Composite blend for cementitious mixtures

Abstract

Cementitious mixtures, including concrete and mortar, are widely used in the construction industry. Various methods have been known to improve the strength properties of cementitious mixtures. For example, reinforced concrete may be used to improve flexural strength. However, there are cost, weight, and other disadvantages associated with these methods. A composite blend including milled synthetic fibers and milled igneous rock, and methods of using the composite blend to form cementitious mixtures with improved strength properties, are disclosed.

Description

COMPOSITE BLEND FOR CEMENTITIOUS MIXTURESFIELD

[0001] The present disclosure relates generally to composite blends for cementitious mixtures. In particular, the present disclosure relates to composite blends used to form cementitious mixtures for construction projects.BACKGROUND

[0002] Cementitious mixtures, including concrete and mortar, are widely used in the construction industry, for building, repairing, and maintaining infrastructures. Concrete and mortar are generally formed by combining a binder, commonly cement, with various other materials, such as water, aggregates, and admixtures. Different cementitious mixtures may have different applications. Concrete, for example, may be used as a main ingredient for structural projects due to its relatively high strength and durability, while mortar may be used as a bonding material to hold concrete blocks, stones, bricks together.SUMMARY

[0003] Since cementitious mixtures are the foundation of modem construction, the strength a cementitious mixture possesses is crucial in determining the types of construction projects it can be used in. For example, only a concrete mixture that possesses high strength may be considered for the erection of high-rise structures.

[0004] While there have been some advancements in developing high strength mixtures, these methods typically result in increased weight of the cement due to the addition of reinforcement material, such as steel strands, and much higher costs. Moreover, these methods commonly achieve higher compressive strength, but show limited improvement in flexural strength. Flexural strength is a measure of the material’s ability to resist deformation under load, and therefore cementitious mixtures with higher flexural strength are desirable in many applications, particularly for large or high-rise structures. Conventional cementitious products are generally known to have poor flexural strength, and usually falls between 10 to 15% of the compressive strength.

[0005] It is therefore desirable to make cementitious mixtures that can achieve higher strengths (e.g., increased compressive strength and increased flexural strength) compared to conventional mixtures, while not creating additional challenges such as increased weight and cost.

[0006] In some embodiments, a composite blend or composition may be used in forming a cementitious mixture. The composite blend or composition may be created using various components, including crushed or milled mineral fibers and rock particles. Use of the composite blend may result in a cementitious mixture with increased compressive strength and flexural strength as compared to conventional cementitious mixtures. This may be achieved without a significant increase in weight of the mixture and / or in cost in making the mixture, as typically associated with higher strength cementitious mixtures.

[0007] In accordance with an embodiment there is provided a composition for addition to a cementitious mixture, the composition comprising milled synthetic mineral fibers and milled igneous rock.

[0008] In accordance with another embodiment there is provided a cementitious comprising: silica sand; cementitious admixtures; water; supplementary cementitious material; and a composition, the composition comprising: milled synthetic mineral fibers having an average length at or below 50 microns; and milled igneous rock, wherein: a silica content of the milled synthetic mineral fibers is at least 40%; and a silica content of the milled igneous rock is at least 40%.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments will be described, by way of example only, with reference to the accompanying figures wherein:

[0010] FIG. 1 is an image of a cross-sectional view of a cementitious mortar beam made using a composite blend, according to one embodiment;

[0011] FIG. 2 is a line graph illustrating the compressive strength of various cementitious mortar cube samples made using the composite blend of FIG. 1, as exhibited at varying times of a compressive strength test cycle;

[0012] FIG. 3 is a bar graph illustrating the compressive strengths of various grades of concrete and an average compressive strength of a cementitious mortar cube made using the composite blend;

[0013] FIG. 4 is a bar graph illustrating the flexural strength of various cementitious mortar beam samples made using the composite blend; and

[0014] FIG. 5 is a bar graph illustrating the available alkali content of various components that may be used in a high-strength cementitious mixture.DETAILED DESCRIPTION

[0015] For illustrative purposes, specific embodiments will now be explained in greater detail below in conjunction with the figures.

[0016] The following description describes embodiments according to the present disclosure in detail.

[0017] Traditional mortar or concrete are products commonly manufactured using cement, water, and aggregates, and may also include admixtures and supplementary cementitious materials. A common type of cement is sometimes referred to as Portland cement or ordinary Portland cement (OPC). The cement acts as a binding agent in both mortar and concrete.Portland cement is a type of hydraulic cement, meaning that it sets and hardens when combined with water. In manufacturing the concrete or mortar mixture, the addition of water activates the cement to bind the mix together and form a solid.

[0018] Aggregates are granular materials, such as gravel, crushed stone, sand, and are often the major constituents in a cementitious mixture. Aggregates can be divided into two categories depending on particle size - fine and coarse. Examples of coarse aggregates include gravel or crushed materials, and examples of fine aggregates include sand, clay, and silt.

[0019] Admixtures are substances that can be used to enhance the behaviour or properties of a concrete or mortar mixture. Depending on the desired properties, different types of admixtures are available for addition to a cementitious mixture. For example, water-reducing admixtures may be used to reduce the amount of water required to form a workable cementitiousmixture. Reducing the water-cement ratio may contribute to a higher strength and durability of the cementitious mixture. Retarding admixtures may be used to slow the setting rate of the cementitious mixture, thereby keeping the mixture workable for longer, and may be useful when the mixture must travel long distances in a mixer or in hot weather conditions. Accelerating admixtures may increase the rate of early strength development of the cementitious mixture, as well as reduce the time required for curing, and may be useful where faster setting times are required such as in cold weather conditions or rapid construction schedules. Other examples of admixture types include air-entraining mixtures, super plasticizers, and corrosion-inhibiting admixtures. Specific examples of admixtures that may be used include cellulose, clays, and gypsum. Supplementary cementitious materials can also be added to improve properties of cementitious mixtures, such as durability or resistance to degradation. Commonly used supplementary cementitious materials in concrete or mortar mixtures include fly ash, furnace slag, and silica fume.

[0020] The properties of traditional mortar or concrete is dependent on various factors, such as the constituents used, the water-cement ratio (w / cm), and the mixing, placement and curing methods that are used. For example, all things being equal, a lower mixing speed may allow a mixture to be workable for longer than a mixture formed with higher mixing speed, and thus may make the mixture more suitable for being transferred over long distances.

[0021] One of the most important properties of concrete or mortar is their strength, as the strength forms the basis of the type of construction projects the concrete or mortar can be used in. A cementitious mixture that possesses the appropriate strength to withstand the loads and stresses it will be subjected to, ensures the structural integrity and safety of the infrastructure. Materials such as concrete and mortars are thus commonly classified based on the strength they possess.

[0022] For example, concrete mixes may often be categorized by grade, the grade being denoted by the letter M and a number in ascending order of 5. The grade defines the minimum compressive strength the concrete should have 28 days after initial construction. An Ml 5 concrete mixture will exhibit a compressive strength of 15 megapascals (MPa) after 28 days, whereas an M40 concrete mixture will exhibit a compressive strength of 40 MPa after 28 days. Similarly, mortar mixes are denoted by a letter type that indicates the compressive strength. Forexample, three common types of mortars used are types M, S and N. Type M achieves a compressive strength of 2500 pound-force per square inch (psi) which translates to approximately 17 MPa, after 28 days, type S 1800 psi (approximately 12.5 MPa) and type N 750 psi (approximately 5 MPa).

[0023] High-strength concrete is typically recognized as a concrete with a compressive strength of at least 45 MPa. For mortars, type M is typically recognized as possessing high strength.

[0024] The strength of a cementitious mixture can have a large impact on the overall direction and / or efficiency of a construction project, as it can determine the amount of material required and the construction methods that may be used. For example, higher strength concrete generally allows for the construction of taller or heavier structures without the need for excessive concrete volumes. Additionally, choosing to use higher strength concrete for a project can allow for the reduction of column and beam dimensions, which can cut down the amount of concrete needed, reduce the dead load of a structure, reduce construction time, and provide increased floor space. Higher strength concrete also typically exhibits increased durability due to greater resistance to environmental factors such as freeze-thaw cycles and abrasion. With respect to mortars, only high strength mortar may be appropriate for load bearing or below grade applications.

[0025] The flexural strength of a cementitious mixture is also critically important in ensuring the structural integrity of a structure. While compressive strength refers to the maximum amount of compressive or crushing load a cementitious product can bear before failing, flexural strength, referred to also as the modulus of rupture, indicates the resistance of a cementitious product to deformation under bending. Unfortunately, the flexural strength of conventional cementitious mixtures is typically relatively low, often falling between 10 to 15% of the compressive strength. The tensile strength, which is the maximum load that a material can support without fracture when being loaded in tension, is also a factor to consider. The tensile strength of conventional cementitious mixtures also is typically relatively low, ranging between 7-15% of the compressive strength.

[0026] In some applications, reinforced concrete may be used for higher the flexural and tensile strength. Reinforced concrete is a composite material where the low tensile and flexural strengths are compensated for by including reinforcement, usually in the form of steel bars, rods or mesh, that are embedded in the concrete mixture before the concrete sets. Since steel possesses high flexural and tensile strength, in combination with the concrete mixture which can be manufactured to have relatively high compressive strength, the reinforced concrete may resist not only compression but also bending and tensile pressures. However, steel-reinforced concrete has certain disadvantages. In addition to resulting in longer construction times due to the time needed to install the steel bars or mesh, steel-reinforced concrete is more expensive than conventional concrete. Additionally, the extra weight added by the steel is substantial, requiring a stronger foundation to be able to support it, further adding to construction costs.

[0027] Another form of reinforced concrete is fiber-reinforced concrete, which incorporates fibers to the concrete mixture. Examples of the types of fibers used include steel, glass, plastic, and polymer. The fibers can be classified as macrofibers or microfibers based on their dimensions, with macrofibers generally having a length greater than 1.5 inches and a diameter greater than 0.3 mm, and microfibers having a length and diameter less than 1.5 inches and 0.3 mm, respectively. Macrofibers, usually of the steel type, are sometimes referred to as structural fibers and can be used to replace some of the traditional steel bar or mesh reinforcement. Microfibers are generally used to help with concrete cracking but typically do not add structural capacity to a concrete product.

[0028] Fiber-reinforced concrete also has a host of drawbacks. For example, similar to steel bar- or mesh-reinforced concrete, fiber-reinforced concrete is more costly and heavy than non-fiber reinforced concrete. Additionally, the orientation of the fibers may affect the properties of the concrete, with uniformly aligned fibers resulting in better performance than randomly oriented fibers. However, controlling the fiber direction is difficult, thus limiting their application. If not mixed and distributed properly and spread uniformly, the fibers can also accumulate in certain areas and form clumps. In terms of appearance, the surface of fiber- reinforced concrete may appear fuzzy or uneven due to some of the fibers being exposed, which can detract from the appearance of the polished surface and also compromise the smoothness. When it comes to microfibers specifically, their use is generally only limited to augmenting theproperties of traditionally reinforced concrete, not as an alternative to traditionally reinforced concrete.

[0029] It has thus remained a challenge to develop concrete products that can exhibit higher flexural and / or tensile strength without the disadvantages of added cost, added weight, more difficult construction, etc.

[0030] It has been unexpectedly discovered that the combination of milled, ground, or crushed synthetic mineral fibers (“milled synthetic mineral fibers”) and milled, ground, or crushed igneous rock (“milled igneous rock”) may improve the strength properties of a cementitious mixture when added to the mixture as a composite blend. In particular, the improvement in flexural strength when the composite blend is added may be significant.

[0031] The composite blend may include milled synthetic mineral fibers of a certain length range. In some embodiments, the effective length range (i.e., the range leading to significantly increased flexural strength) for the milled synthetic mineral fibers is approximately 50 micrometers (um) or less, and is preferably less than approximately 10 um. The effective gauge range for the milled synthetic mineral fibers may similarly be 50 um or less, and preferably less than approximately 10 um The composite blend may also include milled igneous rock of a certain size range. In some embodiments, the effective size range for the igneous rock may be between approximately 2 and 10 um.

[0032] In conventional fiber-reinforced concrete, strength improvement requires alignment of fibers, which typically requires significant processing effort and cost. Additionally, large fibers in conventional fiber-reinforced concrete may provide benefits, for example, by physically bridging cracks that form during the concrete hardening process, thereby preventing crack propagation. Once hardened, the fibers may enhance the energy absorption capacity of the concrete product by bridging the cracks. In contrast, the present composite blend may provide high strength without processing to align fibers, and notwithstanding small fiber sizes. For example, the small dimensions of the synthetic mineral fibers mean that the milled synthetic mineral fibers will randomly orient themselves in the cementitious mixture when the composite blend is added. Although the fibers are not directionally aligned, strength improvements of the cementitious mixture can be observed. Indeed, when synthetic mineral fibers are milled to anaverage length that is greater than approximately 50 um, similar strength improvements are not observed. Only when the length of the milled synthetic mineral fibers crosses below the threshold of about 50um, are significant strength improvements observable in the cementitious mixture, with the most noticeable improvements occurring when the average length of the milled synthetic mineral fibers reaches below lOum.

[0033] Example composite blends in accordance with the present application may include milled synthetic mineral fibers and milled igneous rock in combination. In some embodiments, the composite blend may further include one or both of steel dust and boric oxide which may act as a stabilizer.

[0034] The milled synthetic mineral fibers may be produced by milling or grinding using a ball mill. The milled igneous rock may be produced by milling or grinding using a ball mill or jet mill.

[0035] FIG. 1 shows an image of a cross-sectional view of a cementitious mortar cube 100 made using a composite blend according to the present application. As shown, there are no fibers visible in the image at the depicted magnification level. In contrast, the fibers in conventional fiber-reinforced would be visible to the naked eye due to their dimensions being at least in the millimeter range.

[0036] Non-limiting examples of synthetic mineral fibers that may be milled to the desired dimensions and used in the composite blend include fiberglass, E-glass, ceramic fiber, rockwool fiber, and other manmade mineral fibers. Any combination (i.e., one or more) of such synthetic mineral fibers may be used. In a preferred embodiment, the synthetic mineral fiber(s) chosen may have a silica content greater than 40%. Non-limiting examples of the igneous rock that may be milled to the desired dimensions and used in the composite blend are obsidian, pumice, tachylite, perlite, pitchstone sideromelane, hyaloclastite rock, rhyolite, basalt, and andesite. Any combination of such igneous rock may be used. In a preferred embodiment, the silica content of the igneous rock(s) used may be greater than 40%. In some embodiments, the type of igneous rock(s) used may be extrusive in nature. In some embodiments, the type of igneous rock(s) used may be holohyaline.

[0037] In some embodiments, the ratio of milled synthetic mineral fibers to milled igneous rock present in the composite blend may be 9: 1 by weight. This ratio may represent the maximum percentage by weight of the milled synthetic mineral fibers and the minimum percentage by weight of the milled igneous rock. Accordingly, in some embodiments the composite blend may involve a ratio of milled synthetic mineral fibers to milled igneous rock of approximately 8:2, 7:3, 6:4, 5:5, etc.

[0038] In some embodiments, a high-strength cementitious mixture formed using the composite blend may have the following composition: 1-3% by weight of the composite blend; 50-55% by weight of fine aggregate (e.g., silica sand with an average particle size below 100 um); 25-30% cement (e.g., Portland cement); 3-5% by weight of admixtures; 5-10% by weight supplementary cementitious materials; and water. Without the water, the remaining ingredients of the mixture may be referred to as a dry mixture. In some embodiments, the amount of water that is added to form the high-strength cementitious mixture may be around 15-18% by weight of the weight of the dry mixture. For example, when the constituents of the dry mixture add up to 1 kilogram, the amount of water added to form the high-strength cementitious mixture may be between 150 and 180 grams. A high-strength cementitious mixture formed using this composition ratio may be hereinafter referred to as a first high-strength cementitious mixture type. In some embodiments, the composite blend in a first high-strength cementitious mixture type may have approximately a 9: 1 ratio by weight of milled synthetic mineral fibers to milled igneous rock.

[0039] In some embodiments, the amount of the composite blend that is added may be increased to substantially or entirely replace Portland cement. While Portland cement is the most commonly used cement and has a long history of successful use in construction projects worldwide due to its strength, availability, and affordability, it is also associated with disadvantages, such as environmental impact. For example, Portland cement has a high carbon footprint, as its manufacturing process involves the calcination of limestone, leading to the emission of a large amount of carbon dioxide. Further, the manufacturing process of Portland cement requires high temperatures, which demands significant energy consumption. In addition, Portland cement is prone to cracks and shrinkage, and is known to have slow setting time.

[0040] Therefore, in some embodiments, a high-strength cementitious mixture formed using the composite blend may have the following composition: up to 25% by weight of the composite blend; 50-60% by weight of fine aggregate (e.g., silica sand with an average particle size below 100 um); 5-10% by weight of admixtures; 10-15% by weight of supplementary cementitious materials; and water. In some embodiments, the amount of water that is added may be around 15-18% by weight of the dry mixture. The mixture may additionally include a relatively small amount of Portland cement as compared to the first high-strength cementitious mixture type or a conventional cementitious mixture. In some embodiments, the mixture may include no Portland cement at all. A high-strength cementitious mixture formed using this composition ratio may be hereinafter referred to as a second high-strength cementitious mixture type. In a preferred embodiment, the milled igneous rock used to create a second high-strength cementitious mixture type may be felsic in nature, that is, igneous rock with more than 65% silica content. In some embodiments, the composite blend in a second high-strength cementitious mixture type may have a higher proportion by weight of milled igneous rock compared to the composite blend in a first high-strength cementitious mixture type. For example, the composite blend in a second high-strength cementitious mixture type may have a ratio by weight of approximately 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1 :9 of milled synthetic mineral fibers to milled igneous rock.

[0041] A method for making the composite blend may include milling or grinding synthetic mineral fibers using a ball mill equipped with balls made with a material hard enough to finely mill the synthetic mineral fibers. In some embodiments, a vertical ball mill with a ceramic head may be used to mill the synthetic mineral fibers to the desired dimensions. In some embodiments, the milling or grinding is performed without addition of water, as the fibers may react with water at the dimensions required for the composite blend. The method may further include milling or grinding igneous rock using a ball mill or jet mill. The time it takes to mill to the desired dimensions may depend on various factors, such as the type of mill used, the type(s) of synthetic fiber used, the Mohs hardness of the igneous rock(s) used, and the grade of the feedstock that were originally used to make the synthetic fibers, as will be apparent to a person skilled in the art. The composite blend may subsequently be mixed with ingredients commonly used in cementitious mixtures, such as Portland cement, aggregates, and water (“conventionalcementitious mixture”) to form a high-strength cementitious mixture that exhibits relatively high compressive, flexural, and tensile strength. Various equipment which employ different methods of mixing may be used to mix the components together and form the high-strength cementitious mixture. Examples include tumble mixers, forced action mixers, screw action mixers, or paddle stirrers. In some embodiments, the equipment used to form the high-strength cementitious mixture may depend on the desired end use for the mixture, as will be apparent to a person skilled in the art.

[0042] FIG. 2 is a line graph which shows the compressive strength of various cementitious mortar cube samples made using various composite blends made as described above, as exhibited at varying times of a compressive strength test cycle. The compressive strength test was conducted using the standard method described in American Society for Testing and Materials (ASTM) C109 / C109M and Canadian Standards Association (CSA) A23.2- 1B. Compressive strength values for six samples are shown, labelled A to F. Of these, samples A, B, C, D, and E are cubes made from first high-strength cementitious mixture types. The ratio of milled synthetic mineral fibers to milled igneous rock is approximately 9: 1 in these samples. Sample F is a mortar cube made from a second high-strength cementitious mixture type, and does not contain any Portland cement. The ratio of milled synthetic mineral fibers to milled igneous rock is approximately 5:5 in this sample. The specific compressive strength values as illustrated in FIG. 2 can be found in the below table:Table 1. Compressive Strength Values of First and Second High-Strength Cementitious Mixture Types

[0043] As shown, the compressive strength of the samples at 7 days is 38.5 MPa for sample F corresponding to the second high-strength cementitious mixture type, and ranges between 44.4 and 48.6 MPa for samples A-E corresponding to first high-strength cementitious mixture types. The 28-day compressive strength for samples A-C ranges between about 50 and 54 MPa. Although the 28-day compressive strength was not recorded for samples D and E, given that the strength values trend similar to those of samples A-C at 1 day and 7 days, it can be estimated that the 28-day compressive strength of samples D and E would be similar also (e.g., between 50 and 60 MPa). The 28-day compressive strength for sample F may similarly be estimated to be between 40 and 50 MPa.

[0044] With respect to samples A through E, the 28-day compressive strength exhibited is much higher than the compressive strength of conventional mortar products. In fact, the 28- day compressive strength is comparable to high strength concrete of grades M50 and higher. Referring briefly to FIG. 3, a bar graph compares the compressive strengths of various concrete grades against an average of the recorded 28-day compressive strength values of samples A through C, labelled “CB_Avg(A-C)”. Specifically, the average 28-day compressive strength of samples A through C is 51.9 MPa. As illustrated, this is higher than the 28-day compressive strength of many conventional concrete products, and comparable with concrete products even considered to be high-strength.

[0045] The first high-strength cementitious mixture type does not include coarse aggregates as an ingredient, which is known as being a major contributor to the compressive strength of conventional high-strength concrete. Yet, the 28-day compressive strength exhibited by various samples of the first high-strength cementitious mixture type rival that of conventional high-strength concrete products. This is indicative of the composite blend being responsible for the high strength of the first high-strength cementitious mixture type.

[0046] Further, returning to FIG. 2, it is shown that the compressive strength of sample F is comparable to samples A-E despite containing no Portland cement at all. This further showsthat the composite blend is responsible for the high strength, and additionally provides evidence that the composite blend is also able to fulfill the role of a binding agent that binds the ingredients of the second high-strength cementitious mixture type together.

[0047] FIG. 4 is a bar graph illustrating the 7-day flexural strength of various cementitious mortar beam samples made using the same mixtures as described with respect to FIG. 1. Accordingly, samples A through E correspond to beams made from first high-strength cementitious mixture types with the ratio of milled synthetic mineral fibers to milled igneous rock being approximately 9: 1. Sample F corresponds to a beam made from a second high- strength cementitious mixture type with the ratio of milled synthetic mineral fibers to milled igneous rock being approximately 5:5. Below is a table that lists the specific flexural strength values illustrated by the graph in FIG. 4. The flexural strength values were obtained using the standard method described in ASTM C293.Table 2. Flexural Strength Values of First and Second High-Strength Cementitious Mixture Types

[0048] As shown, the 7-day flexural strength values for the first high-strength cementitious mixture type ranges from approximately 11.7 MPa to 13.9 MPa, and the 7-day flexural strength value for the second high-strength cementitious mixture type is approximately lOMPa. These values represent significant improvement in flexural strength over conventional concrete or mortar mixes. For example, as noted previously, the typical flexural strength of acementitious product is between 10 to 15% of its compressive strength. Using this principle, it would normally be the case that only ultra high-strength concrete products with compressive strength of at least 100 MPa can achieve such flexural strength. Moreover, it is noted that flexural strength increases with age. Given at the values illustrated in FIG. 4 and Table 2 are flexural strength values at 7 days, it can reasonably be inferred that the flexural strength at 28 days will be even higher. Flexural strength values of this nature would typically only be achievable using concrete heavily reinforced with steel bars or mesh and / or bulk fibers, which are associated with a host of issues as previously described. In this context, both macrofibers and microfibers conventionally used to reinforce concrete may be considered “bulk” fibers, since the dimensions of the milled synthetic mineral fibers are several orders of magnitude smaller.

[0049] Tensile strength typically increases and decreases with the flexural strength. Therefore, it can reasonably be stated that the tensile strength values exhibited by the first and second high-strength cementitious mixture types created using would also be significantly higher than those of conventional (not reinforced) cementitious mixtures.

[0050] The use of a composite blend containing milled synthetic mineral fibers and milled igneous rock with the dimensions described above, to form first and second high-strength cementitious mixture types addresses the challenges typically associated with conventional reinforced concrete or mortar. The milled synthetic mineral fibers and milled igneous rock are lightweight, and therefore will not result in much heavier cementitious mixtures. Since synthetic mineral fibers and igneous rock are abundant and not expensive, the first and second high- strength cementitious mixture types are not burdensome from a cost perspective. Since the dimensions of the milled synthetic mineral fibers and milled igneous rock are not visible to the naked eye, appearance defects or surface bumpiness can be avoided also.

[0051] It is believed that high strength may be achieved in the first and second high- strength cementitious mixture types due to at least in part to certain chemical reactions that occur both within the ingredients of the composite blend itself, and between the composite blend and other conventional cementitious materials in the mixtures to achieve high strength. For example, the silica, calcium oxide (lime) and alumina in the milled synthetic mineral fibers and the silica in the milled igneous rock react to form various silicates responsible for high strength development. These reactions can be characterized as such:2CaO + SiO2 - 2CaO.SiO2 (dicalcium silicate)3CaO + SiO2 - 3CaO.SiO2 (tricalcium silicate)CaO + AL2O3 — 3CaO.AL2O3 (tricalcium aluminate)4 CaO + AL2O3 + FE2O3 - 4CaO.AL2O3.FE2O3 (a phase of cement)

[0052] These silicates above are hydrated in the presence of water (or supplementary substances such as gypsum) to produce additional silicates and hydroxides which further strengthen the cement paste / matrix. For example:2CaO.SiO2 +5H2O 3CaO.2SIO2.4H2O + Ca(0H)2 +HEAT

[0053] Since the rate of hydration of tricalcuium aluminate is greater than dicalcium and tricalcium silicate, a gradual formation of strength may be observed over time.

[0054] Both the first and second high-strength cementitious mixture types incorporate milled synthetic mineral fibers and milled igneous rock that are amorphous, i.e., lack long-range order within their atomic structure. For example, the milled igneous rock may be extrusive or holohyaline in nature such that the high-strength cementitious mixtures made using the milled igneous rock are at least partially amorphous. Since amorphous materials do not have a specific atomic configuration, they tend to have higher tensile and fatigue strengths than crystalline materials. Due to the amorphous nature, both the milled synthetic mineral fibers and the milled igneous rock may generally be lacking in atomic structure. The disorganized arrangement may allow for hydration reactions to occur easier, leading to higher strength. Due to the particles of the milled synthetic mineral fibers and the milled igneous rocks being made up of particles of different sizes, it may be difficult for them to “slide” over each other, leading to higher tensile strength. The small dimensions of the mineral fibers and the milled igneous rocks may allow for higher chemical reactivity due to the increased surface area as compared to their bulk counterparts, therefore increasing strength. Higher reactivity may also explain the high early compressive and flexural strength values. For example, in usual circumstances the compressive strength at the 7-day mark is approximately 65% of the compressive strength at 28 days. However, the general trend of the compressive strength of the first and second high-strength cementitious mixture types as shown in Table 1 and FIG. 2 indicates that the 7-day compressivestrength values are greater than 85% of the observed compressive strength values at 28 days. At the same time, long-term strength gains may also be observed. The low thermal conductivity which is characteristic of amorphous materials may allow for the slower dissipation and transfer of heat. This may lead to a more stable cement matric and gradual hydration reactions catalyzed over time by heat transfer, which may assist with longer term strength development.

[0055] The first and second high-strength cementitious mixture types may address the disadvantages of Portland cement described previously. For example, Portland cement is prone to cracks and shrinkage. It is believed that the silicates of the milled synthetic fibers act as small fibers to help bridge cracks, and additionally act as a Pozzolan to produce additional silicates which contribute to the strength and durability of the mixtures. Further, the slower dissipation and transfer of heat may reduce the shrinkage that may normally occur when using conventional cementitious mixtures.

[0056] Further, as described hereinbefore, in some embodiments the second high- strength cementitious mixture type may include no Portland cement at all, or a relatively small amount of Portland cement as compared to the first high-strength cementitious mixture type or a conventional cementitious mixture. Instead, as described, the second high-strength cementitious mixture type may include an increased amount of the composite blend. The types of synthetic mineral fibers that are used for the composite blend may be recycled material, and the types of igneous rock that are used for the composite blend may naturally be abundant on Earth. In this way, using the second high-strength cementitious mixture type instead of a conventional cementitious mixture having Portland cement as a main ingredient, may help to mitigate the environmentally harmful effects of Portland cement.

[0057] FIG. 5 is a bar graph illustrating the available alkali content of five samples. The samples were tested using the standard method described in ASTM C311, with one modification made to measure the amount of sodium and potassium oxides in solutions by inductively coupled plasma atomic emission spectroscopy as per ASTM DI 976. In the context of cementitious mixtures, available alkali content can affect various properties of a mixture, including strength. Alkali activity is theorized to accelerate the pozzolanic reactions and hydration reactions, influencing setting time and leading to early strength development.

[0058] Each of samples 1 through 4 shown in FIG. 5 is composed of a specific type of milled synthetic fiber or milled igneous rock that may be used to form the composite blend. Specifically, samples 1 through 4 are of milled mineral wool fiber, milled obsidian, milled fibreglass fiber, milled ceramic fiber, respectively. Each of the milled fiber samples (samples 1, 3, 4) and milled obsidian sample (sample 2) have a gauge range of less than 10 um. Sample 5 is an example composite blend with a ratio of milled synthetic mineral fiber to milled igneous rock of approximately 9: 1 by weight. The milled synthetic mineral fiber component of the composite blend includes a mix of various types of synthetic milled fibers, specifically milled fibreglass fiber, milled ceramic fiber, and milled mineral wool fiber. The milled igneous rock component of the composite blend includes milled obsidian. The specific proportions of each of the constituents, milled fibreglass fiber, milled ceramic fiber, milled mineral wool fiber, and obsidian are 54%, 27%, 9%, and 10% by weight.as the milled synthetic mineral fiber and obsidian as the milled igneous rock. The specific available alkali content of the five samples as illustrated in FIG. 5 can be found in the below table:Table 3. Available Alkali Content of Various Components for Use in High-Strength Cementitious Mixtures

[0059] As seen, of all the samples, milled obsidian shows the highest available alkali content at 2.29%. It is theorized that other igneous rock types that may be used in the composite blend (as discussed earlier) would possess similar available alkali content. Therefore, there may be a benefit in increasing the portion of igneous rock in the composite blend. This is especiallythe case for the second high-strength cementitious mixture type. In a conventional cementitious mixture, Portland cement is typically the main source of available alkalis. Since the secondary high-strength mixture contains little to no Portland cement, it may be beneficial to formulate the composite blend so that the portion of igneous rock present in the composite blend is higher than for the first high-strength cementitious mixture type, to ensure adequate reactivity and strength development. For example, the ratio of milled synthetic fibers to milled igneous rock for the second high-strength cementitious mixture type may be approximately 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1 :9, etc.

[0060] The composite blend as described herein may be used to develop cementitious products such as concrete or mortar that exhibit high flexural strength in addition to high compressive strength. For example, concrete products can be developed that exhibit all-around high strengths despite not being reinforced using conventional methods. As another example, the composite blend may be used to create a high-strength repair mortar for application to damaged or failing cementitious structures to improve the structural integrity and extend the lifetime of the structures.Conclusion

[0061] Note that the expression “at least one of A or B”, as used herein, is interchangeable with the expression “A and / or B”. It refers to a list in which you may select A or B or both A and B. Similarly, “at least one of A, B, or C”, as used herein, is interchangeable with “A and / or B and / or C” or “A, B, and / or C”. It refers to a list in which you may select: A or B or C, or both A and B, or both A and C, or both B and C, or all of A, B and C. The same principle applies for longer lists having a same format.

[0062] Although the present invention has been described with reference to specific features and embodiments thereof, various modifications and combinations may be made thereto without departing from the invention. The description and drawings are, accordingly, to be regarded simply as an illustration of some embodiments of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention. Therefore, although the present invention and its advantages have been described in detail, various changes,substitutions, and alterations may be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

[0063] The foregoing disclosure is not intended to limit the present disclosure to the precise forms or particular fields of use disclosed. As such, it is contemplated that various alternative embodiments and / or modifications to the present disclosure, whether explicitly described or implied herein, are possible in light of the disclosure. It is to be understood that the forms of disclosure herein shown and described are to be taken as representative embodiments. Equivalent elements, or materials may be substituted for those representatively illustrated and described herein. Moreover, certain features of the disclosure may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the disclosure. Expressions such as “including”, “comprising”, “incorporating”, “consisting of’, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. Having thus described embodiments of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the scope of the present disclosure. Thus, the present disclosure is limited only by the claims.

Claims

1. CLAIMS1. A composition for addition to a cementitious mixture, the composition comprising: milled synthetic mineral fibers; and milled igneous rock.

2. The composition of claim 1, wherein an average length of the synthetic mineral fibers is equal to or less than 50 micrometers.

3. The composition of claim 1, wherein a silica content of the milled synthetic mineral fibers is equal to or greater than 40%.

4. The composition of claim 1, wherein a silica content of the milled igneous rock is equal to or greater than 40%.

5. The composition of claim 1, wherein the milled igneous rock represents no less than 10% by weight of the composition.

6. The composition of claim 1, wherein an average diameter of the milled synthetic mineral fibers is equal to or less than 50 micrometers.

7. The composition of claim 1, wherein an average particle size of the milled igneous rock is equal to or less than 10 micrometers.

8. The composition of claim 1, wherein the milled igneous rock is formed from holohyaline igneous rock.

9. The composition of claim 1, wherein: the milled igneous rock is formed from igneous rock, pumice, tachylite, perlite, pitchstone sideromelane, or hyaloclastite rock; and the milled synthetic mineral fibers are formed from at least one of fiberglass, mineral wool, ceramic fibre or manmade mineral fiber.

10. A dry mixture for addition to a cementitious mixture, the dry mixture comprising: silica sand; cementitious admixtures; supplementary cementitious material; and a composition, the composition comprising: milled synthetic mineral fibers; andmilled igneous rock.

11. The dry mixture of claim 10, wherein an average length of the synthetic mineral fibers is equal to or less than 50 micrometers.

12. The dry mixture of claim 10, wherein an average diameter of the milled synthetic mineral fibers is equal to or less than 50 micrometers.

13. The dry mixture of claim 10, wherein an average particle size of the milled igneous rock is equal to or less than 10 micrometers.

14. The dry mixture of claim 10, wherein a silica content of the milled synthetic mineral fibers is equal to or greater than 40% and a silica content of the milled igneous rock is equal to or greater than 40%.

15. The dry mixture of claim 10, wherein the milled synthetic mineral fibers represents no more than 90% by weight of the composition and the milled igneous rock represents no less than 10% by weight of the composition.

16. A cementitious mixture comprising a dry mixture and water, wherein the dry mixture comprises: silica sand; cementitious admixtures; supplementary cementitious material; and a composition, the composition comprising: milled synthetic mineral fibers; and milled igneous rock.

17. The cementitious mixture of claim 16, wherein an average length of the synthetic mineral fibers is equal to or less than 50 micrometers.

18. The cementitious mixture of claim 16, wherein an average particle size of the milled igneous rock is equal to or less than 10 micrometers.

19. The cementitious mixture of claim 16, wherein a silica content of the milled synthetic mineral fibers is equal to or greater than 40% and a silica content of the milled igneous rock is equal to or greater than 40%.

20. The cementitious mixture of claim 16 further comprising Portland cement or blended cement.

21. The cementitious mixture of claim 20, wherein:a quantity of the silica sand is between 50-55% of the dry mixture by weight; a quantity of the cementitious admixtures is between 3%-5% of the dry mixture by weight; a quantity of the supplementary cementitious materials is between 5-10% of the dry mixture by weight; a quantity of the Portland cement or blended cement is between 25%-30% of the dry mixture by weight; and a quantity of the composition is between 1-3% of the dry mixture by weight; and a quantity of the water is between 15-18% by weight of a weight of the dry mixture.

22. The cementitious mixture of claim 21, wherein the cementitious mixture exhibits a flexural strength of at least 10 megapascals (MPa) as measured at 7 days using the standard method described in American Society for Testing and Materials (ASTM) C293.

23. The cementitious mixture of claim 21, wherein the cementitious mixture exhibits a compressive strength of at least 40 MPa as measured at 28 days using the standard method described in ASTM C109 / C109M.

24. The cementitious mixture of claim 21, wherein the milled synthetic mineral fibers represents no more than 90% by weight of the composition and the milled igneous rock represents no less than 10% by weight of the composition.

25. The cementitious mixture of claim 16, wherein: a quantity of the silica sand is between 50-60% of the dry mixture by weight; a quantity of the cementitious admixtures is between 5-10% of the dry mixture by weight; a quantity of the supplementary cementitious materials is between 10-15% of the dry mixture by weight; and a quantity of the composition is up to 25% of the dry mixture by weight; and a quantity of the water is between 15-18% by weight of a weight of the dry mixture.

26. The cementitious mixture of claim 25, wherein the cementitious mixture is free of Portland cement or blended cement.

27. The cementitious mixture of claim 25, wherein a silica content of the milled igneous rock is at or greater than 65%.

28. The cementitious mixture of claim 25, wherein the cementitious mixture exhibits a flexural strength of at least 10 megapascals (MPa) as measured at 7 days using the standard method described in American Society for Testing and Materials (ASTM) C293.

29. The cementitious mixture of claim 25, wherein the milled synthetic mineral fibers represents between 10% to 80% by weight of the composition and the milled igneous rock represents between 20% to 90% by weight of the composition.

30. The cementitious mixture of claim 25, wherein the milled synthetic mineral fibers represents between 50% to 70% by weight of the composition and the milled igneous rock represents between 30% to 50% by weight of the composition.

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