FR3012823A1 - DEPOLLUTING SLAB - Google Patents

Abstract

The present invention relates to the manufacture of a concrete slab capable of depolluting the atmosphere according to a method which comprises the following steps: a) depositing on a concrete in the fresh state, a material comprising at least i. a hydraulic binder; ii. inorganic, synthetic or metallic aggregates or mixtures thereof; iii. activated carbon; b) applying a pressure on the surface of the concrete obtained after step a).

Description

The present invention relates to the manufacture of a slab capable of depolluting the atmosphere.

In industrial environments, and especially in industrial premises, the atmosphere is often polluted by the presence of pollutants in the air. Among these pollutants, there are volatile organic compounds, nitrogen oxides (NO and NO2), also called NOx, which are notably derived from the combustion of energy (fossil) in thermal engines (vehicle exhaust gases). combustion engine, boilers, industrial processes etc.). Also the problem to be solved by the invention is to provide a new means to clean up the atmosphere. Unexpectedly, it has been demonstrated that it is possible to add activated carbon to the surface of a concrete slab in order to obtain a soil that absorbs pollutants from the air. The present invention relates to a method for producing a depolluting slab, absorbing pollutants from the air, in particular NOx. The invention offers the advantage of participating in the reduction of the concentration of nitrogen oxides, carbon oxides, sulfur oxides, ozone and volatile organic compounds present in the atmosphere. In addition, it should be noted that the slabs are generally subject to other constraints such as heavy traffic of heavy vehicles, or extremely intense loads. They can even be subjected to shocks. Also the slabs are generally subjected to important and premature wear conditions hence the need for them to resist abrasion. One of the advantages of the invention is that the method according to the invention makes it possible to improve the strength of slabs, in addition to absorbing pollutants from the air. In fact, the invention makes it possible to reinforce the concrete slab whose surface will be strongly stressed, by creating an upper layer that is highly resistant to abrasion and to significant mechanical stresses.

Another advantage of the process according to the invention is that it can also be intended for the renovation of old soils, especially soils of the industrial sector. By "slab" is generally meant a monolithic layer of concrete, intended to constitute a ground floor or floor on which it is possibly possible to pour a screed and then possibly lay a coating.

Examples of slabs include parking areas, concrete slabs at service stations, dry areas in paper mills, polished concrete slabs, house or building slabs, ramps, tunnel sidewalks, unloading docks, unloading sidewalks, logistics platforms. Slabs can also be found in the following areas: factory halls, storage halls, shelving halls, aircraft hangars, tunnels, distribution centers, mechanical workshops, workshops and workshops. printers, factories, refineries, laboratories, cold stores, car parks, garages for private cars, hangars and cellars. And more generally, we can also mention the slabs that are in industrial premises, and which are very often in contact with high concentration of pollutants that contribute to air pollution. They are therefore subject to high levels of concentration of toxic gases, such as exhaust gases. The present invention relates to a method of producing a slab which comprises the following steps: a) depositing on a concrete in the fresh state a material comprising at least i. a hydraulic binder; ii. inorganic, synthetic or metallic aggregates or mixtures thereof; iii. activated carbon; b) applying a pressure on the surface of the concrete obtained after step a).

The material of step a) of the process according to the invention may optionally comprise from 5 to 99% of hydraulic binder, preferably from 15 to 50%; from 1 to 95% of mineral, synthetic or metallic aggregates or mixtures thereof, preferably from 40 to 80%; from 0.1 to 4% of activated carbon, preferably from 1 to 5% by weight. The material of step a) of the process according to the invention may optionally also comprise from 0 to 20% of dye, preferably from 3 to 10%, percentages expressed by weight.

A hydraulic binder is a material that picks up and hardens by hydration. Preferably, the hydraulic binder is or comprises a Portland cement. The hydraulic binder of the material of step a) of the process according to the invention may be chosen from Portland cement, Ciments Fondu®, sulphoaluminous cements, calcium aluminate cements, the cement obtained from the clinker described in the patent application WO 2006/018569 and mixtures thereof. The hydraulic binder of the material of step a) of the process according to the invention may comprise cement.

The cement that is suitable for the material of step a) of the process according to the invention is preferably the cement described in accordance with European Standard NF EN 197-1 of February 2001. The cement that is suitable for the material for the material of step a) the process according to the invention may be of the type CEM I, CEM II, CEM III, CEM IV or CEM V.

Preferably, the cement that is suitable for the material of step a) of the process according to the invention is chosen from cements of the following types: - CEM I or CEM II, optionally in admixture with mineral additions, or - CEM III, CEM IV or alternatively, the hydraulic binder of the material of step a) of the process according to the invention comprises at least one cement of CEM I or CEM II type, mixed with additions of the dairy type and / or ashes. flying and / or silica fumes and / or pozzolanic materials and / or metakaolins. These may make it possible to replace the composite cements with slags and / or fly ash of the CEM II / A, CEM II / B, CEM III / A, CEM III / B, CEM III / C, CEM IV / A type, EMC IV / B, EMC V / A or EMC V / B. The hydraulic binder suitable for the material of step a) of the process according to the invention may be a calcium aluminate cement. It is generally a cement comprising a C4A3, CA, C12A7, C3A or C1 1A7CaF2 mineralogical phase or their mixtures, such as, for example, Ciments Fondu®, sulphoaluminous cements, calcium aluminate cements conforming to the European standard NF EN 14647 of December 2006, the cement obtained from the clinker described in the patent application WO 2006/018569, the cement obtained from the clinker described in the patent application WO 2013/023731, the cement obtained from from the clinker described in patent application WO 2013/023729, or mixtures thereof.

The hydraulic binder suitable for the material of step a) of the process according to the invention may be an ettringitic cement, such as, for example, a sulphoaluminous cement additive of calcium sulphate or a calcium aluminate cement additive supplemented with calcium sulphate. The material of step a) of the process according to the invention may optionally comprise mineral additions. Mineral additions are generally materials that can be used as partial substitution for cement. The mineral additions suitable for the material of step a) of the process according to the invention may be chosen from pozzolanic materials, silica fumes, slags, calcined schists, calcium carbonate-containing materials, siliceous additions, fly ash, zeolites, ashes from the burning of plants, calcined clays and mixtures thereof.

The mineral additions suitable for the material of step a) of the process according to the invention can be pozzolanic materials (for example as defined in the European standard NF EN 197-1 of February 2001, section 5.2.3), fumes of silica (for example as defined in the European standard NF EN 197-1 of February 2001 paragraph 5.2.7), slags (for example as defined in the European standard NF EN 197-1 of February 2001 paragraph 5.2.2) calcined schists (for example as defined in the European Standard NF EN 197-1 of February 2001, paragraph 5.2.5), materials containing calcium carbonate, for example limestone (for example as defined in the European standard). NF EN 197-1 of February 2001 paragraph 5.2.6), siliceous additions (for example as defined in the French standard NF P 18-509 of December 1998 paragraph 5), fly ash (for example as defined in European standard NF EN 197-1 of February 2001 section 5.2.4) or their mixtures. The mineral additions suitable for the material of step a) of the process according to the invention may also be ash from the combustion of plants, such as for example ash from the combustion of rice husks. The mineral additions suitable for the material of step a) of the process according to the invention may also be zeolites. Flying ash is usually a powdery particle in the flue gases of coal-fired power plants. It is usually recovered by electrostatic or mechanical precipitation. The chemical composition of a fly ash depends mainly on the chemical composition of the burned coal and the process used in the thermal power plant from which it originated. It is the same for its mineralogical composition. The fly ash used according to the invention may be of siliceous or calcic nature. Preferably, the fly ash used according to the present invention is chosen from those as described in European Standard NF EN 197-1 of February 2001. The slags are generally obtained by rapidly cooling the molten slag resulting from the melting of the iron ore in a blast furnace. The slags that are suitable for the material of step a) of the process according to the invention may be chosen from granulated blast furnace slags according to the European standard NF EN 197-1 of February 2001, paragraph 5.2.2. The silica fumes suitable for the material of step a) of the process according to the invention can be a material obtained by reduction of high purity quartz by charcoal in electric arc furnaces used for the production of silicon and alloys. of ferrosilicon. The silica fumes are generally formed of spherical particles comprising at least 85% by mass of amorphous silica. Preferably, the silica fumes used according to the present invention may be chosen from silica fumes according to European Standard NF EN 197-1 of February 2001, paragraph 5.2.7. The pozzolanic materials suitable for the material of step a) of the process according to the invention may be natural siliceous or silicoaluminous substances, or a combination thereof. Pozzolanic materials include natural pozzolans, which are generally materials of volcanic origin or sedimentary rocks, and calcined natural pozzolans, which are materials of volcanic origin, clays, shales or rocks. sedimentary, thermally activated. The pozzolanic materials may be selected from pumice, tuffs, slag or mixtures thereof. Preferably, the pozzolanic materials that are suitable for the material of step a) of the process according to the invention may be chosen from pozzolanic materials according to the European standard NF EN 197-1 of February 2001, paragraph 5.2.3. Preferably, the mineral additions suitable for the material of step a) of the process according to the invention may be materials containing calcium carbonate, for example limestone and / or fly ash and / or fumed silica.

Preferably, the mineral additions suitable for the material of step a) of the process according to the invention may be silica fines and / or calcareous filler. The calcined clays used suitable for the material of step a) of the process according to the invention can result from the calcination of a clay, kaolinite, associated with various minerals (phyllosilicates, quartz, iron oxides) in variable proportions according to the deposits. They can be obtained either by grinding calcination or by grinding calcination in production units with rotary kilns, trays or so-called "flash" calcination, for example. They are essentially composed of amorphous alumina silicate particles. Preferably, the calcined clays that are suitable for the material of step a) of the process according to the invention can be chosen from metakaolins according to the preliminary draft standard PR NF P 18-513 of December 2011. The material of the step a) of the process according to the invention comprises inorganic, synthetic or metallic granulates or their mixtures. The aggregates can be composed of silica, calcium carbonate, quartz, marble, corundum, ferrosilicon, silicon carbide, chromium slag, iron, steel. In the case of metal aggregates, it may be iron shot, specially treated ductile metal flakes or mixtures thereof.

The aggregates can be aggregates of very high hardness but also of medium hardness. The material of step a) of the process according to the invention may comprise dyes. The dyes typically used in concretes are suitable according to the invention. These are natural or artificial powder pigments that are usually incorporated. Mention may in particular be made of metal oxides or natural ochres. As metal oxide, mention may be made of cobalt oxide (blue color), chromium oxide (green color), iron oxides (yellow, red, brown, black) and titanium oxide (white color) and their mixtures.

The material of step a) of the process according to the invention comprises active charcoal or modified activated charcoal. By "activated carbon" is generally meant a material made essentially of carbonaceous material with a microporous structure. The active carbons may be in the form of a powder, but also in the form of pre-agglomerated powders.

In the latter case it is usually small aggregates (grains or extrudas of a few millimeters long). Activated carbon can be produced by calcining carbon-rich organic raw materials, such as wood, bark, peat, lignite, coal, coconut husks, or pine bark for example . The material resulting from the calcination can then be activated in three distinct ways: either physically via a steam treatment for example, or chemically via a treatment with phosphoric acid for example, or by coupling these two types of treatments, physical and chemical, at the same time. By "modified active carbon" is generally meant an activated carbon grafted with additional chemical functions (for example amine functions or ether functions, cyclodextrin, etc.). Activated carbon may have been premixed with cement. The method according to the invention comprises a step a) where the material described above is deposited on a concrete in the fresh state.

The fresh concrete may be a recently cast concrete or put in place, delivered for example on a construction site by mixer truck. Preferably step a) will take place as soon as the concrete can support the weight of a man leaving only a slight trace. Step a) of the process according to the invention can be carried out in different ways, in particular by dusting, manual or mechanical. In the case of manual dusting, an operator moves on the concrete and throws the material with his hands.

Generally, the material of step a) of the process according to the invention is deposited at a rate of 3 to 10 kg / m 2 of fresh concrete surface. This quantity may vary according to the types of slabs. The method according to the invention comprises a step b) where a pressure is applied on the surface of the concrete obtained in step a). This step makes it possible to penetrate into the concrete the material deposited in step a). The material used in step a) of the process according to the invention is either in the dry state or in the state of slurry. Step b) of the process according to the invention can be done in different ways, in particular by float, manual or mechanical. In the case of a mechanical float, a device called mechanical trowel, helicopter or mechanical winder, can be used. The method according to the invention may further comprise a step c) of smoothing the surface of the concrete obtained after step b). Step c) or step b) can be done in the presence of water. Water can be provided by any means (eg spray) or water may already be present. Steps b) and c) can be simultaneous. In this case an operator can float with different types of blades. According to a variant of the process according to the invention, it is envisaged to repeat step a) several times. For example, it is envisaged a first sprinkling of the material described in step a), then a second and a third dusting. This variant has the advantage of ensuring a regularity of the material described in step a) in the thickness of the concrete layer. According to this variant, step a) is performed in several times. Then step b) continues. According to another variant of the method according to the invention, it is envisaged to repeat steps a) and b) successively. For example, it is contemplated a first sprinkling of the material described in step a), followed by a first float. Then a second dusting of the material described in step a), followed by a second float. In the particular case of the renovation of old soils, the material deposited in step a) will be a slurry. The invention also relates to a slab that can be obtained according to the method of the invention. The slab according to the invention is capable of absorbing pollutants from the atmosphere, in particular NOx. The slab according to the invention is depolluting. The following examples are non-limiting and illustrate the invention.

Examples of embodiments of the invention List of raw materials: Portland cement is a cement CEM I 52.5. This cement is of the CEM I type and the 52.5 strength grade from the Lafarge du Havre plant. The white cement is CEM I 52.5 N CE CP2 NF WHITE cement from the Lafarge plant in Le Teil. Granule 1 is calcium carbonate sold under the name BL200 and originating from the company OMYA. Granule 2 is a siliceous sand of particle size 0/1 mm from the company Palvadeau. The powdered superplasticizer is Dehscofix 158 from the family of naphthalene sulfonates from Hunstman.

The active carbon is Norit SA2 from Cabot. Formulations: The following formulations of material according to step a) of the process according to the invention are prepared: Formula I in kg Formula II in kg Portland cement 0 315 White cement 315 0 Granulate 1 85 85 Granulate 2 547 577 Powder superplasticizer 3 Active carbon 50 20 Making a slab according to the process of the invention: A concrete is poured with a suitable planimetry. The supply is made to the mixer truck, the pump or the crane. The concrete is spread and then tightened with the vibrating needle or the ruler. The equalization of the concrete is done with the vibrating rule, or with the hand rule. The float (step b) begins as soon as the concrete can support the weight of a man leaving only a slight trace. This operation makes it possible to bring back to the surface the humidity necessary for the incorporation of the wear layer.

In the first pass, sprinkle 2/3 of the material according to formula I or formula II. Simultaneously with this dusting, the surface is floated manually for the inaccessible areas or along the formwork, massive, walls, poles, and mechanically for the common parts.

In the second pass, sprinkle the remaining 1/3 of the material according to formula I or formula II. While the first float continues, immediately sprinkle the remaining third which will absorb moisture from the first layer before it evaporates. For greater consistency, sprinkle the second layer perpendicular to the first layer.

The operation of the first float is repeated identically as a second float. When the surface begins to close, the floats are replaced by "smooth" pallets. The smoothing then starts while keeping the blades horizontal. Finally, as the surface of the concrete hardens, a number of smoothings are carried out until a smooth and closed surface is obtained, which is acquired by tilting more and more the blades of the concrete. the helicopter. As for the float, the smoothing is carried out manually in the inaccessible zones, along the walls, forms, massive, and mechanically in the current zones. A rough surface can be obtained by passing a "sheepskin" roll before complete curing of the surface. As soon as the smoothing is completed, a curing product in the aqueous phase is applied by roller or sprayer. The sawing of the joints must be done as soon as possible without dewaxing the concrete.

A slab according to the invention is thus obtained.

Claims (8)

CLAIMS 1- A method of producing a slab which comprises the following steps: a) depositing on a concrete in the fresh state, a material comprising at least i. a hydraulic binder ii. inorganic, synthetic or metallic aggregates or mixtures thereof; iii. activated carbon; b) applying a pressure on the surface of the concrete obtained after step a). 2. The method of claim 1, wherein the material is either in the dry state or in the state of slurry. 3. The method of claim 1, wherein step a) is by dusting, manual or mechanical. 4. The method of claim 1, wherein step b) is by float, manual or mechanical. 5. The method of claim 1, wherein it further comprises a step c) of smoothing the surface of the concrete obtained after step b). 6. The method of claim 1 or 6, wherein step c) or step b) is in the presence of water. 7- slab obtainable by the method of any one of claims 1 to 6. 8- tile according to claim 8 characterized in that it is capable of absorbing pollutants from the atmosphere, including NOx.