FR2999567A1 - Ultra high-performance concrete covered by a polymeric film obtained by polymerization under the action of radiation, useful in an element for the field of construction - Google Patents

Abstract

Ultra high-performance concrete covered by a polymeric film obtained by polymerization under the action of radiation, is claimed. Independent claims are included for: (1) protecting the ultra high performance concrete from efflorescence spots, including applying a composition including monomers and/or the reactive prepolymers to the concrete, and then polymerizing under the action of radiations in order to obtain the polymeric film covering the concrete; and (2) use of the polymeric film obtained by polymerization under the action of radiations to protect the high performance concrete with respect to the efflorescence spots.

Description

The present invention relates to a high-performance concrete, to a method for protecting such a concrete, to an element for the field of construction comprising: such a concrete, as well as a method of manufacturing this element. The present invention relates to the technical field of the aesthetics of a high-performance concrete. It is more particularly the phenomenon of efflorescence, which leads to the appearance of unsightly whitish spots. Efflorescence is a migration of calcium salts from the concrete mass to the surface, under the effect of a flow of water vapor related to the drying of the room and storage conditions. These salts come from the carbonation of lime, they dissolve in water and migrate to the surface by capillarity. When the material dries, the water evaporates, and the salts crystallize, turning into a whitish deposit. This deposit forms spots due to efflorescence, which are named in the following spots of efflorescence. In the case of prefabricated pieces made of high-performance concrete, or even ultra-high performance, these whitish traces can appear during the aging of the concrete part but also during the heat treatment at high temperature. This cure, typically conducted at 90 ° C and 100% relative humidity for 48 hours, is commonly used after demolding to enhance and increase the durability of high performance concrete parts or even ultra-high performance. To remedy the appearance of these bloom spots, various concrete coatings have been proposed. These coatings can be of organic type (for example polymers) or mineral with variants according to their composition and / or their method of application. The organic polymers may be based on polyacrylic acid, polyurethane or silicone. The mineral coatings may be silicate-based. These coatings can be applied to concrete by brush, roller or spray. However, their properties do not make it possible to guarantee a satisfactory effect with regard to efflorescence spots at the concrete / coating interface during a high temperature heat treatment. Indeed, these coatings are still too permeable to the flow of water and calcium salts from the concrete. In addition, since the application of the protective coating is done just after demolding the concrete which still contains a large amount of water, this coating must have good adhesion with the high performance concrete.

Also the technical problem to be solved by the invention is to provide a high performance concrete for which the capacity of the surface to be cleaned is improved, for which the visual appearance of the surface of the concrete remains substantially that of uncoated concrete, for which there is no appearance of light or dark spots on the surface covered by the coating or at the interface between the concrete and the coating, in particular because of the phenomenon of efflorescence of concrete. For this purpose, the present invention relates to a high performance concrete, especially ultra high performance, coated in whole or part of a polymer film obtained by polymerization under the action of radiation. Surprisingly, the inventors have demonstrated that covering a high-performance concrete, in particular at very high performance, with a polymer film obtained by polymerization under the action of radiation, makes this concrete practically insensitive to the appearance of efflorescence spots and also allows an easy cleaning of this concrete by means of solvents, in order to preserve the esthetics of this element in the long term (in particular vis-à-vis visual degradations, such as graffiti). Advantageously, the concrete according to the invention has substantially the same visual appearance as uncoated concrete. The invention offers another advantage that the appearance of light or dark spots on the surface of the concrete according to the invention is avoided.

In addition, the very low intrinsic porosity of the polymer film makes it possible to obtain increased resistance to common stains (acidic fruit juice, liquid containing tannins, oil) which can be removed using a sponge soaked in water. This film has a high resistance to abrasion. The concrete element of the invention therefore advantageously finds its application also to the soil.

Advantageously, the polymer film is obtained by polymerization under the action of ultraviolet radiation. In this case, the film has in particular a very high resistance to abrasion. Advantageously, the concrete has a roughness Ra of from 0.5 μm (microns) to 10 μm, preferably from 0.5 to 7 μm, even more preferably from 0.5 to 5 μm, advantageously 0.5 μm. at 3 pm. This allows a homogeneous coating of the concrete surface by the polymer film. The concrete preferably has a water-cement ratio (W / C) of at most 0.45, preferably at most 0.32, more preferably from 0.20 to 0.27. The concrete may be a concrete containing silica fume. Preferably, the concrete comprises, in parts by weight: 100 of Portland cement; PA12015 EN 50 to 200 of sand having a single particle size with a D10 at a D90 of 0.063 to 5 mm, or a mixture of sands, the finest sand having a D10 at a D90 of 0.063 to 1 mm and the sand the coarser one having a D10 to a D90 of 1 to 5 mm, for example between 1 and 4 mm; 0 to 70 of a pozzolanic or non-pozzolanic material of particles, or a mixture thereof, having an average particle size of less than 15 μm; 0.1 to 10 of a water reducing superplasticizer; and 32 of water, especially 20 to 32 of water. The invention also relates to a process for protecting a high-performance concrete, particularly an ultra-high performance concrete, against efflorescence stains, comprising the following steps: applying a composition comprising monomers and / or reactive prepolymers on all or part of the concrete; - Polymerize this composition under the action of radiation, so as to obtain a polymer film covering all or part of said concrete. This composition comprising monomers and / or reactive prepolymers may be applied by roller or spray, which allows a good distribution of the coating. This composition is capable of crosslinking under the action of radiation, in particular under ultraviolet radiation. This guarantees a very rapid crosslinking, of the order of a few seconds, and completes the monomer, in particular greater than 90%, or even greater than 99%. Advantageously, the temperature of the composition, at the moment when it is applied to the concrete, is less than 35 ° C., preferably less than 30 ° C. This characteristic is advantageous because it makes it possible to limit the local rise in temperature at the surface of the concrete, when it is covered by the composition. Indeed, a significant rise in this temperature of the concrete surface would lead to the inadvertent appearance of efflorescence spots. Also advantageously, this composition is applied to the concrete without being heated. The exact temperature of this composition, when it is deposited on the concrete, depends on the operating conditions and, where appropriate, on the climatic conditions. Advantageously, the method further comprises demolding and heat treatment of the concrete. The steps of application of the composition and polymerization under the action of radiation may occur between the demolding of high performance concrete and the heat treatment.

This thermal treatment of concrete, also called thermal curing, is generally carried out at a temperature above ambient temperature (for example from 20 ° C to 90 ° C), preferably from 60 ° C to 90 ° C. The temperature of the heat treatment is preferably less than the boiling point of the water at ambient pressure. The temperature of the heat treatment is generally less than 100 ° C. The use of an autoclave in which the heat treatment is carried out at high pressure also allows the use of higher heat treatment temperatures. The heat treatment may last, for example, from 6 hours to 4 days, preferably about 2 days. The heat treatment begins after setting, usually at least one day after setting has started, and preferably on concrete which has aged from 1 day to about 7 days at 20 ° C. The crosslinking of the polymer constituting the film induces a strong adhesion with the element exiting the mold, as well as sealing the surface of the concrete with respect to the flow of water and calcium salts. In addition, the crosslinking of the polymer has the advantage of being fast (less than 5 minutes, or even 1 minute), which reduces the cycle and storage times associated with the application and drying of the parts. Finally, the advantage of a highly crosslinked film is to have a very scratch-resistant surface. Advantageously, the polymerization step under the action of radiation is carried out without delay, after the end of the application step of the composition. This avoids any inadvertent degradation of the reactive composition, covering all or part of the concrete. Advantageously, the steps of application of the composition and of polymerization under the action of radiation are carried out as quickly as possible after the end of the demolding step. This makes it possible to avoid the appearance of efflorescence spots on the concrete, which would be due to storage carried out in bad conditions.

The above protection method is particularly suitable for treating a high-performance concrete having at least one of the above characteristics. The invention also relates to a use of a polymer film obtained by polymerization under the action of radiation, to protect against blooming stains a high performance concrete, especially an ultra high performance concrete . The invention also relates to a use of a polymer film obtained by polymerization under the action of radiation, to protect against scratches a high-performance concrete, including ultra-high performance concrete. This polymer film is in particular obtained by polymerization under the action of ultraviolet radiation. This film may have all or some of the above characteristics, presented in relation to the concrete of the invention. The invention also relates to an element for the field of construction comprising a concrete as defined above. The invention finally relates to a method of manufacturing the above element, comprising a method of protecting the concrete as defined above.

Other advantages and characteristics of the invention will become clear from reading the description and examples given by way of purely illustrative and nonlimiting that will follow. By the term "hydraulic binder" is meant according to the present invention a material which takes and hardens by hydration, for example a cement.

By the term "concrete" is meant a mixture of hydraulic binder (for example cement), aggregates, water, optionally adjuvants, and possibly mineral additives, such as for example high performance concrete, Ultra-high performance concrete, self-compacting concrete, self-leveling concrete, self-compacting concrete, fiber concrete, ready-mix concrete or colored concrete. According to this definition, prestressed concrete is also meant. The term "concrete" includes mortars. In this specific case, the concrete comprises a mixture of hydraulic binder, sand, water and possibly additives and possibly mineral additions. The term "concrete" according to the invention denotes indistinctly fresh concrete or hardened concrete. By the term "roughness" is meant irregularities in the micrometer range of a surface that are defined by comparison with a reference surface, and are classified into two categories: asperities or peaks or protuberances, and cavities or hollow. The roughness of a given surface can be determined by measuring a number of parameters. In the present description, parameter Ra, as defined by DIN EN ISO 4287 of October 1998, is used, corresponding to the arithmetic mean of all the ordinates of the profile within a base length. By the term "element for the field of construction" is meant according to the present invention any element of a construction such as for example a foundation, a base, a wall, a beam, a ceiling, a work plan, a pillar, bridge pier, block, block, post, staircase, panel, cornice, or tile. In the present description, including the claims, unless otherwise indicated, the percentages are indicated by weight. The concrete generally has a water porosity of less than 14%, preferably less than 12%, for example less than 10% (determined by the method described in the report Technical Days, AFPC-AFREM , December 1997, pages 121 to 124). PA12015 EN The high-performance concrete according to the invention generally has a compressive strength measured at 28 days greater than or equal to 50 MPa, in particular ranging from 50 MPa to 300 MPa, in particular greater than or equal to 80 MPa, in particular from 80 at 250 MPa. The concrete is preferably ultra-high performance concrete (BUHP), for example containing fibers. An ultra high performance concrete is a particular type of high performance concrete and generally has a compressive strength at 28 days greater than or equal to 100 MPa and in particular greater than or equal to 120 MPa. The coating according to the invention is preferably applied to elements made with ultra-high performance concretes described in patents US6478867 and US6723162 or patent applications EP1958926 and EP2072481. The evaluation of the ease of cleaning the surface of a concrete can be performed by making spots on this surface, letting the stains dry for a few hours, wiping the surface with water or a solvent, using a cloth or sponge. Examples of stains against which the polymer film according to the invention is effective are given in the examples which follow. They include one or more spots caused by markers and markers. The D90, also noted as Dv90, is the 90th percentile of the grain size volume distribution, that is, 90% of the kernels are smaller than D90 and 10% are larger than D90. Similarly, D10, also denoted Dv10, corresponds to the 10th percentile of the grain size volume distribution, ie 10% of the grains are smaller than D10 and 90% are larger than D10. D10. The sand is usually silica sand or limestone sand, calcined bauxite or metallurgical waste particles, the sand may also comprise a crushed mineral hard material, for example, a crushed vitrified slag. The concrete according to the invention is preferably a self-compacting concrete. It preferably has a Vicat setting time of 2 to 18 hours, for example from 4 to 14 hours. BUHPs generally have greater shrinkage at setting due to their higher cement content. The total shrinkage can be reduced by the inclusion, generally from 2 to 8, preferably from 3 to 5, for example about 4 parts, of quicklime, lime or calcium oxide in the mixture before the addition of water. Suitable pozzolanic materials include fumed silica, also known as micro-silica, which is a by-product of the production of silicon or ferrosilicon alloys. It is known as a pozzolanic reactive material. PA12015 EN Its main constituent is amorphous silicon dioxide. The individual particles generally have a diameter of about 5 to 10 nm. The individual particles agglomerate to form agglomerates of 0.1 to 1 μm, and then can aggregate together into aggregates of 20 to 30 μm. The silica fumes generally have a BET surface area of 10 to 30 m 2 / g. Other pozzolanic materials include materials rich in aluminosilicate such as metakaolin and natural pozzolans with volcanic, sedimentary, or diagenic origins. Suitable non-pozzolanic materials also include materials containing calcium carbonate (eg ground or precipitated calcium carbonate), preferably ground calcium carbonate. The ground calcium carbonate may, for example, be Durcal® 1 (OMYA, France). The non-pozzolanic materials preferably have an average particle size of less than 5 μm, for example 1 to 4 μm. Non-pozzolanic materials may be ground quartz, for example 0800 which is a substantially non-pozzolanic silica filler supplied by Sifraco, France. The preferred BET surface (determined by known methods) of calcium carbonate or ground quartz is from 2 to 10 m 2 / g, generally less than 8 m 2 / g, for example from 4 to 7 m 2 / g, preferably less than 6 m2 / g.

Precipitated calcium carbonate is also suitable as a non-pozzolanic material. Individual particles generally have a size (primary) of the order of 20 nm. The individual particles agglomerate into aggregates having a (secondary) size of about 0.1 to 1 μm. The aggregates themselves form clusters having a (ternary) size greater than 1 μm.

A non-pozzolanic material or a mixture of non-pozzolanic materials may be used, for example ground calcium carbonate, ground quartz or precipitated calcium carbonate or a mixture thereof. A mixture of pozzolanic materials or a mixture of pozzolanic and non-pozzolanic materials can also be used.

The concrete according to the invention can be used in combination with reinforcing elements, for example metal and / or organic fibers and / or glass fibers and / or other reinforcing elements described hereinafter. The concrete compositions according to the invention may comprise metal fibers and / or organic fibers and / or glass fibers. The amount by volume of fibers is generally from 0.5 to 8% relative to the volume of the hardened concrete. The quantity of metal fibers, expressed in terms of volume of the final hardened concrete, is generally less than 4% by weight, for example from 0.5 to 3.5% by weight, preferably about 2% by weight. %. The amount of organic fibers, expressed on the same basis, is generally 1 to 8%, preferably 2 to 5%. The metal fibers are generally selected from steel fibers, such as high strength steel fibers, amorphous steel fibers or stainless steel fibers. The steel fibers may optionally be coated with a non-ferrous metal such as copper, zinc, nickel (or their alloys). The individual length (I) of the metal fibers is generally at least 2 mm and is preferably 10 to 30 mm. The ratio l / d (d being the fiber diameter) is generally 10 to 300, preferably 30 to 300, preferably 30 to 100.

Fibers having a variable geometry may be used: they may be creped, waved or hooked at the ends. The roughness of the fibers may also be modified and / or fibers of variable cross section may be used. The fibers can be obtained by any suitable technique, including braiding or wiring multiple wires, to form a twisted assembly.

The bonding of the metal fibers in the cementitious matrix can be promoted by the treatment of the fiber surface. This fiber treatment may be carried out by one or more of the following processes: etching the fibers or depositing a mineral compound on the fibers, in particular by depositing silica or a metal phosphate. The etching can be carried out, for example, by contacting the fibers with an acid and then performing a neutralization. Silica may be deposited by contacting the fibers with a silicon compound, such as a silane, a siliconate or a colloidal silica solution. It will be understood that the silica or phosphate is substantially limited to the surface of the metal fibers in the concrete matrix and is not uniformly dispersed in the matrix. Phosphating treatments are known and are described, for example, in the article by G. LORI N entitled "The Phosphatizing of Metals" (1973), Pub.Eyrolles. In general, a metal phosphate is deposited by implementing a phosphating process, which comprises introducing stripped metal fibers into an aqueous solution comprising a metal phosphate, preferably manganese phosphate or zinc phosphate, and then filtering of the solution to recover the fibers: the fibers are then rinsed, neutralized and rinsed again. In contrast to the usual phosphating process, the fibers obtained must not undergo a finishing step of the greasing type. However, they may optionally be impregnated with an additive in order to provide protection against corrosion or to make it easier to use in a cementitious medium. The treatment of PA12015 FR phosphatation can also be carried out by coating or spraying a solution of metal phosphate on the fibers. Organic fibers include polyvinyl alcohol (PVA) fibers, polyacrylonitrile (PAN) fibers, polyethylene (PE) fibers, high density polyethylene (HDPE) fibers, polypropylene (PP) fibers, homopolymers or copolymers, polyamide or polyimide fibers. Blends of these fibers can also be used. The organic reinforcing fibers used in the invention can be classified as follows: high modulus reactive fibers, low modulus nonreactive fibers and low modulus reactive fibers. The presence of organic fibers makes it possible to modify the behavior of concrete in heat or fire. The fusion of organic fibers makes possible the development of ways in which steam or pressurized water can escape when the concrete is exposed to high temperatures. The organic fibers may be present as individual filaments or as bundles of several filaments. The diameter of the single filament or multiple filament bundle is preferably from 10 μm to 800 μm. The organic fibers may also be used in the form of woven structures or nonwoven structures or a hybrid bundle comprising different filaments. The individual length of the organic fibers is preferably from 5 mm to 40 mm, preferably from 6 to 12 mm. The organic fibers are preferably PVA fibers. The optimum amount of organic fibers used generally depends on the geometry of the fibers, their chemical nature and their intrinsic mechanical properties (eg elastic modulus, yield point, strength).

The ratio l / d, d being the fiber diameter and the length, is generally 10 to 300, preferably 30 to 90. The glass fibers may be single filament (monofilament fiber) or multiple filament ( multifilament fiber) each individual fiber then comprising a plurality of filaments.

The glass fibers may be formed by pouring molten glass into a die. A conventional aqueous sizing composition can then be applied to the glass fibers. Aqueous sizing compositions may include a lubricant, a coupling agent and a film former and optionally other additives. The treated fibers are generally heated to remove water and heat-treat the sizing composition on the surface of the fibers. As an example, the size may be effected by means of a composition which comprises a coupling agent of the silane type. Silane coupling agents include aminosilanes, silane esters, vinyl silanes, methacryloxy silanes, epoxy silanes, sulphurized silanes, ureido silanes, isocyanato silanes and mixtures thereof. Film forming agents include blocked polyurethane film forming materials, thermoplastic polyurethane film forming materials, epoxy resin film forming materials, polyolefins, modified polyolefins, functionalized polyolefins, polyvinyl acetate, polyacrylates, saturated polyester resin film forming materials, unsaturated polyester resin film forming materials, polyether film forming materials, and mixtures thereof. The glass in the fibers is generally resistant to alkalis. The fibers may be sized to promote abrasion resistance and / or filament integrity during concrete mixing. In addition, for multifilament fibers, the size may be provided to avoid or reduce the separation of the filaments during mixing. A coating treatment (or coating) of the glass fibers is carried out so as to avoid or reduce the presence of porosity around the glass fibers in the cementitious matrix. This coating treatment of the glass fibers can be carried out by depositing a mineral compound on the glass fibers comprising silica. Preferably, it is reactive silica having a pozzolanic action. The volume percentage of glass fibers in the concrete is preferably greater than 1% by volume, for example from 2 to 5%, preferably from about 2 to 3%, a preferred value being about 2%.

The diameter of the individual filaments in the multifilament fibers is generally less than about 30 μm. The number of individual filaments in each individual fiber is generally 50 to 200, preferably about 100. The composite diameter of the multifilament fibers is generally 0.1 to 0.5 mm, preferably about 0.3 mm. . They generally have an approximately circular shape in cross section. The glass generally has a Young's modulus greater than or equal to 60 GPa, preferably 70 to 80 GPa, for example 72 to 75 GPa, preferably about 72 GPa. The length of the glass fibers is generally greater than the particle size of the granulate (or sand). The length of the fibers is preferably at least three times larger than the particle size. A mixture of lengths can be used. The length of the glass fibers is generally 3 to 20 mm, for example 4 to 20 mm, preferably 4 to 12 mm, for example about 6 mm. The tensile strength of the multifilament glass fibers is about 1700 MPa or more.

The saturation dose of the glass fibers (Sf) in the composition is expressed by the formula: Sf = Vf x LJD where Vf is the actual volume of the fibers. In the ductile compositions according to the invention Sf is generally from 0.5 to 5, preferably from 0.5 to 3. In order to obtain a good fluidity of the fresh concrete mixture Sf can generally be up to about 2. actual volume can be calculated from the weight and density of glass fibers. Binary hybrid fibers comprising glass fibers and (a) metal fibers or (b) organic fibers and ternary hybrid fibers comprising glass fibers, metal fibers and organic fibers may also be used. A mixture of glass fibers, organic fibers and / or metal fibers can also be used: a "hybrid" composite is thus obtained whose mechanical behavior can be adapted according to the desired performance. The compositions preferably comprise polyvinyl alcohol (PVA) fibers. PVA fibers generally have a length of 6 to 12 mm. They generally have a diameter of 0.1 to 0.3 mm. The use of fiber mixtures with different properties and lengths makes it possible to modify the properties of the concrete that contains them. Suitable cements are the silica-free Portland cements described in "Lea's Chemistry of Cement and Concrete". Portland cements include slag, pozzolana, fly ash, shale, limestone and composite cements. A preferred cement for the invention is CEM I. The cement of the concrete according to the invention is for example a white cement. The water / cement mass ratio of the concrete according to the invention may vary if substitutes for the cement are used, more particularly pozzolanic materials.

The water / binder ratio is defined as the mass ratio between the quantity of water E and the sum of the quantities of cement and of all pozzolanic materials: it is generally from 15 to 30%, preferably from 20% to 25%, percentage in mass. The water / binder ratio may be adjusted using, for example, water reducing agents and / or superplasticizers.

In the "Concrete Admixtures Handbook, Properties Science and Technology", VS Ramachandran, Noyes Publications, 1984: PA12015 EN A water reducer is defined as an additive that reduces the amount of mixing water for a concrete for workability typically given from 10 to 15%. Water reducers include, for example, lignosulphates, hydroxycarboxylic acids, carbohydrates, and other specialized organic compounds, for example glycerol, polyvinyl alcohol, sodium aluminum-methyl-siliconate, sulfanilic acid and casein. Superplasticizers belong to a new class of water reducers that are chemically different from normal water reducers and capable of reducing the amount of mixing water by about 30%. Superplasticizers have been broadly classified into four groups: sulphonated naphthalene formaldehyde condensate (or SNF), (generally a sodium salt); sulphonated formaldehyde melamine condensate (or SMF, acronym for Sulphonated Melamine Formaldehyde Condensate); modified lignosulphonates (or MLS, acronym for Modified Lignosulfonates); and others. Next generation superplasticizers include polycarboxylic compounds such as polyacrylates. The superplasticizer is preferably a new generation of superplasticizer, for example a copolymer containing polyethylene glycol as a graft and carboxylic functions in the main chain such as a polycarboxylic ether. Sodium polysulphonate polycarboxylate and sodium polyacrylates may also be used. The amount of superplasticizer generally required depends on the reactivity of the cement. The lower the reactivity of the cement, the lower the required amount of superplasticizer. In order to reduce the total amount of alkaline, the superplasticizer can be used as a calcium salt rather than a sodium salt.

Other additives may be added to the concrete according to the invention, for example an antifoaming agent (for example, polydimethylsiloxane). It is also silicones in the form of a solution, a solid or preferably in the form of a resin, an oil or an emulsion, preferably in water. The amount of such an agent in the composition is generally at most 5 parts by weight relative to the weight of the cement. The concretes according to the invention may also comprise hydrophobic agents for increasing the repulsion of water and reducing the absorption of water and the penetration into solid structures comprising concretes according to the invention. Such agents include silanes, siloxanes, silicones and siliconates; commercially available products include liquid and solid products which can be diluted in a solvent, for example into granules. PA12015 EN The concrete according to the invention can be prepared by known methods, in particular the mixing of solid components and water, shaping (molding, casting, injection, pumping, extrusion, calendering) and then curing. In order to prepare the concrete according to the invention, the constituents and the reinforcing fibers are mixed with water. The following order of mixing may, for example, be adopted: mixing of the powder constituents of the matrix; introduction of water and a fraction, for example half, of adjuvants; mixed ; introduction of the remaining fraction of adjuvants; mixed ; introduction of reinforcing fibers and other constituents; mixed.

Reinforcing means used in combination with the concrete according to the invention also comprise prestressing reinforcement means, for example, by adhering yarns or by adherent strands, or by post-tensioning, by non-adherent strands or by cables or by sheaths or bars, the cable comprising a set of wires or comprising strands.

The concrete according to the invention will generally be used in "thin elements", for example those having a ratio between length and thickness greater than about 10, generally having a thickness of 10 to 30 mm, for example, coating. In the mixture of concrete components according to the invention, materials in the form of particles other than cement may be introduced as pre-mixtures or dry premix of diluted or concentrated aqueous powders or suspensions. The specific surfaces of the materials are measured by the BET method using a Beckman Coulter SA 3100 apparatus with nitrogen as the adsorbed gas. The concrete according to the invention is coated, in whole or in part, with a polymer film obtained by polymerization under the action of radiation. This type of polymer film obtained by radiation polymerization is also called photocrosslinked polymer or crosslinkable film-forming resin or photosensitive resin. A composition of unpolymerized reactive monomers and / or prepolymers is applied in whole or in part to the concrete. Preferably, this composition is a composition of unpolymerized reactive monomers and prepolymers. This composition generally comprises the following precursors: a prepolymer comprising a resin, which resin comprises one or more, for example 1, 2, 3 or 4 polymerizable group (s) (which may be the same or different), such as unsaturated groups or epoxy groups. Polymerizable groups include acrylate, methacrylate, allyl, vinyl, epoxy and glycidyl. Prepolymers include an acrylic resin, a methacrylic resin a polyester resin, a chlorinated polyester resin, an epoxy resin, a melamine resin, a polyamide resin, a silicone resin, a polyether resin, a polyurethane resin , a polyurea-urethane resin and / or mixtures thereof, the resins comprising one or more polymerizable group (s), such as those listed above. Among these resins, the resins comprising the acrylate group may be partially modified by the action of an amine, generally called "synergistic amines". Among these resins, polyurethanes comprising acrylate groups and epoxides comprising acrylate groups are particularly preferred according to the invention. a monomer comprising one or more, for example 1, 2, 3 or 4 reactive group (s) (which may be the same or different), such as unsaturated groups or epoxy groups. Reactive groups include acrylate, methacrylate, allyl, vinyl, epoxy and glycidyl. Among these monomers, the acrylic esters of alcohols such as isobornyl acrylate (IBOA), diols such as diethylene glycol diacrylate (DEGDA), tripropylene glycol diacrylate (TPGDA), bisphenol A diacrylate, or polyols such as trimethylolpropane triacrylate ( TMPTA), propoxylated glycerol triacrylate (GPTA), pentaerythritol tri- and tetraacrylate, are usable according to the invention. Methyl pentanediol diacrylate (MPDDA) is particularly preferred according to the invention. a photoinitiator, such as, for example, mixtures of benzophenone derivatives and tertiary amines, or cationic systems such as triphenylsulphonium hexafluoroantimonate or, for example, a mixture of oxide acyl phosphines such as Irgacure ™ 819 (BAPO) or Darocur ™ TPO ( Mono acyl phosphine (MAPO)), Darocure TM 4265 (a mixture of MAPO and α-hydroxyketone 50/50) marketed by Ciba and acetophenone-α-hydroxy-α-di-substituted. 2-hydroxy-2-methyl-1-phenylpropanone (Darocure ™ 1173, sold by the company Ciba) and 1-hydroxycyclohexyl-phenylketone (Irgacure ™ 184, sold by the company Ciba) are particularly preferred according to the invention.

One of the preferred compositions according to the invention of unpolymerized reactive monomers and / or prepolymers comprises: - epoxy acrylate oligomer - methyl pentanediol diacrylate (MPDDA) - urethane acrylate oligomer - 2-hydroxy-2-methyl-1-phenylpropane 1one or 1-hydroxy-cyclohexyl phenyl ketone. The composition of unpolymerized reactive monomers and / or prepolymers may comprise from 1% to 10% by weight of photoinitiator, preferably from 2% to 8% and more preferably from 3% to 6%. Preferably, the composition comprises both unpolymerized monomers and reactive prepolymers. In this case, the group constituted by the monomers and prepolymers, apart from any other component, may comprise from 10% to 90% by weight of monomers, preferably from 20% to 80%, and 10% to 90% by weight. prepolymer mass, preferably from 20% to 80%. The composition of monomers and / or unpolymerized reactive prepolymers can be prepared by simple mixing of its components, using any type of mixer. The resulting mixture is stable and can be stored for several months at room temperature and away from direct sunlight.

The composition of unpolymerized reactive monomers and / or prepolymers is applied in whole or in part to the concrete by means of an applicator roller, a brush or a spray or any other means for depositing a layer fine composition on the siding. The composition of unpolymerized reactive monomers and / or prepolymers may be applied in one or more layers. The total thickness of said composition deposited on the concrete is preferably from 5 to 100 microns, more preferably from 10 to 60 microns and even more preferably from 15 to 50 microns. A polymerization may or may not be carried out between the layers. According to a preferred variant of the invention the composition of monomers and / or unpolymerized reactive prepolymers is applied in two 20 micron layers with a polymerization between the two applications, instead of the application of a single layer of 40 microns. The polymerization of the reactive monomers and / or prepolymers takes place under the action of radiation, preferably under the action of waves whose wavelength is in the visible ultraviolet spectrum, or the length of which is wave is shorter still. It is also conceivable that the polymerization takes place under the action of infrared rays. The radiations cause the polymerization by condensation reactions or additions of the precursors of the polymer, in particular the radiation causes the crosslinking of the precursors of the polymer. It is also conceivable that the polymerization takes place under the action of an electron beam. In this case, the composition of unpolymerized reactive monomers and / or prepolymers does not include a photoinitiator, since the energy of the electron beams is sufficient to create the free radicals necessary for the polymerization. Preferably, the polymer film is obtained by the polymerization under the action of ultraviolet radiation. Ultraviolet (UV) rays can excite or decompose the photoinitiator and cause the formation of free radicals or ions which leads to the polymerization of the prepolymer with the monomer. The polymerizations can be carried out at a speed of passage under the UV lamp from 5 meters / minute to 30 meters / minute. The total dose of energy received (in PA12015 FR once or more if necessary) by the composition of monomers and / or reactive prepolymers is preferably 300 to 1200 mJ / cm 2. The polymerization can be carried out in the presence of an inert gas, such as nitrogen, thereby reducing the amounts of photoinitiator in the composition, and also hardening the surface of the polymer film. The polymerization causes the formation of the polymer film. This polymer film is preferably continuous. According to a first variant, this polymer film is located on one side of the concrete or the construction element which comprises this concrete. In particular, one side of the concrete or the construction element which comprises this concrete is entirely coated with the polymer film. According to another variant of the invention, it is possible to apply two or more polymer films, one on top of the other, on the concrete. As a result, the performance of the concrete and the construction element that includes this concrete is improved. The polymer film may further comprise an anti-fungal agent, a coloring agent, pigments, an agent or a mineral filler for improving the adhesion of a joint or a paint or other surface application susceptible to be deposited on the concrete (for example silica, calcium carbonate, titanium dioxide, magnesium carbonate, calcium sulphate, magnesium oxide, calcium hydroxide or a powdery solid).

The resistance of the coating to the scratch is practiced using the so-called "grid" test, according to ISO 2409: 2007 (Paints and varnishes - grid test). Its principle is to make a grid by making parallel and perpendicular incisions in the coating. The incisions must penetrate to the substrate. The incisions are 6 in number and spaced 1 mm apart.

The invention will be described in more detail by means of the following examples, given in a non-limiting manner, in relation with FIG. 1 which illustrates the device for measuring the permeability of a concrete. In what follows, are described successively: the manufacture of an ultra-high performance concrete; the deposition of three coatings on this concrete, one of the coatings being in accordance with the invention and the two others, not in accordance with the invention, being presented by way of comparison; three comparative examples, illustrating the respective behaviors of this concrete coated in accordance with the invention, of this concrete coated with the two comparison coatings, and of this uncoated concrete. PA12015 EN 17 used for EXAMPLES Formulation of ultra-high performance concrete: The formulation (1) of ultra-high performance concrete tests is described in the following table (1): Table (1) Components Proportion (% by mass relative to to the mass of the composition) Portland Cement 31.0 Calcium Filler DURCAL 1 9.3 Silica Fume MST 6.8 Sand BE01 44.4 Tempering Water 7.1 Ductal Adjuvant F2 1.4 The components used are available from following suppliers: (1) White Cement Portland CEM I 52.5 PM ES (2) Filler Lime DURCAL 1 (average particle size of 2.44 μm) (3) Silica Fume MST (4) Sand BE01 (D50 at 307 μm and D10 at 253 μm) (5) Ductal Adjuvant F2 Lafarge-France Teil OMYA SEPR (European Refractory Products Company) Sibelco France (SI FRACO BEDOIN Quarry) Chryso Portland cement is of the type CEM I 52.5 PMES according to the standard EN 197-1. Adjuvant Ductal F2 is a superplasticizer comprising a polyoxyalkylene polycarboxylate in aqueous phase at 30% solids. The silica fume has a median particle size of about 1 micron. The water / cement ratio is 0.26.

It is a concrete having a compressive strength at 28 days greater than 100 M Pa. The ultra high performance concrete according to the formulation (1) was produced using a RAYNERI type mixer. The entire operation was performed at 20 ° C. The method of preparation comprises the following steps: PA12015 EN - At T = 0 seconds: put the cement, calcareous filler, silica fumes and sand in the mixing bowl and mix for 7 minutes (15 revolutions / min); - At T = 7 minutes: add water and half of the adjuvant mass and knead for 1 minute (15 rpm); - At T = 8 minutes: add the remaining adjuvant and knead for 1 minute (15 rpm); - At T = 9 minutes: mix for 8 minutes (50 rpm); - At T = 17 minutes: knead for 1 minute (15 rpm). - From T = 18 minutes: pour the concrete flat in the mold or molds provided for this purpose. Plates (dimensions 150x100x10 mm) were made by molding the concrete according to the formulation (1) in a polyvinyl chloride (PVC) mold. Each plate was demolded 18 hours after contact between cement and water. Each demolded plate was stored at 20 ° C and then at 25 ° C for 14 days. After storage for 14 days, a surface treatment of the plates was performed. The coating (1) according to the invention was applied to one face of the first plate. Comparative coatings (2) and (3) were applied to one side of the second and third plates. No coating was placed on the fourth plate. Process for the deposition of a coating (1) according to the invention of a composition comprising monomers and / or reactive prepolymers: The following chemical compounds have been used to make the coating (1): Coating composition 1 Trade name Chemical name% by weight PhotomerTM 6010 * Oligomer of urethane acrylate 70 PhotomerTM 4071 F * Methyl pentanediol diacrylate 10 (M PDDA) PhotomerTM 3016 F * Oligomer of epoxy acrylate 15 I TM 184 * 1-hydroxy-cyclohexyl-phenylketone 5 * PhotomerTM are marketed by IGM Resins. IrgacureTM is marketed by Ciba. The compounds of the coating (1) were loaded into a mixer and then stirred at ambient temperature until a homogeneous mixture was obtained. The mixture was stable and it could be stored for several months at room temperature and away from direct sunlight. This mixture was applied on the concrete (1) to ultra-high PA12015 FR performance, using a roller applicator then cured under the action of UV radiation. UV can decompose the photoinitiator which leads to the polymerization of acrylic functions.

The polymerization was carried out at a speed of passage under the UV lamp from 5 meters / minute to 30 meters / minute, the received energy dose was sufficient to obtain the most complete polymerization possible and avoid any sticky effect on the surface of the polymer film.

Process for depositing a coating (2) for comparison: The process was carried out at 20 ° C. and included, after waiting for 14 days after demoulding the concrete to be treated, the deposit, on the face of the element of concrete to be treated, an aqueous emulsion (composed of butyl methacrylate, aliphatic esters, carboxylic acids and ether glycol), corresponding to PROTECTGUARD TM Wet Moisture product marketed by Guard Industrie. The coating was deposited by means of a roller moistened with this liquid. Two layers were deposited (2 hours between each application).

Process for depositing a comparison coating (3): The process was carried out at 20 ° C. and comprises, after waiting for 14 days after demolding the concrete to be treated, the deposit, on the face of the concrete to be treated, a first layer of an acrylic polymer diluted in an aqueous solvent (corresponding to the product Solarcir Primer Protec TM sold by the company Grace-Pieri). The emulsion was sprayed in an amount of 40 g / m 2. This process then included a waiting time of 24 hours from the drying of the first layer, then the deposition of a second polyurethane-based layer (corresponding to the Solarcir Protec Mat TM product marketed by Grace-Pieri). This second layer was sprayed in an amount of 80 g / m 2. The plates were then used to perform the various tests and measurements described below.

Measurement of the permeability: PA12015 FR Figure 1 shows the device 10 used for performing a measurement of the permeability of a plate 12. The plate 12 is disposed on spacers 14 to about 5 mm of a horizontal support 16 . The treated face of the plate 12 is the upper face 18. A frustoconical funnel 20 with a vertical axis is placed on the upper face 18, the large-diameter end of the funnel 20 being in contact with the upper face 18. largest diameter of the funnel is 75 mm. A seal 22 covers the contact zone between the funnel 20 and the face 18. The smaller diameter end of the funnel 20 is extended by a graduated pipette 24. A seal 26 covers the zone contact between the funnel 20 and the pipette 24. The permeability measurement test was carried out for each plate after the surface treatment using the test device of FIG. 1 at a temperature of 20.degree. 65% relative humidity. Water was poured into the pipette 24 so as to fill the funnel 20 and the pipette 24 to a height of 250 mm with respect to the face 18. The evolution of the amount of water entering the Plate was measured on the pipette 24. The results were presented in the following Table (2): Table (2) Instant Quantity of water penetrating the: measuring (hours) plate with the plate with the plate with the coating ( 3) comparison (mL / cm 2) uncoated plate (1) according to coating (2) coating the invention comparison (mL / cm 2) (mL / cm 2) (mL / cm 2) 0 0 0 0 0 96 0.05 0.40 0.60 0.30 120 0.05 0.40 0.60 0.30 144 0.05 0.40 1.10 0.30 168 0.05 0.70 1.10 0.30 192 0 , 05 0.70 1.10 0.30 216 0.06 0.90 1.70 0.60 The concrete covered with the coating (1) according to the invention is therefore more impermeable than the concrete covered with the coating (2) or (3) comparison, and also more impervious than uncoated concrete. PA12015 EN Visual Appearance: After the surface treatment, plates were stored at 35 ° C for 10 days in a 100% humidity atmosphere. A visual inspection of the treated face of the plates was made for the formation of bubbles in the coating and for the formation of light and dark spots on the surface and / or at the concrete / coating interface (efflorescence spots). Then the same plates were stored at 60 ° C for 30 days in an atmosphere at 100% humidity. A second visual inspection was then performed to examine the plate surfaces. The results of the visual inspections are presented in the following tables (3) and (4): Table (3) Visual inspection plate with plate with plate with plate without after 10 days coating (1) coating (2) coating ( 3) of coating 35 ° C / 100% according to the invention of comparison comparison of relative humidity Formation of bubbles Pas de - Formation of - formation of bubbles in the bubble in the coating coating Formation of No Yes Yes Yes dark and clear spots Table (4) Visual inspection plate with plate with plate with plate after 30 days coating (1) coating (2) coating (3) with without 60 ° C / 100% according to the invention comparison coating comparison relative humidity Formation of bubbles No formation - Formation of - bubbles in the bubble in the coating coating Formation of No Yes Yes Yes dark and light spots PA12015 EN The concrete covered with the coating (1) according to the invention does not feel no spot or bubble while concrete covered with the coating (2) or (3) for comparing comprise at least one of these defects. Uncoated concrete has stains.

Task formation: Seven days after the surface treatment, plates were subjected to a spot-forming test consisting in using an indelible marker (corresponding to the product Marking Onyx TM marketed by Bic).

After staining, the plates were left in ambient air for four hours at room temperature. After 4 hours, half of the plates were cleaned with a cloth soaked in heptane while the other half was cleaned with a rag soaked in acetone. A photograph of the marked surface of each plate was then taken. The results of a visual comparison of the two photographs were presented in the following table (5): Table (5) Inspection Plates with Plates with Plates with Plates without visual coating (1) Coating (2) with coating (3) ) coating according to the invention comparison comparison Stained with a stain completely disappeared, no degradation of the coating Stain completely disappeared, but the stain completely disappeared, but degradation of the stain marker coating coating slightly indelible and reduced then cleaned with heptane Stained with a stain completely disappeared, no degradation of the coating stain completely disappeared, but degradation of the stain completely disappeared, but degradation of the marker spot coating coating slightly indelible and reduced then cleaned with acetone The concrete covered with the coating (1) presents surface properties allowing e remove the indelible marker stains without solvent-induced degradation. PA12015 EN Scratch resistance: Seven days after the surface treatment, plates were subjected to a scratch resistance test (according to ISO 2409: 2007 (Paints and varnishes - grid test) consisting of a grid by making parallel and perpendicular incisions in the coating After the incisions were made, a photograph of the surface of each plate was taken The results of a visual comparison of the two photographs were presented in the following table (6) : Table (6) Visual inspection Plate with coating Plate with coating (1) (3) of comparison according to the invention Aspect after incisions Slight visible degradation Degradation of coating, fine coating, large incisions do not penetrate incisions penetrate to the substrate up to the concrete substrate The concrete covered with the coating (1) has permissible surface properties Being scratch-resistant, no incisions having cut through the entire thickness of the coating.

PA12015 EN

Claims (11)

REVENDICATIONS1. High performance concrete, especially ultra high performance, coated in whole or in part with a polymer film obtained by polymerization under the action of radiation. 2. Concrete according to claim 1, wherein the polymer film is obtained by polymerization under the action of ultraviolet radiation. 3. Concrete according to claim 1 or 2, wherein the concrete has a roughness Ra of 0.5 pm to 10 pm, preferably from 0.5 to 7 pm, more preferably from 0.5 to 5 pm, advantageously from 0.5 to 3 μm. 4. Concrete according to one of the preceding claims, wherein the concrete has a water-cement ratio (W / C) of at most 0.45, preferably from 0.20 to 0.27. 15 5. Concrete according to one of the preceding claims comprising, in parts by weight: 100 of Portland cement; 50 to 200 of a sand having a single particle size with a D10 at a D90 of 0.063 to 5 mm, or a mixture of sands, the thinnest sand having a D10 at a D90 of 0.063 to 1 mm and the sand the coarser having a D10 to a D90 of 1 to 5 mm, for example between 1 and 4 mm; 0 to 70 of a pozzolanic or non-pozzolanic material of particles, or a mixture thereof, having an average particle size of less than 15 μm; 0.1 to 10 of a water reducing superplasticizer; and 10 to 32 water, especially 20 to 32 water. 6. A process for protecting a high-performance concrete, particularly ultra-high performance, against efflorescence stains, comprising the steps of: - applying a composition comprising monomers and / or reactive prepolymers on all or part of the concrete; - Polymerize this composition under the action of radiation, so as to obtain a polymer film covering all or part of said concrete. PA12015 EN 7. The method of claim 6, wherein the temperature of the composition, when it is applied to the concrete, is less than 35 ° C, preferably less than 30 ° C. 8. The method of claim 6 or 7, further comprising a mold release and heat treatment of the concrete. 9. Use of a polymer film obtained by polymerization under the action of radiation, to protect against blemishes a high-performance concrete, especially ultra-high performance concrete. 10. Element for the field of construction comprising a concrete according to any one of claims 1 to 5. 11. A method of manufacturing the element according to claim 10, comprising a concrete protection method according to one of claims 6 to 8. PA12015 EN