A concrete composition, a concrete marine float, process of manufacture and use thereof

Abstract

The present invention relates to a concrete composition with reduced density, having a high strength and enhanced durability, and a concrete marine float comprising the concrete composition, and their processes of preparation and use thereof.

Description

[0001] A CONCRETE COMPOSITION, A CONCRETE MARINE FLOAT,

[0002] PROCESS OF MANUFACTURE AND USE THEREOF

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a concrete composition with reduced density, having a high strength and enhanced durability, and a concrete marine float comprising the concrete composition, and their processes of preparation and use thereof.

[0005] STATE OF THE ART

[0006] Light-Weight Aggregate Concrete (LWAC) is a type of concrete composition specifically formulated using light-weight aggregates. These specific LWAC have been used in the past for the manufacture of marine floats. The use of LWAC increases the buoyancy of the whole marine float. Examples of light-weight aggregates used in LWAC, notably disclosed in Kim et al. J Korean Soc Coast Ocean Eng. 2017, 29(6), 315-325, include expanded shale aggregate, expanded clays and expanded slate.

[0007] Such LWAC marine floats have notably been developed in order to overcome certain issues associated with conventional concrete marine floats. Conventional concrete marine floats comprise a shell of Normal Weight Concrete (NWC) that surrounds a core that is either hollow or made of buoyant foam. These floats generally form strong, durable, and relatively stable marine structures and are particularly advantageous for use as floating foundations for structural applications such as floating foundations for wind mills. However, marine floats that comprise NWC are extremely heavy, and thus costly to transport to an installation site. Also, their heavy weight requires a deep float to achieve the necessary freeboard, so the marine floats use a relatively large amount of concrete and other materials, which increases the carbon footprint of said marine float.

[0008] Although the lighter floats, made using LWAC, effectively solve some of the problems associated with NWC by reducing their weight, the disadvantage associated with the use of light-weight aggregates in concrete compositions for use in marine environment is a lower concrete strength, elastic modulus and a decreased durability in sea water due to poor resistance to chloride attack, a consequence of increased porosity inherent in LWAC.There is therefore a need for concrete compositions with reduced density which are suitable for structural applications and meet sufficiently high strength requirements and further meet the requirements for applications in marine environments. There is further a need to provide concrete marine floats that satisfy requirements in terms of compressive strength further satisfy requirements in terms of resistance to chloride attack and hence display an improved durability.

[0009] STATEMENT OF THE INVENTION

[0010] It has now been found that using a concrete composition comprising pumice having a density of a light-weight aggregate and a specific particle size, allows to reduce the weight of a marine float comprising said concrete while meeting compressive strength requirements of the concrete and improving chloride resistance.

[0011] The present invention relates to a concrete composition, comprising:

[0012] - from 350 kg / m3to 500 kg / m3of cement;

[0013] - from 150 kg / m3to 650 kg / m3of pumice;

[0014] - from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and

[0015] - from 150 kg / m3to 290 kg / m3of water,

[0016] wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.

[0017] The present invention further relates to a process for the preparation of a concrete composition according to the invention, comprising the mixing of:

[0018] from 350 kg / m3to 500 kg / m3of cement;

[0019] from 150 kg / m3to 650 kg / m3of pumice;

[0020] from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and

[0021] a volume of mixing water in order for the total amount of water in the concrete composition to range from 150 kg / m3to 290 kg / m3,

[0022] wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.

[0023] In another embodiment, the present invention relates to a process for the preparation of a fresh concrete composition, comprising the mixing of:

[0024] from 350 kg / m3to 500 kg / m3of cement;

[0025] from 150 kg / m3to 650 kg / m3of pumice;from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and

[0026] a volume of mixing water in order for the total amount of water in the concrete composition to range from 150 kg / m3to 290 kg / m3,

[0027] wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.

[0028] According to another aspect, the present invention relates to a process for the preparation of a hardened concrete composition according to the invention, comprising:

[0029] (a) providing a fresh concrete composition, preferably obtained according to the process for the preparation of a fresh concrete composition as defined in the present invention;

[0030] (b) a step of setting and hardening the fresh concrete composition of step (a) to obtain a hardened concrete composition.

[0031] The present invention also relates to a process for the manufacture of a concrete marine float, comprising the steps:

[0032] (A) preparing a concrete composition, preferably a fresh concrete composition as defined in the present invention,

[0033] (B) pouring the concrete composition of step (A) into a mold,

[0034] (C) setting and hardening the concrete composition to obtain a buoyant concrete structure, and

[0035] (D) optionally, integrating a buoyancy floating element within the buoyant concrete structure of step (C).

[0036] The present invention relates to a concrete marine float comprising a hardened concrete composition based on a concrete composition as defined in the present invention, or obtained by the process for the manufacture of a hardened concrete composition as defined herein.

[0037] Finally, the present invention relates to the use of pumice for the preparation of concrete composition, or for manufacturing a concrete composition, a fresh concrete composition or a hardened concrete composition as defined in the present invention.

[0038] DETAILED DESCRIPTION OF THE INVENTIONCement: as used herein, cement refers to a mixture of Portland clinker, calcium sulphate and optionally one or more mineral components.

[0039] Calcium sulphate: includes gypsum (calcium sulphate dihydrate, CaSO4.2H2O), hemi-hydrate (CaSO4.1 / 2H2O), anhydrite (anhydrous calcium sulphate, CaSO4) and a mixture thereof. Calcium sulphate produced as a by-product of certain industrial processes may also be used. Preferably, the calcium sulphate content ranges from 0% to 5% by weight of the cement.

[0040] Mineral component: may designate slag (for example, as defined in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.2), pozzolanic materials (for example as defined in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.3), fly ash (for example, as described in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.4), calcined schists (for example, as described in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.5), material containing calcium carbonate, for example limestone (for example, as defined in the European NF EN 197-1 Standard paragraph 5.2.6), limestone components (for example, as defined in the “Concrete” NF P 18-508 Standard), silica fume (for example, as defined in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.7), siliceous components (for example, as defined in the “Concrete” NF P 18-509 Standard), metakaolin or mixtures thereof.

[0041] Concrete: Refers to a composition comprising a cement, sand and aggregates which in presence of water forms a mixture (herein referred to as “fresh concrete”) which sets and hardens by means of hydration reactions and processes and which, after hardening, retains its strength and stability even under water. Specifically, concrete is as defined in the standard NF EN 206+A1:2016.

[0042] In the present disclosure, Normal-Weight Concrete (NWC), refers to concrete having a dry density above 2200 kg / m3, preferably ranging from 2200 and 2400 kg / m3.

[0043] In the present disclosure, Light-Weight Aggregate Concrete (LWAC), refers to concrete having a dry density below 2200 kg / m3, preferably ranging from 1700 and 2100 kg / m3.

[0044] Fresh concrete: refers to a fully mixed concrete composition in a state which makes it possible to compact according to the selected method. Specifically, fresh concrete is as defined in the standard NF EN 206+A1:2016.Hardened concrete: refers to a concrete which is in a solid state, and which has developed a certain strength. Specifically, hardened concrete is as defined in the standard NF EN 206+A1:2016.

[0045] 1 cubic meter of concrete: refers to the quantity of fresh concrete which, after compacting according to the method defined in EN 12350-6, occupies a volume of 1 cubic meter.

[0046] Sand: refers to a natural, synthetic or recycled inorganic compound having a grain size which ranges from 0.063 mm to 4 mm. Preferably, the inorganic compound is selected from the group consisting of siliceous materials, calcareous materials and siliceous and calcareous materials. For the purposes of this application, sand, as defined herein, does not include pumice, as defined below.

[0047] Aggregates: refers to any natural, synthetic or recycled inorganic material which can be used for the preparation of concrete. Aggregates include coarse aggregates, notably gravel or crushed stone, having a particle size ranging from 4 mm to 32 mm.

[0048] Particle size distribution (PSD) is measured using the dry sieve analysis according to the European NF EN 933-1 standard of Mai 2012.

[0049] Pumice: refers to a porous, naturally occurring volcanic glass, with air-filled vesicles formed by the expansion of trapped gases when the molten lava is expelled into the air and flashcools having a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.

[0050] CONCRETE COMPOSITION

[0051] According to a first embodiment, the present invention relates to a concrete composition comprising:

[0052] - from 350 kg / m3to 500 kg / m3of cement;

[0053] - from 150 kg / m3to 650 kg / m3of pumice;

[0054] - from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and - from 200 kg / m3to 290 kg / m3of water,

[0055] wherein the pumice has a dry density ranging from 800 kg / m3to 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.According to another embodiment, the present invention relates to a concrete composition comprising:

[0056] - from 350 kg / m3to 500 kg / m3of cement;

[0057] - from 150 kg / m3to 650 kg / m3of pumice;

[0058] - from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and - from 200 kg / m3to 290 kg / m3of water,

[0059] wherein the pumice has a dry density ranging from 800 kg / m3to 1800 kg / m3, and at least 90 wt.% of the pumice passes through a 6.3 mm sieve, and / or between 30 wt.% and 50 wt.% of the pumice passes through a 1 mm sieve, based on the total weight of the dry pumice.

[0060] Advantageously, the pumice allows the preparation of concrete which develops, upon mixing with water and curing, a dry density, ranging from 1700 kg / m3and 2200 kg / m3,preferably a dry density from 1800 kg / m3to 2100 kg / m3.

[0061] Advantageously, the concrete composition of the present invention, upon mixing with water and curing, displays a 28-day compressive strength higher than or equal to 55 MPa, preferably higher than 60 MPa.

[0062] Furthermore, the concrete composition obtained using the pumice of the present invention displays a similar, preferably improved, durability in marine environments. In particular, the concrete composition obtained using the pumice of the present invention displays an improved resistance to chloride attack compared to concrete compositions with comparable density using other light weight aggregates or even concrete compositions with higher densities.

[0063] The concrete composition is particularly suitable for the production of concrete marine floats.

[0064] a. Cement

[0065] The cement used in the concrete composition according to the invention is preferably the cement that comprises from 35 wt.% to 95 wt.% of Portland clinker, based on the dry weight of the cement. Preferably, the cement comprises from 65 wt.% to 95 wt.% of Portland clinker, based on the dry weight of the cement.Preferably the cement used in the concrete composition of the present invention further comprises calcium sulfate.

[0066] Preferably the cement in the concrete composition according to the invention is CEM I, CEM II, CEM III, CEM IV or CEM V according to the standard NF-EN-197-1 of April 2012, or the standard NF EN 197-5 published in May 2021.

[0067] Preferably the cement in the concrete composition comprises from 35 wt.% to 65 wt.% of one or more mineral components, preferably granulated blast furnace slag, based on the dry weight of the cement.

[0068] Preferably, the cement used in the concrete composition according to the invention is a CEM III cement, or a mixture of different cement types, for example those described according to the standard NF-EN-197-1 of April 2012, or in the standard NF EN 197-5 published in May 2021.

[0069] Generally, the weight ratio of cement to the total amount of mineral components ranges from 30 / 80 to 45 / 70.

[0070] The content of cement in the concrete composition generally ranges from 350 kg / m3to less than 500 kg / m3.

[0071] b. Pumice

[0072] The concrete composition of the present invention further comprises pumice.

[0073] In the present invention, the pumice has a maximum particle size ranging from 0 to 15 mm, preferably from 0 to 12.5 mm, and still more preferably from 0.1 to 12.5 mm as determined by sieve analysis.

[0074] According to an embodiment, at least 90 wt.% of the pumice passes through a 6.3 mm sieve, and / or between 30 wt.% and 50 wt.% of the pumice passes through a 1 mm sieve, based on the total weight of the dry pumice.

[0075] The particle size distribution of the pumice according to the invention is shown in Table 1 below:Table 1: Pumice particle size distribution

[0076] Sieve

[0077] 12.5 8 6.3 4 3.15 2 1 0.5 0.25 0.125 0.063 (mm)

[0078] Passing

[0079] 100 99 95 77 79 55 39 28 20 14 9.4 (%)

[0080]

[0081] The density of dry pumice ranges from 800 to 1800 kg / m3, preferably from 1000 to 1700 kg / m3, and more preferably from 1200 to 1500 kg / m3. Generally, the density of humid pumice ranges from 1350 to 1650 kg / m3.

[0082] “Humid pumice” refers to pumice in which pore spaces, both intergranular and intragranular, are substantially filled with water.

[0083] Generally, pumice displays a content of silicon dioxide (SiO?) ranging from 50% to 80%.

[0084] The content of pumice in the concrete composition generally ranges from 150 kg / m3to 650 kg / m3.

[0085] The content of pumice in the concrete composition refers to dry pumice, i.e. pumice which water content is lower than or equal to 2 wt.% based on the total weight of the dry pumice.

[0086] c. Aggregates and / or sand

[0087] The concrete composition of the present invention further comprises aggregates and / or sand.

[0088] The content of aggregates and / or sand in the concrete composition generally ranges from 500 kg / m3to 1500 kg / m3.

[0089] The content of aggregates and / or sand in the concrete composition refers to dry aggregates and / or sand, i.e. aggregates and / or sand which water content is (respectively) lower than or equal to 2 wt.% based on the total weight of the dry aggregates and / or sand.

[0090] Generally, the aggregates and / or sand used for the preparation of the concrete composition of the invention are normal-weight aggregates and / or sand.Generally, the density of dry aggregates and / or sand ranges from 2200 to 3000 kg / m3, preferably from 2500 to 2700 kg / m3.

[0091] According to the present invention, the concrete composition comprises aggregates and / or sand. The ratio of sand / aggregates can range from 0 / 100 to 100 / 0, preferably from 0 / 100 to 40 / 60.

[0092] d. Optional constituents of concrete composition

[0093] According to the present invention, the cement used in the for the preparation of the concrete composition may comprise one or more admixtures selected from the group consisting of plasticizer, superplasticizer, defoamer, filler, fiber, retarder, accelerator, viscosity-modifying agent, for example one of those described in the EN 934-2 standard as of September 2002, EN 934-3 standard as of November 2009 or EN 934-4 as of August 2009.

[0094] According to an embodiment of the present invention, the cement used for the preparation of the concrete composition may comprise one or more accelerators. In the present invention the accelerator may be selected from the group consisting of calcium formate, calcium nitrates, calcium nitrites, silicate-based products, organic-based products and nanomaterials. According to the present invention, the amount of accelerator in the concrete may be lower or equal to 0.5 wt.% based on the weight of cement. According to the present invention, the amount of accelerator in the concrete composition may be higher or equal to 5.0 wt.% based on the weight of cement.

[0095] According to an embodiment of the present invention, the cement used for the preparation of the concrete composition may comprise one or more viscosity-modifying agents. According to the present invention, the amount of viscosity-modifying agent in the concrete composition may be lower or equal to 0.005 wt.% based on the weight of cement. According to the present invention, the amount of viscosity-modifying agent in the concrete composition may be higher or equal to 0.05 wt.% based on the weight of cement.

[0096] According to the present invention, the concrete composition may further comprise at least one mineral filler. The mineral filler may be limestone. Preferably the concrete composition can comprise from 0 to 150 kg / m3, preferably from 1 to 150 kg / m3.The present invention further relates to a concrete composition having a dry density, after curing for 90 days, ranging from 100 kg / m3and 2200 kg / m3. Advantageously, the obtained concrete composition displays a 28-day compressive strength higher than or equal to 55 Mpa.

[0097] e. Water

[0098] The amount of water in the concrete composition in the fresh state may be characterized by the water-cement ratio (w / c).

[0099] The water-cement ratio is typically defined as the ratio of the weight of water to the weight of cement used for the preparation of a concrete composition in a fresh state.

[0100] In the concrete composition of the present invention, the water-cement may be at least 0.35, preferably ranges from 0.38 and 0.45.

[0101] The amount of water used in the preparation of the concrete composition of the present invention depends on the water content of the pumice, the aggregates, and / or sand used in the concrete composition.

[0102] Therefore, the total amount of water used for the preparation of the concrete composition of the present invention comprises the amount of water present in the pumice, the aggregates, and / or sand used and the amount of mixing water added for the preparation of the fresh concrete.

[0103] In the concrete composition of the present invention, the total amount of water is from 150 kg / m3to 290 kg / m3.

[0104] Advantageously, the hardened concrete composition of the present invention satisfies the requirements in terms of compressive strength while having a lower density. In particular, the hardened concrete composition of the present invention displays a 28-day compressive strength higher than or equal to 55 Mpa, more preferably higher or equal than 60 Mpa. The hardened concrete composition of the present invention has a dry density ranging from 1700 to 2200 kg / m3.

[0105] Furthermore, the hardened concrete composition of the present invention displays a similar, preferably improved, durability in marine environments. In particular, the hardened concrete composition of the present invention displays an improved resistance to chloride attack compared to other light-weight aggregate concrete. Preferably, while hardenedconcrete composition of the present invention displays a lower density and an increased porosity, the hardened concrete composition shows an improved resistance to chlorine attack in marine environments compared to conventional concrete.

[0106] The concrete composition of the present invention is therefore particularly suited for the manufacture of concrete marine floats.

[0107] PROCESS OF MANUFACTURE

[0108] The invention also relates to a process for the preparation of a concrete composition according to the invention, comprising the mixing of:

[0109] from 350 kg / m3to 500 kg / m3of cement;

[0110] from 150 kg / m3to 650 kg / m3of pumice;

[0111] from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and

[0112] a volume of mixing water in order for the total amount of water in the concrete composition to range from 150 kg / m3to 290 kg / m3,

[0113] wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.

[0114] In another embodiment, the invention relates to a process for the preparation of a concrete composition, comprising the mixing of:

[0115] from 350 kg / m3to 500 kg / m3of cement;

[0116] from 150 kg / m3to 650 kg / m3of pumice;

[0117] from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and

[0118] a volume of mixing water in order for the total amount of water in the concrete composition to range from 150 kg / m3to 290 kg / m3,

[0119] wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and at least 90 wt.% of the pumice passes through a 6.3 mm sieve, and / or between 30 wt.% and 50 wt.% of the pumice passes through a 1 mm sieve, based on the total weight of the dry pumice.

[0120] According to an embodiment, the present invention relates to a process for the preparation of a fresh concrete composition, comprising the mixing of:

[0121] from 350 kg / m3to 500 kg / m3of cement;

[0122] from 150 kg / m3to 650 kg / m3of pumice;from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and

[0123] a volume of mixing water in order for the total amount of water in the concrete composition to range from 150 kg / m3to 290 kg / m3,

[0124] wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis, and / or and at least 90 wt.% of the pumice passes through a 6.3 mm sieve, and / or between 30 wt.% and 50 wt.% of the pumice passes through a 1 mm sieve, based on the total weight of the dry pumice .

[0125] According to a particular embodiment, the process for the preparation of a concrete composition, preferably a fresh concrete composition, comprises the steps of :

[0126] (i) providing from 150 kg / m3to 650 kg / m3of pumice having a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis, and / or and at least 90 wt.% of the pumice passes through a 6.3 mm sieve, and / or between 30 wt.% and 50 wt.% of the pumice passes through a 1 mm sieve, based on the total weight of the dry pumice ;

[0127] (ii) mixing the pumice with from 350 kg / m3to 500 kg / m3of cement, from 500 kg / m3to 1500 kg / m3of aggregates and / or sand and a volume of mixing water in order for the total amount of water in the fresh concrete composition to range from 150 kg / m3to 290 kg / m3.

[0128] According to a particular embodiment, the pumice of step (i), the aggregates and / or the sand contain water. Hence the person skilled in the art is capable of adapting the volume of mixing water to be added in step (ii).

[0129] The person skilled in the art determines the amount of water already present in the pumice, the aggregates and the sand, and adjusts the required volume of mixing water.

[0130] According to another particular embodiment, the process for the preparation of a concrete composition, preferably a fresh concrete composition, further comprises a step, between step (i) and (ii), wherein the pumice of step (i) is mixed with from 40 kg / m3to 150 kg / m3of water to obtain a humid pumice.

[0131] The person skilled in the art can then adapt the required amount of mixing water to be added in step (ii).Therefore, according to this particular embodiment, the process for the preparation of a concrete composition, preferably a fresh concrete composition comprises the steps of :

[0132] (i) providing from 150 kg / m3to 650 kg / m3of pumice having a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis, and / or and at least 90 wt.% of the pumice passes through a 6.3 mm sieve, and / or between 30 wt.% and 50 wt.% of the pumice passes through a 1 mm sieve, based on the total weight of the dry pumice;

[0133] (ii) mixing the pumice of step (i) with from 40 kg / m3to 150 kg / m3of water to obtain a humid pumice; and

[0134] (iii) mixing the humid pumice with from 350 kg / m3to 500 kg / m3of cement, from 500 kg / m3to 1500 kg / m3of aggregates and / or sand and a volume of mixing water in order for the total amount of water in the fresh concrete composition to range from 150 kg / m3to 290 kg / m3.

[0135] The invention also relates to a process for the preparation of a hardened concrete composition according to the invention, comprising:

[0136] (a) providing a fresh concrete composition, preferably obtained according to the process for the preparation of a fresh concrete composition of the present invention;

[0137] (b) a step of setting and hardening the fresh concrete composition of step (a) to obtain a hardened concrete composition.

[0138] Preferably the hardened concrete composition displays a 28-day compressive strength of at least 55 MPa, preferably higher than or equal to 60 MPa.

[0139] Preferably the hardened concrete composition has a chlorine resistivity of at least 400 Q.m, preferably at least 500 Q.m at 90 days.

[0140] The invention also relates to a process for the manufacture of a concrete marine float, comprising the steps:

[0141] (A) preparing a concrete composition as defined inthe present invention,

[0142] (B) pouring the concrete composition of step (A) into a mold,

[0143] (C) setting and hardening the concrete composition to obtain a buoyant concrete structure, and

[0144] (D) optionally, integrating a buoyancy floating element within the buoyant concrete structure of step (C).CONCRETE MARINE FLOAT

[0145] The present invention relates to a concrete marine float comprising a hardened concrete composition based on a concrete composition as defined in the present invention, or obtained by the process for the manufacture of a hardened concrete composition as defined herein.

[0146] According to a particular embodiment, the hardened concrete composition used in the preparation of the concrete marine float comprises the pumice as defined previously.

[0147] According to the present invention, the cement, pumice, and aggregates and / or sand are as defined previously.

[0148] The concrete composition used for the preparation of the concrete marine float may comprise one or more admixtures selected from the group consisting of plasticizer, superplasticizer, defoamer, filler, fiber, retarder, accelerator, viscosity-modifying agent, for example one of those described in the EN 934-2 standard as of September 2002, EN 934-3 standard as of November 2009 or EN 934-4 as of August 2009.

[0149] According to an embodiment of the present invention, the concrete composition may comprise one or more plasticizers. According to the present invention, the amount of plasticizer in the concrete composition may be lower or equal to 0.5 wt.% based on the weight of cement. According to the present invention, the amount of plasticizer in the concrete composition may be higher or equal to 2.5 wt.% based on the weight of cement.

[0150] According to an embodiment of the present invention, the concrete composition may comprise one or more superplasticizers.

[0151] The superplasticizers may be in liquid form with a solid content comprised between 10 and 60 wt.%, preferably between 20 and 40 wt.% based on the weight of cement. According to the present invention, the amount of superplasticizer in the concrete composition may be lower or equal to 0.2 wt.% based on the weight of cement. According to the present invention, the amount of superplasticizer in the concrete composition may be higher or equal to 2.0 wt.% based on the weight of cement.According to an embodiment of the present invention, the concrete composition may comprise one or more accelerators. In the present invention the accelerator may be selected from the group consisting of calcium formate, calcium nitrates, calcium nitrites or silicate-based products. According to the present invention, the amount of accelerator in the concrete composition may be lower or equal to 0.5 wt.% based on the weight of cement. According to the present invention, the amount of accelerator in the concrete composition may be higher or equal to 5.0 wt.% based on the weight of cement.

[0152] According to an embodiment of the present invention, the concrete composition may comprise one or more viscosity-modifying agents. According to the present invention, the amount of viscosity-modifying agent in the concrete composition may be lower or equal to 0.005 wt.% based on the weight of cement. According to the present invention, the amount of viscosity-modifying agent in the concrete composition may be higher or equal to 0.05 wt.% based on the weight of cement.

[0153] Mixing water

[0154] The mixing water is the water required to hydrate the cement to provide the fluidity to the concrete obtained in the fresh state. The water retained by the various components of the concrete is not taken into account in the mixing water because it does not participate in the hydration of the cement.

[0155] The amount of mixing water added for the preparation of the concrete marine float of the present invention depends on the water content of the pumice, the aggregates, and / or sand used in the binder preparation.

[0156] Therefore, the total amount of water used for the preparation of the concrete marine float of the present invention comprises the amount of water present in the pumice, the aggregates, and / or sand used and the amount of mixing water added for the preparation of the fresh concrete.

[0157] The amount of water in the concrete composition used for the preparation of the concrete marine float may be characterized by the water-cement ratio (w / c).

[0158] The water-cement ratio is typically defined as the ratio of the weight of water to the weight of cement used for the preparation of fresh concrete.In the concrete used for the preparation of the concrete marine float of the present invention, the water-cement may be at least 0.35, preferably ranges from 0.38 and 0.45.

[0159] In the concrete marine float of the present invention, the total amount of water used is from 150 kg / m3to 290 kg / m3.

[0160] Advantageously, the concrete marine float of the present invention satisfies the requirements in terms of compressive strength while having a lower density. In particular, the concrete used for the preparation of the concrete marine float of the present invention displays a 28-day compressive strength higher than or equal to 55 MPa, more preferably higher or equal than 60 MPa. The concrete used for the preparation of the concrete marine float of the present invention has a dry density ranging from 1700 to 2200 kg / m3.

[0161] Furthermore, the concrete composition used for the preparation of the concrete marine float of the present invention displays a similar, preferably improved, durability in marine environments. In particular, the concrete composition used for the preparation of the concrete marine float of the present invention displays an improved resistance to chloride attack compared to other light-weight aggregate concrete. Preferably, while the concrete marine float of the present invention displays a lower density and an increased porosity, the concrete marine float shows an improved resistance to chlorine attack in marine environments compared to conventional concrete used for the preparation of marine floats.

[0162] The present invention relates to the use of concrete composition as defined in the present invention for the manufacture of a concrete marine float as defined in the present invention.

[0163] Finally, the present invention relates to the use of pumice for the preparation of a concrete composition or concrete marine float or for the manufacture of a fresh or hardened concrete composition as defined in the present invention.

[0164] Examples:

[0165] Density:

[0166] The dry density of concrete is measured according to the standard NF P 18-459 of August 2022.

[0167] The dry density of aggregates and / or sand is understood as density according to EN 12620+A1 : 2008. The dry density of pumice is understood as density according to EN 13055:2016. Both values (dry density of aggregates and of pumice) are measured according to EN 1097-6: 2022.

[0168] Compressive strength:

[0169] The compressive strength is measured on concrete cylinders having a diameter of 113 mm, according to the NF EN 12390-1 standard of February 2003. The compressive strength procedure followed the EN 12390-3:2019 standard.

[0170] Open Porosity:

[0171] Open porosity was measured on concrete disks cut from the 110 mm cylinders according to the NF P18-459 standard of March 2010.

[0172] Elastic modulus: The elastic modulus was measured according to the standard EN 12390-13 of February 2013.

[0173] Corrosion risk:

[0174] Two measurements were used to prove the claimed solution provides improved corrosion protection of steel in concrete. Apparent chloride diffusion coefficient (DRCM) was calculated from the chloride migration test as performed according to XP P18-462 standard of December 2022. The tests were conducted at the age of 90 days on 50 mm thick concrete disks cut from the 100 mm cylinders cured in water. The DRCM calculations were performed as per Section 8 of this standard.

[0175] Surface resistivity measurements were conducted according to EN 12390-19: 2021 standard on 110 mm concrete cylinders after 90 days of curing in water using Proceq Resipod equipment.

[0176] Table 2: Corrosion risk level assessment in terms of resistivity and chloride migration Surface resistivity p Apparent chloride diffusion

[0177] Corrosion risk level [Q-m] coefficient DRCM 10'12[m2 / s]

[0178] <100 >13 High 100-500 13-1 Moderate 500-1000 1-0.4 Low

[0179] >1000 <0.4 Negligible

[0180]

[0181] Table 2 shows the relationship between the chloride diffusion coefficient and the concrete surface resistivity, and their impact on the risk of steel corrosion in concrete.For a chloride diffusion coefficient below 0.4, the risk of corrosion is considered to be negligible.

[0182] Various concrete compositions were prepared, which compositions are shown in Table 3.

[0183] 5

[0184] Table 3: Compositions of concrete mixtures in kg / m3

[0185] CO C3 C4 Raw Material C1 (invention) C2 (invention)

[0186] (Comparative) (Comparative) (Comparative) Cement 430 430 430 430 430 Aggregates 965 875 706 0 803 Limestone filler 85 85 85 85 85 Sand 743 329 0 726 0 Pumice 0 263 507 0 0 Fine Expanded 430

[0187] 0 0 0 0

[0188] clay

[0189] Coarse Expanded 0

[0190] 0 0 0 494

[0191] clay

[0192] Water* 195 239 279 312 263 w / c 0.402 0.402 0.402 0.402 0.402

[0193]

[0194] * water refers to the total amount of water in the compositions

[0195] The cement is a CEM lll / A 42.5N.

[0196] 10 The expanded clay used in example C3 is coarse expanded clay sold under the commercial name Argex NV, AM 4 / 8-700, having the following properties: dry density 1378 kg / m3, particle size ranging from 4 to 8 mm.

[0197] The expanded clay used in example C4 is fine expanded clay sold under the commercial name ARGEX NV, AR 0 / 4-650, having the following properties: dry density 1290 kg / m3,

[0198] 15 particles ranging from 0.063 mm to 4 mm.

[0199] The pumice has a dry density of 1283 kg / m3.

[0200] The concrete compositions display the properties shown in Tables 4 and 5:Table 4: Properties of concrete compositions

[0201] Compressive Strength Elastic modulus

[0202] Dry DRCM (MPa) (GPa) Water

[0203] density (W Por127- 28- 90- osity (%) (kg / m3) m2 / s) day day day

[0204] CO 2312 58.2 81.5 91.7 40.6 11 0.72 C1 2045 49.3 64.7 73.1 32.0 15 0.57 C2 1857 49.3 61.8 69.0 26.8 20 0.40 C3 1911 49.3 58.1 62.3 26.1 20 1.30 C4 1817 - 46.7 51.1 20.1 26 0.56

[0205]

[0206] Table 5: Resistivity

[0207] Resistivity (Q.m)

[0208] 28-day 42-day 56-day 90-day CO 251 315 355 405 C1 278 381 434 592 C2 224 318 393 519 C3 177 207 254 293 C4 181 230 262 314

[0209]

[0210] The results demonstrate that the inventive concrete compositions (C1 and C2) have an improved compressive strength at 7, 28 and 90 days, and have a low risk of corrosion. Surprisingly, the results show that the increased addition of pumice leads to an improvement of the resistance to chloride attack, despite the increased porosity.

[0211] Examples C3 and C4, which both utilize expanded clay, demonstrate that a finer particle size (C4), does not provide an improvement in terms of compressive strength. The expanded clay is however similar in size to pumice and dry density. Although good durability can be achieved, the compressive strength properties cannot be achieved when using expanded clay (C4).These examples demonstrate that the addition of pumice is better compared to other lightweight aggregate concrete.

Claims

CLAIMS1. A concrete composition, comprising:- from 350 kg / m3to 500 kg / m3of cement;- from 150 kg / m3to 650 kg / m3of pumice;- from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; and- from 150 kg / m3to 290 kg / m3of water,wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.

2. The concrete composition of claim 1 , wherein the cement comprises Portland clinker in an amount from 35 wt.% to 95 wt.%, preferably from 65 wt.% to 95 wt.%, based on the dry weight of the cement.

3. The concrete composition of claims 1 or 2, wherein the cement further comprises from 35 wt.% to 65 wt.% of one or more mineral components, preferably granulated blast furnace slag, based on dry weight of the cement.

4. The concrete composition of claims 1 to 3 wherein at least 90 wt.% of the pumice passes through a 6.3 mm sieve, and / or between 40 wt.% and 50 wt.% of the pumice passes through a 1 mm sieve, based on the total weight of the pumice.

5. The concrete composition of any one of claims 1 to 4 wherein the pumice has a dry density ranging from 1000 to 1700 kg / m3, preferably from 1200 to 1500 kg / m3.

6. The concrete composition of any one of claims 1 to 5 wherein the cement further comprises one or more admixtures selected from the group consisting of plasticizer, superplasticizer defoamer, filler, fiber, retarder, accelerator, viscosity-modifying agent.

7. The concrete composition of any one of claims 1 to 6 further comprising from 0 to 150 kg / m3of a limestone, preferably from 1 to 150 kg / m3.

8. The concrete composition of any one of claims 1 to 7, wherein the water to cement weight ratio is from 0.35 to 0.45.

9. A process for the preparation of a concrete composition as defined in any one of claims 1 to 8, comprising the mixing of:from 350 kg / m3to 500 kg / m3of cement;from 150 kg / m3to 650 kg / m3of pumice;from 500 kg / m3to 1500 kg / m3of aggregates and / or sand; anda volume of mixing water in order for the total amount of water in the concrete composition to range from 150 kg / m3to 290 kg / m3,wherein the pumice has a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis.

10. The process for the preparation of a concrete composition according to claim 9 comprising the steps of :(i) providing from 150 kg / m3to 650 kg / m3of pumice having a dry density comprised between 800 kg / m3and 1800 kg / m3, and a maximum particle size ranging from 0 to 15 mm as determined by sieve analysis;(ii) mixing the pumice of step (i) with from 40 kg / m3to 150 kg / m3of water to obtain a humid pumice; and(iii ) mixing the humid pumice with from 350 kg / m3to 500 kg / m3of cement, from 500 kg / m3to 1500 kg / m3of aggregates and / or sand and a volume of mixing water in order for the total amount of water in the fresh concrete composition to range from 150 kg / m3to 290 kg / m3.

11. A process for the preparation of a hardened concrete composition a, comprising:(a) providing a concrete composition obtained according to the process for the preparation of a concrete composition as defined in claim 9;(b) a step of setting and hardening the concrete composition of step (a) to obtain a hardened concrete composition.

12. A process for the manufacture of a concrete marine float, comprising the steps: (A) preparing a concrete composition according to any one of claims 1 to 8,(B) pouring the concrete composition of step (A) into a mold,(C) setting and hardening the concrete composition to obtain a buoyant concrete structure, and(D) optionally, integrating a buoyancy floating element within the buoyant concrete structure of step (C).

13. Use of pumice for the preparation of concrete composition as defined in claims 1 to 8, or for manufacturing the concrete composition as defined in claim 9, or the hardened concrete composition as defined in claim 11 for the manufacturing of a concrete marine float.

14. Use of a concrete composition as defined in any one of claims 1 to 8 for the manufacturing of a concrete marine float.

15. A concrete marine float comprising a hardened concrete composition based on a concrete composition as defined in any one of claims 1 to 8, or obtained by the process for the manufacture of a hardened concrete composition as defined in claim 11.

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