute to activation. In certain examples, enhanced nucleation of hydration products may occur. In certain examples, improved interaction between carbonate phases and aluminosilicate phases may occur. These mechanisms support operability across the broader dosage ranges described. A skilled person, having regard to the SCM type, particle size characteristics, and intended application, would be able to determine an appropriate activator dosage within the stated ranges without undue experimentation.

[0120] Activators include some or all of the above-referenced components and are preferably prepared in dry powder form. One function of the activator is to activate cementitious materials such as natural or synthetic pozzolans so that they act as a binder rather than simply being a filler. The activators of the invention are believed to speed up the pozzolanic reaction by way of their surface reactivity which is in some examples provided by generation of electrostatic forces meaning that the strength gain of the resulting concrete (containing the activator plus additional cementitious materials such as natural or synthetic pozzolans) is achieved at a similar or higher rate to cement-based concrete without activator.

[0121] Concrete comprising activators of the invention plus natural or synthetic pozzolans have a higher rate of strength development and ultimate strength than concrete comprising only natural or synthetic pozzolans. Example 2b and other examples demonstrate this effect. Activators of the invention also have the surprising effect of activating cement and optionally fillers to be more effective binders as shown by the examples.

[0122] Natural pozzolans are siliceous or silico-aluminous materials and are composed of various chemical compounds, including silica, alumina, iron oxide, calcium oxide, magnesium oxide, and potassium oxide. These compounds are responsible for the pozzolanic activity of natural pozzolans and their ability to contribute to the strength and durability of concrete. Where concrete comprises natural pozzolans, their properties play a critical role in the performance of the concrete.

[0123] The reactivity of natural pozzolans is related to their content of reactive silica and alumina, as well as the amorphousness of their structure. These properties determine the pozzolanic activity, which is the ability of the natural pozzolan to react with calcium hydroxide in the presence of water to form calcium silicate hydrate (CSH) and other cementitious compounds that contribute to the strength and durability of the concrete.

[0124] Silicon dioxide (silica) is the primary component of natural pozzolans, accounting for up to 90% of their composition. It is a key component in the formation of the pozzolanicreaction, and it contributes to the development of the strength and durability of the resulting concrete. The amount of reactive silica in the natural pozzolan is an important factor in its pozzolanic activity. Aluminium oxide (alumina) is another important component of natural pozzolans, and it plays a key role in the formation of the pozzolanic reaction. Alumina reacts with calcium hydroxide to form calcium aluminate hydrates, which contribute to the strength and durability of the concrete.

[0125] The percentage of each of the chemical compounds found in natural pozzolans can vary depending on the type of natural pozzolan and its geological origin. Controlling the chemical composition of natural pozzolans before using them in concrete mixtures is important to ensure that they result in the desired concrete properties once mixed. They must also be compatible with the other ingredients in the mix and not create compounds detrimental to concrete structure.Seawater composition

[0126] The water used in the concrete composition may comprise seawater, brackish water, or other saline water sources. The salt content in seawater varies depending on the location and environmental factors but generally contains about 35 grams of dissolved salts per litre (35 g / L).

[0127] In various embodiments, the water used in the concrete composition may comprise total dissolved salt concentrations of at least about 5 g / L. In some embodiments, the salt concentration may range from about 5 g / L to about 45 g / L. Within this range, representative examples include about 5 to about 25 g / L, about 25 to about 45 g / L, about 30 to about 40 g / L, about 32 to about 38 g / L, about 35 to about 40 g / L, or about 35 to about 45 g / L.

[0128] The invention is particularly effective in addressing challenges associated with saline water having salt concentrations in a range from about 25 g / L to about 45 g / L, which encompasses typical seawater and moderately elevated salinity conditions. In this range, high salt content may otherwise pose increased risks of reinforcement corrosion, altered hydration behaviour, and reduced mechanical performance. The invention is also effective in reducing concrete performance variability when saline water having salt concentrations from about 5 g / L to about 45 g / L is used.

[0129] The specific salt concentration in seawater is influenced by various environmental and geographic features. For instance, open ocean waters typically exhibit a stable salinity of approximately 35 g / L due to the balance of evaporation and precipitation. In contrast, enclosed or semi-enclosed seas such as the Mediterranean Sea may exhibit higher salinity levels, commonly around 38-39 g / L, due to high evaporation rates and limited freshwater inflow.

[0130] Brackish waters, such as those found in estuaries, river deltas, or coastal lagoons, typically exhibit lower salt concentrations, for example from about 5 g / L to about 20 g / L, due to dilution by freshwater inflows. These environments may also experience seasonal or tidal fluctuations in salinity. High-salinity regions such as the Red Sea or Persian Gulf often exhibit salinity levels exceeding 40 g / L. These elevated concentrations are due to intense evaporation rates, minimal precipitation, and restricted exchange with open ocean waters. Conversely, areas like the Baltic Sea, which receive substantial freshwater input from rivers and have limited saltwater inflow, exhibit much lower salinity, typically around 7-8 g / L. Coastal areas near or regions with high rainfall may show variability in salinity within a single location, ranging from brackish to near-standard oceanic salinity levels, depending on tidal mixing and seasonal variations.

[0131] In further embodiments, the water may comprise higher concentrations of dissolved salts exceeding those of typical seawater, such as concentrations greater than about 45 g / L. Such higher-salinity waters may include hypersaline natural waters, desalination concentrates, industrial saline waters, produced waters, or inland saline groundwaters. In these embodiments, the concrete composition may be adapted, for example by selection of binder chemistry, supplementary cementitious materials, admixtures, or curing conditions, to accommodate increased ionic strength and to mitigate potential impacts on setting behaviour, hydration kinetics, or long-term durability.

[0132] The composition of dissolved salts in seawater is relatively consistent in open ocean waters, with sodium chloride (NaCI) comprising approximately 77% of the total salts by weight. Magnesium chloride (MgCh) contributes around 10.9%, followed by sodium sulfate (Na2SO4) at 4.7%, calcium chloride (CaCh) at 2.6%, and potassium chloride (KOI) at 1.5%. In areas with higher or lower total dissolved salts, the relative proportions of these salts remain similar, but the absolute concentrations vary. These variations can influence both the hydration reactions and the durability of the resulting material and are therefore relevant to the performance of concrete prepared using saline water.Effect of seawater on cement hydration and early strength

[0133] The present invention comprises the use of a pozzolan-based activator admixture for preparation of a concrete composition comprising saltwater. Presence of additional pozzolanic materials in the activator with the features described herein (for example activator components, composition and / or particle size) provide decreased permability, which leads to increased durability and long-term strength. This is demonstrated in Example 11, which shows that using saltwater (either seawater or artificial seawater) in the composition results in a significant increase in compressive strength at early and later curing times compared to the control. Specifically, day 1 strength increased by 38%, day 3 by 39%, and day 7 by 24%. Furthermore, the addition of activator admixture X4 to thecomposition further enhances strength at all time points, with increases of 26% at day 1, 23% at day 3, and 17% at day 7 compared to compositions without the activator.

[0134] Example 11 also confirms that the effect of the activator in increasing strength is maintained even in the presence of saltwater, demonstrating that the activator is effective regardless of the water source. The combination of saltwater and activator admixtures of the invention results in an additive effect on strength development, leading to a total strength increase of 60% at day 1, 55% at day 3, and 33% at day 7 compared to the control (which contains neither saltwater nor activator).

[0135] These findings indicate that the activator admixture is compatible with saltwaterbased formulations and remains effective in enhancing hydration and curing processes. Additionally, the results confirm that neither natural nor artificial seawater substantively impairs the performance of the activator, suggesting that its strengthening effect is primarily due to its interaction with the cementitious matrix rather than being influenced by the ionic composition of the mixing water. Accordingly, Example 11 demonstrates that the use of saltwater and activator admixtures of the invention together provides a robust and effective means of improving the mechanical performance of cementitious compositions, particularly in coastal or marine construction applications where seawater is readily available.

[0136] Concrete compositions containing activator admixtures of the present invention have been developed for use in pozzolanic concrete. These admixtures accelerate the chemical reactions of pozzolans, enabling rapid strength development, improved workability, and enhanced durability, even in the presence of seawater. Long term, the activator admixtures are believed to counteract the adverse effects of salts in seawater by promoting the formation of stable and durable cementitious compounds, reducing the risk of reinforcement corrosion, and enhancing the overall performance of concrete.

[0137] Without wishing to be bound by theory, it is believed that the pozzolanic materials found in the activators of the invention enable the production of stable and durable cementitious compounds to assist activator admixtures in mitigating the effects of seawater ions. These include calcium silicate hydrate (CSH), which forms a dense, stable matrix to enhance strength and reduce permeability, limiting the ingress of disruptive ions such as sodium and magnesium. Calcium aluminate hydrate (CAH) resists sulphate and chloride attack, forming a protective barrier that stabilises seawater salt interactions. Calcium magnesium silicate hydrate (CMSH) binds magnesium in a stable, non-expansive matrix, preventing deleterious reactions. Friedel's salt (calcium oxychloride) immobilises chloride ions, reducing their ability to corrode reinforcement steel. Hydrotalcite-like phases, formed from magnesium and aluminium ions, act as chloride scavengers and further stabilise the matrix. Additionally, ettringite enhances volume stability, and magnesium silicate hydrate(MSH) binds magnesium ions, mitigating their disruptive effects on hydration reactions and ensuring strength retention in high-salinity environments.

[0138] The pozzolanic reactions initiated by the addition of pozzolans to the concrete mixture mitigate the deleterious effects of rapid and early cement hydration, particularly the excessive production of calcium hydroxide (Ca(OH)2), when seawater is used. These reactions consume Ca(OH)2 by converting it into stable cementitious compounds such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH). By reducing the concentration of free Ca(OH)2, the pozzolanic reactions limit the availability of hydroxide ions that can react with seawater salts, thereby minimising the risk of expansive reactions and softening of the matrix. Additionally, the reduction in early hydration heat generation results in a more controlled setting process, enhancing the durability and mechanical properties of the concrete. These combined effects ensure that seawater-prepared concrete achieves improved long-term stability and performance in marine and coastal environments.

[0139] The activator admixtures of the present invention, comprising two or more pozzolans (synthetic or natural), further act as salt-neutralising or stabilising agents to mitigate the adverse effects of sodium chloride and magnesium chloride. The reactive silicates or chelating agents present in the admixtures interact with these salts, reducing their disruptive influence on the hydration process. Additionally, the admixtures mitigate the effects of magnesium ions, which can otherwise form deleterious compounds that compromise strength. This stabilisation ensures the retention of compressive strength, even in high-salinity environments, enabling the production of durable and high-performing concrete suitable for marine and coastal applications.

[0140] Accordingly, in one example, there is provided a method of increasing bound chloride fraction in a saltwater concrete composition, the method comprising incorporating an activator admixture into a concrete composition comprising cementitious material and saltwater, wherein the activator admixture comprises a pozzolan component comprising a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions have different median particle sizes; and the first and second pozzolan portions have different chemical compositions. In this example, chloride ions present in the composition are chemically and / or physically bound within hydration products of the cementitious matrix.

[0141] Further experimental evidence supporting the chloride management effects of the present invention is provided in Examples 12 to 20 and the accompanying Figures. These Examples demonstrate that activator admixtures comprising multi-modal pozzolan components, as described herein, provide measurable reductions in chloride ion mobility, increases in chloride binding fraction, and improvements in overall chloride resistance when used in saltwater concrete compositions.

[0142] In Example 18, chloride migration testing performed in accordance with nonsteady-state chloride migration protocols demonstrates that saltwater concrete compositions containing the activator admixture exhibit a reduced non-steady-state chloride migration coefficient (Dnssm) relative to corresponding compositions prepared without the activator. As illustrated in Figure 12, the addition of the activator reduces the effective migration rate of chloride ions through the cementitious matrix. This reduction is attributable to both densification of the microstructure and increased chemical binding of chloride ions within hydration products.

[0143] Without wishing to be bound by theory, it is believed that the presence of multimodal pozzolanic particles promotes the formation of additional calcium silicate hydrate (CSH), calcium aluminate hydrate (CAH), hydrotalcite- 1 ike phases, and Friedel's salt, thereby reducing the connectivity of capillary pores and limiting the transport pathways available to chloride ions. Accordingly, in certain examples, the method provides a reduction in chloride ion mobility of at least 10% relative to a control composition lacking the activator admixture.

[0144] Example 20 and Figures 16 and 17 demonstrate that incorporation of the activator admixture increases the proportion of chloride present in bound form relative to total chloride content. Acid-soluble chloride measurements (representing total chloride) and water-soluble chloride measurements (representing free chloride) confirm that a greater fraction of chloride ions are immobilised within hydration phases in compositions containing the activator. In some examples, at least 30% of total chloride present in the concrete composition is chemically and / or physically bound within hydration products. For example within Friedel's salt and hydrotalcite- 1 ike phases. In specific examples, significantly higher binding fractions are observed relative to saltwater control mixes without activator. These findings support the methods wherein the activator increases bound chloride fraction in saltwater concrete.

[0145] Measured reductions in water-soluble chloride concentration are observed in activator-containing compositions relative to equivalent saltwater control mixes. In some examples, water-soluble chloride concentration is reduced by at least 20%. The reduction in free chloride directly correlates with reduced corrosion risk for embedded reinforcement and improved long-term durability.

[0146] Examples 12 to 16 further demonstrate that the activator admixtures of the invention maintain or improve compressive strength while simultaneously improving chloride resistance performance metrics. Figures 13A, 13B, 14, 15, 19 and 20 show that strength enhancement occurs in freshwater and saltwater systems and across various supplementary cementitious material substitutions, including but not limited to fly ash and natural pozzolans.

[0147] The combined effects of reduced permeability, reduced chloride mobility, increased chloride binding, and maintained or enhanced compressive strength result in improved chloride resistance of the saltwater concrete composition. Accordingly, in some examples, the method provides improved chloride resistance relative to a corresponding saltwater composition prepared without the activator admixture.

[0148] It has been observed that the multi-modal particle size distribution of the activator pozzolan component contributes significantly to chloride management performance. Fine particles in the sub-2 pm range promote rapid early hydration reactions and densification, while coarser particles in the 10-80 pm range contribute to continued pozzolanic reactivity and long-term matrix refinement. This synergistic interaction reduces capillary porosity and enhances chloride binding capacity. Examples comparing activators of differing chemical composition (e.g., A+ and K4e) are provided.

[0149] The chloride management effects described herein are observed in natural seawater, artificial seawater, and saltwater compositions containing dissolved salts at concentrations between approximately 5 g / L and 45 g / L. The invention therefore enables the production of durable structural concrete in coastal, marine, offshore and high-salinity environments without requiring freshwater sources.

[0150] Magnesium sulphate (MgSCh) in seawater can cause sulphate attack through crystallisation, leading to expansion and cracking in the concrete matrix. The addition of a pozzolanic activator admixture to the concrete composition mitigates this effect by several mechanisms. First, the admixture enhances the formation of stable cementitious compounds, such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH), which densify the concrete matrix and reduce permeability, limiting the ingress or migration of MgS04. Second, the reactive pozzolan components in the admixture preferentially bind magnesium ions, forming non-expansive compounds such as magnesium silicate hydrate (MSH) and hydrotalcite-like phases, which prevent the disruptive reactions associated with sulphate attack. Finally, the admixture promotes a more controlled hydration process, reducing the availability of free calcium hydroxide, which can otherwise react with sulphate ions to form expansive ettringite. These combined effects significantly improve the durability and performance of concrete exposed to high-sulphate environments, improving long-term structural integrity.

[0151] The invention provides activator admixtures adapted for use with seawater in concrete production. These admixtures enable the use of seawater without compromising the long-term mechanical properties, durability, or environmental sustainability of the resulting concrete. By accelerating pozzolanic reactions and stabilising the interaction of seawater salts with cementitious materials, the invention ameliorates or overcomes challenges associated with seawater-based concrete.Applications of seawater concrete

[0152] Seawater-prepared concrete has a broad range of potential applications, particularly in marine and coastal environments where traditional concrete may be prone to degradation. Examples include sea walls, which require high durability and resistance to chloride-induced corrosion to withstand constant exposure to seawater. Jetties and piers benefit from seawater-prepared concrete due to its enhanced resistance to saltwater intrusion and structural weakening. Similarly, coastal foundations and offshore platforms rely on the long-term durability provided by this innovative material to ensure safety and stability under harsh environmental conditions. Additional applications include breakwaters, harbour structures, and underwater structures or tunnels, where resistance to both chemical and mechanical wear is critical. The use of seawater-prepared concrete can also extend to precast marine elements, such as culverts and retaining walls, as well as low-cost housing and road infrastructure in coastal areas where freshwater is scarce, enabling sustainable development and reduced construction costs.

[0153] In one example, the invention provides an activator comprising an activated pozzolan. In one example, the pozzolan is selected from a natural pozzolan and a synthetic pozzolan. In one example, the invention provides a natural pozzolan wherein the pozzolan has undergone a process which activates it. In one example, the activation process comprises at least one of application of an electrostatic charge, grinding the pozzolan to a desired particle size and controlling the particle size distribution. Similarly, synthetic pozzolans will have undergone processes that provide high levels of surface activation. This can occur during their production which is typically through thermal activation during production of fly ash or slag or other high temperature processes.

[0154] Preferably the activated pozzolans comprised in an activator have a moisture content of less than about 5%. Even though the activators of the present invention can be produced and used with a moisture content of greater than 5%, enhanced stability, mixing and formulation is achieved at lower moisture contents. Therefore, in a further example, the activator comprises a moisture content of less than about 3%. The moisture content may be adjusted to be within this range, or maintained within this range if material obtained is already at the desired moisture content.

[0155] The inventors have found that activators combined with natural or synthetic pozzolans act as a binder with surprisingly good workability, strength and durability in saltwater concrete compositions. In saline environments, these properties enable the binder to replace a portion of cement that would otherwise be required in a conventional saltwater concrete mixture while maintaining structural performance. In certain examples, a saltwater concrete composition comprising an activator comprising natural or synthetic pozzolans added at between 0.25-10% w / w of cementitious material, optionally between 0.5-8% w / w, and in certain implementations between 1-4% w / w of cementitious material, yields a concrete with substantially the same or improved workability, compressive strength and durability compared with comparable saltwater concrete compositions without activator.Cementitious material refers to the total amount of binder material active during preparation of the concrete. In certain examples, the cementitious material comprises Portland cement, optionally in combination with supplementary cementitious materials.

[0156] By way of illustration, approximately 111 kg of cement in a saltwater concrete composition can be reduced and replaced with non-active filler components such as sand and aggregate through incorporation of approximately 7.2 kg of an activator comprising pozzolans, while achieving substantially the same strength and durability under saline conditions. This example is illustrative of the cement-reduction capability of the activator within the dosage ranges described herein and is not intended to limit the scope of operable activator quantities. A person skilled in the art, having regard to the salinity of the mixing water, the type and proportion of supplementary cementitious materials, and the required mechanical and durability performance characteristics, would be able to select an appropriate activator dosage within the stated ranges to achieve comparable results in saltwater concrete systems.

[0157] Pozzolans can be described in terms of their chemical composition. The pozzolans are present in activators in a range and in proportions which assist in achieving the chemical composition described below. These activators provide the user with a concrete product with enhanced durability, strength and setting time. The inventors have shown that activators of the invention can be prepared from materials in a wide range of chemical compositions. In some examples, the activator chemical composition comprises SiO2 at a range from 20-80% by volume of the activator. In some examples, the activator chemical composition comprises AI2O3 in a range of 5-40% by volume of the activator. In an alternative embodiment, the invention comprises the following chemical composition range:;0158] In one particular example, the chemical composition comprises SiO2 at a range from 30-40%, and AI2O3 in a range from 7-10% by volume of the activator. The above percentages can be achieved using multiple pozzolan minerals, combined in proportions that are able to be ascertained by those of skill in the art and as described herein.

[0159] As referred to herein, a different chemical composition refers to a difference of at least 5% w / w in the amount of silicon dioxide (SiCb) or aluminium oxide (AI2O3) between the first and second pozzolan portions. In certain examples, the difference in silicon dioxide content between the first and second pozzolan portions is at least 5%, at least 10%, or at least 15% w / w. In certain examples, the difference in aluminium oxide content between the first and second pozzolan portions is at least 5%, at least 10%, or at least 15% w / w. The difference may relate to one or both of silicon dioxide and aluminium oxide.

[0160] A compositional difference of at least 5% w / w in silicon dioxide or aluminium oxide between the first and second pozzolan portions is sufficient to create a measurable difference in surface chemistry, dissolution kinetics and reactive phase availability during hydration. Even a 5% variation in oxide composition between two mineral fractions can alter the relative availability of silicate and aluminate species in the pore solution, thereby modifying the rate and pathway of secondary hydration reactions. In certain examples, a difference of at least 10% w / w in silicon dioxide or aluminium oxide provides a more pronounced differentiation in reactivity between the first and second pozzolan portions. At this level of compositional divergence, the two portions contribute distinctly to hydration reactions, with one portion preferentially enhancing silicate-driven C-S-H formation and the other contributing to aluminate-driven carboaluminate or related phase development. This compositional distinction supports synergistic interaction within the binder matrix. In certain examples, a difference of at least 15% w / w in silicon dioxide or aluminium oxide results in clearly differentiated mineralogical behaviour between the first and second pozzolan portions. At this level of divergence, the portions exhibit materially different pozzolanic reactivity profiles and dissolution rates, which enhances the ability to tailor early-age strength development, long-term strength gain, and microstructural densification through controlled multi-component interaction. The compositional difference may relate to silicon dioxide, aluminium oxide, or both. A difference in silicon dioxide content influences silicate-driven hydration and C-S-H nucleation kinetics. A difference in aluminium oxide content influences aluminate reactivity and the formation of carboaluminate and related hydration products. In certain examples, differences in both oxides are present, providing complementary and synergistic effects within the cementitious system. The inventors have found that such defined compositional differentiation between discrete pozzolan portions contributes to enhanced activation behaviour compared to a system comprising chemically homogeneous pozzolan particles of similar size distribution.

[0161] As referred to herein, a different median particle size refers to a difference in the Dv50 median particle size of the first pozzolan portion relative to the Dv50 median particle size of the second pozzolan portion. In certain examples, the Dv50 of the first pozzolan portion differs from the Dv50 of the second pozzolan portion by at least 5% relative to the smaller Dv50 value. In certain examples, the difference in Dv50 is at least 10%, at least 20%, or at least 50%. In certain examples, the absolute difference in Dv50 between the first and second pozzolan portions is at least 0.5 pm, at least 1 pm, at least 5 pm, or at least 10 pm.

[0162] In certain examples, the first and second pozzolan portions occupy distinct particle size regions and form separate peaks within a bi-modal or multi-modal particle size distribution of the activator. In such examples, the first pozzolan portion comprises an intermediate particle size fraction and the second pozzolan portion comprises a coarse particle size fraction.

[0163] In examples where the activator comprises an intermediate particle size fraction and a coarse particle size fraction, the intermediate particle size peak may range from 0.5-1.5 pm and the coarse particle size peak may range from 10-80 pm. The inventors have found that this structured separation of particle size domains facilitates optimal interstitial filling, whereby particles of the intermediate fraction occupy void spaces between particles of the coarse fraction. This enhances packing density within the binder matrix and contributes to microstructural densification during hydration.

[0164] As referred to herein, a "different median particle size" relates to the Dv50 median particle size of the first pozzolan portion relative to the Dv50 median particle size of the second pozzolan portion, each measured independently prior to blending into the activator. In certain examples, the Dv50 of the larger portion is at least 2x the Dv50 of the smaller portion (i.e., at least a 100% relative difference). Such a difference represents a minimum threshold at which the two portions occupy measurably distinct particle size regimes and exhibit divergent packing and surface area behaviour.

[0165] In certain examples, the Dv50 of the larger portion is at least 4x, at least 6x, or at least lOx the Dv50 of the smaller portion. These progressively larger separations correspond to increasing structural differentiation between the particle fractions. At differences of 4x and above, the portions contribute distinctly to packing hierarchy. At differences of 6x and above, the intermediate fraction functions primarily as an interstitial filler relative to the coarse fraction. At differences of lOx and above, the particle populations occupy clearly separated size domains consistent with the formation of discrete peaks in a bi-modal or multi-modal particle size distribution.

[0166] In certain examples, the absolute difference in Dv50 between the first and second pozzolan portions is at least 10 pm, optionally at least 20 pm, at least 30 pm, or at least 50 pm. Differences within these ranges correspond to particle populations residing in different size bands rather than reflecting minor statistical variation within a single distribution.Absolute separations of 20-50 pm are consistent with the intermediate (sub-2 pm) and coarse (10-80 pm) peak regions described herein.

[0167] In certain examples, the first and second pozzolan portions occupy distinct particle size regions and form separate peaks within a bi-modal or multi-modal particle size distribution of the activator. In such examples, the first pozzolan portion comprises an intermediate particle size fraction and the second pozzolan portion comprises a coarse particle size fraction. The presence of discrete peaks confirms that the portions are intentionally differentiated particle populations rather than merely a broadened unimodal distribution.

[0168] In one example, there is provided a method of producing a saltwater concrete composition comprising the steps of:a. obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;b. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c. providing a plasticiser;d. forming an activator admixture comprising the pozzolan component and the plasticiser;e. combining the activator admixture with cementitious material and saltwater to form the saltwater concrete composition,wherein the activator admixture may be formed prior to addition of saltwater or may be formed in situ during mixing of the cementitious material and saltwater, wherein the pozzolan component may be combined with the cementitious material prior to addition of saltwater, and the plasticiser may be added to the cementitious material either before or after addition of the pozzolan component and prior to addition of saltwater,wherein the pozzolan component comprises a chemical composition comprising 20- 80% w / w silicon dioxide and 5-40% w / w aluminium oxide, andwherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

[0169] In certain examples, the pozzolan component and plasticiser are pre-combined to form a dry activator admixture prior to addition to the cementitious material. Pre-blending may promote uniform coating or intimate association of the plasticiser with the pozzolan particles, thereby enhancing dispersion and reactivity upon hydration. In certain examples, the pozzolan component is first dry-blended with the cementitious material prior to addition of saltwater. The plasticiser may then be added to the dry blend, or may be introduced during mixing prior to or concurrent with addition of saltwater. Dry pre-blending of the pozzolan component with cementitious material can promote homogeneous distribution of the differentiated particle fractions within the binder matrix. In certain examples, the pozzolan component and plasticiser are not pre-blended as a discrete activator admixture but instead are combined in situ during mixing of the cementitious material and saltwater. In such embodiments, formation of the activator occurs during the mixing process, and the functional interaction between the pozzolan component and plasticiser is achieved within the wet mix. The inventors have found that staged addition of the pozzolan component and plasticiser prior to hydration can improve dispersion, reduce agglomeration of fine particle fractions, and enhance surface interaction between the differentiated pozzolan portions and the cementitious phases. This can promote more efficient activation of the pozzolanic material and improved microstructural development. The order of addition may therefore be selected according to practical considerations such as batching method, plantconfiguration, transport conditions, or desired rheological performance, without departing from the scope of the invention.

[0170] In certain examples, the pozzolan component comprises 20-80% w / w silicon dioxide (SiCb) and 5-40% w / w aluminium oxide (AI2O3). This compositional range encompasses natural and synthetic pozzolans capable of participating in secondary hydration reactions within a cementitious system. Silicon dioxide within this range provides reactive silicate species for formation of calcium silicate hydrate (C-S-H) phases, while aluminium oxide contributes to aluminate reactivity and the formation of carboaluminate and related hydration products. The lower bounds ensure sufficient reactive oxide content to meaningfully contribute to hydration chemistry, while the upper bounds accommodate mineralogical variability across different pozzolan sources without compromising binder integrity.

[0171] In certain examples, the pozzolan component comprises 40-80% w / w silicon dioxide and 10-40% w / w aluminium oxide. Compositions within this range exhibit increased availability of reactive silicate and aluminate phases, promoting enhanced pozzolanic reactivity and improved contribution to binder microstructure. Higher silicon dioxide content within this range supports sustained C-S-H development, while aluminium oxide levels of 10% or greater promote formation of stabilising aluminate-containing hydration phases. This compositional window may provide improved synergy when the activator comprises differentiated pozzolan portions.

[0172] In certain examples, the pozzolan component comprises 30-40% w / w silicon dioxide and 7-15% w / w aluminium oxide. This narrower compositional range may correspond to particular mineral classes or engineered pozzolan blends in which balanced silicate and aluminate reactivity is desired. Within this range, the relative proportions of silicon dioxide and aluminium oxide may be tailored to optimise early-age strength development, chloride binding capacity, and long-term microstructural densification. Such compositions may be particularly suitable where controlled differentiation between first and second pozzolan portions is employed.

[0173] In embodiments where the first and second pozzolan portions comprise different chemical compositions within the ranges described above, the differentiation in oxide content contributes to distinct dissolution kinetics and reactive phase availability. A higher silicon dioxide portion may preferentially enhance silicate-driven C-S-H formation, while a comparatively higher aluminium oxide portion may contribute to aluminate-driven phase development. The defined compositional ranges therefore provide a framework within which controlled chemical differentiation can be achieved while maintaining overall compatibility with cementitious hydration processes.

[0174] In one example, the invention provides a method of producing an activator composition comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a second pozzolan portion with a second chemical composition;b. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c. mixing the pozzolan component with a plasticiser to produce an activator composition,wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide, and 5-40% aluminium oxide, wherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

[0175] In one example, the pozzolan component comprises 40-80% w / w silicon dioxide and 10-40% w / w aluminium oxide.

[0176] In one example, the pozzolan component comprises 30-40% w / w silicon dioxide and 7-15% w / w aluminium oxide.

[0177] In one example, the invention provides a method of producing an activator for use as an admixture for concrete comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a first particle size Dv50,b. obtaining a second pozzolan portion with a second chemical composition and a second particle size Dv50;c. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;d. mixing the pozzolan component with a plasticiser to produce an activator compositionwherein the first and second pozzolan portions comprise different Dv50 median particle sizes and / or different chemical compositions.

[0178] The plasticiser may be a powdered plasticiser. In one example, the mixing period is at least five minutes. This ensures that the different materials blend and facilitates the interstitial filling referred to herein which assists in providing a concrete / mortar product with the enhanced properties described herein. The plasticiser may be present at varying concentrations depending on the application of the concrete and the water demand and placement properties. In some example the plasticiser is present at 8-40%, 10-40%, or 10 to 25% w / w of activator. Without wishing to be bound by theory, it is believed that the plasticiser interacts with the pozzolan components to facilitate a stable powdered mixture with properties that enable enhanced reactivity. This enhanced reactivity leads to the unexpected early strength observed in trials outlined in the examples. This unexpected activity of the activator components and optionally additional supplementary cementitious materials added to the mix is believed to be at least partially achieved by the electrostaticactivation of activator particles resulting in their reduced clumping, and enhanced interstitial filling as described herein.

[0179] In one example, the method of producing an activator for use as an admixture for concrete comprises a step of applying an electrical charge to one or more activator components. The activator components may comprise any one of the activator, the pozzolan component, the first, second or a further pozzolan portion, or the plasticiser.

[0180] The activator admixtures of the present invention may include pozzolans and a plasticiser in powdered form. During the mixing process, these components may be subjected to electrostatic forces, which may be generated by a variety of mechanisms. In one example, as the mixture undergoes mechanical agitation, friction between the particles causes them to acquire an electrostatic charge. This phenomenon increases the surface energy of the particles, making them more reactive. Alternatively, an external electrical charge can be applied to the admixture to achieve the same effect, enhancing the activation process further. It is important to distinguish this process of mixing from the process of intergrinding which reduces particle size and can also impart increased reactivity to interground particles.

[0181] When the components are mixed, the generated electrostatic forces are believed to result in the particles repelling each other. This repulsion prevents the particles from clumping together, ensuring a uniform dispersion of the pozzolans and plasticiser throughout the concrete / mortar mix. This uniform dispersion assists in achieving a consistent and homogeneous concrete microstructure. An improved microstructure also minimises the occurrence of weak points within the concrete. This results in a more consistent material with improved mechanical properties. Additionally, the uniform dispersion contributes to a reduction of pore size and connectivity within the concrete, which enhances its overall durability and resistance to environmental factors as exemplified in example 4.

[0182] Electrostatic activation is believed to significantly increase the chemical reactivity of the pozzolans within the concrete mix. Pozzolans such as those described herein typically react with calcium hydroxide, a by-product of the cement hydration process. This reaction results in the formation of additional cementitious compounds, notably calcium silicate hydrate (CSH) from SiO2 and CAH from AI2O3 which make up the primary binding phase in concrete and are essential for the concrete's strength and durability. This increased formation of CSH and CAH directly correlate with higher compressive and tensile strength in the concrete. By increasing the surface energy of the pozzolans through electrostatic activation, their reactivity is enhanced thus leading to a more efficient and accelerated pozzolanic reaction, producing more CSH and CAH. The presence of additional CSH and CAH improves the overall strength and durability of the concrete, contributing to its long-term performance.

[0183] The improved dispersion of pozzolans and plasticiser within the concrete mix, believed to result from electrostatic activation, plays a significant role in reducing the concrete's permeability. The formation of additional CSH and CAH helps to fill the pores within the concrete, decreasing the pore size and connectivity. This reduction in porosity leads to decreased permeability, enhancing the concrete's resistance to water and chemical ingress. Consequently, the concrete becomes more durable and better suited for use in harsh environments. Example 4 describes experiments carried out which exemplify the increased durability and performance of activator containing concrete with respect to water resistance, chloride penetration, and reduction in voids.

[0184] Concrete that incorporates the electrostatically activated admixture demonstrates enhanced durability. The increased strength and reduced permeability contribute to the concrete's ability to withstand environmental degradation. This includes improved resistance to freeze-thaw cycles, sulphate attack, and alkali-silica reaction. The enhanced durability makes this concrete suitable for use in a wide range of demanding construction applications, where long-term performance is critical.

[0185] In one example, an external electrostatic field is applied to the dry powder form of the activator. The mixture of pozzolans and plasticiser is placed in a chamber equipped with electrodes that generate an electrostatic field with voltages ranging from 20 to 50 kV. The electrodes can deliver a power output of 2 to 10 kW, ensuring a strong and consistent electrostatic field. The flow rate of the powder through the chamber is maintained at a rate which achieves a power delivery of at least 0.1 to 0.6 kWh / kg of activator powder. This power delivery ensures uniform exposure to the electrostatic field and a uniform charge distribution across the particles.

[0186] In a further example, the dry powder activator is charged using an electrostatic spraying technique. The pozzolans and plasticiser mixture is fed through an electrostatic spray gun, which imparts a charge to the particles as they are sprayed onto a collection surface. The spray gun operates at voltages of 30 to 60 kV, with a power output of 1 to 3 kW. The flow rate of the powder through the spray gun is controlled at a rate to achieve at least 0.1 to 0.6 kWh / kg of activator powder. The charged particles are collected and subsequently prepared for use in a concrete or mortar mixture.

[0187] In another example, the activator comprising pozzolans and a plasticiser is subjected to triboelectric charging in a fluidized bed. The dry powder is fluidised using a stream of air, optionally at a flow rate of 50 to 200 m3 / hr. As the particles collide with each other and the walls of the fluidised bed chamber, which are typically lined with a triboelectric material, they become triboelectrically charged. Preferably the voltage generated during this process is between 5 to 25 kV. In one example, the activator is subjected to an electrical charge of between about 0.1 to 0.6 kWh / kg of activator powder.This method utilises the principles of triboelectric charging to generate electrostatic forces, enhancing the properties of the activator for use in concrete.

[0188] In one example, the electrostatic charge applied to the activator components is generated through the mechanical mixing process itself. The dry powder form of the activator, comprising pozzolans and a plasticiser, is subjected to mixing in a mixer. The mixer operates at a speed of 1500 to 3000 rpm, generating friction between the particles. This friction induces electrostatic charges. The power output of the mixer can be adjusted between 1 to 5 kW to control the intensity of the mixing process. This method leverages the inherent frictional forces in mixers to induce the electrostatic effect, enhancing the reactivity and dispersion of the activator components. It will be appreciated by those of skill in the art that mixing and application of an electrostatic charge using this method does not require the size reduction of particles that may be achieved through intergrinding. Intergrinding negatively affects particle size distribution within a mixture, causing larger particles to experience a proportionally greater size reduction compared to smaller particles. This leads to an homogenisation of particle sizes which compromises the benefits of using multiple particle sizes achieved through interstitial filling as referred to herein.

[0189] In a further example, an electrostatic charge is applied to the activator using a corona discharge. The mixture of pozzolans and plasticiser is passed through a region where a high-voltage electrode generates a corona discharge. The electrode operates at voltages ranging from 40 to 80 kV, with a power output of 2 to 6 kW. The flow rate of the powder through the corona discharge region is maintained at a rate sufficient to achieve an electrical charge of between about 0.1 to 0.6 kWh / kg of activator powder. The ions produced by the corona discharge attach to the activator particles, imparting an electrostatic charge in a controlled and efficient way.

[0190] In a further example, the activator components are subjected to electrostatic fluidisation. The pozzolans and plasticiser mixture is placed in an electrostatic fluidised bed where a combination of fluidisation and electrostatic charging occurs. In one example the fluidising air is ionised at a voltage of 15 to 35 kV. The fluidised and ionised air passes through the powder, charging the particles. The power output for ionizing the air is typically between 0.1 to 0.6 kWh / kg of activator powder. This dual action of fluidisation and charging achieves both dispersion and reactivity of the activator components.

[0191] In one example, the pozzolan component comprises a chemical composition comprising 40-80% w / w silicon dioxide, and 10-40% aluminium oxide. In a further example, the pozzolan component comprises a chemical composition of 20-80% w / w silicon dioxide, and 5-40% aluminium oxide.

[0192] In a further example, the invention provides a method of preparing an activator composition comprising the steps of:a. obtaining a first natural pozzolan portion with a first Dv50 particle size;b. combining the first natural pozzolan portion with a second natural pozzolan portion with a second Dv50 to produce an activator composition,wherein the activator composition comprises a chemical composition comprising 40-80% w / w silicon dioxide, and 10-40% aluminium oxide, and wherein the first and second Dv50 particle size differs by at least 10pm.In one example the method comprises applying an electrostatic charge to the activator composition. In one example, electrostatic charge is applied by way of the power delivery of at least 0.1 to 0.6 kWh / kg of activator powder.

[0193] As will be appreciated by the above examples, the unexpected efficacy of the activator when combined with other concrete components is at least partially determined by the chemical and physical properties of the pozzolan component and the activator composition. The pozzolan component may be produced by combining one pozzolan compound with at least one other pozzolan compound to result in the preferred properties described.

[0194] In one example, preparation of the pozzolanic component of the activator composition, for example the method and activator of the preceding paragraph, may further comprise the steps of:a. identifying a chemical composition of at least two pozzolans;b. calculating the required amount of pozzolan a first pozzolan and a second pozzolan to achieve a chemical composition of the pozzolan component in a pre-determined range;c. combining the calculated amounts of pozzolans to produce an activator.

[0195] The ways in which pozzolan compounds can be selected and combined to result in the inventive compositions are able to be readily determined by those of skill in the art, in accordance with standard testing and combinatorial procedures. Those of skill in the art would calculate the requisite amount of corresponding pozzolan materials to achieve a pozzolan component within the prescribed range of chemical compositions described herein.

[0196] Although admixtures are typically provided in a liquid form, it is preferable to formulate and store the activators of the invention when in a dry powdered form. For example, the moisture content of the components or portions of the activator should preferably result in an activator with a moisture content of less than 5%. Moisture content can be measured according to standard methods known to those of skill in the art.

[0197] If the moisture content is too high, for example 5% or over, the formulation machinery can malfunction and block due to machinery becoming fouled, especially air pumps designed to transport dry material thorough tubes. Further, when a plasticiser or superplasticiser is used in the activator composition, this component can react with water and partially set or reduce effective surface area of the activator components. This resultsin decreased efficiency of binding, and difficulty in storage or transportation of the activator prior to concrete formulation.

[0198] To achieve the desired moisture content, components of the activator may require drying according to known processes. One unexpected advantage of using pozzolans for the preparation of an activator is that it can be dried if the moisture content rises to be too high, for example over 5%, or 3% depending on the application and stability of the product required. In contrast, cement-containing compositions bind to each other and cannot be used if the material gets wet or beyond a threshold moisture content.

[0199] In one example, the activator comprises pozzolan portions which each comprise a moisture content of less than about 5%. In a further example, the pozzolan portions each comprise a moisture content of less than about 3%.

[0200] In one example, the activator comprises a moisture content of less than about 5%. In a further example, the activator comprises a moisture content of less than about 3%.

[0201] The moisture content may be adjusted to be within this range, or maintained within this range if material obtained is already at the desired moisture content.

[0202] The invention described herein comprises an activator comprising a natural or synthetic pozzolan that may have a multi-modal particle size distribution. In one example, the multi-modal distribution comprises at least two distinct peaks of particle size frequency or volume density - i.e. a bi-modal distribution as shown in the figures. In another example, the multi-modal distribution comprises at least three distinct peaks of particle size frequency - i.e. a tri-modal distribution. In some examples, the distribution comprises a multi-modal distribution which is defined as more than two distinct peaks of particle size frequency. For example 4, 5, 6, 7, 8, 9 or 10 distinct peaks.

[0203] In one aspect, the invention provides an activator admixture for producing concrete, the activator comprising a pozzolan component and a plasticiser component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes.

[0204] In one example the multi-modal particle size distribution is achieved by adding two or more pozzolan portions, wherein each pozzolan has a Dv50 different to every other pozzolan portion. In one example, the Dv50 differs by at least 10pm. Although the Dv50 of distinct portions used to formulate the pozzolan component will be different, it will be appreciated that the resultant pozzolan component found in the activator will have mixed portions. Therefore the pozzolan component will have a single Dv50 median particle size but portions with distinct particle size distributions, the median particle size of which can be measured and reported separately. Where particle size analysis indicates that there aredistinct particle size distribution peaks (for example in the particle size volume density graphs shown in the figures), these peaks can be attributed as being the original Dv50 values of the pozzolan portions combined to produce the pozzolan component. The difference between the distinct Dv50 values indicates that different particle sizes are present in the composition.

[0205] The particle size distributions of the present invention provide unique reactive properties and strength. Without wishing to be bound by theory, it is believed that this enhancement is at least partially explained by the different particle size portions filling interstitial spaces within the other portions to provide an enhanced matrix and therefore enhanced strength. For example, particles from a first pozzolan portion fills at least a plurality of interstices between particles of at least one of a second pozzolan portion and a third pozzolan portion. In some examples, particles of a second portion of particles fills at least a plurality of interstices between a third portion of particles. This unique arrangement of particles contributes to the water resistance, durability, and tensile and compressive strength of the resultant mortar or concrete as observed in the examples. The portions of pozzolan particles described herein may be from natural pozzolans, each with a different chemical composition.

[0206] As will be understood by those of skill in the art, the particle size of each particle of a composition will vary about a mean. In some examples, the median of the volume distribution is used to describe the particle size and is referred to as "Dv50" or D(v,0.5). This parameter describes the maximum particle diameter below which 50% of the sample volume exists - also known as the median particle size by volume.

[0207] To determine the Dv50, a sample of the material is analysed using a particle size analysis technique. Such techniques will be known to those of skill in the art but by way of example, they may be selected from sieve analysis, laser diffraction, and sedimentation. Alternatively, the particle size may be defined in terms of size and volume density at that size (for example see tables in example 1 and 2 derived according to Test protocol 3).

[0208] In the examples described herein, the activator comprises a portion of pozzolan particles comprising a coarse particle size, and a second portion of pozzolan particles comprising an intermediate particle size. In one example, activators described herein may further comprise a third portion of pozzolan particles comprising a fine particle size.

[0209] Examples la, lb, 1c, 2a, 2b, 5 and 6 provide example of activators comprising at least bi-modal particle size distributions. Each activator provides enhanced concrete properties (strength and / or workability) compared to control mixes. The activators described may also include a plasticiser. In some examples, the plasticiser comprises a particle size of 100-200pm. This component of the activator can be observed in the volume density graphs for the examples as a minor peak above 100pm.

[0210] The inventors have found that the specific particle size distribution of natural or synthetic pozzolans included in the activator significantly enhances reactivity within saltwater concrete compositions. In particular, the presence of at least two pozzolan portions differing in median particle size promotes improved particle packing and increased surface interaction in the presence of dissolved salts. This enhanced reactivity contributes to improved hydration kinetics in saline environments. In certain examples, the activator promotes increased formation of hydration products capable of binding chloride ions. In certain examples, the activator contributes to refinement of pore structure in saltwater concrete.

[0211] This enhanced performance enables the activator to be incorporated at relatively low dosages while still achieving significant improvements in saltwater concrete properties. In certain examples, the activator may be added at between 0.25-10% by weight of cementitious material, optionally between 0.5-8%, and in certain implementations between 1-4%, to achieve measurable improvements in compressive strength development, chloride binding capacity, reduction in chloride mobility, and overall durability relative to comparable saltwater concrete compositions lacking the activator.

[0212] In some examples, the specific surface area (SSA) of the activator admixture comprises between 350-1000m2 / kg. It will be appreciated by those of skill in the art that the SSA of an admixture, particularly when incorporating pozzolans into concrete, significantly influences both the speed of setting and the strength development of the concrete. The inventors have found that the use of porous particles and a portion of particles of intermediate size (i.e. 0.5-1.5pm) increases the reactive surface area, thereby accelerating the pozzolanic reaction with calcium hydroxide during cement hydration. Fine particles (i.e. less than about 0.3pm) are not required to achieve the benefits of the activators described herein. This enhanced reactivity leads to a faster setting time and contributes to early strength gain. Additionally, the higher SSA achieved by porous particles can increase the water demand as these particles absorb more water. The activator admixtures of the invention balance this increased water demand with a plasticiser (water reducer) provided at pre-determined concentrations to ensure that the absorption is balanced by availability of free water for cement hydration. This avoids the undue stiffening of the mix. This balance is exemplified in the examples provided below where the slump (workability) of the activator containing mixes is maintained at a level substantially equivalent to mixes not including activator. This balance ensures that workability and early strength are provided as features of the concrete produced using the activator admixtures of the invention.

[0213] In one example, the invention comprises a pozzolan component comprising a mixture wherein at least 90% of particles comprise a particle size between 1 - 180pm. In one example at least 50% of the volume of particles of the pozzolan component comprise less than 40pm i.e. (Dv5040pm). In another example at least 50% of the volume ofparticles of the pozzolan component comprise less than 50pm i.e. (Dv50 50pm). In another example the activator may comprise a Dv50 of from 10 to 50pm). As referred to herein, a "pozzolan component" means the part of the activator composition which is made from pozzolanic compounds i.e. not including plasticiser or any other added, non-pozzolan components.

[0214] In one example, the activator comprises a pozzolan component comprising at least two pozzolan portions. In some examples, the activator may comprise a third or further pozzolan with the same or different Dv50. The proportions of the pozzolans can be adjusted by those of skill in the art to achieve the particle size distribution described below. In one example, the particle size distribution comprises:• 15-55% of particles are less than 15 pm;• 50-80% of particles are less than 40 pm; and• 70-100% of particles are less than 90 pm.

[0215] In a further example, the particle size distribution comprises:• 30-40% of the activator comprises particles less than 15 pm,• 50-65% of the activator comprises particles less than 40 pm,• 75-90% of the activator comprises particles less than 90 pm.

[0216] Example la describes an activator (Gamma) comprising natural pozzolans wherein the activator comprises a Dv50 of about 24.2pm, particle size less than 15 pm made up about 38%, particles less than 40 pm made up about 65%, and particles less than 90 pm made up about 90%.

[0217] Example lb describes an activator (Omega2) comprising natural pozzolans wherein the activator comprises a Dv50 of about 31pm, particle size less than 15 pm made up 34%, particles less than 40 pm made up 55%, and particles less than 90 pm made up 78%.

[0218] In a further aspect, the invention provides a method of producing an activator for use as an admixture for concrete comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a first particle size Dv50,b. obtaining a second pozzolan portion with a second chemical composition and a second particle size Dv50;c. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;d. mixing the pozzolan component with a plasticiser to produce the activator.In one example the plasticiser comprises a powdered plasticiser.

[0219] In one example, the mixing step is carried out for a period of at least five minutes.

[0220] In one example, the activator comprises an intermediate particle size and a coarse particle size. In one example the intermediate particle size peak is in a range of 0.5-1.5pm and the coarse particle size peak is in a range between 10-80pm. The examples illustrate this property of the activators of the invention whereby a volume density peak corresponding to intermediate particles is observed in a range of 0.5-1.5pm and the coarse particle size peak comprises a range between 10-80pm. The first pozzolan component exhibits a volume density peak of between 0.3 and 1.5% for particles at between 0.5pm and 1.5pm and a second pozzolan component exhibits a volume density peak of greater than 3% between 10 and 80pm. In some examples, a volume density ratio of a first peak to a second peak comprises 1:2 to 1:30, preferably 1:3 to 1:8, wherein the peaks may correspond to the first and second pozzolan portions. These peak ranges may correspond to the Dv50 values of a first and second pozzolan portion.

[0221] Accordingly, in one example, the activator comprises a first pozzolan portion which comprises an intermediate particle size with a range of 0.5-1.5pm and a second pozzolan portion comprises a coarse particle size with a range of 10-80pm. In another example, the activator comprises a first pozzolan portion which exhibits a volume density peak of between 0.3 and 1.5% for particles at between 0.5pm and 1.5pm and the second pozzolan portion exhibits a volume density peak of greater than 3% between 10pm and 80pm.

[0222] As referred to herein, a "volume density peak" refers to a local maximum in the differential particle size distribution curve, for example when particle size is measured using laser diffraction techniques. The particle size distribution is determined as a function of particle diameter and expressed as percentage volume of particles within discrete size intervals. A volume density peak corresponds to a particle size region in which the differential volume percentage reaches a local maximum relative to adjacent particle size intervals. Particle size measurements, including DvlO, Dv50 and Dv90 values and differential volume density distributions, may be determined using methods known to those of skill in the art, for example laser diffraction analysis in accordance with standard practice. In certain examples, measurements are performed using a laser diffraction particle size analyser under dry dispersion or wet dispersion conditions, as appropriate for the material being analysed.

[0223] In examples where two or more volume density peaks are present, the peaks correspond to distinct particle size fractions within the pozzolan component. Such peaks may represent intermediate and coarse particle size regions, respectively, and may be separated by a relative minimum in the differential volume distribution curve.

[0224] Interstitial filling is a critical factor in optimizing the performance of the concrete mix, particularly when using a powdered plasticiser, extended mixing times, and an activator with varying particle sizes. Where the plasticiser comprises a powdered form, the intermediate particles enhance the interstitial filling between larger cement and aggregate particles. This improved packing density reduces voids and enhances the workability, compaction, and ultimately, the strength and durability of the concrete.

[0225] In examples where the mixing step is carried out for a period of at least five minutes, the extended mixing time ensures the uniform distribution of both intermediate and coarse particles throughout the mix. This uniformity is essential for effective interstitial filling, which minimizes segregation and leads to a more homogenous concrete structure with superior mechanical properties.

[0226] In examples where the activator comprises an intermediate particle size and a coarse particle size, with the intermediate particle size peak ranging from 0.5-1.5 pm and the coarse particle size peak ranging from 10-80 pm, the inventors have found that this combination of particle sizes facilitates optimal interstitial filling. The intermediate particles effectively fill the gaps between the coarse particles, resulting in a densely packed microstructure. This dense packing reduces the porosity of the concrete, leading to increased strength, reduced permeability, and enhanced overall durability of the concrete product.

[0227] Plasticisers, "water reducers", or "superplasticisers" are chemical compounds used in concrete to improve the workability of fresh concrete. When added to the concrete mixture, plasticisers reduce the amount of water required for proper workability, which helps to improve the strength and durability of the concrete by reducing water-cement ratio and minimising porosity, cracking, and shrinkage. Unless the mix is "starved" of water, the strength of concrete is inversely proportional to the amount of water added or watercement (w / c) ratio. Therefore, in order to produce stronger concrete, less water is added. To avoid "starving" the mix, it may be necessary to use plasticisers or superplasticisers.

[0228] Plasticisers work by adsorbing onto the binder (e.g., cement) particles and creating a repulsive force between them, which helps disperse the particles and reduce the viscosity of the mixture. This results in a more fluid and cohesive concrete mixture that can be easily moulded or placed without segregation or bleeding.

[0229] Different types of plasticisers are available, including lignosulfonates, sulfonated melamine formaldehyde condensates, naphthalene sulfonate formaldehyde condensates, and polycarboxylates. Each type of plasticiser has its own specific properties and benefits, and the selection of a plasticiser depends on the required workability, strength, and durability of the concrete mixture.

[0230] In one example, the activator comprises a plasticiser. The inventors have found that the plasticiser and a pozzolanic mix with defined properties (particle size distributionand chemical composition) together create a synergistic effect that results in speeding up the pozzolanic reaction in concrete by two to three times. As a result, concrete containing activator comprising plasticiser plus pozzolans gains strength faster at each age of strength setting.

[0231] Accordingly, in some examples, the activator admixture described herein comprises at least one of: a polycarboxylate plasticiser; a naphthalene plasticiser, a superplasticiser; a lignosulphonate plasticiser; a dry form plasticiser; and a dry powder polycarboxylate superplasticiser.

[0232] In one example, the activator according to the present invention comprises a polycarboxylate (PCE) plasticiser. Use of pozzolans in the activator can also increase viscosity of the mix and can reduce workability. Therefore, to counteract this effect, the activators of the present invention may comprise a plasticiser.

[0233] Plasticisers also include superplasticisers or "high range water reducers".Superplasticisers provide a higher rate of water reduction while maintaining strength. In one example, the plasticiser used in the activators described in herein is a superplasticiser, otherwise known as a high range water reducer. Although the activators of the invention may be prepared without a plasticiser, it will be appreciated that this will significantly reduce the workability due to the limited ability to reduce water. Strength would also be compromised in mixes without plasticisers. The activators described herein may be prepared without a plasticiser which is then added subsequently by the concrete formulator rather than the activator manufacturer. This is particularly the case where specialised plasticisers are required, for example for underwater structures, high strength structures, or corrosion resistant concrete.

[0234] In many examples of concrete mixtures, liquid plasticisers are added. The inventors have however found that the activator compositions of the present invention show particular efficacy when a plasticiser in dry form is used. In one example, the plasticiser of any activator or concrete mixture described herein comprises a dry powder plasticiser. In this example, the plasticiser may comprise a polycarboxylate plasticiser. The plasticiser may comprise a superplasticiser and may be a polycarboxylate superplasticiser, again preferably in dry powdered form. Dry powdered format plasticiser comes in the form of granules or powder, which can be easily measured, stored, and mixed with other concrete ingredients. In contrast, liquid plasticisers can be messy to handle and may require special containers or precautions for storage and transportation. In addition, powdered plasticisers provide advantages in being able to blend with the dry format pozzolans and disperse evenly throughout the mixture. They enable the preparation of the activator without having to measure and handle liquids during concrete preparation. The powdered format plasticisers offer better control over dosage compared to liquid plasticisers. They are also easier to measure and enable adjustment of the amount of dry powder plasticiser added tothe concrete mix, ensuring precise and consistent results. Liquid plasticisers, on the other hand, can be more difficult to measure accurately, leading to variations in the plasticising effect.

[0235] In one example, the activator comprises a plasticiser at a percentage (w / w) of from about 8% to 40% or 10% to about 40%. In some examples, this range is about 10% to about 25%, depending on types of pozzolans and the required purpose of the concrete. In another example, the activator comprises a ratio of pozzolan component to plasticiser at a ratio of from 11:1 to 1.5:1, or 9:1 to 1.5:1 or 9:1 pozzola plasticiser to about 3:1 pozzolan: plasticiser. In another example, the plasticiser is added to the activator at 8-40% w / w of the activator. It will be appreciated by those of skill in the art that the addition of plasticiser at such high concentrations in the activator admixture is a clear indicator that the activator is not a major portion of the concrete mixture; instead, it represents a minor proportion of the concrete composition.

[0236] It is desirable for the plasticiser to be prepared with a weight average particle size which achieves maximum efficacy in adsorbing onto, and mixing with the natural pozzolan portions of the activator. To achieve these improvements in reaction efficiency and mixing, in one example, the plasticiser present in the activator has a Dv50 of from about 50-500pm. In another example, the plasticiser present in the activator has a Dv50 of from about 100-200pm.

[0237] In one example, there is provided an activator for use as an admixture for concrete comprising:a) a pozzolan component comprising at least two pozzolans comprising distinct particle sizes and chemical compositions; andb) a powdered plasticiser with a particle size from 50-500pm;wherein the pozzolan component and plasticiser have been mixed for over 5 minutes.Effective mixing of the activator components is required to provide a stable admixture composition for addition to other concrete components.

[0238] There is a prevailing view in the art that pozzolanic concrete has slower strength gain, especially early strength development when compared to ordinary concrete prepared using Ordinary Portland Cement (OPC). Typically, ordinary concrete (using OPC) exhibits faster early strength development within the first few days after casting. This is due to the rapid hydration reaction of the Portland cement. Pozzolanic concrete has in the past been associated with slower early strength development because the pozzolanic reaction is slower to start. The pozzolanic materials react with calcium hydroxide (a byproduct of cement hydration) to form additional calcium silicate hydrate (C-S-H), but this process takes more time to initiate compared to the hydration of OPC.

[0239] In several of the experimental examples provided herein natural and industrial pozzolans were also added as supplementary cementitious materials (SCMs) to partially replace cement. These mixes were assessed with and without the inclusion of an activator admixture. In some example the natural pozzolans that were used were limestone and pumicite, along with industrial pozzolan fly ash.

[0240] The inclusion of a pozzolan in concrete mixes demonstrates a delayed pozzolanic reaction that causes a boost in compressive strength typically seen from day 7 onwards. As noted above, the pozzolanic reaction occurs as a secondary reaction after cement hydration once calcium hydroxide becomes available. This reaction forms calcium silicate hydrates (C-S-H) which influence strength development. Pozzolanic reactions are described as "delayed reactions" as they occur at later stages with free calcium hydroxide that become available after cement hydration. These reactions continue to occur until there is no more free calcium hydroxide meaning there can be a continued increase in strength for up to and beyond 56 days. The pozzolanic reaction explains why there can be a boost in strength in pozzolanic containing mixes at day 7 and beyond.

[0241] The inventors have found that the powdered activators of the invention comprising a combination of components including a plasticiser and a pozzolanic mix with properties referred to herein, (for example particle size distribution, specific surface area, electrostatic charge and chemical composition) together create a synergistic effect that is achieved through interaction of the plasticiser and pozzolans, and pozzolans with each other. This speeds up the pozzolanic reaction in concrete by two to three times and the strength of concrete containing activator as an admixture is accelerated at each age of strength setting. Further, the final strength of concrete containing activator is higher than that of concrete without the activator.

[0242] The synergistic effect further creates denser packing of particles achieved by the interaction of the plasticiser and pozzolans, and pozzolans with each other which leads to increased strength and durability of the hardened concrete. The additional reactive cementitious compounds formed through pozzolanic reactions contribute to improved compressive strength, reduced permeability, and enhanced resistance to chemical attack. Thus, both chemical and mechanical properties of pozzolans are important to achieve the synergistic effect and improve hardened concrete or mortar properties.

[0243] Another example of the efficacy and synergism of activators according to the present invention is demonstrated in saltwater concrete compositions by the relatively small dosage of activator required to enable substantial cement reduction while maintaining structural performance. In certain examples, activator may be incorporated at between 0.25-10% w / w of cementitious material, optionally between 0.5-8%, and in certain implementations between 1-4%, to permit reduction of cement content in saltwater concrete by 20-50% without compromising compressive strength development acrossmeasured curing ages. The examples demonstrate that strength performance in saline environments can be maintained or improved relative to corresponding saltwater compositions lacking the activator.

[0244] Another example of the efficacy and synergism of the present invention in saltwater systems is the enhanced performance of concrete containing natural or synthetic pozzolans as fillers when the activator is present. In saline mixing conditions, the activator promotes reactivity of supplementary cementitious materials that would otherwise function primarily as fillers. Cement reduction of greater than 30% relative to a comparable saltwater concrete mix may be achieved by incorporating natural or industrial pozzolans together with the activator. In certain examples, the activator contributes to improved chloride binding. In certain examples, the activator contributes to reduced chloride mobility. In certain examples, the activator contributes to maintained or enhanced compressive strength development under saline conditions.

[0245] By way of illustration, a 20 MPa saltwater concrete mixture may typically require approximately 250 kg of cement to achieve the desired strength. In one example, approximately 30% of the 250 kg cement (i.e. approximately 75 kg) may be removed. The activator may then be incorporated at between 0.25-10% by weight of the remaining cementitious material, optionally between 0.5-8%, and in certain implementations between 1-4%. In one illustrative calculation, if 30% cement reduction results in approximately 175 kg remaining cementitious material, an activator dosage within 1-4% corresponds to approximately 1.75-7 kg of activator. The remaining volume equivalent to the removed cement may be replaced by (a) substantially inactive filler such as aggregate and / or sand and / or (b) supplementary cementitious materials. This example is illustrative and does not limit the operable dosage ranges described herein. In saltwater concrete compositions, reduction of cement content may contribute to reduced embodied carbon emissions while maintaining compressive strength and durability performance in saline environments.

[0246] Example 1c demonstrates this effect using an activator "Pi" containing a specific particle size distribution of natural pozzolans. The cement used in the "control 2" mix is 386kg / m3compared to 275kg / m3in the activator mix - a 28.8% reduction in cement mass. The bulk of the concrete is made up by inactive filler - i.e. aggregate. The concrete strength as shown in Figure l.c.ii is substantially the same at day 1,3,7 and 28 for the activator and control mixes.

[0247] Also in example 2a (Figure 2.a.ii), when the same amount of cement is included in the control and the activator mix (see control 1 - 275kg / m3), the strength of the concrete is increased in the activator mix - day 1= 240% stronger, day 3= 187% stronger, day 7= 163% stronger, day 28= 145% stronger.

[0248] The reduced-cement concrete mixture also exhibits enhances flowability, cohesiveness, and stability, making the mix easier to pump, place, and finish. This isparticularly beneficial in large-scale construction projects where concrete needs to be transported over long distances or in challenging environments.

[0249] Measuring the chemical composition of a natural pozzolan is an important step in determining its suitability for use in concrete activators. A representative sample of the natural pozzolan is prepared for analysis which may involve drying the sample and grinding it to a fine powder to ensure homogeneity. Several methods for measuring the chemical composition of natural pozzolans will be known to those of skill in the art. These include X-ray fluorescence (XRF), atomic absorption spectroscopy (AAS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX).• XRF is a commonly used technique because it is fast, accurate, and can analyze a wide range of elements. In this method, a sample of the natural pozzolan is bombarded with X-rays, causing the atoms in the sample to emit characteristic fluorescent X-rays. The energy and intensity of these X-rays are detected and analyzed to determine the elemental composition of the sample.• Atomic absorption spectroscopy (AAS) involves vaporizing the sample and passing a beam of light through the vapor. The absorption of the light by the sample is proportional to the concentration of the element being analyzed, allowing for quantitative analysis of the element.• Inductively coupled plasma-optical emission spectroscopy (ICP-OES) involves vaporizing the sample in an argon plasma and analyzing the light emitted by the excited atoms using a spectrometer. The intensity of the emitted light is proportional to the concentration of the element being analyzed.• Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) is a microscopy technique that involves viewing the natural pozzolan particles under a microscope and measuring the X-rays emitted by the atoms in the sample. The chemical composition of the sample can be determined by analyzing the X-ray spectra.

[0250] Once the chemical composition data has been obtained, it can be analyzed using statistical software to determine the concentrations of different elements and their relative proportions. The results are then used to evaluate the quality of the natural pozzolan and optimize its use in concrete mixtures.

[0251] Measuring the particle size distribution of natural pozzolans is an important step in determining their suitability for use in concrete, as well as their potential performance in terms of strength, durability, workability, and aesthetics. Several methods for measurement of particle size and particle size distribution will be known to those of skill in the art. A first step is to prepare a sample of natural pozzolan for analysis. This typically involves taking a representative sample of the natural pozzolan and drying and sieving the sample to remove any impurities or oversized particles.

[0252] There are several methods available for measuring particle size distribution, including laser diffraction, sedimentation, and microscopy.• Laser diffraction is a commonly used technique because it is fast, accurate, and can measure a wide range of particle sizes. In laser diffraction, the natural pozzolan sample is dispersed in a liquid medium, such as water or alcohol, and passed through a laser beam. The laser light is scattered by the particles in the sample, and the scattering pattern is captured by a detector. The intensity of the scattered light is related to the size of the particles, and the distribution of sizes is calculated using mathematical algorithms.• Sedimentation: In sedimentation analysis, the natural pozzolan sample is dispersed in a liquid medium and allowed to settle under gravity. The settling rate of the particles is related to their size, and the particle size distribution is calculated using mathematical equations.• Microscopy: Microscopy techniques involve viewing the natural pozzolan particles under a microscope and measuring their size manually. This method can be timeconsuming and labour-intensive but can provide high-resolution images and accurate measurements.

[0253] Once the particle size distribution data has been obtained, it can be analysed using statistical software to determine the mean particle size, the spread of the distribution, and other parameters that may be of interest.

[0254] In one example, activators of the present invention may be prepared using the following steps:1. Measurement of moisture content of each pozzolan portion and adjustment to be less than 5%. Alternatively, the moisture content of the pozzolan mixture may be adjusted to be less than 3%. This preferred range of moisture content enables the mixing and storage of the components and to ensure there is substantially no water in the mix to react with the plasticiser in the Activator.2. Chemical composition analysis and amendment - pozzolans (also referred to herein as pozzolanic material) are analysed to identify their chemical composition. The percentage by weight or molar concentration of each chemical compound of interest is determined in each pozzolanic material. The proportions of different pozzolans are then amended to achieve the required chemical composition (within the ranges specified herein).3. Particle size determination and amendment - The particle size is adjusted to be in a specified range for each pozzolan of a specified chemical composition. Larger pozzolan particles may be size-reduced e.g. by grinding to form a ground pozzolan mixture of a particular particle size. The ground pozzolan may be obtained as a waste "side-stream" from larger pozzolan rocks used for other purposes.4. Measurement of particle size distribution and amendment if necessary - The distribution of particle sizes is important to balance the reactivity and setting speed of the concrete. The distribution is controlled by combining pozzolan sources with known particle size distribution with other sources to provide a required distribution comprising polydisperse particle sizes.5. Mixing of activator components and a plasticiser in required proportion - the activator components referred to herein are mixed in a suitable mixing apparatus. This mixing step should be carried out for at least 5 minutes to achieve sufficient mixing of the different activator components. A further processing step of grinding, for example in a ball mill is undesirable because it results in an inconsistent particle size reduction (i.e. larger particles will be size reduced to a larger extent than smaller particles which can upset the balance of particle size distribution in the activator product. This further grinding step also increases energy demand and concomitant embodied carbon.

[0255] In one example, the activator is in a liquid form. In this example, the method of preparation comprises mixing the dry activator mixed with a suitable solvent, for example water, at an appropriate ratio for storage, transport and final formulation with other concrete components. In one example, the liquid activator is formulated with the solvent at a w / w ratio of activator: solvent about 1:2, about 1:1, about 2:1.

[0256] A key advantage of using a dry form activator is to maintain a stable activator: solvent ratio on preparation. Where liquid forms of the activator are prepared, for example according to the above formulations, the activator: solvent ratio may change due to evaporation of the solvent, or settling of active components and incorrect mixing prior to final formulation.

[0257] In some embodiments, the activator components are blended without intergrinding. Intergrinding in this context refers to the grinding of various components to effect particle size homogenisation, reduction and mixing. Intergrinding the components is energetically costly which can increase the overall carbon emissions. The presently provided activators of the invention may comprise components that are blended rather than interground.

[0258] Heating of the activator components is energetically costly which can increase overall carbon emissions associated with production of concrete. The present invention does not require thermal treatment of the activator. Therefore in some examples described herein, the activator is not heated prior to mixing.

[0259] Concrete is composed of three key components - aggregates, cement and water. Admixtures including plasticisers are also used most of the time. Aggregate provides mechanical stability by acting as a filler material, binding the cement paste together and forming a solid matrix. The strong interlocking nature of aggregates enhances the overall compressive strength and load-bearing capacity of concrete structures. Since aggregatesoccupy a significant volume in concrete, they help to reduce the cost by replacing cement with aggregates.

[0260] Aggregates are described herein as coarse or fine. Coarse aggregates are particulates that are greater than about 4.75mm. The usual range employed is between 9.5mm and 37.5mm in diameter. Fine aggregates are usually sand or crushed stone that are less than 9.55mm in diameter. Typically, the most common size of aggregate used in construction is 20mm. A larger size, 40mm, is more common in mass concrete.

[0261] One form of fine aggregate is sand. Sand is a granular material composed of small particles with a particle size ranging from 0.0625 mm to 2mm in diameter. In its natural form, it is found in various geological formations, such as riverbeds, beaches, deserts, and quarries. As a fine aggregate in concrete, it fills the voids between larger aggregates to enhance the workability and cohesiveness of the concrete mix. Those of skill in the art will appreciate that the term "sand" also encompasses fine aggregates that are not of mineral origin such as sand substitutes. These include, for example, manufactured sand, washed bottom ash, glass powder or quarry dust. Sand is a relatively inexpensive and available component compared to other concrete components. In some examples of the invention provided herein, cement is replaced with sand, coarse aggregates plus activator to make up the solids proportion when using lower cement proportion. Sand also has a much lower carbon footprint than cement, is cheaper and requires less processing.

[0262] Water plays a vital role in hydrating the cement to form a strong and durable binder. This binder acts to bind the aggregates and sand together and hardens over time, creating a solid and cohesive structure. Water reacts with plasticisers to modify the rheology and flow characteristics of the concrete. Water is also involved in the curing process, where it helps maintain the necessary moisture levels for proper cement hydration and strength development. The water-to-cement (w / c) ratio is a critical parameter that affects the strength, durability, and overall performance of concrete. It represents the amount of water relative to the amount of cement in the mixture. The w / c ratio should be carefully controlled to achieve the desired strength while maintaining adequate workability and durability. An excessive water content can weaken the concrete and lead to increased porosity, reduced strength, and increased permeability.

[0263] In one example the activators of the invention allow a reduction in water usage compared to preparation of concrete without activators (but with plasticisers or water reducers). The water reduction achieved with the activator can range between 10-45%, as compared to control concrete with and without the plasticisers / water reducers. On top of contributing to strength increase in concrete, this feature of the activator has particular utility in environments where water is scarce, or where substantial water usage is undesirable (e.g. for cost factors).

[0264] In one example the cementitious materials in the binder are selected from Portland cement and supplementary cementitious materials.

[0265] Supplementary Cementitious Materials (SCMs) are finely divided materials that are used in conjunction with Portland cement in concrete or mortar mixtures. The proportion of SCMs in a concrete mix is however limited by the inherently unreactive properties of most SCMs. Some SCMs are used as non-reactive fillers rather than reactive components. Where high substitutions of SCMs are attempted in concrete mixtures, substandard concrete properties are observed such as reduced compressive strength, reduced durability, increased setting time and reduced workability.

[0266] In one example, SCMs comprise natural pozzolans e.g. pumice, fly ash, slag, silica fume, metakaolin (thermally activated kaolin clay), and rice husk ash. Natural Pozzolans are also used as SCMs but sometimes presented as fillers, rather than active components.SCMs may further comprise a material selected from the group consisting of Trass flour, recycled glass, fly ash, bottom ash, cenospheres, glass bubbles, slag, clays, calcined clays, partially calcined clays, kaolinite clays, lateritic clays, illite clays, crystalline silica, silica flour, cement kiln dust, volcanic rock, natural pozzolans, mine tailings, diatomaceous earth, zeolite, shale, ground vitrified pipe, agricultural waste ash, ground granulated blast furnace slag, bentonite, pumice, and any combination thereof. In some examples, the activator admixtures of the invention are provided in combination with one or more pozzolan SCMs. In these examples, the activator activates the SCM to provide an SCM with enhanced reactivity versus the SCM alone. This important effect of the activators of the invention is shown in example 8 and 10 and enables cement (high embodied carbon) to be replaced by SCMs (lower embodied carbon) without losing the binding capability that is typically observed when substituting cement with SCMs.

[0267] Portland cement is a manufactured material produced via a process called clinkerisation, which involves heating a mixture of limestone, clay, and other minor ingredients at high temperatures. The resulting clinker is then ground into a fine powder, which is known as Portland cement. The chemical composition of Portland cement primarily consists of calcium silicates, including tricalcium silicate and dicalcium silicate. These compounds are responsible for the cement's ability to harden and gain strength through hydration when mixed with water. Other compounds, such as calcium aluminate, calcium sulfate (gypsum), and minor additives, may also be present, depending on the specific cement type. In some examples, the cementitious material comprises a Portland cement suitable for wells. Portland cements that are suited for use in the disclosed compositions include, but are not limited to, API Class A, C, G, H, low sulphate resistant cements, medium sulphate resistant cements, high sulphate resistant cements, other construction cements, or combinations thereof. The API class A, C, G, and H cements are classified according to API Specification 10. Additional examples of Portland cements suitable for use in the present disclose include, without limitation, those classified as ASTM Type I, II, III,IV, or V as described below. In some examples, the cementitious material comprises a class C cement. In some examples, the cementitious material comprises a class G cement. For Portland cement types, ASTM C150 describes:^0268] When water is added to Portland cement, it undergoes a series of exothermic chemical reactions known as hydration. During hydration, the cement particles react with water, forming calcium silicate hydrate (C-S-H) gel and other compounds. This gel acts as a binder, binding the aggregates together to create a solid and durable concrete matrix.

[0269] Examples 1 and 2 relate to preparation of a concrete mix with compressive strength of 20, 25 and 40 MPa. The effects of the Activator and SCMs described in these examples are applicable to other concrete strengths. Those of skill in the art will be readily able to determine the respective modifications to the concrete mixes described herein to achieve concrete of different tensile strength. In one example, the invention provides activators and concrete formulations suitable for the production of 20MPa, 25MPa, 30MPa, 35MPa, 40MPa or 50MPa concrete. In general terms:20MPa concrete:• Non-structural applications such as levelling beds, pathways, and minor construction works. Foot traffic i.e. footpaths and house slabs25MPa concrete:• Residential Buildings for elements like footings, slabs, and non-structural walls. • Lightly Loaded Pavements: It can be used for pathways, driveways, and lightly trafficked areas where heavy loads are not expected.35MPA Concrete:• Residential and Commercial Construction: Grade 35 concrete is suitable for a wide range of applications, including foundations, beams, columns, and structural walls in both residential and commercial buildings.• Light Industrial Floors: It can be used for warehouse floors or light industrial facilities where moderate strength and durability are required.40MPA Concrete:• High-Rise Buildings: Grade 40 concrete is commonly used in the construction of tall buildings, providing the required strength for structural components like columns and cores.• Bridges and Infrastructure: It is suitable for bridge decks, piers, abutments, and other critical infrastructure components where higher strength and durability are necessary.• Heavy-Duty Industrial Floors: Grade 40 concrete is used in industrial settings with heavier loads and higher abrasion resistance requirements.50MPA Concrete:• High-Performance Structures: Grade 50 concrete is employed in structures where exceptional strength, durability, and resistance to aggressive environments are crucial, such as high-rise buildings, bridges, and marine structures.• Precast Elements: It is commonly used in the production of precast concrete elements, such as precast beams, columns, and panels, due to its high strength and early strength development.

[0270] The ratio of cement to aggregates is adjusted in higher grade concrete to provide a higher proportion of cement which contributes to achieving the increased strength.Cement is the binding agent in standard concrete, and it contributes significantly to its strength therefore higher cement content enables the product to withstand higher loads and stresses.

[0271] In some examples, the activator and associated inventions described herein enable higher grade concrete to be prepared using the same or lower amount of cement.

[0272] In other examples, the activator and associated inventions described herein enable concrete of the same grade to be prepared using a lower amount of cement compared to standard concrete mixtures.

[0273] The water-to-cement ratio may also be reduced at higher grades to ensure better hydration and strength development. The ratio of fine aggregate to coarse aggregate may be adjusted. Also, larger aggregate sizes are used for higher-grade concretes, while smaller aggregate sizes are used for lower-grade concretes. Lower-grade concretes (e.g. 20-25Mpa) typically use smaller aggregate sizes, such as fine sand and small-sized coarse aggregates. These sizes contribute to improved workability and better bonding between cement and aggregates. Moderate-Grade Concretes (e.g., 35MPA and 40MPA) use a balanced combination of fine and coarse aggregates. This helps achieve a good balance between workability and strength. The sizes of the aggregates are typically larger than those used in lower-grade concretes but not as large as in higher-grade concretes. Higher-Grade Concretes (e.g., 50MPA and above) incorporate larger aggregate sizes. Coarse aggregates with larger particle sizes are used to enhance the strength and load-bearing capacity of theconcrete. These larger aggregates provide greater interlocking and mechanical properties, resulting in a higher-strength concrete.

[0274] As demonstrated in the saltwater concrete examples described herein, concrete compositions prepared using saltwater as the mixing water component are capable of achieving structurally suitable compressive strengths despite the presence of dissolved chlorides. In the examples, saltwater comprising dissolved salts at concentrations representative of marine or brackish environments was combined with cementitious material and the activator admixture comprising first and second pozzolan portions having different median particle sizes and different chemical compositions. The resulting compositions developed compressive strengths of at least 20 MPa at 28 days, as determined in accordance with NZS 3112 Part 2.

[0275] Further, the examples demonstrate that compressive strengths of at least 25 MPa, and in certain compositions at least 30 MPa, at 28 days may be achieved in saltwater-based concrete systems incorporating the activator admixture. Achievement of such strength levels in the presence of dissolved salts confirms that the activator mitigates the strength reduction typically associated with chloride-containing mixing water. In comparative examples lacking the activator, reduced early-age and 28-day strengths were observed relative to corresponding activated compositions.

[0276] Without wishing to be bound by theory, it is believed that the combined particle size distribution and chemically distinct pozzolan fractions enhance binder reactivity, promote formation of additional calcium silicate hydrate (C-S-H) and alumina-containing phases, and increase chloride binding capacity within the hardened matrix. The examples support that such mechanisms contribute not only to maintaining compressive strength of at least 20 MPa, but to enabling performance levels of at least 25 MPa or at least 30 MPa at 28 days in saltwater concrete compositions. The saltwater concrete examples further indicate that the activator-containing compositions exhibit refined pore structure and reduced chloride mobility relative to non-activated saltwater controls, while simultaneously achieving structural-grade compressive strengths. These results confirm that the activator enables the practical production of saltwater concrete suitable for structural applications, including those requiring compressive strengths of 20 MPa or greater, optionally 25 MPa or greater, and in certain implementations 30 MPa or greater at 28 days.

[0277] Concrete properties can be measured to ensure that the material is suitable for its intended use and meets the required standards and specifications. Specific measurements of concrete properties include:

[0278] Compressive strength - the ability of the material to resist compressive forces. Compressive strength is measured by subjecting a test specimen of concrete to compressive loads until it fails. The maximum load that the specimen can withstand is recorded as the compressive strength of the concrete (in kilo Newtons kNt or Mega Pascals MPa).• Tensile strength: This refers to the ability of concrete to resist tension or stretching forces. Tensile strength is typically much lower than compressive strength, and it can be measured using various test methods, such as the splitting test or the flexural test.

[0279] Durability: This refers to the ability of concrete to resist deterioration over time due to various factors such as exposure to moisture, chemicals, and freeze-thaw cycles. Durability can be measured using various test methods, such as the water absorption test, the sulphate resistance test, and the freeze-thaw resistance test.• Workability: This refers to the ease with which concrete can be mixed, placed, and finished. Workability can be measured using various test methods, such as the slump test, the flow test, and the compacting factor test.• Density: This refers to the mass per unit volume of concrete and is typically measured using a density meter or by calculating the mass and volume of a test specimen.

[0280] The time it takes for the concrete mixture to begin to stiffen and lose its workability is termed the setting time. The setting time of pozzolanic concrete is an important factor that can affect its overall performance and durability. In a construction setting, timeframes and costs can also be dictated by the setting time of the concrete. A longer setting time is often beneficial for pozzolanic concrete, as it can allow more time for the mixture to fully hydrate and for the pozzolan to react with the cement, resulting in a stronger and more durable final product. A longer setting time can also be beneficial for workability, allowing more time for the mixture to be properly placed and finished before it begins to set. This can be particularly important in large or complex construction projects where the concrete needs to be placed quickly and efficiently, but also needs to maintain its workability long enough to be properly finished.

[0281] In some circumstances, a shorter setting time can be beneficial, such as in colder weather or in applications where the concrete needs to be load-bearing or supporting weight quickly. The inventors have found that activators comprising pozzolans can actually result in a decrease in the initial setting time and therefore unexpectedly provide early strength.

[0282] The invention provides concrete compositions comprising activators as described herein. The concrete compositions may be prepared according to mixing processes known by those of skill in the art, and using equipment typically used in the art. Concrete compositions comprise at least a coarse aggregate, a fine aggregate and a binder. While those of skill in the art will be able to determine specific concrete mixtures according to the materials and application of the concrete, the following non-limiting examples provide ranges of concrete and activator components that may be present:;0283] In one example, the coarse aggregate and fine aggregate combined comprise 60-80% of the composition.

[0284] In one example, the invention provides a concrete composition comprising:a. an activator;b. cementitious material; andc. aggregate.

[0285] As will be understood by those skilled in the art, the binder required in a concrete composition may be formed by combining the cementitious material with the activator described herein. The activator functions as a minor but reactive component of the binder and contributes to the overall binding capacity of the system. In certain examples, the activator may be provided at between 0.25-10% by weight of cementitious materials, optionally between 0.5-8%, and in certain implementations between 1-4% of the total dry weight of cementitious materials. The precise dosage may be selected according to the type and proportion of supplementary cementitious materials present, the reactivity of the binder components, and the desired mechanical and durability performance of the resulting concrete composition.

[0286] The activator in the above concrete composition may be an activator as described anywhere within the specification as an activator of the invention. In particular examples, the activator may comprise one or more properties selected form the group consisting of at least a bi-modal particle size, natural or synthetic pozzolans; a chemical composition comprising 40-80% silicon dioxide and 10-40% aluminium oxide; Dv50 of less than 40pm; or a particle size distribution defined by:a. 30-40% of the activator comprising particles less than 15 pm;b. 50-65% of the activator comprising particles less than 40 pm; and c. 75-90% of the activator comprising particles less than 90 pm.

[0287] In one example, the activator may comprise one or more properties selected form the group consisting of at least a bi-modal particle size, natural pozzolans; a chemical composition comprising 40-80% silicon dioxide and 10-40% aluminium oxide; Dv50 of less than 40pm; or a particle size distribution defined by:a. 30-40% of the activator comprising particles less than 15 pm;b. 50-65% of the activator comprising particles less than 50 pm; and c. 75-90% of the activator comprising particles less than 90 pm.The cement quantity is typically determined by the mass of cement in kg.

[0288] In one example, the invention provides a method of preparing a reduced cement concrete composition comprising:a. determining a quantity of cement required for a concrete mixture; b. reducing the cement quantity by a reduction factor to provide a reduced cement quantity;c. determining an activator quantity based on the reduction factor;d. determining a filler quantity based on the reduction factor;wherein the activator comprises an activator as described herein.

[0289] In one example, the reduction factor is selected from the group consisting of at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, or at least about 60%. In one example, the reduction factor is selected from the group consisting of <10%, <20%, <30%, <40%, <50% or <60%. In one example, the reduction factor is 10% to 50%

[0290] In one example, when the reduction factor is less than or equal to about 35%, the activator quantity comprises at least 3% w / w of total cementitious material. In another example, when the reduction factor comprises less than or equal to about 50%, the activator quantity comprises at least 3.5% w / w of total concrete composition.

[0291] In one example, the filler quantity comprises the difference between the cement quantity (i.e. the original quantity of cement required by the standard mix) and the reduced cement quantity, minus the activator quantity. This provides a method for the skilled person to reduce the quantity of cement used in a concrete mix by replacing it with filler and activator.

[0292] In a further example, the method further comprises preparing a concrete mixture comprising the reduced cement quantity, the activator quantity and the filler quantity.

[0293] The one or more filler may be selected from the group consisting of SCMs, fly ash, slag, silica fume, metakaolin, rice husk ash, synthetic pozzolan, natural pozzolan, aggregate and / or sand.

[0294] In some examples, the invention provides a concrete composition comprising SCMs and an activator admixture. In some examples, up to 50% of cement is substituted with a binder which is a combination of activator plus natural or synthetic SCMs.

[0295] For the avoidance of doubt, references herein to cement being "substituted" or "replaced" by a binder comprising activator and natural or synthetic supplementary cementitious materials (SCMs) are intended to describe the compositional structure of the cementitious material on a weight basis. In such examples, the cementitious material comprises natural or synthetic pozzolan supplementary cementitious material in an amount of at least 10% by weight of the total cementitious material. In certain examples, the cementitious material comprises at least 20%, at least 30%, at least 40%, or up to 50% by weight of natural or synthetic pozzolan supplementary cementitious material.

[0296] As used herein, substitution does not require any particular intent or mental act, but instead refers to the presence of supplementary cementitious material within the cementitious fraction at the stated proportion relative to the total cementitious material.

[0297] Figures 9A and 9B illustrate the invention showing the substitution of cement with a portion of SCMs plus activator. The proportions shown in these figures are exemplary and not to scale and not intended to limit the scope of the invention. Without wishing to be bound by theory, it is believed that when activator admixtures described herein are combined with pozzolanic SCMs and cement in the presence of water, the hydration and pozzolanic reactions synergise to produce more CSH and a high-performance hydraulic binder. This binder exhibits equivalent or greater strength and reduced porosity compared to standard concrete containing OPC. In particular, traditional pozzolanic mixtures exhibited slower strength development which made them less suitable for construction projects with tight timelines. The present invention provides admixtures that avoids this drawback by maximising the initial reactivity of the pozzolans to enable the true potential of pozzolanic concrete to be realised in a process that is energy-efficient and low in carbon emissions. This substitute binder has similar properties to cement but with significantly lower carbon emissions.

[0298] When the activator is combined with the SCMs, water and Ordinary Portland Cement, a series of reactions occur which augment the cement hydration reactions and create additional chemical bonds. This results in a similar strength gain and workability compared with OPC, and superior durability. In standard concrete (figure 9A), Ordinary Portland Cement (OPC) is combined with water and aggregate (sand or rocks). The OPC combines with water and undergoes the hydration reaction to form concrete. In 9B, the pozzolanic reaction is leveraged to provide a hybrid chemical process which combines the hydration reaction with the pozzolanic reaction. This hybrid reaction involves:a. the cement hydration reaction to produce calcium hydroxide (Ca(OH)2); andb. the pozzolanic reactions in which the Ca(OH)2 is hydrolysed and consumed in the pozzolanic reactions by reaction with SiO2 and AI2O3 in the presence of water.c. This reaction forms compounds possessing cementitious properties to augment the strength and durability of standard concrete.

[0299] When water is added to Ordinary Portland Cement it undergoes hydration, producing calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)2). Pozzolanic materials (SiO2 and AI2O3) in the mix react with calcium hydroxide to form additional C-S-H, which is the primary binding phase in concrete, responsible for its strength and durability. Therefore the pozzolanic components of the reaction generate additional C-S-H, contributing to a denser and more robust microstructure. This additional C-S-H fills the voids and pores within the concrete, reducing its porosity and permeability. This less permeable material is more resistant to environmental factors such as freeze-thaw cycles, sulphate attack, alkalisilica reaction and the ingress of harmful substances. Example 3 illustrates this reduction in porosity and permeability and shows how the activator admixtures contribute to these beneficial effects.

[0300] In some examples, the invention provides a concrete composition comprising SCMs and an activator admixture. In some examples, up to 50% of cement is substituted with a binder which is a combination of activator plus natural or synthetic SCMs. For example 10% may be replaced which provide moderate levels of carbon emission reduction and may be appropriate for concrete compositions that require high cement content. In other examples, 20%, 25% or 30% cement substitution may be used with pozzolanic SCMs replacing the cement. These provide higher levels of cement substitution for enhanced carbon emission reduction. Activators of the invention are active to ensure that strength is not appreciably affected at these substitution levels. In other examples, higher levels of cement substitution may be achieved, for example 40, 50 or 60% substitution. At these levels there are substantial benefits in the reduction of carbon emissions but concrete strength may be negatively affected at very high substitution levels. For some applications, the strength is less important. Further, SCMs which already exhibit high surface activation (e.g. fly ash) may be used as a substitute for the cement, and, in tandem with activator admixtures of the invention, these high levels of substitution can still provide high strength concrete compositions.

[0301] Accordingly, in some examples, the invention provides a concrete composition comprising:a. an activator admixture as described hereinb. cementitious material, andc. aggregate.The aggregate may comprise a coarse aggregate and a fine aggregate. The concrete composition may be designed to exhibit a compressive strength determined in accordancewith NZS3112 part 2 at day 28 is greater than 20MPa or 25MPa. In some examples the concrete composition comprises cement and pozzolanic SCM filler wherein the pozzolanic SCM filler is present in an amount of 10 to 50% w / w of cementitious material, for example up to 10%, up to 20%, up to 25%, up to 30%, up to 40% or up to 50% SCM.

[0302] The activator admixture described herein may be defined independently of any particular concrete composition. In certain implementations, the invention provides an activator admixture comprising a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, and wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions. The activator may optionally further comprise a plasticiser component and may exhibit a multi-modal particle size distribution as described in the examples. The activator may be provided as a dry powder composition suitable for storage, transport and later incorporation into cementitious systems.

[0303] The examples demonstrate that the structural characteristics of the activator — including the presence of at least two pozzolan portions differing in particle size and chemistry — confer enhanced reactivity when incorporated into cementitious matrices. Accordingly, in certain aspects the activator may be characterised structurally without reference to a specific end-use composition. The saltwater and limestone-containing concrete examples confirm that this structurally defined activator provides unexpected performance improvements when incorporated into blended cement systems.

[0304] In other implementations, the activator may be defined in terms of its functional performance in cementitious compositions. In particular, the activator may be formulated for enhancing strength development in concrete compositions comprising limestone and / or saltwater. The examples demonstrate that incorporation of the activator materially improves early-age and / or later-age compressive strength relative to corresponding control compositions lacking the activator. In saltwater systems, the activator further improves chloride binding and reduces chloride mobility. In limestone-containing systems, the activator enhances reactivity of carbonate phases and improves strength development despite clinker reduction.

[0305] Accordingly, the activator may be defined as an activator admixture for use in enhancing compressive strength development in concrete compositions comprising limestone or saltwater. The activator may alternatively be defined as an activator admixture for use in reducing chloride ion mobility, increasing bound chloride fraction, or improving durability in saltwater concrete compositions.

[0306] In further aspects, the invention provides the use of the activator admixture in cementitious systems. The examples support use of an activator admixture comprising a first pozzolan portion and at least a second pozzolan portion, the portions differing in particle size and chemical composition, for improving compressive strength in limestone-containing concrete compositions. The examples further support use of the activator admixture for reducing chloride ion mobility, reducing non-steady-state chloride migration coefficient, or increasing bound chloride fraction in saltwater concrete compositions.

[0307] The performance improvements observed in the examples arise from the structural features of the activator, including its multi-modal particle size distribution and chemically distinct pozzolan portions. The activator therefore constitutes a distinct and patentable composition per se, as well as a composition suitable for use in enhancing performance of limestone-containing and saltwater concrete systems.

[0308] The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference. Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

[0309] Whilst it will be appreciated that various features of the embodiments may be combined, they may also be used independently of each other.

[0310] It should be noted that the above-mentioned examples illustrate rather than limit the disclosure, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.EXAMPLES

[0311] The following examples illustrate embodiments of the invention. Examples in the past tense involve the manufacture and use of activators according to the invention and cement-activator blends that use such activators. Examples in the present tense are hypothetical in nature but illustrative of embodiments within the scope of the invention.

[0312] Where the chemical composition and / or particle size distribution of a named activator are described in one example, that same composition and particle size distribution apply to that named activator when referenced in other examples, unless otherwise expressly stated.

[0313] Throughout the examples, standardised test procedures were followed. Tests are carried out on concrete or mortar, either in the laboratory or in the field, to determine its properties. This information may then be used in a number of ways: to determine whether the concrete complies with the requirements of a specification; to forecast how it will perform in service; to determine the effect of different materials; or simply to determine whether some change is necessary in the mix proportions, e.g. the water content.

[0314] Concrete and mortar is required to have certain properties at two distinct stages: when it is still plastic and when it has hardened. The plastic-state properties determine the ease with which it can be placed and finished, the hardened state properties, how well it willperform in the completed structure. The methodology and relevance of these tests is described below:Sampling

[0315] It is essential that the test results are representative of the concrete being tested. Hence, it is essential that the test sample be representative of the concrete from which it is taken. NZ Standard 3112 sets out procedures for obtaining representative samples from freshly mixed concrete for either consistence (slump) tests or the moulding of specimens for other tests.

[0316] NZS 3104 imposes a number of requirements on the sampling of concrete. Where the sample is being taken to check the quality of the concrete being supplied to a project, it requires that samples be taken after completion of mixing but prior to site handling.Generally, this means that the concrete is sampled at the job site from the delivery truck, although sampling at the concrete plant after mixing is permitted.There are two types of 'sampling' methods:1. Snatch sample. In this case a single sample is taken from one position in the concrete.2. Representative sample. In this case three or more samples are taken from different positions in the concrete and are then mixed together to form the single sample.

[0317] To ensure that samples are representative of the concrete being delivered to the site, they should be collected in a random manner, i.e. the batches of concrete or delivery units from which the individual samples are taken must be selected randomly, e.g. by using a list of random numbers to select batches. When a consistence or slump test only is to be performed, the test sample should be taken from the delivery or mixer truck immediately after the first 0.1 m3of concrete has been discharged.Plastic-state Properties

[0318] When first mixed, concrete is normally plastic and workable, i.e. able to be placed in formwork and compacted with relative ease. The bulk of concrete delivered to construction sites is workable and cohesive without being fluid or over-wet. Both workability and cohesiveness are important characteristics of concrete in its plastic state. Workability, because it determines the ease with which the concrete can be placed and compacted; cohesiveness, because it determines the tendency of the components in the concrete to segregate one from the other during handling and placing. A concrete may be workable but lack cohesion resulting in segregation, honeycombing and similar defects.

[0319] The workability and cohesiveness of fresh concrete should suit the particular placing conditions and the compaction equipment available. Concrete with 'low' workability will normally require a large compactive effort to achieve maximum density, whilst 'high' workability concrete will be relatively easy to compact.

[0320] Mortar testing is preferred in some instances due to its simplified composition, offering greater consistency and control over variables compared to concrete. It isolates binder properties without the influence of coarse aggregates, facilitating more precise and reproducible results. Additionally, mortar allows for accelerated testing cycles and is ideal for studies focused on cementitious material behaviour.

[0321] Procedures used for the testing of plastic concrete have been standardised by Standards Australia and Standards New Zealand AS 1012 or NZS 3112 Part 1.Test 1 - Workability testing - The Slump Test

[0322] The slump test is fully described in Australian Testing standard AS 1012.3.1 and NZS 3112 Part 1 Section 5. The equipment required to conduct the test comprises a mould (the hollow frustum of a cone 200 mm in diameter at the bottom, 100 at the top, and 300 mm high) made of galvanised sheet metal and fitted with handles and foot-pieces; a steel tamping rod; a rule; and auxiliary equipment such as a scoop, a steel tray and a container in which to collect the sample to be tested. The test is conducted by first obtaining a representative sample of the concrete to be tested. The slump cone is filled with the concrete to be tested in three approximately equal volumes, each layer being rodded 25 times to compact it before the next layer is added. Surplus concrete is struck off the top of the cone which is then removed from the concrete by lifting it slowly and the concrete allowed to subside. The amount by which the top of the cone drops (from the initial 300mm height) is measured and is known as the slump. If, in subsiding, the concrete cone shears or collapses, the test should be repeated using a fresh portion of the sample. If the concrete again shears or collapses, this fact should be recorded as it indicates a lack of cohesiveness in the mixture.Test 2 - Compressive Strength

[0323] Concrete is a naturally strong material in compression, i.e. it can resist high crushing loads. It is relatively weak in tension, i.e. it cracks fairly readily if stretched or bent. It is therefore normally reinforced with steel when it is to be subjected to tension or bending. The compressive strength of concrete is a measure of its ability to resist loads which tend to crush it. When test specimens are fabricated, cured and crushed in accordance with NZS 3112 Part 2, any variation in their compressive strengths should reflect variations in the properties of the concretes, rather than the specimens or the test procedures. It is assessed by measuring the maximum resistance to crushing offered by a standard test specimen. Compression test specimens used for concrete testing were 100mm diameter x 200mm high cylinders. Compression test specimens used for mortar testing were 50x50x50mm cubes. The samples were tested in accordance with NZS3112 part 2.Test 3 - Particle size analysis

[0324] Dry samples were dispersed in water and analysed using a Malvern MasterSizer 3000 according to manufacturer's instructions.Test 4 - Chemical composition analysis

[0325] Dry samples were analysed for chemical composition using Borate fusion I X-ray fluorescence spectrometry according to manufacturer's instructions.

[0326] Unless stated otherwise, samples were prepared according to NZS 3112 Part 1 Section 5, and slump, strength, chemical composition and particle size were tested according to the procedures described in the test protocols 1, 2, 3 and 4 above.Activator development

[0327] In examples 1 and 2 below, concrete activators were tested with natural pozzolans of varying particle size.Example la

[0328] Aim - This experiment tested the effect of different chemical compositions for a given particle size distribution, i.e. similar median particle size Dv50, of a natural pozzolancontaining activator and a plasticiser on compressive strength (at day 1, 3, 7 and 28).

[0329] Methodology - Two sets of concrete mixes were prepared:• Control mix - 20MPa grade concrete.• 2x Activator mix - 20MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3% of cementitious material. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump).The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:

[0330] Samples were prepared according to NZS 3112 Part 1 Section 5. Strength, chemical composition and particle size were tested according to the procedures described in the test protocols 2, 3 and 4 above.

[0331] ResultsSee figures:Figure l.a.i - Comparison of strength over time for activator versus control concrete.Figure l.a.ii - Particle size and volume density of particles for activator gamma.Table 1 showing particle size and % volume under for activator gamma.Figure l.a.iii - Particle size and volume density of particles for activator Omicron.3.9 | 14.44 | 74 | 82.02 300 98.1 | 1190 | 100 Table 2 showing particle size and % vo ume under for activator Omicron.

[0332] Conclusions1. Replacement of standard plasticiser with an activator improved compressive strength at each day of strength setting.2. Activator omicron exhibited increased compressive strength compared to control and gamma activator at each day of strength setting. This indicates that the increase in Silicon Dioxide improves strength.3. Activator omicron exhibited increased compressive strength compared to control and gamma activator at each day of strength setting. This further indicates the increase in overall sum of Silicon Dioxide and Aluminium Oxide improves strength.Based on these experiments, further testing was carried out to test different median particle sizes for a given chemical composition of the activator.Example lb

[0333] Aim - This experiment tested the effect of different particle size medians Dv50 of a natural pozzolan-containing activator, for a given chemical composition and plasticiser level, on strength (at day 1, 3, 7 and 28). The experiment also tested the impact of the pozzolan-containing activator on slump retention.

[0334] Methodology - Two sets of concrete mixes were prepared:• Control mix - 25Mpa grade concrete. Standard aggregates composition. The coarse and fine aggregate amounts are determined according to a standard but proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• 2x Activator mix - 25Mpa grade concrete, as control, with Plasticiser fully replaced by the Activator described below at 3% of total cementitious material by weight and sand volume slightly adjusted to maintain density of the control mix. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Aggregate content was same as control.The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:

[0335] Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0336] ResultsSee figures:Figure l.b.i - Slump loss of concrete over time for control and activator-containing concrete.Figure l.b.ii - Comparison of strength over time for activator versus control concrete showing that the activators produced concrete with higher compressive strength at all time points. Data for day 28 still to come.Figure l.b.iii - Particle size and volume density of particles for activator Tau.Figure l.b.iv - Particle size and volume density of particles for activator Omega2.Table showing particle size and % volume under for activator Tau.Table showing particle size and % volume under for activator 0mega2.

[0337] Conclusions1. Both activator-containing concretes show significant strength gains as compared to control concrete. This indicates that within the indicated median particle size range Dv(50) < 40 pm, the activator is effective in increasing compressive strength at Dv(50) = 26.3 pm and Dv(50) = 31.1 pm for a given chemical composition.2. Activator Omega2 had increase median particle size, and increase of particle size in each of the defined ranges (which is indicated by decrease % of particles that fall within the specified range). This slightly increased early strength gains (for day 1 and day 3) as compared with the activator tau with a smaller median size. This is of particular interest, because usually strength is increased with decrease in particle size of the pozzolans.3. Both activator-containing concretes shown significant improvement in slump retention as compared to control concrete. This indicates that the activator is effective in increasing slump retention as well as increasing compressive strength.Example 1c

[0338] Aim - This experiment tested the effect of activator containing natural pozzolans on workability (slump) and compressive strength (at day 1,3,7,28) of concrete using Portland cement only as a binder. The aim was to increase the grade of concrete, without increasing cement content. Alternatively, the aim is to test the ability of natural-pozzolans containing activator to reduce cement content in concrete without affecting its workability and strength.

[0339] Methodology - Three sets of concrete mixes were prepared:• Control mix 1 - 25MPa grade concrete. Standard aggregates composition. The coarse and fine aggregate amounts are determined according to a standard but proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• Control mix 2 - 40MPa grade concrete. Standard aggregates composition. The coarse and fine aggregate amounts are determined according to a standard but proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• lx Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3% of cementitious material. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per Control 1.The following concrete compositions were mixed:<<<

[0340] The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0341] ResultsSee figures:Figure l.c.i - Slump loss of concrete over time showing that workability of control 2 and activator retained workability to a similar extent.Figure l.c.ii - Comparison of strength over time for 25MPa concrete, 40MPa concrete, and activator-containing concrete using 25MPa concrete's cement volume with strength at 1, 3, 7 and 28 days post-pour.Figure l.c.iii - Particle size and volume density of particles for activator Pi.Table showing particle size and % volume under for activator Pi.

[0342] Conclusions1. Adding the activator (Pi) at 3% of cementitious material (while removing the plasticiser) to a 25MPa concrete increased the workability and strength of concrete at each age of strength setting.2. Adding the activator at 3% of cementitious material (while removing the plasticiser) increased the grade of concrete from 25MPa to 40MPa. The cement-content in control 1 mix achieved a 25MPa concrete. The activator-containing mix with cement at the same level as control 1 (25MPa) presents similar strength to 40MPa concrete. This means that pozzolanic activator with optimised particle size distribution can increase the grade of concrete by more than 1 grade without increasing cement content of the mix.Specifically, 40MPa concrete performance can be achieved with 29% less cement content, when activator is used at 3% of the resulting cementitious material, without negatively affecting strength and workability of concrete.3. Activator-containing concrete also used substantially less water when compared to both 25MPa and 40MPa control mixes with 33% and 24% less water used respectively.Based on these experiments, further tests were carried out to understand the cement reduction that can be achieved for a given grade of concrete, using the activator and natural pozzolanic SCMs.Example 2a

[0343] Aim - This experiment tested the ability and the extent of a natural pozzolancontaining activator to activate natural pozzolanic SCMs to act like a cement binder. The aim is to replace cement with natural pozzolanic SCMs without detrimental impacts on strength and workability.

[0344] MethodologyTwo sets of concrete mixes were prepared:• Control mix 1 - 25MPa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• 7x Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3-4% of cementitious material. Cement is replaced with natural pozzolans at levels between 0%-40%. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per the control.The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0345] ResultsSee figures:Figure 2.a.i - Slump loss of concrete over time showing good workability for all activatorcontaining concrete mixtures.Figure 2.a.ii - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete at all cement-reduction levels had compressive strength substantially equal to or greater than control at 1, 3, 7 and 28 days post-pour. Figure 2. a . iii - Particle size and volume density of particles for activator Pi.Figure 2.a.iv - Particle size and volume density of particles for activator Tau.Table showing particle size and % volume under for activator Pi.Table showing particle size and % volume under for activator Tau.

[0346] ConclusionsThe following observations were made in relation to cement replacement using activators comprising natural or synthetic pozzolans:1. It is possible to replace a portion of Portland cement with natural pozzolanic supplementary cementitious materials without loss of workability or compressive strength at measured timepoints when the activator is incorporated.2. Activator incorporation enabled cement replacement with natural pozzolans at levels up to and including 40% by weight of cementitious material while maintaining structural performance.3. In certain examples, increased cement replacement levels may be accompanied by increased activator dosage within the ranges described herein. For example, replacement levels up to approximately 35% were achieved using an activator dosage of approximately 3% by weight of cementitious material. Replacement levels ofapproximately 40% were achieved using an activator dosage of approximately 4% by weight of cementitious material. The activator dosage may be selected within the broader operable range of 0.25-10% depending on the extent of cement substitution.4. In certain examples, increasing activator dosage resulted in increased workability. In certain examples, increasing activator dosage improved slump retention. These rheological improvements may arise from enhanced particle dispersion and packing effects.5. Further cement replacement levels may be achieved by tailoring the chemical composition of the activator. In certain examples, increasing the proportion of silicon dioxide within the activator enhanced compressive strength at approximately 30% cement reduction levels. In certain examples, such compositional adjustment enabled higher strength even at reduced plasticiser levels. Tailoring of activator composition may therefore be used to balance strength development, workability and cement reduction targets.Example 2b

[0347] Aim - This experiment tested the ability and the extent of a natural pozzolancontaining activator to activate synthetic pozzolanic SCMs (Slag) to act like a cement binder. The aim is to replace cement with synthetic SCMs without detrimental impacts on strength and workability.

[0348] MethodologyThree concrete mixes were prepared:• Control mix 1 - 40Mpa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• Control mix 2 - 40Mpa grade concrete, with 50% of cement replaced by synthetic pozzolanic SCMs - Slag. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• lx Activator mix - 40Mpa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3.5% of cementitious material. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per control.The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0349] ResultsTable showing particle size and % volume under for activator Tau.See figures:Figure 2.b.i - Slump loss of activator-containing concrete over time showing significant improvement in workability vs. both controls.Figure 2. b. i i - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete with 50% less cement produced compressive strength greater than controls 1 and 2 at all tested ages - 1, 3, 7 and 28 days post-pour. Figure 2. b. iii - Particle size and volume density of particles for activator Tau.

[0350] Conclusions1. Concrete samples made from natural pozzolan-containing activator maintained workability and strength when 50% of the cement in a standard mix was replaced with synthetic pozzolanic SCMs.2. Strength and workability were significantly higher for the Activator enhanced mix vs both control mixes which respectively comprised:a. no cement reduction; andb. similar cement reduction.3. Activator-containing concrete enables the replacement of cement with synthetic pozzolans at over 50% replacement. This indicates that the pozzolanic activators of the invention enhance the binding activity of synthetic pozzolans at a higher efficiency than the enhancement of binding activity of natural pozzolans.4. At higher cement replacement levels, higher dosage of activator can be used, for example 3.5% for 50% replacement levels.5. With increase of the activator dosage, the workability and slump retention further increase.6. Based on the data, it is expected that higher cement replacement percentage is possible e.g. 60% or 70% while maintaining equal or greater strength compared to cementcontaining control samples. This is predictable based on the significant strength surplus that was observed at each age of strength setting.7. The pozzolans containing activator can activate both natural and synthetic pozzolans to become an effective binder similar or better in properties to cement.Example 2c

[0351] Aim - This experiment tested the ability and the extent of a natural pozzolancontaining activator to activate natural pozzolanic SCMs to act like a cement binder.Two sets of concrete mixes were prepared:• Control mix 1 - 35MPa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• KNP mix - 35MPa grade concrete, as control, but with an added mid-range plasticiser and 20% of cement replaced by KNP activated natural pozzolans. Water content is adjusted to achieve target slump on mixing of 60mm (+-20mm permissible tolerance on slump). Sand and aggregates as per the control.• Control mix 2 - 25MPa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3-5% of cementitious material. 20% cement is replaced with natural pozzolans. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per the control.The following concrete compositions were mixed:< < <The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0352] ResultsTable showing particle size and % volume under for activator Pi.Figure 3 - Comparison of strength over time for KNP activated natural pozzolans vs control and Activator activated pozzolans vs. control, both at 20% cement replacement levels. Figure 4 - Particle size and volume density of particles for activator Pi.

[0353] Conclusions1. KNP Activated natural pozzolans achieved slightly lower strength than control concrete at 20% cement replacement levels.2. Natural pozzolans at 20% cement replacement levels activated by the activator, achieved at least 25% increase in strength at each tested age of strength setting as compared to control.3. This indicates that activator is more effective at activating the natural pozzolans in achieving compressive strength that the KNP patented technology to activate natural pozzolans.4. Further cement replacement levels with natural pozzolans are possible of up to 40%, with the activator, as presented in example 2a, and for 50% and above for industrial pozzolans.Example 3 - carbon emission reduction through use of activators of the invention

[0354] Activators of the invention provide the ability to reduce the carbon emissions associated with preparation of a volume of concrete. This example illustrates the carbon emission reductions associated with the concrete mix ratios described in example 2c when applied to a larger scale concrete preparation project - two concrete mixes comprising activator of the invention versus a control mix.Volume of concrete to be used in the project - 100m3Grade of concrete - 25 MPaThree concrete mixes prepared:• Control mix - 25MPa grade concrete.• 2x Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3% of cementitious material and 30% and 40% cement replaced by NZ natural pozzolan (pumice).The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:

[0355] ResultsThe embodied carbon emissions of each mix were estimated using Neocrete eCalculator, a tool developed by an independent LCA assessor - Edge Environment to estimate the embodied carbon emissions per m3of concrete in NZ, using average NZ data for embodied carbon for each of the materials used.Life cycle assessment (LCA) per m3of the ready mix concrete in New Zealand

[0356] ConclusionsConcrete containing activator with cement replacement with NZ natural pozzolans at 30% and 40% has less embodied carbon than control, by 21% and 28%, respectively.Example 4 - Analysis of permeability of activator-containing concreteAim

[0357] This experiment tested the special durability characteristics of concrete with significant cement reduction levels, partly replacement by natural pozzolans and containing the activator.

[0358] MethodologyConcrete with cement replaced by an activator of the invention was analysed for special durability characteristics:• water permeability BS EN 12390-8:2019 "Depth of penetration of water under pressure"• water absorption AS 1012.12• water sorptivity ASTM C1585• Rapid chloride penetrationSample cores of concrete were prepared and allowed to set for 28 - 56 days.

[0359] Results0360] ConclusionsConcrete prepared using an activator of the invention with 30% reduced cement in the mix, and provided• enhanced resistance to water penetration over and above control concrete with no cement reduction• enhanced resistance to chloride penetration over and above control concrete with no cement reduction• reduced volume of voids and immersed and boiled absorption• enhanced sorptivity, i.e. reduced initial and secondary rate of absorptionThis demonstrates the ability of the concrete containing the activator to have significantly enhanced durability characteristics at significantly lower cement levels, which is partly explained by the tighter microstructure of concrete as a result of optimal chemical and physical properties of the activator.Example 5

[0361] Aim - This experiment tested various activators of the invention to exemplify their ability to increase compressive strength in mortar at different time points while maintaining cement content compared to a control with no activator and substantially the same mortar mix design.

[0362] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Three different activators were used - XI, X2 and X3. The mixes contained 25% less cement than standard concrete mixtures demand and this was replaced with natural pozzolan (NZ pumice).The activators had the following particle sizes and chemical compositions:For Activator XI the particle size distribution is shown in Figure 5A and the table below:For Activator X2 the particle size distribution is shown in Figure 5B and the table below:For Activator X3 the particle size distribution is shown in Figure 5C and the table below:Activator Particle characteristics:< < <

[0363] Predictive Method for Estimating 28-Day Compressive StrengthTo estimate the 28-day compressive strength of concrete samples where direct measurements were unavailable, a predictive modeling approach was employed. This method leverages the strength development trends observed in other samples to provide accurate predictions.Data Input - The available compressive strength data for the concrete samples was recorded at 1, 3, and 7 days. The 28-day strength was missing for three samples denoted as X2, X4, and X5.Model Selection - A logarithmic growth model was chosen to represent the relationship between compressive strength and time. The chosen model reflects the common understanding that the rate of strength gain in concrete decreases over time. The equation used for the prediction was as follows:Strength=axln(day+b)+c where:• Strength is the compressive strength of the concrete at a given day,• day is the time in days,• a, b, and c are parameters to be determined from the data.Curve Fitting - For each of the samples, the above model was fitted to the known data points (1-day, 3-day, and 7-day strengths). The fitting process was carried out using nonlinear regression to optimize the parameters a, b, and c such that the model best matched the observed data.Prediction - Once the model parameters were determined, the model was used to extrapolate the compressive strength at 28 days. These predicted values were derived based on the logarithmic trend of strength gain observed in the earlier days and are consistent with the expected behaviour of concrete strength development over time.

[0364] ResultsConcrete properties are provided in Figure 5D and in the table below.*28-day data is predicted based on the model outlined and in accordance with samples with substantially identical 1,3 and 7 day results.

[0365] ConclusionsAll activators of the invention provide increased compressive strength at days 3, 7 and 28 compared to control while maintaining workability (slump).Activator X2 exhibits significantly higher early strength (days 1, 3 and 7) compared to XI and X3.Example 6

[0366] Aim - This experiment tested various activators of the invention to exemplify their ability to increase compressive strength in mortar at different time points while maintaining cement content compared to a control with no activator and substantially the same mortar mix design.

[0367] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Two different activators were used - X2 and X4.The activators had the following particle sizes and chemical compositions:For Activator X2 the particle size distribution is shown in Figure 5B and the table in Example 5For Activator X4 the particle size distribution is shown in Figure 6A and the table below:Activator Particle characteristics:<<<Where 28 day data was not yet available, the predictive model in example 5 was used to predict it.

[0368] ResultsConcrete properties are provided in Figure 6B and in the table below.*28-day data is predicted based on the predictive model outlined for example 5.

[0369] Conclusions - All activators of the invention provide increased compressive strength at days 3, 7 and 28 compared to control while maintaining workability (slump). Example 7

[0370] Aim - This experiment tested activators of the invention to exemplify their ability to maintain or increase compressive strength in mortar at different time points with reduced cement.

[0371] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:as described in Example 6.

[0372] ResultsConcrete properties are provided in Figure 7 and in the table below.

[0373] ConclusionsThe activator of the invention increased compressive strength at days 1, 3, 7 and 28 compared to control while maintaining workability (slump). Cement reduction of 10% was achieved while maintaining increased compressive strength compared to control.Example 8

[0374] Aim - This experiment tested activators of the invention to exemplify their ability to maintain or increase compressive strength in mortar containing fly ash at different time points with reduced cement.

[0375] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Activator X2 was used. The X2 activator had the particle size characteristics and chemical composition as described in Example 5.

[0376] Results - Concrete properties are provided in Figure 8 and in the table below.* - These values were predicted based on the model described in relation to example 5.

[0377] Conclusions - The experiment using activator X2 exhibits higher strength in the 45% substitution versus the 12% fly ash sample and control due to the higher amount of pozzolanic material able to be activated by the activator. For the high (60%) fly ash substitution, there is a higher water demand to maintain workability. At this high substitution, the excess water required results in a reduction in compressive strength as compared to the lower substation (but is still higher than control). Without activator, the high water demand prevents the fly ash from being usable as a substitute. The activatorcontaining concrete enables the use of high substitution levels of fly ash without negatively affecting the workability.

[0378] The activator of the invention maintained or increased compressive strength at days 1, 3, 7 and 28 compared to control while maintaining workability (slump). Cement reduction of 30% was achieved with addition of varying amounts of fly ash at activator percentage between 2.3 and 3.7.Example 9 - Surface Activation via electrolysis

[0379] Aim - This experiment tests the ability and extent of a pozzolan-containing activator, which is subjected to an electrical charge, to activate pozzolanic supplementary cementitious materials (SCMs) to function as a cement binder. The objective is to replace cement with SCMs without detrimental impacts on strength and workability.

[0380] Methodology - Six concrete mixes are prepared:1. Control mix 1: 25 MPa grade concrete. The coarse and fine aggregates are prepared according to a proprietary composition by a third party. The amount of these components do not vary across the three treatments proposed herein, but can vary when used in situ for concrete production. A skilled person in the art would be able to readily determinesuitable aggregate components and mass required. A powdered polycarboxylate plasticiser is used.2. Control mix 2: 25 MPa grade concrete, with 30% of cement replaced by synthetic pozzolanic SCMs (Slag). The coarse and fine aggregates are provided in the same proportions as in mix 1. A powdered polycarboxylate plasticiser is used.3. Activator mix 3 (XO): 25 MPa grade concrete, with 30% of cement replaced by synthetic pozzolanic SCMs (Slag) and a standard (non-electro-activated) activator added at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1. A powdered polycarboxylate plasticiser is used.4. Electro-activated mix 4 (XVI): 25 MPa grade concrete, with 30% of cement replaced by natural pozzolans (NZ pumice) with electro-activated activator described below at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1.5. Electro-activated mix 5 (XV2): 25 MPa grade concrete, with 30% of cement replaced by synthetic pozzolanic SCMs (Slag) with electro-activated activator described below at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1.6. Electro-activated mix 6 (XV3): 25 MPa grade concrete, with 30% of cement replaced by fly ash with electro-activated activator described below at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1.Water content for each mix is adjusted to achieve a target slump on mixing of 180 mm (±40 mm permissible tolerance on slump). Sand and aggregates as per control.The following concrete compositions are mixed:The electro-activated mix contains an activator subject to an electrica charge before formulation with other concrete components. The activator is formulated to have the chemical composition provided for X2 in example 5 above.

[0381] Electro-Activation Process:A non-conductive container is used to hold the powdered activator. The container is equipped with two electrodes made of an inert material (e.g., graphite or platinum) to prevent any unwanted reactions with the admixture. A direct current (DC) power supply with adjustable voltage and current settings is connected to the electrodes. The powdered activator is evenly spread within the container, ensuring good contact with the electrodes. The depth of the powder should allow for efficient electro-activation while avoiding excessive resistance. The power supply is set to a low voltage (12V) and current (2A). The current is passed through the powdered admixture for a duration of 30 minutes to one hour. This timeframe is sufficient to induce electrical activation. During electro-activation, the powder is gently stirred using a non-conductive stirrer at regular intervals (every 5-10 minutes) to ensure uniform exposure to the electric field. After the activation period, the electrical current is turned off, and the powder is allowed to cool and settle. This step ensures that the entire batch of the activator is uniformly charged and ready for use in concrete mixes.

[0382] ResultsResults show that control mix 2 has lower strength compared to the control 1. In accordance with earlier embodiments of the invention, activator X0 exhibits equivalent slump with improved compressive strength versus control 1 and control 2. The electroactivated XVI, XV2 and XV3 concrete shows increased strength at time points 1,3,7 compared to the activator X0 due to the enhanced surface activation leading to higher reactivity with pozzolan replacements.

[0383] ConclusionsElectro-activated activator provides increased early strength due to the enhanced surface activation of the activator particles and increased binding activity with pozzolan SCMs (e.g. synthetic or natural pozzolans).At higher cement replacement levels, the dosage of activator may be increased within the operable ranges described herein. For example, cement replacement levels of approximately40% may be achieved using an activator dosage of approximately 3.5% by weight of cementitious material, and replacement levels of approximately 50% may be achieved using an activator dosage of approximately 4% by weight of cementitious material. The relationship between cement substitution level and activator dosage may be selected according to the type and proportion of supplementary cementitious materials and the desired mechanical performance of the resulting concrete composition.Based on the data, it is expected that a higher cement replacement percentage is possible (e.g., 60% or 70%) while maintaining equal or greater strength compared to cementcontaining control samples. This is predictable based on the significant strength surplus observed at each age of strength setting.The electro-activated activator can activate both natural and synthetic pozzolans to become an effective binder similar to or better in properties than cement.This example demonstrates the enhanced performance of concrete when using an electroactivated activator, highlighting the potential benefits of applying an electrical charge to the activator prior to inclusion in the concrete mix.Example 10

[0384] Aim - This experiment tested activators of the invention to exemplify their ability to maintain or increase compressive strength in mortar at different time points with reduced cement.

[0385] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Activator X2 was used which had the particle size characteristics and chemical composition as described in Example 5.

[0386] ResultsConcrete properties are provided in Figure 10 and in the table below.

[0387] Conclusions25% and 50% reduction in cement and replacement with natural pozzolan significantly reduced compressive strength at all time points.When activator was added at 3% of cementitious material, compressive strength for both 25% and 50% pozzolan substituted mixes increased significantly compared to the respective mixes not containing activator X2.Example 11This example investigated the effects of different water sources, including potable water, artificial sea water, and natural sea water, on the fresh and hardened properties of mortar in the presence or absence of an activator admixture. Workability and strength development were assessed.

[0388] MethodologyMixes with and without the activator were adjusted to achieve substantially identical spread with different water demands, leading to variations in the water-to-cement (w / c) ratio. Three different treatments were assessed:1. Control - potable water without (1A) and with (IB) activator.2. Salt Water collected from St Heliers Bay, Auckland, and filtered using a size 4 coffee filter with a fineness of 20 pm,a. no activator (2A) - Constant water-cement ratio, constant cement content. b. with activator (2B) - Constant w / c ratio, constant cement content, 3% X4 activator.3. Artificial sea water (Instant Ocean, "IO"). IO prepared according to manufacturer instructions using an Instant Ocean Aquarium Sea Water kit, which contains a mix of salts, including magnesium, potassium, and calcium chlorides at the following concentrations: MgCI = 1.2 g / L, KCI = 0.35 g / L, CaCI = 0.4 g / L, NaCI 15.8g / L. Thematerial was diluted in potable water at the recommended proportion of 33 g IO per IL of water, with an assumed density of 1.020.a. no activator (3A) - Constant water-cement ratio, constant cement content. b. with activator (3B) - Constant w / c ratio, constant cement content, 3% X4 activator.

[0389] Water samples were tested for Chloride ion concentration (using ion chromatography). Each treatment comprised 4 experimental replicates (i.e. different mix prepared), and four technical replicates (i.e. four measurements of separate mortar specimens from a single experimental replicate at the same time point). All tests used activator X4 which had the particle size characteristics and chemical composition as described in Example 6.

[0390] Fresh mortar tests conducted included slump and slump loss after 30 and 60 minutes. Strength tests included mortar assessment at 1-day, 3-day, 7-day, and 26 or 28-day. Samples of all three water types were analysed for chloride and organic content analysis.

[0391] ResultsSlump and strength results are shown in the table below ± standard error.Figure 11 shows the strength gain over time across the different treatments.

[0392] ConclusionsUsing saltwater (either seawater or artificial seawater) increases day 1,3, 7 and 26 / 28 day strength compared to control. Day 1 increased by 38%, day 3 increased by 39%, day 7 by 24%. No difference was observed between adding seawater or artificial seawater.Addition of activator admixture X4 to the composition provides increased strength at all time-points. Day 1 increased by 26%, Day 3 increased by 23% and day 7 increased by 17%.

[0393] The effect of the activator in increasing strength is maintained even in the presence of saltwater. This shows that the activator admixture is effective in enhancing early and later-stage compressive strength regardless of the water source used in the composition. The combined use of saltwater (either seawater or artificial seawater) and activator admixture results in an additive effect on strength development. Specifically, the composition incorporating both saltwater and activator exhibits a total strength increase of 60% at day 1, 55% at day 3 and 33% at day 7 compared to the control (no seawater or activator) at each measured time point.

[0394] This demonstrates that the activator is compatible with saltwater-based formulations and remains effective in optimising the hydration and curing process of the cementitious material. The observed improvements in mechanical performance indicate that the activator admixture plays a role in facilitating enhanced early-stage strength gain, which is advantageous for applications requiring rapid setting and high initial strength.

[0395] Furthermore, the results confirm that neither the presence of natural seawater nor artificial seawater impairs the function of the activator admixture. This suggests that the activator interacts primarily with the cementitious matrix rather than being significantly affected by the ionic composition of the mixing water. Accordingly, the use of activator admixtures in combination with saltwater presents a viable approach for improving the mechanical performance of concrete, particularly in coastal or marine construction applications where seawater may be used as a mixing component.

[0396] These findings support the advantageous properties of the composition, particularly in environments where access to fresh water is limited or costly, therebyexpanding the potential applications of the technology in both conventional and resource-constrained construction settings.Example 12 - Compressive Strength of concrete made using salt water

[0397] This example investigated the effects of different water sources, including potable water, and sea water, on the hardened properties of concrete in the presence or absence of an activator admixture. A comparison of the effect of salt water at the same water-binder ratio was also performed. Strength development was assessed at different time points. Methodology

[0398] Three treatments were used to prepare concrete mixes:Treatment 1 - Freshwater control plus cement.Treatment 2 - Salt water plus super plasticiser (Rockbond 6.16N Hyper-Plasticiser) plus cement.Treatment 3 - Salt water plus activator admixture plus cement.Treatments 2 and 3 had the same water-to-binder (w / b) ratio. Workability, air, density, and strength development were assessed. Salt water was seawater obtained from St Heliers Bay, Auckland, New Zealand as described in example 11 with equivalent salt composition. Treatments 2 and 3 were prepared at an identical water-to-binder (w / b) ratio of 0.44 in order to directly compare the effect of the activator admixture with that of a conventional superplasticiser. The superplasticiser was included in Treatment 2 to achieve comparable workability at the reduced water content.For each treatment, three independent technical replicate batches were prepared. Reported values represent the mean of three replicates.Activators K4e, A+ were analysed for chemical composition and particle size data. A+ is reported in this example for convenience but is applicable to other examples.

[0399] Mix DesignResultsParticle size data for activator K4e, A+, PT1 and PT2 is as follows and shown in Figure 12:Table showing particle size and % volume under for activator K4e, A+, PT1 and PT2.Particle size graphs are shown in Figure 13A.< < <

[0400] The table below and Figure 13 shows compressive strength development at 1, 3, 7 and 28 days for each treatment, with each bar representing the mean of three independent replicates and error bars indicating standard variation between replicates.

[0401] Statistical analysis of 28-day compressive strength values was performed using one-way ANOVA. The analysis produced a p-value of approximately 0.03 (<0.05), indicating that at least one treatment mean differed significantly from the others. Post-hoc Tukey HSD testing indicated that the saltwater + activator treatment demonstrated a statistically significant increase in strength relative to the freshwater control. The saltwater + waterreducer treatment did not differ significantly from either group at the selected confidence level.Conclusions

[0402] Treatment 2 (salt water with 100% cement) demonstrated increased strength relative to the freshwater control at all measured ages. Compared to Treatment 1, compressive strength increased by approximately 103% at day 1, 29% at day 3, 16% at day 7, and 8% at day 28.

[0403] Treatment 3, comprising activator admixture K4e at approximately 3% by weight of cementitious material, demonstrated further increases in compressive strength at all ages relative to both control mixes. Compared to Treatment 2 (salt water control), compressive strength increased by approximately 23% at day 1, 9% at day 3, 10% at day 7, and 10% at day 28. Compared to the freshwater control (Treatment 1), strength increases were approximately 150% at day 1, 40% at day 3, 27% at day 7, and 19% at day 28. Notably, the activator-containing mix outperformed the superplasticiser-containing saltwater mix at equivalent water-to-binder ratio, demonstrating that the observed strength increase is not attributable solely to water reduction effects.

[0404] Initial workability of Treatment 3 (145 mm slump) was greater than that of Treatment 2 (87 mm slump), while the freshwater control exhibited the highest initial slump (approximately 190 mm). Yield values were similar across all mixes, indicating no adverse impact on fresh or hardened concrete properties. Air content varied between treatments, with Treatment 3 exhibiting approximately 4.4% air, compared to 3.8% for the saltwater control and 1.2% for the freshwater control. The water-to-binder ratio (W / B) was identical (0.44) for Treatments 2 and 3. The freshwater control exhibited a higher W / B ratio of 0.59.

[0405] These results demonstrate that the strength-enhancing effect of the activator is maintained in saltwater-based concrete systems. Inclusion of the activator enhances early-stage strength development while maintaining acceptable workability characteristics.Example 13 - Effect of activator admixture in salt water concrete Methodology

[0406] All activator-containing trials were prepared with activator A+ at approximately 3% by weight of total cementitious material. Water content was adjusted in each mix to achieve a target 0-minute slump of approximately 180-200 mm, such that initial workability was substantially equivalent across treatments. This experiment investigated the use of natural sea water as described in example 11, in the presence and absence of activator admixture A+, on the fresh and hardened properties of concrete. Three treatments were prepared:Treatment 1 - Freshwater control (100% cement)Treatment 2 - Saltwater control (100% cement)Treatment 3 - Saltwater plus activator A+ (100% cement)All mixes contained 350 kg / m3Ordinary Portland Cement. Activator A+ was used with the chemical composition and particle size as described in example 12.Results

[0407] Abbreviation key for examples:Average compressive strengths from days 1, 3, 7, 28 and 56 are shown in Figure 14 and the table below.Conclusion

[0408] Treatment 2 (saltwater with 100% cement) demonstrated increased compressive strength relative to the freshwater control at all measured ages. Compared to Treatment 1, compressive strength increased by approximately 31% at day 1, 15% at day 3, 4% at day 7, 6% at day 28, and 1% at day 56.

[0409] Treatment 3, comprising activator admixture A+ at approximately 3% by weight of cementitious material, demonstrated further increases in compressive strength at all ages relative to both control mixes. Compared to Treatment 2 (saltwater control), compressive strength increased by approximately 36% at day 1, 32% at day 3, 35% at day 7, 26% at day 28, and 38% at day 56. Compared to the freshwater control (Treatment 1), increases were approximately 78% at day 1, 53% at day 3, 40% at day 7, 34% at day 28, and 39% at day 56.

[0410] Initial workability was substantially equivalent across all treatments (approximately 180-190 mm slump). Yield values were comparable, indicating no adverse impact on fresh or hardened concrete properties. Air contents were within acceptable ranges.

[0411] The results demonstrate that inclusion of the activator enhances strength development in saltwater-based concrete systems while maintaining comparable workability characteristics.Example 14 - Salt water concrete with activator and 30% substitution with fly ash Methodology

[0412] This experiment investigated the effect of 30% fly ash as partial cement replacement in concrete prepared using natural seawater. The presence and absence of activator admixture A+ was evaluated. Water content was adjusted to achieve a target slump of approximately 180-200 mm at 0 minutes.

[0413] Activator A+ was used at approximately 3% by weight of total cementitious material and had the chemical composition and particle size described in Example 12. Three treatments were prepared:Treatment 1 - 100% cement with saltwaterTreatment 2 - 70% cement + 30% fly ash with saltwaterTreatment 3 - 70% cement + 30% fly ash with saltwater and activator A+Results

[0414] Workability across all treatments was within the target range. Compressive strength results from days 1, 3, 7, 28 and 56 are shown below and in Figure 15.Conclusion

[0415] Treatment 3 (70% cement, 30% fly ash, and 3% activator A+) demonstrated increased compressive strength relative to Treatment 2 (70% cement, 30% fly ash without activator) at all measured ages. Compared to Treatment 2, compressive strength increased by approximately 39% at day 1, 49% at day 3, 57% at day 7, 42% at day 28, and 37% at day 56. When compared with Treatment 1 (100% cement with saltwater), Treatment 3 exhibited lower strength at early ages (approximately 34% lower at day 1, 13% lower at day 3, and 3% lower at day 7), followed by higher strength at later ages (approximately 16% higher at day 28 and 20% higher at day 56). Workability was maintained within thetarget slump range of approximately 180-195 mm across all treatments. Yield values were comparable, indicating no adverse impact on fresh or hardened concrete properties.

[0416] These results demonstrate that inclusion of the activator enhances strength development in saltwater-based concrete systems incorporating fly ash replacement, particularly at later ages.Example 15 - Seawater Concrete with 30% Pl ReplacementMethodology

[0417] This example investigated the effect of 30% natural pozzolan (Pl) as partial cement replacement in concrete prepared using seawater. The presence and absence of activator admixture A+ (approximately 3% by weight of cementitious material) was evaluated. Water content was adjusted to achieve a target 0-minute slump of approximately 180-200 mm. Three treatments were prepared:• Treatment 1 - 100% cement with seawater• Treatment 2 - 70% cement + 30% Pl with seawater• Treatment 3 - 70% cement + 30% Pl with seawater and activator A+Chemical composition and particle size of Activator A+ is shown in example 12.Results

[0418] Workability across treatments remained within the targeted slump range.Results are shown in the table above and figure 16.Conclusion

[0419] Treatment 2 (70% cement, 30% Pl with seawater) exhibited reduced compressive strength relative to the 100% cement seawater control at all measured ages. Strength decreased by approximately 68% at day 1, 56% at day 3, 52% at day 7, 39% at day 28, and 34% at day 56.

[0420] Treatment 3 (70% cement, 30% Pl with 3% activator A+) demonstrated increased compressive strength relative to Treatment 2 at all measured ages. Compared to Treatment 2, strength increased by approximately 57% at day 1, 45% at day 3, 59% at day 7, 50% at day 28, and 36% at day 56.

[0421] When compared with Treatment 1 (100% cement with seawater), Treatment 3 exhibited lower strength at early and later ages (approximately 50% lower at day 1, 36% lower at day 3, 24% lower at day 7, 8% lower at day 28, and 10% lower at day 56).

[0422] Workability was maintained within the targeted slump range of approximately 190-200 mm. Yield values were comparable across treatments. The treated mix operated at a lower water-to-binder ratio (0.56) compared to the untreated Pl mix (0.69).

[0423] These results demonstrate that inclusion of the activator enhances strength development in seawater-based concrete systems incorporating Pl pozzolanic replacement, although the resulting strength does not fully match that of 100% cement systems.Example 16 - Seawater Concrete with 30% Fly Ash and Different Activators

[0424] This example investigated the effect of different activator admixtures in concrete comprising 30% fly ash replacement and prepared using seawater. Water content was adjusted to achieve a target slump of approximately 180-200 mm at 0 minutes.Four treatments were prepared:• Treatment 1 - 70% cement + 30% fly ash with seawater (control)• Treatment 2 - 70% cement + 30% fly ash with seawater and activator A+• Treatment 3 - 70% cement + 30% fly ash with seawater and activator PT2• Treatment 4 - 70% cement + 30% fly ash with seawater and activator PT1Each activator was included at approximately 3% by weight of cementitious material (10.5 kg / m3). The chemical composition and particle size data of the activators are shown in example 12.Results

[0425] Average compressive strengths (MPa) were:Compressive strength development is shown in Figure 17.

[0426] All activator-containing treatments exhibited higher compressive strength than the control at all measured ages. PT2 demonstrated the highest early-age strength at day 1. A+ demonstrated the highest strength at day 28. At day 56, PT2 exhibited the highest overall strength, closely followed by A+ and PT1.

[0427] Treatment 2 (A+) demonstrated increased compressive strength relative to the control by approximately 39% at day 1, 49% at day 3, 57% at day 7, 42% at day 28, and 37% at day 56.

[0428] Treatment 4 (PT1) demonstrated increased compressive strength relative to the control by approximately 64% at day 1, 38% at day 3, 41% at day 7, 27% at day 28, and 36% at day 56. Treatment 3 (PT2) demonstrated increased compressive strength relative to the control by approximately 93% at day 1, 50% at day 3, 55% at day 7, 39% at day 28, and 45% at day 56. When comparing activators directly, PT2 exhibited the greatest early-age strength enhancement, whereas A+ demonstrated strong mid-term strength performance at day 28. By day 56, PT2 and A+ exhibited comparable strength levels. These results demonstrate that inclusion of activator admixtures of varying compositions enhances strength development in seawater-based concrete systems incorporating fly ash replacement. Differences in early and later age performance are observed depending on activator composition.Example 17 - Chloride migration testing

[0429] Chloride migration testing shows how easily chlorides can move through concrete. This is an important test for concrete durability, especially for concrete containing steel reinforcement in its core. Chloride penetration depths, rate of penetration, and non-steady state migration coefficients were analysed to assess the vulnerability of each test to chlorideingress. Lower values indicate greater resistance to chloride ingress, indicating better longterm durability, offering higher degrees of protection for steel reinforcement.Methodology

[0430] Three treatments were used to prepare two replicate concrete cylinders per treatment. Two 50mm sample slices were taken from each of the concrete cylinders, one slice having an external face. Multiple measurements across the specimen face were used to minimise local variability effects.The two sets of data from each of the samples are presented below.Treatment 1 - Control using freshwater - This sample represented the baseline comprising a typical Portland cement mix with no additives.Treatment 2 - Control using salt water as described in example 11 with no activator - This mix was prepared in the same way as the control mix treatment 1 except salt water instead of freshwater.Treatment 3 - Salt water as described in example 11 with activator admixture - A+ as defined in example

[0431] Chloride migration testing was performed using an independent testing laboratory according to NT Build 492 (Non-Steady-State Chloride Migration Test). Cylindrical concrete specimens were prepared and cured under water-saturated conditions prior to testing. Cylinders were received in physically undamaged condition and maintained in water at approximately 23°C until sample preparation. Immediately prior to testing, each cylinder was sectioned to obtain test slices of predetermined depth measured from the as-cast upper surface. In the present example:a. A first specimen was obtained from a depth of approximately 100-150 mm from the top surface.b. A second specimen was obtained from a depth of approximately 0-50 mm from the top surface.

[0432] Each test specimen slice had a nominal diameter of approximately 100 mm and a thickness of approximately 45-50 mm. Following cutting, the specimens were vacuum saturated to ensure a consistent moisture condition prior to exposure to the chloride migration test.The chloride migration test was conducted under the following controlled conditions:a. Catholyte solution: 10 ± 0.1% w / w sodium chloride (NaCI)b. Solution temperature: approximately 22 ± 2°Cc. Applied voltage: 15.0 V DCd. Age of specimens: 43-44 days.e. Test duration: 24 hoursThe specimen was subjected to an applied electrical potential across opposed faces while one face was exposed to a sodium chloride solution. On application of voltage, electrical current was monitored. Initial current was recorded, and the system was allowed to stabilise. Temperature at the specimen surface was measured at the beginning and conclusion of the migration phase to ensure test validity.

[0433] Penetration depth was measured at multiple lateral positions across the exposed face to obtain a representative profile. An average penetration depth was calculated from these measurements. The non-steady-state chloride migration coefficient (Dnssm) was calculated using the measured penetration depth, test duration, applied voltage, specimen thickness, and temperature, according to established migration modelling equations.Results

[0434] Results shown in table below and Figure 18.>>Conclusions

[0435] Treatment 1 - Control using freshwater - The rate of penetration ranged from 0.056 to 0.062 mm-V"1-hr1which indicates moderate chloride transport through the concrete.Of the two slices the average chloride migration coefficient is 18.65. This indicates low durability in marine environments.Treatment 2 - Control using salt water with no activator - results show a high chloride migration rate due to the increase in Cl ions from the salt water. In the first test run there were multiple breakthrough readings at various measurements, meaning that chlorides completely penetrated through the sample. Treatment 2 exhibited very high penetration rates of >0.100 mm-V"1-hr1, which also corresponds to the high migration coefficients that exceed an average of 34, therefore confirming this mix has very poor chloride resistance. Treatment 3 - Salt water plus 3% activator - The addition of activator admixture to the mix significantly reduced the rate of chloride diffusion. An average chloride diffusion of 15.95 was lower than in treatment 1 freshwater control.

[0436] Without wishing to be bound by theory, it is believed that addition of the activator admixture binds the Cl- ions resulting in lesser migration.Treatment 3 produced concrete which exhibited lower rates of penetration ranging from 0.048-0.053 mm-V“1-hr1, which coincides with the reduced migration coefficients of 13.8-18.1 x 10“12m2 / s. This indicates presence of the activator admixture in the mix improves resistance to chloride migration.Example 18 - Water ingress (absorption) testing

[0437] Absorption testing was carried out on the specimen samples obtained as described in Example 17. This testing determines the porosity of concrete samples and how vulnerable they are to water ingress. The testing was carried out by following ASTM C642 testing procedures.Results

[0438] Water Absorption (% mass)

[0439] Water absorption between the two control samples does not differ significantly. Treatment 3 using activator admixture shows increased resistance to water absorption. Without wishing to be bound by theory, this is believed to be due to the denser microstructure achieved through interstitial filling resulting from the effect of the activator admixture.

[0440] Volume of Permeable Voids (%)

[0441] This set of testing analyses the pore structure within cured concrete samples. Saltwater (treatment 2) results in slightly denser pore structure than freshwater concrete (treatment 1). On addition of the activator (treatment 3) the pore structure exhibits higher density (i.e. lower % porosity). A reduction in voids results in a strength increase in hardened concrete.Example 19 - Chloride ion content

[0442] Chloride ions play a significant role in the long-term durability of reinforced concrete. Free chloride ions are known to initiate and propagate corrosion of embedded steel reinforcement, which can lead to cracking, spalling and structural deterioration. For this reason, saltwater is generally avoided in conventional concrete production.

[0443] The addition of activator admixtures according to the present invention was evaluated for its effect on total and free chloride ion content within cementitious systems.Methodology

[0444] Chloride content testing was carried out on samples prepared as described in example 17 in accordance with AS 1012.20.1 (Acid-Soluble Chloride Content) and AS 1012.20.2 (Water-Soluble Chloride Content). Two analytical methods were employed: Test 1 - Acid-soluble chloride content - The entire specimen was dissolved in acid to determine the total chloride content present in the sample. This measurement includes both chemically bound and unbound (free) chloride ions.Test 2 - Water-soluble chloride content - The specimen was soaked in water and the chloride content of the extract was measured. This method quantifies the unbound chloride ions that are available to migrate and potentially interact with steel reinforcement.ResultsSeven concrete compositions were analysed. These are set out in the table below and results shown in Figures 19 (100% cement samples) and figure 20 (70% cement + 30% pumicite) and as set out in the table below:Cement Control Samples

[0445] Comparison of samples 583 (freshwater control) and 584 (saltwater control) shows a substantial increase in both total and water-soluble chloride content when saltwater is used in the mix. This confirms that incorporation of saltwater introduces significant free chloride ions into the concrete system.

[0446] Comparison of samples 584 and 589 isolates the effect of the activator in saltwater-based mixes. The addition of the activator resulted in a marked reduction in total chloride content and a reduction in water-soluble chloride content.

[0447] The reduction in water-soluble chloride indicates that a lower proportion of chloride ions remain available to initiate reinforcement corrosion.Pumicite-Containing Mixes

[0448] Figure 20 shows that the effect of the activator was particularly pronounced in mixes incorporating 30% pumicite as a cement replacement. Sample 588 (saltwater with pumicite, no activator) exhibited relatively high water-soluble chloride content. When Activator A+ was added (sample 590), a substantial reduction in water-soluble chloride was observed.The percentage of bound chloride may be calculated using:(Total chloride-Water-soluble chloride)- - - TT-ot.a ,l c Lh, ,l -oride - >< I00Using this calculation:• Sample 588 exhibited approximately 8% bound chloride.• Sample 590 exhibited approximately 49% bound chloride.This significant increase demonstrates enhanced chloride binding capacity when the activator is combined with pumicite. Figure 21 illustrates these results.

[0449] Without wishing to be bound by theory, it is believed that the activator enhances the reactivity of the pozzolanic component, increasing formation of reaction products capable of chemically or physically binding chloride ions within the hardened matrix.Conclusions

[0450] The chloride binding results align with the findings from example 18 - Chloride migration testing, and example 19 - Water absorption and permeable void testing. The combined data indicate that addition of the activator:• Reduces total chloride content in saltwater systems,• Reduces the proportion of free (water-soluble) chloride ions,• Increases chloride binding capacity,• Reduces chloride migration coefficients, and• Produces a denser microstructure with reduced permeable voids.

[0451] A reduction in chloride migration coefficient indicates reduced ionic transport through the concrete matrix. Increased chloride binding further limits the availability of aggressive ions capable of initiating steel corrosion. Overall, the testing demonstrates that addition of the activator admixture improves resistance to chloride ingress and enhances durability of saltwater-based concrete systems.Example 20

[0452] This example will investigate the acid-soluble chloride content in different water sources, including potable water, artificial sea water, and natural sea water, and their impact on mortar performance. The study will assess chloride migration and binding capacity in the presence or absence of an activator admixture.

[0453] MethodologyMixes with and without the activator will be adjusted to achieve substantially identical spread, leading to variations in the water-to-cement (w / c) ratio. The chloride content of the water sources will be determined before mixing and monitored in hardened mortar specimens over time.

[0454] Three different treatments will be assessed:1. Control - Potable water without (1A) and with (IB) activator.2. Treatment A - Salt water collected from St Heliers Bay, Auckland, and filtered using a size 4 coffee filter with a fineness of 20 pm:o No activator (A-) - Constant water-cement ratio, constant cement content. o With activator (A+) - Constant w / c ratio, constant cement content, 3% X4 activator.3. Treatment B - Artificial sea water (Instant Ocean, "IO"). IO will be prepared according to manufacturer instructions using an Instant Ocean Aquarium Sea Water kit, which contains a mix of salts as noted in Example 11. The material will be diluted in potable water at the recommended proportion of 33 g IO per IL of water, with an assumed density of 1.020.

[0455] Each treatment will comprise 4 experimental replicates (i.e., different mix preparations) and four technical replicates (i.e., four measurements of separate mortar specimens from a single experimental replicate at the same time point). Chloride content analysis will be conducted on hardened mortar samples to assess both free and bound chloride levels. All tests will use activator X4, which has the particle size characteristics and chemical composition described in Example 6. Chloride content will be determined using an acid-soluble chloride extraction method at each time point.

[0456] Expected ResultsThe chloride content in the control samples will remain minimal, whereas the natural and artificial sea water samples will contain significantly higher chloride concentrations. The presence of the activator will reduce free chloride migration within the mortar matrix and reduce porosity. Activator mixes will exhibit less variation in strength between replicates.Clauses

[0457] The following numbered clauses define further optional embodiments of the invention described herein. The clauses are provided for the purpose of illustrating combinations of features disclosed in the specification and are not intended to limit the scope of the invention as defined in the claims.

[0458] Features described in relation to one clause may be combined with features described in any other clause, unless the context clearly indicates otherwise. Any feature described in relation to an activator admixture may also apply, where appropriate, to a concrete composition comprising the activator, to a method of producing the activator, to a method of producing a saltwater concrete composition, or to the use of the activator.Clause 1. An activator admixture for producing saltwater concrete, the activator comprising a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes or different chemical compositions.Clause 2. The activator of Clause 1, further comprising a powdered plasticiser component mixed with the pozzolan component.Clause 3. The activator of Clause 1 or Clause 2, wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.Clause 4. The activator of any preceding Clause, wherein the Dv50 of the activator is less than 50 pm.Clause 5. The activator of any preceding Clause, wherein the activator comprises an electrostatic charge.Clause 6. The activator of any preceding Clause, wherein the first pozzolan portion comprises an intermediate median particle size in a range of 0.5-1.5 pm and the second pozzolan portion comprises a coarse median particle size in a range of 10-80 pm.Clause 7. The activator of any preceding Clause, wherein the pozzolan component exhibits a first volume density peak within 0.5 pm to 1.5 pm and a second volume density peak within 10 pm to 80 pm.Clause 8. The activator of any preceding Clause, wherein the particle size distribution is defined by:(a) 15-55% of particles are less than 15 pm;(b) 50-80% of particles are less than 40 pm; and(c) 70-100% of particles are less than 90 pm.Clause 9. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least 2x the Dv50 of the first pozzolan portion.Clause 10. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least 4x the Dv50 of the first pozzolan portion.Clause 11. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least 6x the Dv50 of the first pozzolan portion.Clause 12. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least lOx the Dv50 of the first pozzolan portion.Clause 13. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 10 pm.Clause 14. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 20 pm.Clause 15. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 30 pm.Clause 16. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 50 pm.Clause 17. The activator of any preceding Clause, wherein the first and second pozzolan portions occupy distinct particle size domains and form separate peaks within a bi-modal or multi-modal particle size distribution of the activator.Clause 18. The activator of any preceding Clause, wherein particles of the first pozzolan portion occupy interstitial spaces between particles of the second pozzolan portion.Clause 19. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in silicon dioxide content by at least 5% w / w.Clause 20. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in silicon dioxide content by at least 10% w / w.Clause 21. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in silicon dioxide content by at least 15% w / w.Clause 22. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in aluminium oxide content by at least 5% w / w.noClause 23. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in aluminium oxide content by at least 10% w / w.Clause 24. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in aluminium oxide content by at least 15% w / w.Clause 25. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in one or both of silicon dioxide and aluminium oxide content.Clause 26. The activator of any preceding Clause, wherein the activator is formulated for addition at between 0.25-10% by weight of cementitious material in a saltwater concrete composition.Clause 27. A method of producing an activator composition comprising:(a) obtaining a first pozzolan portion with a first chemical composition and a second pozzolan portion with a second chemical composition;(b) combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component; and(c) mixing the pozzolan component with a plasticiser to produce the activator composition, wherein the pozzolan component comprises 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.Clause 28. The method of Clause 27, wherein the activator comprises an electrostatic charge applied by electrostatic spraying, triboelectric charging, corona discharge, electrostatic fluidisation, or mechanical mixing-induced friction.Clause 29. A saltwater concrete composition comprising:(a) an activator according to any one of Clauses 1-26;(b) cementitious material;(c) aggregate; and(d) saltwater.Clause 30. The composition of Clause 29, wherein the saltwater comprises dissolved salts at a concentration of at least about 5 g / L.Clause 31. The composition of Clause 30, wherein the dissolved salts comprise sodium chloride and magnesium chloride.Clause 32. The composition of any of Clauses 29-31, wherein the compressive strength determined in accordance with NZS 3112 Part 2 at 28 days is at least 20 MPa.Clause 33. The composition of Clause 32, wherein the compressive strength is at least 25 MPa.Clause 34. The composition of Clause 33, wherein the compressive strength is at least 30 MPa.IllClause 35. A method of producing a saltwater concrete composition comprising combining: (a) an activator according to any one of Clauses 1-26;(b) cementitious material;(c) aggregate; and(d) saltwater.Clause 36. The method of Clause 35, wherein the composition develops a compressive strength of at least 25 MPa at 28 days.Clause 37. Use of an activator according to any one of Clauses 1-26 for improving compressive strength in a saltwater concrete composition.Clause 38. Use of an activator according to any one of Clauses 1-26 for reducing chloride ion mobility in a saltwater concrete composition.Clause 39. Use of an activator according to any one of Clauses 1-26 for increasing bound chloride fraction in a saltwater concrete composition.Clause 40. Use of an activator according to any one of Clauses 1-26 for reducing nonsteady-state chloride migration coefficient relative to a corresponding saltwater concrete composition not comprising the activator.Clause 41. A method of producing a saltwater concrete composition comprising:(a) obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;(b) combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;(c) providing a plasticiser;(d) forming an activator admixture comprising the pozzolan component and the plasticiser; and(e) combining the activator admixture with cementitious material and saltwater to form the saltwater concrete composition,wherein the activator admixture may be formed prior to combination with the cementitious material or may be formed during combination with the cementitious material, wherein the plasticiser may be combined with the pozzolan component before addition to the cementitious material or may be introduced into the concrete mix concurrently with or subsequent to the pozzolan component,wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide, andwherein the first and second pozzolan portions comprise different median particle sizes.

Claims

What we claim is:

1. A concrete composition comprising an activator admixture, cementitious material and saltwater, the activator admixture comprising a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

2. The concrete composition of claim 1, wherein the activator pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide, and 5- 40% w / w aluminium oxide.

3. The concrete composition of claim 1 or 2 wherein the activator comprises a plasticiser present at between about 8% and 40% w / w of the activator admixture.

4. The concrete composition of any of the preceding claims wherein the saltwater comprises dissolved salts of at least about 5g / L, optionally between 5 and 45g / L.

5. The concrete composition of claim 4 wherein the dissolved salts comprises sodium chloride (NaCI) and magnesium chloride and wherein the dissolved salts comprises from about 70% to about 85% sodium chloride.

6. The concrete composition of any of the preceding claims, further comprising fibre reinforcement selected from polymeric, basalt, or glass fibres.

7. The concrete composition of any of the preceding claims wherein the activator comprises an electrostatic charge.

8. The concrete composition of any of the preceding claims wherein the activator first pozzolan portion comprises an intermediate median particle size in a range of 0.5- 1.5pm and the activator second pozzolan portion comprises a coarse median particle size in a range of 10-80pm.

9. The concrete composition of any of the preceding claims, further comprising a reinforcing material and a corrosion inhibitor selected from the group consisting of passivating agents, chloride scavengers, cathodic inhibitors, anodic inhibitors, oxidation inhibitors, electrochemical inhibitors, nitrite-based inhibitors, organic inhibitors, silane / siloxane treatments, galvanic protection systems and polymeric barrier coatings.

10. The concrete composition of any of the preceding claims wherein the activator pozzolan component exhibits a first volume density peak of between 0.3 and 1.5% for particles at between 0.5pm and 1.5pm and a second volume density peak of greater than 3% between 10pm and 80pm.

11. The concrete composition of any of the preceding claims wherein the activator particle size distribution is defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm.

12. The concrete composition of any of the preceding claims wherein one or more natural or synthetic pozzolans comprises at least about 60% by weight of the activator.

13. The concrete composition of any of the preceding claims wherein the activator comprises a plasticiser and the ratio between the activator pozzolan component and the plasticiser comprises from about 11:1 pozzola plasticiser to about 1.5:1 pozzolan: plasticiser.

14. The concrete composition of any of the preceding claims, wherein the activator comprises a plasticiser selected from the group consisting of a polycarboxylate plasticiser; a naphthalene plasticiser, a superplasticiser; a lignosulphonate plasticiser; a dry form plasticiser; and a dry powder polycarboxylate superplasticiser.

15. The concrete composition of claim 3, 13 or 14 wherein the plasticiser comprises a Dv50 of from 50-500pm or 100-200pm.

16. The concrete composition of any of the preceding claims wherein the activator is present in an amount of from 0.25-10% of cementitious materials in the concrete composition.

17. The concrete composition of any of the preceding claims wherein the cementitious materials comprises Portland cement and at least one pozzolanic supplementary cementitious material (SCM) selected from the group consisting of fly ash, slag, silica fume, metakaolin, rice husk ash, synthetic pozzolan, natural pozzolan and pumice.

18. The concrete composition of claim 17 wherein the pozzolanic SCM is present in an amount of 10 to 50% w / w of cementitious material.

19. The concrete composition of claim 17 or 18 wherein the pozzolanic SCM comprises both natural pozzolan and fly ash, each present in an amount of 10 to 50% w / w of cementitious material.

20. The concrete composition of any of claims 17 to 19 wherein limestone is present in an amount of 10 to 100% w / w of pozzolanic SCM.

21. The concrete composition of any of the preceding claims wherein the composition comprises cementitious material comprising Portland cement at a quantity selected from the group consisting of less than 50%, less than 60%, less than 70%, less than 80% or less than 90% cement.

22. The concrete composition of any of the preceding claims wherein the compressive strength determined in accordance with NZS3112 part 2 at day 28 is greater than 20MPa.

23. The concrete composition according to any of the preceding claims wherein the composition comprises cementitious material comprising:a. a supplementary cementitious material comprising fly ash at a quantity of between about 10% to about 50%, optionally about 20% to about 40%; and b. the balance made up of Portland Cement.

24. A concrete structure comprising the concrete composition of any one of claims 1 to 23.

25. A method of producing a saltwater concrete composition comprising the steps of: a. obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;b. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c. providing a plasticiser;d. forming an activator admixture comprising the pozzolan component and the plasticiser;e. combining the activator admixture with cementitious material and saltwater to form the saltwater concrete composition,wherein the activator admixture may be formed prior to addition of saltwater or may be formed in situ during mixing of the cementitious material and saltwater, wherein the pozzolan component may be combined with the cementitious material prior to addition of saltwater, and the plasticiser may be added to the cementitious material either before or after addition of the pozzolan component and prior to addition of saltwater, andwherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

26. The method of claim 25 wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.

27. The method of claim 25 or 26 wherein the activator comprises an electrostatic charge.

28. The method of any of claims 25 to 27 wherein the electrostatic charge is applied to the activator by way of external electrical fields generated by electrodes, electrostatic spraying techniques, triboelectric charging in a fluidised bed, corona discharge methods, electrostatic fluidisation, and mechanical mixing-induced friction.

29. The method of any of claims 25 to 28 wherein the activator comprises a particle size distribution defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm.

30. The method of any of claims 25 to 29 wherein the activator comprises 20-80% w / w silicon dioxide, 5-40% w / w aluminium oxide, and wherein the concrete composition develops a compressive strength of at least 25MPa at 28 days, and wherein thecomposition comprises at least 10% by weight of natural or synthetic pozzolan supplementary cementitious material, based on the total cementitious material.

31. The method of any of claims 25 to 30 wherein the concrete composition comprises activator admixture at 0.25-10% by weight of cementitious material.

32. The method of any of claims 25 to 31 wherein the plasticiser comprises 8-40% w / w of the activator admixture composition.

33. The method of any of claims 25 to 32 wherein the plasticiser is mixed with the pozzolan component substantially simultaneously to the step of combining the activator admixture composition with cementitious material and saltwater.

34. A method of reducing chloride ion mobility and / or chloride ingress in a saltwater concrete composition comprising an activator admixture, cementitious material and saltwater, the method comprising adding the activator admixture to the cementitious material and saltwater, wherein the activator admixture comprises a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

35. A method of increasing bound chloride fraction in a saltwater concrete composition comprising an activator admixture, cementitious material and saltwater, the method comprising adding the activator admixture to the cementitious material and saltwater, wherein the activator admixture comprises a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

36. A method of improving chloride resistance of a saltwater concrete composition comprising an activator admixture, cementitious material and saltwater, the method comprising adding the activator admixture to the cementitious material and saltwater, wherein the activator admixture comprises a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

37. The method of any one of claims 34 to 36 wherein saltwater concrete composition is as claimed in any of claims 1 to 23.

38. The method of any one of claims 34 to 36 wherein non-steady-state chloride migration coefficient is reduced by at least 10% relative to a control composition.

39. The method of any one of claims 34 to 38 wherein at least 30% of total chloride is present as bound chloride.

40. The method of any one of claims 34 to 39 wherein water-soluble chloride concentration is reduced by at least 20%.

41. The method of any one of claims 34 to 40 wherein permeable void content is less than 13%.

42. The method of any one of claims 34 to 41 wherein the composition develops compressive strength of at least 25 MPa at 28 days.

43. The method of any one of claims 34 to 42 wherein the saltwater comprises dissolved salts of at least about 5g / L, optionally between 5 and 45g / L.

44. The method of claim 34 or 43 wherein the dissolved salts comprises sodium chloride (NaCI) and magnesium chloride and wherein the dissolved salts comprises from about 70% to about 85% sodium chloride.

45. The method of one of claims 34 to 44, wherein the activator pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide, and 5- 40% w / w aluminium oxide.

46. The method of one of claims 34 to 45 wherein the activator comprises an electrostatic charge.

47. The method of one of claims 34 to 46 wherein the activator first pozzolan portion comprises an intermediate median particle size in a range of 0.5-1.5pm and the activator second pozzolan portion comprises a coarse median particle size in a range of 10-80pm.

48. The method of one of claims 34 to 47 further comprising a reinforcing material and a corrosion inhibitor selected from the group consisting of passivating agents, chloride scavengers, cathodic inhibitors, anodic inhibitors, oxidation inhibitors, electrochemical inhibitors, nitrite-based inhibitors, organic inhibitors, silane / siloxane treatments, galvanic protection systems and polymeric barrier coatings.

49. The method of one of claims 34 to 48 wherein the activator pozzolan component exhibits a first volume density peak of between 0.3 and 1.5% for particles at between 0.5pm and 1.5pm and a second volume density peak of greater than 3% between 10pm and 80pm.

50. The method of one of claims 34 to 49 wherein the activator particle size distribution is defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm.

51. The method of one of claims 34 to 50 wherein the pozzolan component of the activator admixture comprises one or more natural or synthetic pozzolans and comprises at least about 60% by weight of the activator.

52. The method of one of claims 34 to 51 wherein the activator comprises a plasticiser and the ratio between the activator pozzolan component and the plasticiser comprises from about 11:1 pozzolan: plasticiser to about 1.5:1 pozzolan: plasticiser.

53. The method of one of claims 34 to 52 wherein the activator comprises a plasticiser present at between about 8% and 40% w / w of the activator admixture.

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