EP4182282A1

EP4182282A1 - Method for manufacturing a concrete formulated on the basis of activated slag

Info

Publication number: EP4182282A1
Application number: EP21746466.8A
Authority: EP
Inventors: Artur KIIASHKO; Laurent Frouin; Paul-Alexandre FRANCO; François CUSSIGH
Original assignee: Vinci Construction SAS; Ecocem Materials Ltd
Current assignee: Vinci Construction SAS; Ecocem Materials Ltd
Priority date: 2020-07-20
Filing date: 2021-07-19
Publication date: 2023-05-24
Also published as: AU2021312020A1; BR112023000557A2; FR3112546A1; US20230242447A1; WO2022018037A1; CA3183456A1; FR3112546B1; AU2021312020B2

Abstract

Method for manufacturing a concrete from activated slag, comprising at least the steps consisting of: a) arranging a premixture P of water and granulates, the temperature of the premixture P being at least equal to 10°C, b) arranging an activation system A comprising at least a co-binder, a chelating agent, an alkali metal carbonate and a carbonated material different from the alkali metal carbonate, c) incorporating the activation system A and a slag S by mixing them into the premixture P, the activation system A and slag S being introduced successively and/or simultaneously, d) continuing the mixing until a fresh concrete is obtained, and e) allowing the fresh concrete to cure.

Description

Title: PROCESS FOR MANUFACTURING A FORMULATED CONCRETE BASED ON ACTIVE Slag

Technical area

The present invention relates to a low-carbon concrete, in particular to a low-carbon structural concrete, formulated on the basis of slag, in particular activated slag. The invention also relates to a method for manufacturing such a concrete.

Prior technique

The use of cement concretes, conventionally considered as structural concretes, poses a concern in terms of environmental impact. In view of their composition, namely a mixture of aggregates and sand agglomerated by a cement-based binder, generally Portland cement, these concretes contribute significantly to CO2 emissions, mainly due to the manufacture of clinker, an essential constituent of cement. Portland. In order to reduce the environmental impact of concretes, it has been proposed to replace, generally partially, the clinker by other compounds. Thus, different classes of cement, with clinker contents lower than those of Portland cement, have been developed. However, for clinker contents that are too low, the strength of the concrete is insufficient for the concrete to be used as structural concrete.

Another alternative solution to reduce the environmental impact of concrete is the replacement of a cement-based binder by an activated slag-based binder. A slag is considered to have a very low carbon footprint, as it is usually a by-product of the metallurgical industry, particularly generated during the manufacture of cast iron. An activated slag is a slag, to which is added at least one activator, making it possible to accelerate the reaction of the slag with the water. WO 2019/110134 and WO 2019/110280 more particularly propose a binder formulation based on activated slag comprising at least one slag, at least one activator and at least one chelating agent and/or a source of chelating agent, as well as a wet composition comprising the binder, water and at least one aggregate. However, until now, it is very difficult to implement an activated slag concrete on a construction site, in particular to form a structuring element, because the performance achieved by such a concrete is insufficient compared to a cement concrete.

In particular, these concretes do not reproduce the properties of conventional concretes, in terms of:

- fluidity over a sufficient period of time to transport the concrete and set it in place;

- short-term mechanical strength (about a day), in particular to enable formwork to be stripped quickly and not slow down the worksites;

- long-term mechanical strength (about 28 days) to be able to use the concrete as structural concrete;

- robustness, in particular with respect to variations in water content, as well as site conditions such as temperature;

- shrinkage, which must be limited to maintain the dimensions of the molded element during reaction and drying.

There therefore remains a need for an activated slag concrete with improved performance in these respects.

The invention specifically aims to provide an activated slag concrete giving satisfaction in these terms.

Against all expectations, the inventors have found that these objectives can be achieved in particular via the adjustment of a particular preparation process for an activated slag concrete.

Disclosure of Invention

Thus, the present invention relates, according to a first aspect, to a method for manufacturing an activated slag concrete, comprising at least the steps consisting in: a) Having a pre-mixture P of water and aggregates, the temperature of said premix P being at least equal to 10°C, preferably 15°C, b) Having an activation system A comprising at least one co-binder, a chelating agent, an alkali metal carbonate and a carbonated material distinct from said alkali metal carbonate, c) incorporating, under mixing, into said premix P, said activation system A and a slag S, said activation system A and slag S being introduced successively and/or simultaneously, d) prolonging said mixing until a fresh concrete is obtained, and e) allowing said fresh concrete to harden.

According to a first variant, step c) implements said activation system A in the form of a premix P′ with a slag S. Such a premix P′ can still be qualified as a binder in the sense of the invention.

According to a second variant, step c) comprises the incorporation of the slag S following that of the activation system A.

According to a third variant, step c) comprises the incorporation of the activation system A following that of the slag S.

The first and second variants are preferred.

According to a particular embodiment, the method further comprises the incorporation of at least one adjuvant chosen in particular from plasticizers, superplasticizers and mixtures thereof, in particular in step c) or d).

As can be seen from the examples below, such a process makes it possible to significantly improve the performance of an activated slag concrete compared to a usual on-site concrete manufacturing process.

Advantageously, steps c) to d), or even a) to d), of the method can be carried out in a concrete plant, preferably a concrete plant with a forced-action mixer. This type of mixer has blades that rotate around a vertical or horizontal axis, or two horizontal axes, and create a high shear of the material favoring the quality and speed of the mixture.

While for concretes made from traditional cements, the order of introduction of the various constituents has no major impact on the properties of the mixture, the inventors have discovered that the introduction of the activation system A into a pre-mixture P allows, against all expectations, to significantly increase the working time of an activated slag concrete.

As illustrated in the examples which follow, such a method makes it possible in particular to form and maintain a fresh concrete with a high fluidity, in particular a concrete of class of consistency S4 according to standard NF EN 206/CN, for a duration of at least 2 hours, ie at least about 3 times longer than with a conventional process.

In addition, the presence of the co-binder required according to the invention advantageously makes it possible to limit the shrinkage of the concrete, to improve its resistance at a young age, and to obtain better robustness of the formulation, in particular with respect to variations in the ambient temperature, in the nature and source of the aggregates and in their humidity, as well as variations in the water/slag ratio S, or even in the water/(slag ratio S + activation system A).

Finally, the implementation of the premix P at a temperature at least equal to 10°C, preferably 15°C, makes it possible to improve the robustness of the process with respect to variations in ambient temperature.

According to another of its aspects, the present invention relates to an activated slag concrete obtained by the process according to the invention.

A concrete in accordance with the invention has, in addition to the advantage of being a low-carbon, or even very low-carbon, concrete, the great advantage of being able to be used as structural concrete.

According to yet another of its aspects, the invention relates to a fresh activated slag concrete obtained at the end of step d) of the process according to the invention.

This fresh concrete notably provides enough time to set it up on site before it sets.

According to yet another of its aspects, the invention relates to a concrete reinforced with activated slag comprising steel reinforcements and an activated slag concrete according to the invention.

The invention also relates to a structuring element comprising an activated slag concrete according to the invention.

Finally, it relates to a prefabricated element comprising an activated slag concrete according to the invention.

By “fresh concrete”, we mean concrete in the phase following mixing and before setting, i.e. concrete that has the capacity to deform and/or flow.

By the adjective "dry", we characterize a material devoid of mixing water. In the rest of the text, the weight ratios are expressed in dry extract.

Furthermore, the term "binder" refers in the rest of the text to the whole of the activation system A with the slag S. Thus, the mass of the binder is the total mass of the activation system A and of the slag S .

detailed description

Process for producing an activated slag concrete

As emerges from the foregoing, the process of the invention requires the presence of a premix P, an activation system A and a slag S.

Premix P

Step a) of the process consists in having a pre-mixture P of water and aggregates, the temperature of which is at least equal to 10°C, preferably at least equal to 15°C.

The term aggregate refers to a broad category of particulate materials used in construction.

The aggregates can be chosen from fillers, sands, grit, gravel, gravel, crushed rock, slag, crushed or recycled concrete, geosynthetic aggregates, expanded shale, expanded clay and mixtures thereof.

In particular, the fillers can be chosen from fly ash, silica fume, pozzolans, and calcined shale and mixtures thereof. Crushed rock can be formed from siliceous, calcareous, and/or silico-calcareous rocks.

Preferably, the aggregates are chosen from materials that comply with article 10 of standard NF P 18-545.

Preferably, the aggregates have a size of less than 32 mm.

Most often, the aggregates used on a site are in wet form given that they are most often handled in an outdoor atmosphere. The method of the invention advantageously also makes it possible to consider this type of wet aggregate, by nature less easy to handle than dry aggregates for the manufacture of activated slag concrete.

These aggregates are generally considered at a weight proportion varying from 65% to 80% relative to the total weight of the fresh concrete.

Furthermore, the premix P is prepared with water brought to a suitable temperature to adjust the temperature of said premix P to a value at least equal to 10°C, preferably at least equal to 15°C. This pre-mix temperature P makes it possible, via solubilization of the reactive species involved in the first hours of the fresh concrete, to significantly stimulate the reaction of the slag S with the water as soon as it is incorporated into the pre-mix P.

In fact, controlling the temperature of the premix P is above all decisive when the ambient temperature is below 10°C. The inventors have in fact observed that a temperature below 10°C slows down or even prevents the setting and/or the rise in strength of the concrete.

Consequently, the water used to form the premix P is preferably at a temperature varying from 10°C to 85°C.

According to a preferred embodiment, the premix P is at a temperature at least equal to 15°C in step a), or even at a temperature varying from 15°C to 25°C.

Activation system A

This activation system A comprises at least a co-binder, a chelator, an alkali metal carbonate and a carbonate material distinct from the alkali metal carbonate. Preferably, the activation system A is in the form of a dry mixture, and in particular of a powder. a) Co-binder

The co-binder can be an aerial or hydraulic binder, preferably a hydraulic binder suitable for use according to standard NF EN 206/CN. For example, the co-binder can be lime, clinker or Portland cement. Preferably, the co-binder is a calcium ion precursor. In particular, the co-binder is capable of releasing calcium ions when it is brought into contact with water.

The co-binder is advantageously characterized by a Blaine fineness (ASTM C 204) (Bf) expressed in cm ² /g and in increasing order of preference:

- 500 < Bf < 10000;

- 1000 <Bf<9000;

- 2000 < Bf < 8000.

The co-binder content used in the process is advantageously low, in particular less than 20%, and preferably less than 10% by mass relative to the mass of the binder.

According to a preferred embodiment, the method uses the co-binder at a content of less than 5% by mass, in particular varying from 1% to 5% by mass, relative to the total mass of said activation systems A and slag S. As a variant, the process preferably uses the co-binder and the slag S in a co-binder/slag S weight ratio varying from 1% to 5%.

Advantageously, the presence of co-binder in the activation system A makes it possible to reduce the shrinkage of the concrete during setting and drying. In addition, the co-binder makes it possible to accelerate the rise in strength of the concrete, and to achieve a resistance class at least equal to C30/37 at 28 days according to standard NF EN 206/CN. Finally, the co-binder contributes to the robustness of the process with respect to the raw materials, the water/binder ratio and the temperature. b) Chelating

Within the meaning of the invention, the term chelating agent covers any compound endowed with the capacity to chelate or to form such a compound. Preferably, the chelating agent is a compound endowed with this ability.

Advantageously, this or these chelating agent(s) is a chelating agent for the calcium ion or the aluminum ion, and preferably for the calcium ion.

The chelating agent can be chosen from:

- phosphonates, preferably monophosphonates and/or diphosphonates; - phosphates, preferably tripolyphosphates and/or hexametaphosphates;

- carboxylates, preferably polyacrylates, citrates, tartrates and/or gluconates;

- amines;

- their derivatives, their salts;

- and mixtures thereof; preferably chosen from PBTC (phosphonobutane-l,2,4-tricarboxylic acid), ATMP (amino-trimethylene phosphonic acid), HEDP (1-hydroxyethylidene-1,1-diphosphonic acid), DTPA (diethylene triamine acid pentaacetic acid), DCTA (diaminocyclohexanetetra-acetic acid), PAA (polyacrylic acid), PPA (phosphino-polyacrylate), PMA (poly maleic acid), MAT (maleic acid terpolymer), SPOCA (sulfonated phosphonocarboxylic acid ), PPCA (poly-phosphono carboxylic acid), EDTMP (ethylenediaminetetramethylene phosphonic acid), and DTPMP (diethylenetriamine-pentamethylenephosphonic acid), their derivatives, their salts and their mixtures.

In particular, the chelating agent may be chosen from phosphonates, preferably monophosphonates and/or diphosphonates, and more preferably from HEDP (1-hydroxyethylidene-1,1-diphosphonic acid) and EDTMP (ethylenediaminetetramethylene phosphonic acid).

More particularly, the chelating agent can be chosen from the chelating agents proposed in documents WO 2019/110134 and WO 2019/110280 from the company ECOCEM. Among these chelating agents, the following compound is particularly interesting:

[Chem 1]

Furthermore, the method can implement the chelating agent and the slag S in a weight ratio of the chelating agent relative to the slag S varying from 0.001% to 2%, preferably from 0.01% to 1%, and more preferably from 0 .1% to 0.7%. As a variant, the method can also implement the chelating agent and the binder in a weight ratio of the chelating agent relative to the binder varying from 0.001% to 2%, preferably from 0.01% to 1%. c) Alkali metal carbonate

Activation system A also includes at least one alkali metal carbonate.

The alkali metal carbonate is implemented as an activator of the water/slag reaction, also called activator in the remainder of the text. The alkali metal carbonate therefore makes it possible to accelerate the water/slag reaction.

The alkali metal carbonate promotes setting and/or curing and/or hardening of the S slag.

The alkali metal carbonate can be in solid, hydrated or anhydrous form, for example in the form of a powder or else in a liquid form, for example in solution or suspension. Preferably, the alkali metal carbonate is in the form of a powder.

In particular, activation system A comprises at least one alkali metal carbonate chosen from sodium carbonates, potassium carbonates, lithium carbonates and mixtures thereof.

Preferably, the activation system A comprises at least one alkali metal carbonate chosen from sodium carbonates, potassium carbonates and their mixture, and more preferably comprises at least sodium carbonate.

The process according to the invention can implement the alkali metal carbonate and the slag S in an alkali metal carbonate/slag S weight ratio varying from 2% to 12%, preferably from 6% to 10%.

As a variant, the method can implement the alkali metal carbonate and the binder in an alkali metal carbonate/binder weight ratio varying from 2% to 11%, preferably from 5% to 9%.

Furthermore, the concentration of the alkali metal carbonate, preferably sodium carbonate, in the water can vary from 100 g/L to 300 g/L, preferably from 150 g/L to 250 g/L. d) Carbonate material distinct from said alkali metal carbonate

Activation system A further comprises at least one carbonated material distinct from the alkali metal carbonate, also called carbonated material in the remainder of the description. In particular, activation system A comprises at least one alkaline earth metal carbonate.

Preferably, the carbonated material comprises at least calcium carbonate. In particular, the carbonated material distinct from the alkali metal carbonate is in the form of at least one material chosen from limestone, dolomite, precipitated calcium carbonate, chalk, marble, aragonite, travertine, tufa and mixtures thereof, and preferably comprises at least, or even consists of, limestone.

Preferably, the carbonated material is implemented in the form of a co-product(s) of different industries, or in its natural or synthetic form.

The carbonated material can be a crystalline solid or an ionic solid.

According to an advantageous mode of the invention, the carbonated material is a powder whose median size D50 can be chosen from the following categories: a'I) D50 is included in the interval ]250 μm - 40 mm], for example [ 5 - 15mm]; a’2) D50 is in the range ]16.0 - 250.0 µm], for example [90 - 110 µm]; a’3) D50 is within the range ]6.0 - 16.0 pm], for example [9 - 11 pm]; a'4) D50 is in the range ]3.0 - 6.0 pm], for example [3.5 - 5.5 pm]; a'5) D50 is in the range ]0.9 - 3.0 µm], preferably [1.0 - 2.0 µm], for example [1.4 - 1.6 µm]; a'6) D50 is within the range ]0.02 - 0.9 pm], for example [0.49 - 0.51 pm]; a’7) and mixtures thereof.

An example of a class a’6) carbonate material is precipitated calcium carbonate (PCC).

The carbonated material, preferably in powder form, may comprise (in dry mass percentage relative to the carbonated material): aaΐ) 100% of class a' carbonated material 1), or aa2) 100% of class a carbonated material '3), or aa3) between 90% and 10%, preferably between 80% and 30%, of carbonate material of class a' 1), and between 10% and 90%, preferably between 20% and 70% of carbonated material of class a'2), or aa4) between 1% and 40%, preferably between 10% and 30%, of carbonated material of class a'3), or aa5) between 1% and 20%, preferably between 5% and 15%, of carbonated material of class a'3), and between 99% and 80%, preferably between 95% and 85% class a'5 carbonate material). Furthermore, the specific surface of the carbonated material, obtained by the BET method, can range from 1 to 60 m ² /g, for example from 20 to 30 m ² /g and/or from 3 to 13 m ² /g.

Furthermore, the method uses the carbonated material and the slag S in a carbonated material/slag S weight ratio which can vary from 1% to 50%, preferably from 3% to 35% and more preferably from 5% to 15% . As a variant, the method uses the carbonated material and the binder in a carbonated material/binder weight ratio which can vary from 1% to 35%, preferably from 3% to 25% and more preferably from 5% to 20%.

According to one embodiment, the activation system A can also comprise at least one co-activator, different from the alkali metal carbonate. e) Co-activator

The co-activator can be chosen from the group comprising lime, soluble chloride and/or fluoride and/or sulphate salts, their hydrates, their anhydrous forms and their mixtures. Preferably, the co-activator can be chosen from the group comprising at least lime, NaCl, CaCh, NaF, NaiSiFe, KC1, NaiSCE, K2SO4, CaSCE, their hydrates, their anhydrous forms and their mixtures.

In particular, the process can implement the co-activator and the slag S in a co-activator/slag S weight ratio varying from 0.001% to 30%, preferably from 0.01% to 16%, and more preferably from 0.05% to 10%.

As a variant, the process can implement the co-activator and the binder in a co-activator/binder weight ratio varying from 0.001% to 20%, preferably from 0.01% to 14%, and more preferably from 0. 05% to 9%.

In step b) of the process of the invention, the activation system A as defined above, can be implemented as such or in the form of a premix P′ with a slag S. The implementation of a premix P', which can also be described as a binder, is particularly advantageous in the case of the preparation of concrete directly on site, because it allows better control of the proportions of the mixture. . In addition, the process on site is in this case facilitated and accelerated.

Milkman S

The slag S can be implemented in the form of the pre-mixture P' as described previously, or in individualized form in the powder state.

Conventionally, slag is used in the form of a co-product(s) from different industries, or in its natural or synthetic form. In general, the slag is a powder or a slurry.

Preferably, the slag S comprises at least one ground blast-furnace slag (in English “Ground granulated blast-furnace slag”, GGBS). In particular, the slag S can be a GGBS.

A GGBS is a granular material usually obtained by rapid cooling with water of molten slag from smelting iron ore in a blast furnace, followed by grinding to improve the reactivity of the GGBS. GGBS is an amorphous alumino-silicate glass, essentially composed of S1O ₂ , CaO, MgO, and Al ₂ O ₃ .

The GGBS is preferably manufactured according to European standard NF EN 15167-1.

The chemical composition of the slag S may be as follows, in dry weight percentage relative to the slag S:

[Table 1]

According to a preferred mode of the invention, the slag S is a powder whose median size D50 can be chosen from the following categories: a1) D50 is included in the interval ]7.0 - 20.0 μm], ]7 .0 - 60 µm] or ]7.0 - 100.0 µm] (eg standard GGBS); a2) D50 is in the range ]3.0 - 7.0 µm] (eg a thin GGBS); a3) D50 is in the range ]0.5 - 3.0 µm], preferably [1.0 - 2.0 µm] or [0.5 - 2.0 µm] (e.g. an ultra- end) ; and a4) mixtures thereof.

The term "median size" of a set of particles, denoted D50, is the size dividing the particles of this set into first and second populations equal in mass, these first and second populations comprising only particles having a larger or smaller size respectively, at the median size.

In another embodiment, the slag powder S comprises (in dry mass percentage relative to the slag S): a1) 100% of class al slag powder), or a2) between 99% and 50%, preferably between 99% and 60%, of slag powder of class a1), and between 1% and 50%, preferably between 1% and 40% of slag powder of class a2), or a3) between 1% and 40% , preferably between 1 and 30% of class a3 slag powder).

The slag S can also have a Blaine fineness (Bf) (ASTM C 204 standard), expressed in cm ² /g, such that, in increasing order of preference:

- 500 < Bf < 20000;

- 1000 <Bf<10000;

- 2000 <Bf<8000;

- 3000 <Bf<7000;

- 3500 < Bf < 6000.

According to a variant of the invention, the slag S comprises 70% to 99.1% by mass, preferably 80% to 99.1% by mass, relative to the mass of the slag S, of particles such that 2500 <Bf <8000, preferably 3500 <Bf <7000, and 30% to 0.1% by mass, preferably 20% to 0.1% by mass, relative to the mass of the slag S, of particles such as 8000 <Bf < 16000, preferably 10000 < Bf < 14000.

As a side note, GGBS is a hydraulic binder and the slag alone can then react with water.

Preferably, the method uses the slag S in a slag S/binder weight ratio which can vary from 30% to 95%, preferably from 50% to 92% and more preferably from 60% to 90%. According to a particularly preferred embodiment, the activation system A is in the form of a premix P' with a slag S, the premix P' comprising at least:

- a GGBS,

- a co-binder, preferably chosen from hydraulic binders,

- a chelating agent chosen from HEDP, EDTMP and their mixture,

- limestone,

- sodium carbonate, in particular with a sodium carbonate / GGBS ratio of 6 to

10%.

In the case where the activation system A is in the form of a pre-mixture P′, the latter may also comprise at least one filler, for example fly ash, silica fume, pozzolans, calcined shale or mixtures thereof.

Co-binder(s), chelator(s), carbonate material(s) other than alkali metal carbonate, alkali metal carbonate(s) , the co-activator(s), the slag(s) and the filler(s) may have other characteristics as described in applications WO 2019/110134 and WO 2019/110280 .

The process according to the invention considers in its step c) the incorporation under mixing in said premix P, of said activation system A and of a slag S, said activation system A and slag S being introduced in such a way successive and/or simultaneous.

According to a first embodiment, the activation system A and the slag S are introduced successively into the pre-mixture P. For example, the activation system A can be incorporated before or after the slag S in the pre-mixture. -mixture P. Preferably, the activation system A is incorporated before the slag S in the pre-mixture P. This first embodiment is particularly advantageous in the case where bulk slag is already available in one of the silos of the concrete plant and/or if the aggregates have a particularly high humidity rate (typically greater than 6%).

According to another embodiment, the activation system A of step b) is in the form of a premix P' with the said slag S, and the said activation system A and slag S are simultaneously incorporated into the pre-mix P. This process can in particular be advantageous in the case of the manufacture of precast concrete or in the case of a fairground concrete plant, which are less demanding in terms of the transport time of the concrete.

Advantageously, the method according to the invention is devoid of any stage of dry mixing of the activation system A with said aggregates.

The slag S is incorporated into the pre-mix P so that the water/binder ratio is adapted to the manufacture of the concrete, in particular to the reaction of the slag S with water, to the rise in strength of the concrete and to the fluidity of the fresh concrete required.

In particular, the method uses water, the activation system A and the slag S in a water/(activation system A + slag S) ratio varying from 0.1 to 1, preferably from 0, 2 to 0.55, and more preferably from 0.3 to 0.5. The weighing devices and the system for controlling the water content of the aggregates must make it possible to regulate the water content of the concrete with an accuracy of 10 litres/m ³ .

Furthermore, the mixing is preferably carried out in a mixer. Preferably, the mixing in step(s) c) and/or d) can be carried out with a forced-action mixer.

Step d) consists in prolonging said mixing until a fresh concrete is obtained, in particular in a forced-action mixer.

Advantageously, the fresh concrete shows a subsidence at the Abrams cone (NL EN 12350-2 standard) greater than or equal to 160 mm, preferably varying from 160 mm to 210 mm.

In particular, the fresh concrete obtained in step d) is characterized by a slump greater than or equal to 160 mm.

The concrete obtained by the process advantageously falls within consistency class S4 or S 5, preferably S4, according to standard NF EN 206/CN.

Such fresh concrete has a fluidity making it possible in particular to manufacture piles, diaphragm walls, soles, stringers, slabs, floors, posts, beams and/or sails. Preferably, the fresh concrete retains a slump greater than or equal to 160 mm over a sufficiently long period to be able to put it in place.

In particular, fresh concrete exhibits a slump greater than or equal to 160 mm for a period of at least 60 min, or even at least 90 min, preferably at least 120 min.

The method may further comprise a positioning step dl) between the kneading step d) and the hardening step e).

In particular, the fresh concrete can be placed in a formwork element, in particular in a formwork, then preferably compacted using internal or external vibration. For example, the fresh concrete can be placed in a formwork element comprising at least one reinforcement, in particular a reinforcement cage.

Step e) consists of allowing said fresh concrete to harden.

In general, the slag S, the activation system A and the water present in the fresh concrete react, allowing the concrete to set. The strength of the concrete then increases over time.

Step e) can take place at ambient temperature and humidity, for example outdoors on a building site or in a prefabrication factory.

The temperature can be controlled in step e). For example, the concrete can be subjected to a temperature varying from 15 to 80° C., preferably from 20 to 65° C., and more preferably from 25 to 50° C., in particular for 1 to 48 h, or even for 5 to 36 h.

It is also possible for step e) to include cycles increasing and decreasing in temperature, at a relative humidity greater than or equal to 40%, preferably 80%, and more preferably equal to 100%, under a pressure varying from 8 at 12 atm, or a pressure of 1 atm.

The method may further comprise a drying step f) following step e).

As stated previously, the process according to the invention can also comprise the implementation of at least one adjuvant in step c) and/or in step d), in particular chosen from plasticizers, superplasticizers and mixtures thereof, and in particular among superplasticizers.

Additive(s)

The adjuvant(s) can be incorporated into the premix P in the form of a premix with the activation system A. If necessary, they can also be incorporated in the form of a premix with the premix P'. As a variant, the adjuvant(s) can be incorporated into the premix P after the activation system A, or even after the activation system A and after the slag S.

The adjuvant(s) may be incorporated in a solid, in particular a powder, or liquid form.

The process can implement as an adjuvant at least one superplasticizer or plasticizer chosen from NBSP (naphthalene-based superplasticizers), PNS (polynaphthalene sulfonates), MBSP (melamine-based superplasticizers), PMS (polymelamines sulfonates), HCA (hydroxycarboxylic acids), (P)AA (poly(acrylic acid)), LS (lignosulfonates), in particular ammonium, calcium or sodium lignosulfonates, PCE (polycarboxylic ethers), PCAs (polycarboxylic acids), phosphonates, their salts and/or their derivatives and their mixtures.

In particular, the process can implement as an adjuvant at least one superplasticizer or plasticizer chosen from NBSP (naphthalene-based superplasticizers), PNS (polynaphthalene sulfonates), LS (lignosulfonates) and mixtures thereof, preferably selected from PNS, LS and mixtures thereof.

As a variant, the superplasticizer can be chosen from MBSPs, PMSs, NBSPs, PNSs, PCEs and mixtures thereof.

Furthermore, the method can implement the superplasticizer(s) or plasticizer(s) in a weight ratio of the superplasticizer(s) or plasticizer(s) relative to the slag S varying from 0.05% to 2% , preferably from 0.1% to 1%, and more preferably from 0.2% to 0.5%. As a variant, the method can implement the superplasticizer(s) or plasticizer(s) in a weight ratio of the superplasticizer(s) or plasticizer(s) relative to the binder varying from 0.05% to 2%, preferably from 0.1% to 1%, more preferably from 0.2% to 0.5%.

The method can also implement as an adjuvant at least one compound chosen from water retainers, thickeners, defoamers, biocides, pigments, flame retardants, air entrainers, retarders, accelerators, fibers, dispersion powders, wetting agents, polymer resins, complexing agents other than chelating agent, polymer dispersions, shrinkage reducing agents, and mixtures thereof.

The adjuvant(s), in particular of the superplasticizer type, may comprise other characteristics or other compounds as described in applications WO 2019/110134 and WO 2019/110280.

Activated slag concrete

The invention also relates to an activated slag concrete obtained by the method as described above.

In particular, this concrete has a compressive strength at 1 day of at least 1 MPa, in particular 5 MPa, or even 15 MPa according to standard NL EN 12390-3 depending on the curing temperature varying in particular by 15° C to 80°C.

The activated slag concrete can advantageously be stripped 1 day after step c).

In particular, activated slag concrete falls under at least resistance class C30/37, preferably falls under resistance class C30/37, according to standard NF EN 206/CN. Such a concrete is characterized by a characteristic compressive strength at 28 days on a cylindrical specimen of at least 30 MPa, and on a cubic specimen of at least 37 MPa. The activated slag concrete has in particular a compressive strength at 28 days sufficient to form piles, diaphragm walls, footings, stringers, slabs, floors, posts, beams and/or sails. In particular, activated slag concrete falls within consistency class S4 or S5, preferably consistency class S4, according to standard NF EN 206/CN, for a period of at least 60 min, in particular at least 90 min, and more particularly at least 120 min.

This characteristic provides fresh activated slag concrete with satisfactory workability.

Activated slag fresh concrete

The invention also relates to a fresh activated slag concrete obtained at the end of step d) of the method described above.

Such fresh concrete has a fluidity allowing it to be poured before it loses its fluidity.

Structuring element and prefabricated element

The invention also relates to a concrete reinforced with activated slag, comprising steel reinforcements and an activated slag concrete as described above.

In particular, the steel reinforcements can be of various shapes, and in particular in the form of wires, rounds, bars, or welded mesh.

Furthermore, the invention relates to a structuring element comprising activated slag concrete as described above, the structuring element preferably being a pile, a diaphragm wall, a footing, a sill, a slab, a floor, a post, beam or wall.

In particular, the structuring element can be manufactured directly on a construction site or in a prefabrication factory. For example, the structuring element may comprise a concrete reinforced with activated slag as described previously.

According to a preferred embodiment, the structuring element is manufactured directly on a construction site.

The invention also relates to a prefabricated element comprising an activated slag concrete as described above. In particular, the prefabricated element can be manufactured according to the method described previously, in particular in a prefabrication factory or on a construction site. The prefabricated element can for example be obtained by fairground prefabrication. For example, the prefabricated element may comprise a concrete reinforced with activated slag as described previously.

Brief description of the drawings

[Fig 1] represents the Abrams cone slump results of an activated slag concrete obtained by the process of the invention according to example 1 (symbols □) or 2 (symbols D) or obtained by a method excluding the invention according to example 3 (symbols ·).

[Fig 2] represents the results of spreading with the Abrams mini-cone (expressed as a percentage) of an activated slag mortar obtained by the process of the invention according to the mode of introduction of example 2 with a water and aggregates at 20°C (symbols 0), water at 60°C and aggregates at 5°C (symbols □) and water and aggregates at 5°C (symbols A). [Fig 3] represents the average shrinkage measured on 3 specimens of the same activated slag concrete obtained by the process according to the invention.

[Fig 4] represents the compressive strength of an activated slag concrete obtained by a method according to the invention with a water/binder ratio of 0.34 (symbols A), 0.36 (symbols 6) and 0, 38 (□ symbols).

Examples

Material and methods

The following raw materials were used:

- Semi-crushed sand-limestone aggregates with a density of 2530 kg/m ³ and water absorption of 1.3%;

- Slag from the Ecocem factory in Fos-sur-Mer, produced according to European standard (NF EN 15167-1). The particle size is characterized by D10=1.38 μm; D50=12.16µm and D90=34.87µm. The particle size values are determined with a laser diffraction particle sizer from the company Malvern named “MASTERSIZER 3000”, according to the liquid dispersion method. The Blaine fineness is 4500 cm ² /g;

- Co-binder: this is a clinker whose Blaine fineness is 3100 cm ² /g and the components main chemicals are as follows: CaO (67% by mass), Si0 ₂ (21% by mass), Fe ₂ 0 ₃ (5% by mass), SO3 (3% by mass);

- Anhydrous sodium carbonate (NaiCCL), 99% purity, marketed by Solvay;

- Calcium carbonate, with a median diameter D50=1 pm and a BET specific surface of 80,000 cm ² /g;

- HEDP.4Na chelating agent;

- PNS type superplasticizer (dry extract 32%).

Abrams cone slump measurements are taken on concrete (figure 1) according to standard NF EN 12350-2 at a temperature of 20°C, Abrams mini-cone slump measurements are taken on mortar (figure 2) according to the provisions of standard NF EN 12350-8 using the MBE mini-cone (Abrams cone on a ½ scale) instead of the Abrams cone.

The shrinkage is measured on specimens of dimension 7× ⁷ ×28 cm 3 kept at 20° C. and 50% relative humidity according to standard NF P 15-433.

The compressive strength is measured for the concretes on specimens with a diameter of 110 mm and a height of 200 mm according to standard NF EN 12390-3. For mortars, the compressive strength is measured on 4cm x 4cm x 16cm prisms according to standard NF EN 196-1.

Example 1

Preparation of a concrete according to the invention (method 1)

An activation system is prepared by dry mixing sodium carbonate, calcium carbonate, chelating agent and co-binder in the proportions indicated in table 2 in mass percentage.

The concrete is prepared by mixing in the following constituents with a mixer, in the proportions detailed in Table 2, according to the following sequence:

Aggregates; Water at a temperature enabling an equilibrium temperature to be obtained with the aggregates of between 15°C and 25°C;

Mixing for 30 seconds;

Activation system; - Mixing for 30 seconds;

Milkman;

Mixing for 30 seconds;

Superplasticizer;

Final mixing for 3 minutes.

[Table 2]

Example 2 Preparation of a concrete according to the invention (method 2) The activation system is prepared as in Example 1.

A premix of the activator system and the slag is prepared by dry mixing.

Aggregates;

Water at a temperature allowing to obtain an equilibrium temperature with the aggregates between 15°C and 25°C;

Mixing for 30 seconds;

Pre-mixing of the activator system and the slag;

Mixing for 30 seconds;

Superplasticizer;

Final mixing for 3 minutes.

Example 3

Preparation of a concrete outside the invention (method 3)

The activation system is prepared as in Example 1.

A premix of the activation system and the slag is prepared as in example 2.

The concrete is prepared by mixing in the following constituents (which are at ambient laboratory temperature, i.e. 20°C) in a mixer, in the proportions detailed in Table 2, according to the following sequence:

Aggregates;

Pre-mixing of the activator system and the slag;

Dry mix for 30 seconds;

Water ;

Mixing for 30 seconds;

Superplasticizer;

Final mixing for 3 minutes.

Example 4

Abrams cone sag test Abrams cone sag tests are carried out for methods 1, 2 and 3, detailed respectively in examples 1, 2 and 3, with composition A of table 2.

The results, shown in Figure 1, show that methods 1 and 2 according to the invention make it possible to maintain a fluid concrete consistency, characterized by a slump greater than 160 mm, for more than 2 hours. On the contrary, in the case of method 3 outside the invention, the concrete lost its fluid concrete consistency after 45 minutes.

Spreading tests with the Abrams mini-cone are also carried out according to method 2, detailed in example 2, with the proportions of equivalent concrete mortar corresponding to composition A (see table 3 below) for a pre- mixture of aggregates and water at different temperatures.

[Table 3]

The following three tests are carried out: i) The water and the aggregates are conditioned at 20°C before mixing, and the premix P obtained has a temperature of 20°C; ii) The aggregates are conditioned at 5°C, and are mixed with water at 60°C, forming a premix P having a temperature of 27°C iii) The water and the aggregates are conditioned at 5°C before their mixture, and the premix P obtained has a temperature of 5°C.

FIG. 2 represents the results of the mini-cone spreading obtained. In the two cases where the pre-mixture of water and aggregates obtained has a temperature above 15° C. (case i) and ii) above), the consistency of the mortar is kept fluid for at least 1 hour. On the contrary, G use of materials that do not comply with the recommendations of temperatures, as in the case of the pre-mixture of water and aggregates at 5°C (case iii) above), causes a rapid stiffening of the mortar and does not make it possible to obtain the maintenance of a fluid consistency.

Example 5 Results of withdrawal

The shrinkage measurements are carried out for 3 test specimens obtained with composition A.

The curve in figure 3 corresponds to the average of the deformations measured on each of the three prisms of the same concrete. It shows that the shrinkage of a concrete according to the invention is comparable to the shrinkage of a traditional cement concrete.

Example 6

Strength of concrete composition conforming and not conforming to the invention

Resistance measurements are carried out for concretes prepared with compositions B (outside the invention) and C (according to the invention).

In addition, concretes whose composition includes:

- an excess of 10 L of water (composition B or C with 182 kg/m ³ of water for 400 kg/m ³ of slag), or

- a water defect of 10 L (composition B or C with 162 kg/m ³ of water for 400 kg/m ³ of slag) are carried out to evaluate the robustness of the composition.

The results for composition C according to the invention are reported in Figure 4. The impact of the amount of water in the mixture hardly modifies the mechanical strength of the specimens obtained. In addition, a compressive strength greater than 40 MPa is measured at 28 days.

On the contrary, the results for composition B outside the invention, reported in Table 4, show that the concrete sees its hardening extremely slowed down in the case of an excess of water. Rc represents the compressive strength measured at different ages of the concrete. [Table 4]

Claims

1. Method for manufacturing an activated slag concrete, comprising at least the steps consisting in: a) Having a pre-mixture P of water and aggregates, the temperature of said pre-mixture P being at least equal to 10°C, b) Having an activation system A comprising at least one co-binder, a chelating agent, an alkali metal carbonate and a carbonated material distinct from the alkali metal carbonate, c) Incorporating under mixing into said pre -mixture P, said activation system A and a slag S, said activation system A and slag S being introduced successively and/or simultaneously, d) Prolonging said mixing until a fresh concrete is obtained, and e) Allow said fresh concrete to harden.

2. Process according to claim 1, in which said pre-mixture P is at a temperature at least equal to 15° C. in step a).

3. Process according to claim 1 or 2, in which said activation system A of step b) is in the form of a premix P′ with said slag S, and said activation system A and slag S are simultaneously incorporated into the premix P.

4. Method according to any one of the preceding claims, further comprising the incorporation of at least one adjuvant chosen in particular from plasticizers, superplasticizers and mixtures thereof.

5. Method according to any one of the preceding claims, using said co-binder at a content of less than 5% by mass relative to the total mass of said activation system A and slag S, also called mass of binder.

6. Process according to any one of the preceding claims, in which the said slag S comprises at least one ground blast-furnace slag.

7. A method according to any preceding claim, wherein said co-binder is a calcium ion precursor.

8. Method according to any one of the preceding claims, in which said activation system A comprises at least one alkali metal carbonate chosen from sodium carbonates, potassium carbonates and mixtures thereof, and more preferably comprises at least sodium carbonate.

9. Process according to any one of the preceding claims, in which the said carbonated material distinct from the alkali metal carbonate is in the form of at least one material chosen from limestone, dolomite, precipitated calcium carbonate, chalk , marble, aragonite, travertine, tufa and mixtures thereof, preferably comprises at least limestone.

10. Process according to any one of the preceding claims, in which the said chelating agent(s) is a chelating agent for the calcium ion or the aluminum ion, and preferably for the calcium ion.

11. Process according to any one of the preceding claims, in which the said chelating agent is chosen from phosphonates, preferably monophosphonates and/or diphosphonates, and more preferably from HEDP (1-hydroxyethylidene-1,1-diphosphonic acid). and EDTMP (ethylenediaminetetramethylene phosphonic acid).

12. Process according to any one of the preceding claims, using the alkali metal carbonate and the slag S in an alkali metal carbonate/slag S weight ratio varying from 2% to 12%, preferably from 6% to 10% .

13. Process according to any one of the preceding claims, using the co-binder and the slag S in a co-binder/slag S weight ratio varying from 1% to 5%.

14. Process according to any one of the preceding claims, using the chelating agent and the slag S in a weight ratio of the chelating agent relative to the slag S varying from 0.001% to 2%, preferably from 0.01% to 1%, and more preferably from 0.1% to 0.7%.

15. Process according to any one of the preceding claims, using water, the activation system A and the slag S in a water/(activation system A + slag S) ratio varying from 0.1 to 1. , preferably from 0.2 to 0.55, and more preferably from 0.3 to 0.5.

16. Method according to any one of claims 4 to 15, implementing as an adjuvant at least one superplasticizer or plasticizer chosen from NBSP (naphthalene-based superplasticizers), PNS (polynaphthalene sulfonates), LS ( lignosulphonates) and mixtures thereof, preferably chosen from PNS, LS and mixtures thereof.

17. Method according to any one of the preceding claims, in which steps c) to d), or even a) to d), are carried out in a concrete plant, preferably a concrete plant with a forced action mixer.

18. Activated slag concrete obtained by the process according to any one of the preceding claims.

19. Concrete according to the preceding claim, falling under at least resistance class C30/37, preferably falling under resistance class C30/37, according to standard NF EN 206/CN.

20. Concrete according to claim 18 or 19, falling within consistency class S4 or S5, preferably consistency class S4, according to standard NF EN 206/CN, for a period of at least 60 min, in particular of at least 90 min, and more particularly of at least 120 min.

21. Fresh activated slag concrete, obtained at the end of step d) of the process according to any one of claims 1 to 17.

22. Reinforced activated slag concrete, comprising steel reinforcements and an activated slag concrete according to any one of claims 18 to 20.

23. Structuring element comprising an activated slag concrete according to any one of claims 18 to 20, the structuring element preferably being a pile, a diaphragm wall, a footing, a sill, a slab, a floor, a post, a beam or a veil.

24. Precast element comprising an activated slag concrete according to any one of claims 18 to 20.