Clay-based composition for building material

Abstract

Clay-based composition for construction materials. The invention relates to a clay-based composition for construction materials, particularly for hydraulic binders such as cement, comprising: - one or more "flash-cured" clays obtained by flash calcination of the clay(s) into particles at a temperature between 600 and 900°C for a few seconds, followed by rapid cooling, and - crystalline silica oxide, or quartz, in particles. The invention also relates to a binder, particularly a hydraulic binder, comprising such a composition, a process for manufacturing such a composition, and the use of washing fines to manufacture such a composition.

Description

Title of the invention: Clay-based composition for building material technical field

[0001] The present invention relates to the field of construction materials, and more particularly to new compositions for construction materials, their manufacturing processes and their uses for the production, in particular of hydraulic binders such as concrete or mortar. Previous technique

[0002] There are two types of cement, so-called hydraulic cements such as Portland cements, and so-called geopolymer cements.

[0003] Portland cement is a widely used material in the construction industry, but its manufacture requires, on the one hand, the consumption of numerous resources and, on the other hand, produces a significant amount of pollutants responsible, among other things, for global warming and acid rain. Furthermore, its production required the firing of limestone and clay at very high temperatures, on the order of 1450°C.

[0004] Geopolymer cements are based on mineral geopolymer formed by the polymerization of aluminosilicate oxides in the presence of an alkaline activator.

[0005] The production of geopolymer cement is significantly more ecological than the production of hydraulic cement since the formation of one tonne of hydraulic cement generates about 1 tonne of CO2, whereas one tonne of geopolymer cement generates only about 0.1 tonne of CO2.

[0006] However, geopolymer cements have a higher economic cost, which limits their uses.

[0007] It is also known to heat-treat clays, and more specifically kaolins, intended for use in hydraulic or geopolymer cements, particularly to obtain a dehydrated form, more specifically meta-kaolins. The dehydrated form of clays, or meta-clays, is more advantageous for use in cements. Such heat treatment notably reduces the energy resources required for cement production. Description of the invention

[0008] The present invention aims to solve the various technical problems stated above. In particular, the present invention aims to provide a composition for a construction material that further reduces the environmental impact of manufacturing the construction material. More specifically, the present The invention aims to propose the use of industrial process residues for the manufacture of a composition for construction material.

[0009] Thus, according to one aspect, a clay-based composition is proposed for use as a construction material, particularly as a hydraulic binder such as cement. The composition comprises: - one or more "flash-treated" clays obtained by flash calcination of the clay(s) into particles at a temperature between 600 and 900°C for a few seconds, followed by rapid cooling, and - of crystallized silica oxide, or quartz, in particles.

[0010] Thus, the composition according to the present invention is based on residues from industrial processes for washing mineral materials, for example, from washing excavated soil, quarry materials (sand or aggregates), or sediments. Such residues have the particular advantage of containing a significant proportion of clays necessary for preparing a binder. The use of such residues therefore saves the resources typically required for clay extraction.

[0011] Furthermore, and in order to further limit the environmental impact of the composition according to the invention, the clays are heat-treated at a temperature between 600°C and 900°C for a few seconds, followed by cooling, in order to obtain a dehydrated form of these clays which is particularly advantageous for the manufacture of binders. Such heat treatment is made possible, and particularly advantageous, by the fact that the recovered composition, resulting from the washing of mineral materials, is already in the form of fine particles (or powder, or in a pulverized form), and therefore does not necessarily need to be ground beforehand, but possibly just deagglomerated.

[0012] Indeed, flashed clay, or flashed meta-clay, is obtained by flash calcination, unlike "conventional" meta-clay, which is obtained by calcination in a rotary kiln for at least 5 hours. In both cases, the clay is activated by water desorption. The production of flashed meta-clay requires significantly less energy, is a low-CO2 emission process, and is less complex than that of conventional meta-clay, since the heating period lasts only a few seconds and no subsequent grinding is necessary. Furthermore, the clay preparation prior to heat treatment is minimal. Its environmental impact is therefore lower, and its cost is reduced.

[0013] Finally, the composition according to the present invention also comprises crystallized silica oxide, or quartz. The presence of this oxide follows directly from the origin of the composition, since crystallized silica oxide, or quartz, is present in mineral materials. The composition according to the present invention thus advantageously exploits the presence of this oxide, mixed with the clays, which is also in granular (or powdered) form. Quartz particles can therefore advantageously form a mineral filler in the binder obtained from the composition according to the invention. Indeed, quartz increases the compactness, and therefore the strength, of the final binder, but is often difficult and expensive to grind due to its hardness. In the case of the present invention, the presence of quartz, already in granular form, improves the mechanical properties of the final binder without increasing the cost or resources required for its manufacture.

[0014] Thus, the composition according to the invention advantageously utilizes residues from mineral material washing processes, conventionally called "washing fines," which are often unused and cumbersome, to form a composition rich in clay and quartz in the form of particles. The composition according to the invention results directly from the heat treatment of such residues at a temperature between 600°C and 900°C for a few seconds, followed by cooling, to obtain, with limited resources, a composition for construction materials.

[0015] Preferably, the mass percentage, in particular in dry matter, of crystallized silica oxide is greater than or equal to 5%, preferably greater than or equal to 10%, and more preferably between 5% and 60%, or even between 10% and 40%.

[0016] The composition according to the invention being obtained from the residues of mineral material washing processes, it therefore comprises a relatively high quantity of crystallized silica oxide, or quartz, which remains unchanged during the heat treatment (flash calcination) applied for the dehydration of the clays.

[0017] Preferably, the ratio, particularly in dry matter, of the mass percentage of crystallized silica oxide to the mass percentage of a "flashed" clay or "flashed" clays is between 0.2 and 3, preferably between 0.3 and 1.5.

[0018] The composition according to the invention thus comprises similar proportions of clays and quartz, the clays being heat-treated for their use in the binder, and the quartz playing the role of mineral filler for the binder.

[0019] Preferably, the crystallized silica oxide is mixed with the clay(s) before flash calcination.

[0020] The composition according to the invention is obtained from a mixture of clay and quartz particles, in particular those obtained from washing mineral materials. The clay and quartz particles can thus be heat-treated simultaneously, the quartz remaining stable at a temperature of 900°C in particular, to prepare the composition according to the present invention.

[0021] Preferably, the mass percentage of limestone is greater than or equal to 2%, preferably greater than or equal to 5%, and more preferably between 5% and 40%.

[0022] The composition according to the present invention may also include limestone, particularly and advantageously also obtained from the washing of mineral materials. The limestone particles already present make it possible to reduce the amount of limestone to be added to the composition according to the present invention to form the binder. In particular, a flash calcination temperature below 800°C makes it possible to activate the clays without calcining the limestone. The presence of limestone in the composition according to the present invention is therefore advantageous for the use of said composition in the manufacture of a binder, and also makes it possible to utilize a compound that is sometimes important in the residues from washing mineral materials.

[0023] Preferably, 90% by mass, preferably 95% by mass, of the particles of the composition have a size measured according to standard NF EN ISO 17892-4, less than or equal to 100pm, preferably less than or equal to 70pm.

[0024] The composition according to the invention is derived from residues that are already in particle form, which allows the heat treatment to be applied directly without necessarily requiring a prior grinding step, to obtain a composition according to the invention also in particle form. A deagglomeration step for any aggregates may be carried out prior to the heat treatment, if necessary.

[0025] Preferably, the composition comprises metakaolin and at least one flash clay other than metakaolin. In other words, the composition according to the invention does not exclusively comprise metakaolin as a flash clay.

[0026] According to another aspect, a binder, in particular a hydraulic binder, comprising in particular a clay-based composition as described above, is also proposed.

[0027] The binder thus comprises both heat-treated clay, quartz as a mineral filler, and possibly limestone.

[0028] The binder thus obtained can be left as is. The binder thus obtained can also be mixed with standard cement, for example at a ratio of 10% to 70%, preferably 20% to 40% by mass.

[0029] The binder thus obtained can also be mixed with other components chosen from: ground blast furnace slag, limestone fillers, fly ash, chemical activators, additives, etc.

[0030] According to another aspect, a mortar or concrete comprising a composition as described above, or a binder, in particular hydraulic, as described above, is also proposed.

[0031] According to another aspect, a process for manufacturing a clay-based composition for obtaining a binder, in particular a hydraulic binder such as cement, is also proposed, in which: - Particles are recovered from the washing of mineral materials, containing a or several clays and crystallized silica oxide, or quartz, - a heat treatment is applied at a temperature between 600 and 900°C for a few seconds, followed by rapid cooling, to said particles, so as to obtain a composition based on "flash" clay intended for the manufacture of a binder, in particular hydraulic.

[0032] The particles resulting from the washing of mineral materials, or fines, have a composition (clay, quartz, and possibly limestone) and a shape (fine particles) suitable for heat treatment of the clays they contain in order to obtain a composition for a construction material. The use of such particles to prepare a composition for a construction material is all the more advantageous since such fines are currently underutilized or not utilized at all, and are therefore generally stored without a specific purpose, making them bulky and costly.

[0033] Washing mineral materials consists of separating fine particles from larger fractions. Such separation is achieved in particular using a liquid solution, primarily water. The washing process may therefore include desliming and / or screening and / or classification steps.

[0034] Preferably, the particles from the washing are previously de-clumped and / or de-agglomerated and / or crushed and / or separated, for example sieved, in order to obtain particles with a desired particle size.

[0035] Preferably, the mass percentage of crystallized silica oxide is greater than or equal to 5%, preferably greater than or equal to 10%, and more preferably between 10% and 40%.

[0036] Preferably, the ratio, in particular in dry matter, of the mass percentage of crystallized silica oxide to the mass percentage of a "flashed" clay or "flashed" clays is between 0.2 and 1.2, preferably between 0.3 and 1.

[0037] According to another aspect, it is also proposed to use particles from the washing of mineral materials, such as particles from the washing of quarries, sediments or spoil, the particles including in particular unflashed clay and quartz, for the manufacture of a binder, in particular hydraulic.

[0038] The use of such particles, or fines, makes it possible on the one hand to valorize a residue, or waste, from an industrial process, while making it possible to obtain a composition already in the form of particles, which makes it suitable for an optimized thermal treatment, and whose composition is compatible, or even adapted, to the manufacture of a binder, in particular hydraulic.

[0039] Preferably, the particles from the washing of mineral materials are flashed at a temperature between 600 and 900°C for a few seconds, followed by rapid cooling. Description of the implementation methods

[0040] The description will be described in more detail and illustrated by the following non-limiting examples.

[0041] The first example relates to a composition of fines from washing mineral materials, making it possible to obtain, after flash calcination, a composition according to the invention.

[0042] The composition of the first example was obtained by X-ray diffraction, after quartering, drying at 40°C and fine grinding.

[0043] The analyses were, for example, carried out on a Rigaku Miniflex 600 diffractometer (goniometer 0.20) with the following analysis conditions: 40 kV, 15 mA (copper tube); divergence slits 0.625°, anti-diffusion slit open; D / teX Ultra fast detector, Ni filter; step size 0.02°, counting time 5 degrees per minute.

[0044] The mass percentages obtained are as follows: 13% alpha-SiO2 (Quartz) 3% of KAlSi3O8 (Microcline) 2% NaAlSi3O8 (Albite) 34% CaCO3 (Calcite) 5% Ca(Fe, Mg)(CO3)2 (Ankerite) 41% clays (smectites, chlorites, kaolinite, illite, mica).

[0045] After flash calcination of the composition of the first example, a composition according to the present invention is obtained with substantially similar proportions, but with meta-clays, in particular meta-kaolin, in place of clays.

[0046] The first example of fine composition therefore makes it possible to obtain, after flash calcination, a composition comprising meta-clays, quartz and limestone, which makes it particularly suitable for the manufacture of a binder, especially hydraulic.

[0047] Furthermore, the powdered form of the washing fines allows, on the one hand, flash calcination treatment without necessarily requiring a prior grinding step, but possibly just a step of aggregate deagglomeration. On the other hand, it allows obtaining a composition according to the present invention which is also in powdered form, making its use for the manufacture of a binder advantageous.

[0048] The second example relates to a composition of fines from washing mineral materials, making it possible to obtain, after flash calcination, a composition according to the invention.

[0049] The composition of the second example was obtained by X-ray diffraction, after quartering, drying at 40°C and fine grinding.

[0050] The mass percentages obtained are as follows: 35% alpha-SiO2 (Quartz) 6% of KAlSi3O8 (Microcline) 6% NaAlSi3O8 (Albite) 15% CaCO3 (Calcite) 37% clays (smectites, chlorites, kaolinite, illite, mica).

[0051] The fines also have a passing (or sieving) at 80pm of 92.8% measured according to standard NF P 94-056.

[0052] After flash calcination of the composition of the second example, a composition according to the present invention is obtained with substantially similar proportions, but with meta-clays, in particular meta-kaolin, in place of clays.

[0053] The second example of fine composition therefore makes it possible to obtain, after flash calcination, a composition comprising meta-clays, quartz and limestone, which makes it particularly suitable for the manufacture of a binder, especially hydraulic.

[0054] The third example relates to a composition of fines from washing mineral materials, making it possible to obtain, after flash calcination, a composition according to the invention.

[0055] The composition of the third example was obtained by X-ray diffraction, after quartering, drying at 40°C and fine grinding.

[0056] The mass percentages obtained are as follows: 34% alpha-SiO2 (Quartz) 5% of KAlSi3O8 (Microcline) 5% NaAlSi3O8 (Albite) 9% CaCO3 (Calcite) 44% clays (smectites, chlorites, kaolinite, illite, mica).

[0057] The fines also have a passing (or sieving) at 80pm of 94.4% measured according to standard NF P 94-056.

[0058] After flash calcination of the composition of the third example, a composition according to the present invention is obtained with substantially similar proportions, but with meta-clays, in particular meta-kaolin, in place of clays.

[0059] The third example of fine composition therefore makes it possible to obtain, after flash calcination, a composition comprising meta-clays, quartz and limestone, which makes it particularly suitable for the manufacture of a binder, especially hydraulic.

[0060] Thus, with the residues from mineral washing processes, it is possible to obtain a composition for construction materials. In particular, the valorization of such residues, in combination with their powdered form suitable for a flash calcination makes it possible to obtain a composition for construction material, and in particular for hydraulic binder, requiring less energy or environmental resources than compositions of the prior art, while also having the advantage of including quartz in powder form and possibly limestone, also in powder form.

Claims

Demands

1. Clay-based composition for construction material, in particular for hydraulic binder such as cement, comprising: - one or more "flash-fired" clays obtained by flash calcination of the clay(s) in particles at a temperature between 600 and 900°C for a few seconds, followed by rapid cooling, and - crystallized silica oxide, or quartz, in particles in which the ratio of the mass percentage of crystallized silica oxide to the mass percentage of a "flash-fired" clay or clays is between 0.2 and 1.

2.

2. Composition according to claim 1, wherein the mass percentage of crystallized silica oxide is greater than or equal to 5%, preferably greater than or equal to 10%, and more preferably between 10% and 40%.

3. Composition according to claim 1 or 2, wherein the ratio of the mass percentage of crystallized silica oxide to the mass percentage of a "flash" clay or "flash" clays is between 0.3 and 1.

4. Composition according to any one of the preceding claims, wherein the crystallized silica oxide is mixed with the clay(s) before flash calcination.

5. Composition according to any one of the preceding claims, wherein the mass percentage of limestone is greater than or equal to 2%, preferably greater than or equal to 5%, and more preferably between 5% and 40%.

6. Composition according to any one of the preceding claims, wherein 90% by mass, preferably 95% by mass, of the particles of the composition have a size measured according to standard NF EN ISO 17892-4, less than or equal to 100pm, preferably less than or equal to 70pm.

7. Binder, in particular hydraulic, comprising in particular a clay-based composition according to any one of the preceding claims.

8. Mortar or concrete comprising a composition according to any one of claims 1 to 6, or a binder, in particular hydraulic, according to the preceding claim.

9. A method for manufacturing a clay-based composition for obtaining a binder, in particular a hydraulic binder such as cement, in which : - Particles are recovered from the washing of mineral materials, containing one or more clays and crystallized silica oxide, or quartz, - A heat treatment is applied to the particles at a temperature between 600 and 900°C for a few seconds, followed by rapid cooling, in order to obtain a "flash-treated" clay-based composition intended for the manufacture of a binder, particularly a hydraulic one. in which the ratio of the mass percentage of crystallized silica oxide to the mass percentage of a "flash" clay or "flash" clays is between 0.2 and 1.

2.

10. A process according to the preceding claim, wherein the mass percentage of crystallized silica oxide is greater than or equal to 5%, preferably greater than or equal to 10%, and more preferably between 10% and 40%.

11. A process according to claim 9 or 10, wherein the ratio of the mass percentage of crystallized silica oxide to the mass percentage of a "flashed" clay or "flashed" clays is between 0.3 and 1.