Low-cement concrete

Abstract

Low-cement concrete. The present invention relates to a fresh concrete composition comprising at least: i) a hydraulic binder comprising: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder, - 45% to 75% by weight of filler relative to the total weight of said binder, and - 5% to 15% by weight of ultrafine aggregate relative to the total weight of said binder, being selected from hydraulic admixtures, pozzolanic admixtures, ultrafine cements and mixtures thereof, ii) at least one superplasticizer or plasticizer, iii) water, and iv) aggregates. Figure for the abstract: None

Description

Title of the invention: Low-cement concrete technical field

[0001] The present invention relates to a structural concrete formulated from a binder with a low clinker and high filler content, in particular having a fluid consistency in the fresh state. The invention also relates to a method for manufacturing such concrete. Previous technique

[0002] The use of cement concrete, conventionally considered as structural concrete, poses a concern in terms of environmental impact. More specifically, this type of concrete requires the application of a Portland cement-based binder to agglomerate a mixture of aggregates and sand. However, the manufacture of clinker, an essential component of Portland cement, contributes significantly to CO2 emissions.

[0003] In order to reduce CO2 emissions related to concrete production, it has been proposed to partially replace clinker with one or more alternative materials such as blast furnace slag, fly ash, silica fume, metakaolin, or even limestone or siliceous fillers. However, a significant substitution of clinker content generally has the effect of negatively impacting the properties of structural concrete, particularly its mechanical strength and durability. The reactivity of these alternative materials therefore usually determines their substitution rate in structural concrete to maintain the required quality levels. For example, blast furnace slag, which is a latent hydraulic binder, allows for high replacement rates, up to more than 80%. However, the slag resource, already used in concrete, is limited.Fly ash, for its part, has a pozzolanic effect that allows for a clinker replacement rate of up to approximately 50%. Here again, resources are limited and will eventually disappear due to the harmful environmental impact of thermal power plants. Regarding ultrafine additives used in concrete, such as silica fume or metakaolin, they are usually incorporated in small quantities, for example, 5% to 20% of the binder mass, due to their cost and their higher water requirement compared to cement. As for other common additives such as limestone or siliceous fillers, these are virtually inert and therefore do not allow for a significant reduction in clinker content.

[0004] The report “Eco-efficient cements: Potential, economically viable solutions for a low-CO2, cement-based materials industry”, published by UNEP (United Nations Environment Programme) in 2016, proposes the use of calcined clays, in particular metakaolin, combined with limestone filler to replace up to 50% of the clinker. Thus, Antoni et al. [1] propose mortar formulations in which cement is partially replaced by a mixture of metakaolin and limestone filler in a metakaolin:limestone filler weight ratio of 2:1 and in a water / binder ratio of 0.5. However, the proportion of ultrafines in these compositions is high, implying a high cost and a high water demand.

[0005] Finally, low-cement concrete compositions using a very low water content were also proposed in WO 2007 / 132098. However, fresh concrete obtained from such compositions does not exhibit the fluidity, and in particular the viscosity, required for use on construction sites.

[0006] There therefore remains a need for a low clinker content concrete that does not have the disadvantages of the prior art.

[0007] In particular, there remains a need for a low clinker content concrete having on the one hand a fluid consistency and low viscosity in the fresh state, allowing its use on construction sites, in particular for its transport and / or placement, and on the other hand a mechanical resistance allowing it to be used as structural concrete.

[0008] There also remains a need for a low-cost, low-clinker concrete.

[0009] The invention aims precisely to provide a low-clinker, high-filler concrete that meets these requirements. In particular, it aims to provide a new low-clinker concrete composition that effectively improves the compromise between, on the one hand, workability, combined with high fluidity and low viscosity, of the fresh concrete, and on the other hand, the mechanical strength of the hardened concrete.

[0010] Contrary to expectations, the inventors found that these objectives can be achieved via a composition according to the invention. Description of the invention

[0011] Thus, the present invention relates, according to a first aspect, to a fresh concrete composition comprising at least: i) 350 kg / m3 to 550 kg / m3 of hydraulic binder, referred to as binder, comprising: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder and whose particles have a D50 greater than 11 pm and a Blaine specific surface area less than or equal to 5500 cm2 / g, - 45% to 75% by weight as filler relative to the total weight of said binder, and whose particles have a D70 less than or equal to 63 pm, and - 5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder and whose particles have a specific surface area BET greater than or equal to 5 m2 / g or a D50 less than or equal to 8 pm, and being chosen from hydraulic additions, pozzolanic additions, ultrafine cements and their mixtures, ii) at least 0.05% by weight, expressed as dry extract relative to the total weight of said binder, of superplasticizer or plasticizer, iii) water in a water / binder mass ratio varying from 0.3 to 0.45, and iv) aggregates.

[0012] By "fresh concrete" we mean concrete as obtained after mixing its various constituents and before it sets, that is to say, concrete which has the capacity to deform and / or flow.

[0013] The inventors have thus developed an original fresh concrete mix for producing low-clinker concrete. This mix is ​​advantageous in several respects. As the examples below will show, it provides a good compromise between mechanical strength on the one hand, and the fluidity and viscosity of the fresh concrete on the other. Furthermore, it produces concrete with significantly reduced CO2 emissions compared to traditional concrete due to the low clinker content, and the reduction of water in the concrete mix further optimizes the environmental performance of the mix. Finally, such concrete can be advantageously used as structural concrete and can achieve strength classes of at least C25 / 30, or even C30 / 37.In particular, the selection of the components of the ternary mixture forming the binder and their proportions allows, by adjusting the water / binder ratio and the superplasticizer(s) or plasticizer(s), to obtain a fresh concrete composition whose paste, separating the aggregates, has a volume and viscosity adapted to achieve a fluid consistency as required for use on a construction site, while promoting binder reactivity and granular packing to achieve excellent mechanical strength properties after setting and at 28 days.

[0014] The invention also relates to the use of a hydraulic binder, in particular as described in the present invention, comprising: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder and whose particles have a D50 greater than 11 pm and a Blaine specific surface area less than or equal to 5500 cm2 / g, - 45% to 75% by weight as filler relative to the total weight of said binder, and whose particles have a D70 less than or equal to 63 pm, and -5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder and whose particles have a specific surface area BET greater than or equal to 5 m2 / g or a D50 less than or equal to 8 pm, and being chosen from hydraulic additions, pozzolanic additions, ultrafine cements and their mixtures, and having a clinker / filler weight ratio of at least 0.32, to form fresh concrete having an Abrams cone slump greater than or equal to 160 mm, preferably greater than or equal to 180 mm, measured according to standard NF EN 12350-2 at a temperature of 20°C after mixing, and a viscosity less than or equal to 9 seconds, preferably less than or equal to 6 seconds, measured by the inverted cone method according to standard XP PI8-469 at a temperature of 20°C after mixing.

[0015] The hydraulic binder is particularly advantageous for forming fresh concrete of fluid consistency and low viscosity, corresponding to the properties required for pouring concrete on a construction site or as prefabricated elements.

[0016] The invention also relates to the use of a fresh concrete composition, in particular according to the invention, comprising at least: i) a hydraulic binder comprising: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder and whose particles have a D50 greater than 11 pm and a Blaine specific surface area less than or equal to 5500 cm2 / g, - 45% to 75% by weight as filler relative to the total weight of said binder, and whose particles have a D70 less than or equal to 63 pm, and -5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder and whose particles have a specific surface area BET greater than or equal to 5 m2 / g or a D50 less than or equal to 8 pm, and being chosen from hydraulic additions, pozzolanic additions, ultrafine cements and their mixtures, ii) at least one superplasticizer or plasticizer, iii) water and (iv) aggregates, and whose slump on the Abrams cone test is greater than or equal to 160 mm, measured according to standard NF EN 12350-2 at a temperature of 20°C after mixing, and whose viscosity is less than or equal to 9 seconds, measured by the inverted cone test method according to standard XP P18-469 at a temperature of 20°C after mixing, to form a hardened concrete having a compressive strength greater than or equal to 25 MPa, preferably greater than or equal to 30 MPa, measured on rollers according to standard NF EN 12390-3, 28 days after contacting said binder with water.

[0017] In addition to possessing the fluid consistency and low viscosity properties required in the fluid state for use on a construction site or for pre-construction In the preparation of prefabricated elements, the composition of fresh concrete allows the formation of hardened concrete possessing the mechanical properties required for structural concrete.

[0018] The invention relates to a method for preparing hardened concrete comprising the application of a hydraulic binder comprising: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder and whose particles have a D50 greater than 11 pm and a Blaine specific surface area less than or equal to 5500 cm2 / g, - 45% to 75% by weight as filler relative to the total weight of said binder, and whose particles have a D70 less than or equal to 63 pm, and -5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder and whose particles have a specific surface area BET greater than or equal to 5 m2 / g or a D50 less than or equal to 8 pm, and being chosen from hydraulic additions, pozzolanic additions, ultrafine cements and their mixtures, and whose clinker / filler weight ratio is at least 0.32.

[0019] The binder can be used in the form of a fresh concrete composition according to the invention. In particular, the process uses a fresh concrete composition having the flow properties described above, and makes it possible to obtain structural concrete.

[0020] The process for preparing hardened concrete can advantageously be implemented on a construction site.

[0021] The uses and the method according to the invention are particularly advantageous for forming a structural element such as a pile, a diaphragm wall, a footing, a stringer, a slab, a floor, a column, a beam or a wall.

[0022] Finally, the invention relates to a hardened concrete obtained from the composition of fresh concrete according to the invention or obtained from the process according to the invention.

[0023] The adjective "dry" characterizes a material devoid of water.

[0024] In the following text, weight ratios are expressed in dry extract.

[0025] For the purposes of the invention, the expression "compound content", for example "content of "Filler" covers the application of a single filler or a mixture of several fillers. Detailed description i) Hydraulic binder

[0026] The composition of fresh concrete comprises from 350 kg / m3 to 550 kg / m3 of hydraulic binder. The quantity of hydraulic binder varies according to the type of concrete considered and its adjustment clearly falls within the expertise of a person skilled in the art.

[0027] For example, for self-compacting concrete, the hydraulic binder content is higher than for conventional concrete, and in particular in the order of 450 kg / m3 to 550 kg / m3.

[0028] According to another embodiment, the composition of fresh concrete can comprise from 350 kg / m3 to 450 kg / m3 of hydraulic binder.

[0029] In the rest of the text, the hydraulic binder is also referred to as the binder. A) Portland Clinker

[0030] Portland clinker, also referred to in this description as clinker, can be used in the form of isolated Portland clinker and / or in the form of Portland cement. Preferably, the clinker is used in the form of Portland cement, in particular chosen from among the cements defined in the European standard NF EN 197-1, in particular of type CEM I, CEM II, CEM III, CEM IV or CEM V.

[0031] Preferably, the clinker is implemented in the form of a Portland cement chosen from CEM I and CEM II / A.

[0032] A CEM I comprises at least 95% clinker. A CEM II / A comprises at least 80% clinker. For example, CEM I and CEM II / A may further comprise a material selected from slags, silica fume, pozzolans, fly ash, calcined shale, limestone, and mixtures thereof. CEM II may be a CEM II / AS, a CEM II / AD, a CEM II / AP, a CEM II / AQ, a CEM II / AV, a CEM II / AW, a CEM II / A-T, a CEM II / AL, a CEM II / A-LL, or a CEM II / AM.

[0033] In particular, the clinker is implemented in the form of a Portland cement chosen from CEM I, CEM II / AL, CEM II / A-LL and their mixtures, preferably in the form of a CEM I, in particular a CEM I 52.5 N.

[0034] For example, the binder may comprise from 20% to 40% by weight of CEM I relative to the total weight of said binder.

[0035] The clinker particles have a D50 greater than 1 Ipm, preferably greater than or equal to 12 pm, more preferably ranging from 12 pm to 25 pm, in particular from 12 pm to 20 pm.

[0036] In particular, the clinker particles have a D90 greater than or equal to 30 pm.

[0037] In particular, the clinker particles have a D97 greater than 35 pm.

[0038] The percentiles or “percentiles” 50th (D50), 70th (D70), 87th (D87), 90th (D90) and 97th (D97) of a The particle sizes in powders correspond to the percentages, by mass, of 50%, 70%, 87%, 90%, and 97%, respectively, on the cumulative particle size distribution curve of the powder, with the particle sizes listed in ascending order. For example, 70% by mass of the particles in a powder have a size smaller than D70, and 30% by mass have a size larger than D70. Sizes and percentiles can be determined using a particle size distribution obtained with a laser diffraction particle size analyzer, particularly using the liquid dispersion method. For example, this could be a particle size analyzer from the Malvern company called the "MASTERSIZER 3000". The 50th percentile, D50, is still commonly referred to as the "median diameter".

[0039] The clinker particles have a Blaine specific surface area less than or equal to 5500 cm² / g, in particular less than or equal to 5200 cm² / g, and more particularly ranging from 3000 cm² / g to 5200 cm² / g. The Blaine specific surface area is measured according to standard NF EN 196-6.

[0040] Thus, clinker is advantageously used in the form of a cement different from an overground cement.

[0041] The hydraulic binder comprises 20% to 40% by weight of clinker relative to the total weight of said binder. The binder may comprise at least 23% by weight, preferably 25% to 40% by weight, and more preferably 25% to 35% by weight of clinker relative to the total weight of said binder.

[0042] The composition of fresh concrete may include from 70 kg / m3 to 220 kg / m3 of clinker, preferably from 75 kg / m3 to 150 kg / m3 of clinker. B) Filler

[0043] The filler particles have a D70 less than or equal to 63 pm.

[0044] The filler can be chosen from among the fillers defined in standard NF EN 12620.

[0045] In particular, the filler is chosen from quasi-inert fillers and their mixtures.

[0046] By quasi-inert filler, we mean a type I mineral addition according to standard NF EN 206 / CN. In particular, a quasi-inert filler differs from a hydraulic or pozzolanic admixture. A filler is considered quasi-inert because it has no predisposition to react with water or cement.

[0047] A person skilled in the art knows how to select a quasi-inert filler from among the usual constituents of a binder intended to form a concrete.

[0048] The filler can be chosen from calcareous fillers such as calcium carbonate, siliceous fillers such as quartz, silico-calcareous fillers, and mixtures thereof, in particular from calcareous fillers, siliceous fillers and mixtures thereof.

[0049] Preferably, the filler comprises at least one calcareous filler, and more preferably the filler is a calcareous filler.

[0050] Calcareous fillers can for example be calcareous additions as defined in standard NF P 18-508.

[0051] Limestone fillers are particularly advantageous for their low environmental impact and availability.

[0052] The filler can be characterized by a Blaine specific surface area ranging from 2000 cm2 / g to 9000 cm2 / g, preferably from 3500 cm2 / g to 7000 cm2 / g.

[0053] The binder comprises from 45% to 75% by weight of filler relative to the total weight of said binder. The binder may comprise from 45% to 70% by weight, preferably from 45% to less than 65% by weight, in particular from 50% to 58% and more particularly from 50% to 55% by weight of filler relative to the total weight of said binder.

[0054] In the case of clinker implemented in the form of Portland cement in- Since the cement itself incorporates a filler as described above, the quantity of filler introduced with the cement is taken into account when assessing the filler content in the binder. This is notably the case for a CEM II / AL.

[0055] The composition of fresh concrete may include from 160 kg / m3 to 400 kg / m3 of filler, preferably from 200 kg / m3 to 300 kg / m3 of filler. C) Ultrafine particle size material

[0056] The ultrafine particle size material is advantageously a reactive mineral powder in a cementitious environment. More specifically, it is selected from hydraulic admixtures, pozzolanic admixtures, ultrafine cements, and mixtures thereof. For example, hydraulic and pozzolanic admixtures are type II admixtures according to standard NF EN 206 / CN.

[0057] By definition, a hydraulic addition is a mineral addition that reacts with water. For example, it could be ground slag.

[0058] A pozzolanic addition is a mineral addition that reacts with calcium hydroxide in the presence of water. Examples include silica fume, metakaolin, calcined clays, fly ash, and natural pozzolans.

[0059] An ultrafine cement is in particular a cement of class CEM I, CEM II, CEM III, CEM IV or CEM V according to the European standard NF EN 197-1 or similar, the grinding of which is finer than that of ordinary cements of these same classes.

[0060] The ultrafine particle size material can be selected from slags, silica fume, metakaolin, calcined clays, fly ash, natural or artificial pozzolanic additions, ultrafine cements of class CEM I, CEM II, CEM III, CEM IV or CEM V, and their mixtures, in particular from blast furnace slags, silica fume, metakaolin, calcined clays, natural or artificial pozzolanic additions, ultrafine cements of class CEM I, CEM II, CEM III, CEM IV or CEM V and their mixtures.

[0061] Metakaolin is usually obtained by calcining clay composed mainly of kaolinite at temperatures ranging from 600°C to 900°C. For example, metakaolin can be chosen from among metakaolins conforming to standard NF P 18-513.

[0062] Silica fume is usually a by-product of metallurgy and the production of silicon or ferrosilicon. Silica fume is generally composed of spherical particles comprising at least 85% by mass of amorphous silica. The silica fume may be selected from silica fumes conforming to standard NF EN 13263-1.

[0063] Fly ash can be chosen from fly ash conforming to the European standard NF EN 450-1.

[0064] Classically, the slag is ground blast furnace slag (in English "Ground granulated blast-fumace slag", GGBS).

[0065] A GGBS is a granular material generally obtained by rapid cooling with water of molten slag from the smelting of iron ore in a blast furnace, followed by grinding to improve the reactivity of the GGBS. The GGBS is an amorphous aluminosilicate glass, essentially composed of SiO2, CaO, MgO, and Al2O3. The GGBS is preferably manufactured according to the European standard NF EN 15167-1.

[0066] Ultrafine cements used as ultrafine particle size material can be overground cements. Examples of cements that can be used as ultrafine particle size material include the Spinor® range of cements marketed by EQIOM, in particular the materials sold under the names "Spinor® A6", "Spinor® Al2" and "Spinor® A32".

[0067] The ultrafine particle size material may also be a filler made from by-products of, among other things, stainless steel production. For example, it may be the product sold under the name Fillinox® by the company Orbix.

[0068] The particles of the ultrafine particle size material may have a D50 less than or equal to 8 pm, in particular ranging from 1 to 8 pm.

[0069] The particles of the ultrafine particle size material may have a D90 less than or equal to 30 pm, preferably ranging from 4 pm to 30 pm, in particular from 10 pm to 30 pm. In particular, the particles of the ultrafine particle size material may have a D90 greater than 1 pm, or even greater than or equal to 3 pm.

[0070] The ultrafine particle size material may have a specific surface area obtained by the BET (Brunauer-Emmet-Teller) method greater than or equal to 5 m2 / g, preferably ranging from 5 m2 / g to 35 m2 / g, in particular from 10 m2 / g to 25 m2 / g.

[0071] The ultrafine particle size material can be characterized by a Blaine specific surface area greater than or equal to 5500 cm2 / g, preferably ranging from 6500 cm2 / g to 12000 cm2 / g, in particular from 7000 cm2 / g to 10000 cm2 / g.

[0072] The hydraulic binder comprises from 5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder. The hydraulic binder generally comprises at least 7% by weight, in particular from 7.5% to 14% by weight or even from 11% to 14% by weight of ultrafine particle size material relative to the total weight of said binder.

[0073] In the case of clinker used in the form of Portland cement comprising an ultrafine particle size material, the quantity of this ultrafine particle size material introduced with the cement is taken into account in evaluating the ultrafine particle size material content in the binder. For example, in the case of CEM II / AD, the quantity of silica fume present in the cement is taken into account in calculating the ultrafine particle size material content of the fresh concrete mix, provided that the particle size distribution is consistent effectively meets the requirements of the invention for the ultrafine particle size material.

[0074] The composition of fresh concrete may include from 20 kg / m3 to 80 kg / m3 of ultrafine particle size material, preferably from 30 kg / m3 to 60 kg / m3.

[0075] The clinker, filler, and ultrafine particle size material may constitute at least 80% by weight, preferably at least 90% by weight, more preferably at least 95% by weight, or even more than 99% of the total weight of said binder. The binder may also consist solely of the clinker, filler, and ultrafine particle size material.

[0076] Preferably, the clinker and filler are used in a clinker / filler weight ratio of at least 0.32, preferably greater than or equal to 0.4. The clinker / filler weight ratio is generally less than or equal to 1.8, preferably less than or equal to 1.0, and more preferably less than or equal to 0.7. According to a preferred embodiment, it varies from 0.4 to 0.7. These weight ratios are particularly advantageous for achieving high mechanical properties of hardened concrete, while ensuring a fluid consistency of this concrete in its fresh state. At values ​​below these ratios, it has been observed that the high mechanical properties of the hardened concrete can indeed be maintained, but at the expense of the fluid and low-viscosity consistency of the fresh concrete and therefore its workability. ii) Superplasticizer or plasticizer

[0077] The composition of fresh concrete may include a superplasticizer or plasticizer selected from NBSPs (naphthalene-based superplasticizers), PNSs (polynaphthalene sulfonates), MBSPs (melamine-based superplasticizers), PMSs (polymelamine sulfonates), HCAs (hydroxycarboxylic acids), (P)AAs (poly(acrylic acid)), LSs (lignosulfonates), in particular ammonium, calcium or sodium lignosulfonates, PCEs (polycarboxylic ethers), PCAs (polycarboxylic acids), phosphonates, their salts and / or derivatives and mixtures thereof.

[0078] In particular, the superplasticizer(s) or plasticizer(s) are chosen from PCEs (polycarboxylic ethers), PCAs (polycarboxylic acids), phosphonates, NBSPs (naphthalene-based superplasticizers), PNSs (polynaphthalene sulfonates), LSs (lignosulfonates) and mixtures thereof, preferably chosen from PCEs (polycarboxylic ethers), PCAs (polycarboxylic acids), phosphonates and mixtures thereof.

[0079] The composition comprises at least 0.05% by weight, expressed as dry extract relative to the total weight of said binder, of superplasticizer or plasticizer. In particular, the composition may comprise from 0.05% to 1% by weight, preferably from 0.1% to 0.5% by weight, expressed as dry extract relative to the total weight of said binder, of superplasticizer or plasticizer.

[0080] In particular, the superplasticizer(s) or plasticizer(s) is used in the composition of fresh concrete at a rate of 0.2 kg / m3 to 5 kg / m3, preferably from 0.5 kg / m3 to 2 kg / m3, expressed as dry extract.

[0081] The use of at least one superplasticizer or plasticizer is advantageous in several respects. This compound advantageously deflocculates binder particles, and in particular ultrafine particles. It is thus possible, on the one hand, to obtain a fluidity suitable for on-site application with a low water content in the concrete, and on the other hand, to increase the reactivity of the ultrafine particles and therefore the compressive strength of the concrete. iii) Water

[0082] Water is used in the composition of fresh concrete in a water / binder mass ratio varying from 0.3 to 0.45.

[0083] The water is formed from all the water present in the composition of fresh concrete, i.e. the mixing water, and the water added to the composition with the superplasticizer or possible admixtures.

[0084] Preferably, the fresh concrete composition uses water in a water / binder mass ratio varying from 0.3 to 0.4, preferably greater than 0.32, more preferably of at least 0.34, or even varying from 0.36 to 0.4.

[0085] The composition of fresh concrete may include from 130 kg / m3 to 200 kg / m3 of water, preferably more than 140 kg / m3, and more preferably more than 150 kg / m3 of water.

[0086] The water / binder ratio according to the invention differs in particular from that usually used to characterize cements or binders, where the quantity of water is usually equal to half the dosage of binder. iv) Aggregates

[0087] The term aggregate refers to a broad category of particulate materials used in construction. For the purposes of this invention, the term aggregate excludes fillers as defined above.

[0088] The aggregates may be selected from sands, fine sands, gravels, pebbles, crushed rock, slag, crushed or recycled concrete, geosynthetic aggregates, expanded shale, expanded clay, and mixtures thereof. For example, crushed rock may be formed from siliceous, calcareous, and / or silico-calcareous rocks. Preferably, the aggregates comprise at least sand, gravel, or mixtures thereof.

[0089] For example, aggregates are chosen from materials conforming to article 10 of standard NF P 18-545.

[0090] Preferably, the aggregates have a size less than 32 mm. Preferably, the aggregates include at least one material with a particle size between 6 mm and 32 mm.

[0091] The size of the aggregates, or particle size, corresponds to the diameter of the smallest sphere circumscribed about the particle. It can be measured by sieving.

[0092] Most often, aggregates used on a construction site are in a wet form, given that they are usually handled outdoors. Water / binder ratios take into account the water resulting from the moisture content of the aggregates.

[0093] Aggregates may be present in a weight proportion ranging from 55% to 85% of the total weight of the fresh concrete, or in a volume proportion ranging from 55% to 70% of the total volume of the fresh concrete. In particular, aggregates are used in the composition of fresh concrete at a rate of 1300 kg / m³ to 2000 kg / m³, preferably from 1500 kg / m³ to 1800 kg / m³. Composition of fresh concrete

[0094] The set of aggregates whose size is greater than or equal to 63 pm forms a granular skeleton.

[0095] The mixture of the binder, water, superplasticizer(s) or plasticizer(s), and, where applicable, trapped air and sand particles with a diameter of less than 63 µm, forms a paste. Advantageously, this paste allows the particles of the granular skeleton to be separated from one another.

[0096] Preferably, the volume of said paste is greater than or equal to 115%, in particular 120%, or even between 120% and 135%, of the porous volume of the granular skeleton, also called the void volume of the granular skeleton.

[0097] The porous volume of the granular skeleton, also called the void volume of the granular skeleton, can be measured from the compactness of the granular skeleton obtained after vibration of all the particles of the granular skeleton. It can also be established according to the compressible packing model [2] from the compactness measurement of each category of particles composing the granular skeleton.

[0098] An excess of paste volume relative to the porous volume of the granular skeleton ensures good spacing between the particles of the granular skeleton, promoting the flow of fresh concrete. Furthermore, the water / binder ratio required in the fresh concrete helps to limit the viscosity of the paste. The combination of an excess of paste volume with the required water / binder ratio is advantageously useful for ensuring that the fresh concrete mix has a viscosity suitable for its placement on a construction site or in a prefabrication plant, and in particular for ensuring a fluid consistency.

[0099] The composition of fresh concrete may also include one or more admixture(s) selected from water retainers, thickeners, antifoams, biocides, pigments, flame retardants, air entrainers, etc. retarders, accelerators, fibers, dispersion powders, wetting agents, polymer resins, complexing agents, polymer dispersions, shrinkage reducing agents, and mixtures thereof.

[0100] In particular, the fresh concrete composition has a viscosity of less than or equal to 9 seconds, preferably less than or equal to 6 seconds, or even less than 6 seconds, measured by the inverted cone method according to standard XP P18-469 at a temperature of 20 °C after mixing, i.e. after obtaining a homogeneous mixture of all its components.

[0101] It may have an Abrams cone slump greater than or equal to 160 mm, preferably greater than or equal to 180 mm, measured according to standard NF EN 12350-2 at a temperature of 20°C after mixing.

[0102] The fresh concrete mix advantageously produces concrete that is at least as fluid as concrete of consistency class S4 according to standard NF EN 206 / CN. In particular, the fresh concrete mix can have the consistency required for self-compacting concrete. Specifically, it produces concrete of consistency class S5 according to standard NF EN 206 / CN. Hardened concrete preparation process

[0103] Hardened concrete can be prepared by a process comprising the implementation of a hydraulic binder as described above.

[0104] The process according to the invention may include at least the steps of: a) forming said fresh concrete composition by mixing its components; b) where appropriate, pouring the fresh concrete composition, and c) allowing said fresh concrete composition to harden to obtain said hardened concrete.

[0105] The various mixing techniques known to those skilled in the art can be used. For example, the fresh concrete mix can be formed by successively adding the components under mixing conditions, with the mixing process continued until the fresh concrete is obtained. Mixing can be carried out in a conventional mixer, in particular a forced-action mixer. Those skilled in the art know how to adjust the duration or power of the mixing to obtain a homogeneous fresh concrete mix.

[0106] The fresh concrete composition can be poured according to the usual methods known to those skilled in the art.

[0107] After the fresh concrete mix has hardened, in particular by hydration and / or hardening, a hardened concrete such as a structural element is obtained. In particular, the hardened concrete obtained may be in the form of a pile, a diaphragm wall, a footing, a beam, a slab, a floor, a column, a beam or a wall. Hardened concrete

[0108] Hardened concrete can be obtained from the fresh concrete composition described above, or from the process as described above.

[0109] The hardened concrete according to the invention is advantageously a concrete whose mechanical strength is at least as high as that of a concrete belonging to strength class C25 / 30. In particular, the hardened concrete is a concrete belonging to strength class C25 / 30 or C30 / 37, and more particularly to strength class C25 / 30.

[0110] Hardened concrete may have a compressive strength greater than or equal to 3 MPa, preferably greater than or equal to 5 MPa, measured according to standard NF EN 12390-3, 24h after contact of the binder with water and storage at a temperature of 20°C.

[0111] Preferably, the hardened concrete has a compressive strength greater than or equal to 25 MPa, preferably greater than or equal to 30 MPa, measured on cylinders according to standard NF EN 12390-3, 28 days after contacting said binder with water.

[0112] Such hardened concrete is particularly useful for forming structural elements. Preferably, the hardened concrete is in the form of a pile, diaphragm wall, footing, stringer, slab, floor, column, beam or wall.

[0113] Hardened concrete may be in the form of a structural element, in particular a prefabricated or cast element, especially a structural element of a building or civil engineering structure such as infrastructure or superstructure. Materials and methods

[0114] The following raw materials were used:

[0115] - CEM I 52.5 N cement from Le Havre supplied by the company Vracs de l'Estuaire de surface specific Blaine 4700 cm2 / g and having a median diameter D50 of 12 pm;

[0116] - Betocarb HP EN limestone filler supplied by Omya having a D87 of 63 pm;

[0117] - superplasticizer marketed by the company Chryso under the name Optima 175;

[0118] - 0 / 4 Pécy limestone sand supplied by the company A2C;

[0119] - 4 / 20 Pécy limestone gravel supplied by the company A2C;

[0120] - Ultrafine particle size materials: Ultra-fine Moerdijk slag marketed by the company Ecocem whose median diameter D50 is 2.25 pm; DP Les Clavaux silica fume marketed by the company Ferropem whose specific surface area BET is 21.5 m2 / g; Metakaolin Argicem Fumel marketed by the company Argeco whose specific surface area BET is 17.5 m2 / g; CEM III Spinor A32 marketed by the company Eqiom, whose median diameter D50 is 6 pm. Measurements on equivalent concrete mortars

[0121] It is known that the physical specificities of equivalent concrete mortars are representative of the physical specificities of the corresponding concretes.

[0122] Viscosity is measured for equivalent concrete mortars by determining the flow time in a mini "V" funnel at a temperature of 20°C according to the methodology of standard NF EN 12350-9.

[0123] Spread measurements are carried out on equivalent concrete mortar at a temperature of 20°C according to the provisions of standard NF EN 12350-8 using the MBE mini cone (Abrams cone with Yi scale).

[0124] Compressive strength is measured for equivalent concrete mortars on 4cm x 4cm x 16cm prisms according to standard NF EN 196-1 at 24 h and 28 days. Measurements on concretes

[0125] The volume of the granular skeleton is established according to the compressible stacking model [2].

[0126] Viscosity is measured after mixing for fresh concrete compositions by determining the flow time in a "V" funnel ("V funnel") at a temperature of 20°C according to the provisions of standard XP PI8-469.

[0127] Abrams cone slump measurements are carried out after mixing on fresh concrete compositions at a temperature of 20°C according to the provisions of standard NF EN 12350-2.

[0128] Compressive strength is measured for hardened concretes on cylindrical specimens of diameter 110 mm and height 220 mm according to standard NF EN 12390-3 at 18 h, 24 h, 7 days and 28 days. Example 1

[0129] Preparation of equivalent concrete mortars conforming and not conforming to the invention for different cement contents

[0130] The binder is prepared by dry mixing of cement (CEM), limestone filler (FC) and metakaolin (MK) in the proportions indicated in Table 1.

[0131] The equivalent concrete mortar is prepared by mixing sand, binder, superplasticizer and water, the water / binder weight ratio (W / L) and the superplasticizer content, expressed in commercial weight, being indicated in Table 1.

[0132] The binders used in tests A and B comprise 35% and 12.5% ​​cement respectively. Test A Control B CEM binder (kg / m3) 140 50 MK (kg / nF) 50 50 FC (kg / m3) 210 300 Sand 0 / 4 (kg / m3) 1038 1038 S uperplasticizer (kg / m3) 5.8 5.9 E / L 0.4 0.4 Example 2

[0134] Preparation of equivalent concrete mortars conforming and not conforming to the invention for different metakaolin contents

[0135] Equivalent concrete mortars are prepared according to the protocol detailed in example 1 in the proportions indicated in table 2.

[0136] The binders used in tests A, C, D, E and F comprise respectively 12.5%, 0%, 5%, 10% and 15% metakaolin.

[0137] [Tables2] Test A Control C Test D Test E Test F Binder CFM (kg / m3) 140 140 140 140 140 MK (kg / m3) 50 0 20 40 60 FC (kg / m3) 210 260 240 220 200 Superplasticizer (kg / m1) 5.8 2.6 4.0 5.0 6.2 Sand 0 / 4 (kg / mJ) 1038 1038 1038 1038 1038 W / L 0.4 0.4 0.4 0.4 0.4 Example 3

[0138] Preparation of equivalent concrete mortars conforming and not conforming to the invention

[0139] Equivalent concrete mortars are prepared according to the protocol detailed in example 1 in the proportions indicated in table 3. The volume of paste corresponds to the percentage of the volume of paste relative to the porous volume of the granular skeleton.

[0140] The composition of Test Control G is free of superplasticizer. The composition of Test Control H has a higher water-to-liquid ratio than Test A. Test A Control G Control H Binder CEM (kg / m3) 140 140 140 MK (kg / m3) 50 50 50 FC (kg / m3) 210 210 210 Superplasticizer (kg / m3) 5.8 0 4 Sand 0 / 4 (kg / m3) 1038 1038 975 W / L 0.4 0.4 0.5 Dough volume (%) 126 126 140 Example 4

[0142] Characterization of the equivalent concrete compositions and mortars obtained in examples 1 to 3

[0143] The results of the measurements of spread, viscosity and compressive strength, measured according to the methods detailed in the Materials and Methods chapter, are reported in Table 4.

[0144] As the tests were carried out on equivalent concrete mortars, the measured values ​​are given for comparison purposes. In particular, due to the strength measurements on 4x4x16 cm³ prismatic specimens, the minimum target strength at 28 days for obtaining a concrete strength class of C25 / 30 is 30 MPa. Similarly, obtaining a fluid consistency corresponds to a mortar spread of more than 250 mm, and the maximum mortar viscosity for obtaining a concrete viscosity of less than 9 seconds is 7 seconds. Spread (mm) Viscosity (s) Rc24 h (MPa) Re?sj (MPa) Test A (35% CEM, 12.5% ​​MK) 350 5.6 8 2 36.3 Control B (12.5% ​​CEM) 4.4 1-9 11.4 Control C (0% MK) - 4.6 7.9 23.7 Test D (5% MK) - 5.6 9.3 30.0 Test E (10% MK) * 6.4 9.1 32.0 Test F (15% MK) - 6.0 7.8 40.8 Control G (without superplasticizer) 100 not measurable 9.5 28.6 Control H (E / L=0.5) 330 2.7 4.2 18.7

[0146] As shown in Table 4, the compressive strength at 24 h and 28 days is higher for test A compared to the control test B with lower cement content, for a substantially similar viscosity.

[0147] Furthermore, the compressive strength increases for tests C to F and A when the metakaolin content increases from 0% to 15% in the binder, for a viscosity of less than 7 seconds.

[0148] Control Test G shows that the absence of superplasticizer negatively impacts compressive strength and slump compared to Test A, which includes superplasticizer. Furthermore, viscosity could not be measured for Control Test G due to the mortar's lack of fluidity. As for Control Test H, compared to Test A, it shows a loss of compressive strength when the water-to-liquid ratio increases from 0.4 to 0.5. Example 5

[0149] Preparation and characterization of concretes according to the invention

[0150] Fresh concrete compositions are prepared by mixing 30 L batches in a forced-action laboratory mixer at an ambient temperature of 20°C, in the proportions indicated in Table 5 in kg / m³ for the cement-formed binder (CEM), limestone filler (FC), and an ultrafine particle size material (UF), the superplasticizer (SP), the aggregates, and water. Effective water includes the mixing water and the water added with the superplasticizer. The paste volume corresponds to the percentage of the paste volume relative to the porous volume of the granular skeleton.

[0151] [Tables5] Test No. 1 Test No. 2 Test No. 3 Test No. 4 Test No. 5 CEM 100 140 140 140 100 FC 250 230 210 210 250 CF Slag 50 Silica fume 30 50 Metakaolin 50 CEM 111 50 Sand 840 840 850 850 840 Gravel 840 840 850 850 840 SP (dry extract) 0.9 1.2 1.2 1.0 1J Effective water 155 155 155 154 155 Paste volume (%) 126 127 125 125 128

[0152] The results obtained on fresh concrete are reported in Table 6.

[0153] [Tableauxô] Test #1 Test #2 Test #3 Test #4 Test #5 Slump (mm) 180 210 200 220 220 Consistency Class S4 S4 S4 S4 S4 Viscosity (s) 6.5 2.9 3.0 4.2 2.0

[0154] The compressive strength results obtained on the hardened concrete are reported in table 7 and expressed in MPa. Test #1 Test #2 Test #3 Test #4 Test #5 18 h 3.7 5.7 5.2 7.9 2.5 24 h 5.9 7.7 11.6 3.3 7 days 24.7 26.6 28.4 31.7 15.8 28 days 31.1 40.4 30.5 38.3 31.3

[0156] As can be seen from these results, the concretes in tests Nos. 1 to 5 all fall within consistency class S4 and at least strength class C25 / 30. Furthermore, they all exhibit a viscosity of 6.5 seconds or less, measured by the inverted cone method according to standard XP PI8-469 at a temperature of 20°C. List of documents cited

[0157] [1] Antoni et al., Cernent and Concrète Research, 2012, 42, 1579-1589;

[0158] [2] F. De Larrard, “Granular Structures and Concrete Formulation”, Studies and Research Research from the Laboratories of Bridges and Roads, Engineering Structures OA 34, 2000.

Claims

Demands

1. Composition of fresh concrete comprising at least: i) from 350 kg / m3 to 550 kg / m3 of hydraulic binder, referred to as binder, comprising: - from 20% to 40% by weight of Portland clinker relative to the total weight of said binder and whose particles have a D50 greater than 11 pm and a Blaine specific surface area less than or equal to 5500 cm2 / g, - from 45% to 75% by weight of filler relative to the total weight of said binder and whose particles have a D70 less than or equal to 63 pm, and - from 5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder and whose particles have a BET specific surface area greater than or equal to 5 m2 / g or a D50 less than or equal to 8 pm, and being selected from hydraulic additions, pozzolanic additions, ultrafine cements and mixtures thereof, ii) at least 0.05% by weight, expressed as dry extract relative to the total weight of said binder, of superplasticizer or plasticizer,iii) water in a water / binder mass ratio varying from 0.3 to 0.45, and iv) aggregates.

2. Fresh concrete composition according to claim 1, wherein the clinker and filler are implemented in a clinker / filler weight ratio of at least 0.32, preferably greater than or equal to 0.4, more preferably from 0.4 to 0.

7.

3. Fresh concrete composition according to claim 1 or 2, wherein said binder comprises from 45% to 70% by weight, preferably from 45% to less than 65% by weight, and more preferably from 50% to 58% by weight in filler relative to the total weight of said binder.

4. Fresh concrete composition according to any one of the preceding claims, wherein said binder comprises at least 23% by weight, preferably from 25% to 40% by weight, and more preferably from 25% to 35% by weight of clinker relative to the total weight of said binder.

5. Fresh concrete composition according to any one of the preceding claims, wherein said binder comprises at least 7% by weight, in particular from 7.5% to 14% by weight of ultrafine particle size material relative to the total weight of said binder.

6. Fresh concrete composition according to any one of the preceding claims, wherein the filler comprises at least one limestone filler, preferably wherein the filler is a limestone filler.

7. Composition of fresh concrete according to any one of the claims previous, in which the ultrafine particle size material is chosen from slags, silica fume, metakaolin, calcined clays, fly ash, natural or artificial pozzolanic additions, ultrafine cements of class CEM I, CEM II, CEM III, CEM IV or CEM V, and mixtures thereof, and preferably from blast furnace slags, silica fume, metakaolin, calcined clays, natural or artificial pozzolanic additions, ultrafine cements of class CEM I, CEM II, CEM III, CEM IV or CEM V and mixtures thereof.

8. Fresh concrete composition according to any one of the preceding claims, wherein the clinker is implemented in the form of Portland cement, preferably selected from CEM I and CEM IRA.

9. Fresh concrete composition according to any one of the preceding claims, wherein the superplasticizer(s) or plasticizer(s) are selected from PCEs (polycarboxylic ethers), PCAs (polycarboxylic acids), phosphonates, NBSPs (naphthalene-based superplasticizers), PNSs (polynaphthalene sulfonates), LSs (lignosulfonates) and mixtures thereof, preferably selected from PCEs (polycarboxylic ethers), PCAs (polycarboxylic acids), phosphonates and mixtures thereof.

10. Fresh concrete composition according to any one of the preceding claims, comprising from 0.05% to 1% by weight, preferably from 0.1% to 0.5% by weight, expressed as dry extract relative to the total weight of said binder, of superplasticizer or plasticizer.

11. Fresh concrete composition according to any one of the preceding claims, wherein the water / binder mass ratio varies from 0.3 to 0.4, preferably greater than 0.32, more preferably of at least 0.34, or even varies from 0.36 to 0.

4.

12. Fresh concrete composition according to any one of the preceding claims, wherein the aggregates comprise at least one material having a particle size of between 6 mm and 32 mm, in particular the aggregates comprise at least sand, gravel or mixtures thereof.

13. A fresh concrete composition according to any one of the preceding claims, wherein the mixture of the binder, water, superplasticizer(s) or plasticizer(s) and, where applicable, entrapped air and sand particles of diameter less than 63 µm, forms a paste, with the volume of said paste being greater than or equal to 115%, in particular 120%, or even between 120% and 135%, of the porous volume of the granular skeleton.

14. Fresh concrete composition according to any one of the preceding claims, having a viscosity less than or equal to 9 seconds, preferably less than or equal to 6 seconds, measured by the inverted cone method according to XP P18-469 at a temperature of 20 °C after mixing.

15. Fresh concrete composition according to any one of the preceding claims, having an Abrams cone slump greater than or equal to 160 mm, preferably greater than or equal to 180 mm, measured according to standard NF EN 12350-2 at a temperature of 20°C after mixing.

16. Use of a hydraulic binder comprising: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder, the particles of which have a D50 greater than 11 pm and a Blaine specific surface area less than or equal to 5500 cm² / g, - 45% to 75% by weight of filler relative to the total weight of said binder, the particles of which have a D70 less than or equal to 63 pm, and - 5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder, the particles of which have a BET specific surface area greater than or equal to 5 m² / g or a D50 less than or equal to 8 pm, and being selected from hydraulic admixtures, pozzolanic admixtures, ultrafine cements and mixtures thereof, and having a clinker / filler weight ratio of at least 0.32, to form fresh concrete having a slump measured by the Abrams cone greater than or equal to 160 mm, preferably greater than or equal to 180 mm,measured according to standard NF EN 12350-2 at a temperature of 20°C after mixing, and with a viscosity of less than or equal to 9 seconds, preferably less than or equal to 6 seconds, measured by the inverted cone method according to standard XP P18-469 at a temperature of 20°C after mixing.

17. Use according to the preceding claim of a hydraulic binder as defined according to any one of claims 1 to 8.

18. Use of a fresh concrete composition comprising at least: i) a hydraulic binder comprising: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder and whose particles have a D50 greater than 11 pm and

19.

20.

21. a Blaine specific surface area less than or equal to 5500 cm2 / g, - 45% to 75% by weight of filler relative to the total weight of said binder, with particles having a D70 less than or equal to 63 µm, and - 5% to 15% by weight of ultrafine particle size material relative to the total weight of said binder, with particles having a specific surface area BET greater than or equal to 5 m² / g or a D50 less than or equal to 8 µm, and being selected from hydraulic additions, pozzolanic additions, ultrafine cements and their mixtures, ii) at least one superplasticizer or plasticizer, iii) water and (iv) aggregates, and whose slump in the Abrams cone is greater than or equal to 160 mm, measured according to standard NF EN 12350-2 at a temperature of 20°C after mixing, and the viscosity is less than or equal to 9 seconds measured by the inverted cone method according to standard XP P18-469 at a temperature of 20°C after mixing, to form a hardened concrete having a compressive strength greater than or equal to 25 MPa, preferably greater than or equal to 30 MPa, measured on cylinders according to standard NF EN 12390-3, 28 days after contacting said binder with water. Use according to the preceding claim of a fresh concrete composition according to any one of claims 1 to 15. A method for preparing hardened concrete comprising the application of a hydraulic binder including: - 20% to 40% by weight of Portland clinker relative to the total weight of said binder and whose particles have a D50 greater than 11 pm and a Blaine specific surface area less than or equal to 5500 cm2 / g, - from 45% to 75% by weight in filler relative to the total weight of said binder and whose particles have a D70 less than or equal to 63 pm, and - from 5% to 15% by weight in ultrafine particle size material relative to the total weight of said binder and whose particles have a specific surface area BET greater than or equal to 5 m2 / g or a D50 less than or equal to 8 pm, and being chosen from hydraulic additions, pozzolanic additions, ultrafine cements and their mixtures, and whose clinker / filler weight ratio is at least 0.

32. Method according to the preceding claim, wherein said binder is implemented in the form of a fresh concrete composition according to any one of claims 1 to 15.

22. A method according to the preceding claim, comprising at least the steps of: a) forming said fresh concrete composition by mixing its components; b) if necessary, pouring the fresh concrete composition, and c) allowing said fresh concrete composition to harden to obtain said hardened concrete.

23. Hardened concrete obtained from the fresh concrete composition according to any one of claims 1 to 15 or obtained from the process according to any one of claims 20 to 22.

24. Hardened concrete according to the preceding claim, having a compressive strength greater than or equal to 25 MPa, preferably greater than or equal to 30 MPa, measured on cylinders according to standard NF EN 12390-3, 28 days after contacting said binder with water.

25. Hardened concrete according to claim 23 or 24, said hardened concrete being in the form of a structural element, in particular a prefabricated or cast element, in particular a structural element of a building or public works structure such as in infrastructure or superstructure.