EP3154919A1

EP3154919A1 - Photovoltaic concrete, production method thereof and construction element comprising such concrete

Info

Publication number: EP3154919A1
Application number: EP15727958.9A
Authority: EP
Inventors: Isabelle Dubois-Brugger; Matthieu Horgnies
Original assignee: Lafarge SA
Current assignee: Lafarge SA
Priority date: 2014-06-13
Filing date: 2015-06-05
Publication date: 2017-04-19
Also published as: CA2951332A1; WO2015189096A1; MA39974A; FR3022240A1; US20170141719A1

Abstract

The invention relates to concrete with a smooth surface, coated completely or partially with a polymer film obtained by means of radiation-induced polymerisation, said film in turn being coated completely or partially with a thin photovoltaic film.

Description

PHOTOVOLTAIC CONCRETE, METHOD FOR MANUFACTURING THE SAME, AND CONSTRUCTION ELEMENT COMPRISING SUCH CONCRETE

The present invention relates to a photovoltaic concrete, a method of manufacturing such a concrete, a member for the field of construction comprising such a concrete, and a method of manufacturing this element.

The present invention aims at the technical field of the production of electricity from renewable energies, in particular solar energy, thanks to the photovoltaic effect.

Cities include many buildings, buildings, structures or infrastructure (including transportation) with high surface capacity, which would be relevant to use to produce electricity from solar energy. For this purpose, it becomes interesting to use the concrete surfaces available on the many works present in the cities. However, the application of solar panels on the facades or more generally on concrete surfaces is long and expensive, and requires a lot of manpower. In addition, it requires prior manufacture of solar panels in the factory.

It is also known from EP 2 190 032 a fiber cement panel on which is applied by gluing a photovoltaic thin layer. This bonding takes place using an adhesive applied by vacuum lamination and hot on the fiber cement board, previously coated with a polymer film.

Therefore, the technical problem to be solved by the invention is to provide a concrete intended for the construction of buildings, buildings, structures or infrastructures and capable of producing electricity, without having recourse to the use and the installation of solar panels or photovoltaic thin film bonding.

For this purpose, the subject of the present invention is a concrete having a smooth surface, coated in whole or in part with a polymer film by polymerization under the action of radiation, said film itself being coated in whole or in part with a photovoltaic thin layer.

Surprisingly, the inventors have shown that the fact of covering a concrete having a smooth surface, by means of a first polymer film and then covering said film with a photovoltaic thin film makes it possible to obtain a photovoltaic concrete which can transform the photovoltaic energy from solar radiation into electrical energy.

Advantageously, the smooth surface of the concrete combined with the very low intrinsic porosity of the polymer film makes it possible to obtain a surface that makes it possible to obtain good adhesion of the photovoltaic thin film. The invention offers another advantage that the concrete is characterized by a smooth surface condition, very little rough and homogeneous, with sizes of surface defects (depth of the grooves and / or heights of asperities) less than one micrometer.

In addition, the concrete used according to the invention may be a structural concrete, that is to say preferably having performance in accordance with the NF EN 1992-1 -1 standard of October 2005.

The advantage of the process according to the invention is that it does not require a bonding step of the photovoltaic thin film. Indeed, according to the method of the invention, the photovoltaic thin film is directly manufactured in the layer formed by the polymer film. This manufacture does not consist in an assembly or bonding between the polymer film and the photovoltaic thin film. This is an in situ fabrication of the photovoltaic thin film. There is no assembly according to the method of the invention, of prefabricated element, likewise the method according to the invention does not require adhesive bonding.

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 indistinctly refers to the concrete in the fresh state and in the cured state, and also includes a cement slurry or a mortar.

Process

First, the invention relates to a method of manufacturing a photovoltaic concrete, comprising the following steps:

- have a concrete;

- Applying a composition comprising monomers and / or unpolymerized reactive prepolymers on all or part of the surface of the concrete;

- Polymerize this composition under the action of radiation, so as to obtain a polymer film covering all or part of the concrete surface; - Sputtering, chemical vapor deposition, ion deposition, plasma deposition, electron bombardment, laser ablation, molecular beam epitaxy, or thermo-evaporation of at least one photovoltaic thin film directly onto the film polymer.

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. 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.

This composition comprising monomers and / or unpolymerized 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%; the coating obtained being homogeneous and crosslinked throughout its thickness.

The method according to the invention may optionally comprise a step of polishing the concrete surface before the application of the composition comprising monomers and / or unpolymerized reactive prepolymers.

According to another variant, the method according to the invention may comprise a step after hardening of the concrete, mechanical treatment by roughing, and then polishing. This treatment gives a perfectly smooth surface.

Advantageously, the method further comprises demolding and / or heat treatment of the concrete. The steps of application of the composition and polymerization under the action of radiation may occur between the release of the concrete and the heat treatment.

Advantageously, the method according to the invention does not include a step of bonding the photovoltaic thin film to the polymer film.

This thermal treatment of concrete, also called thermal curing, is generally carried out on ultra-high performance concretes, 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.

Preferably, the concrete used according to the process of the invention has a surface, before coating with the polymer film, having a roughness Ra of from 0.5 μηη to 10 μηι, preferably from 0.5 to 7 μηι, even more preferably from 0.5 to 5 μηι, advantageously from 0.5 to 3 μηι.

By the term "roughness" is meant the irregularities of the order of one micrometer of a surface which are defined by comparison with a reference surface, and are classified in two categories: asperities or "peaks" or "protuberances" , and cavities or "hollows". The roughness of a given surface can be determined by measuring a number of parameters. In the remainder of the description, parameter Ra (measured by a confocal Micromesure full-field 3D confocal optical profilometer) is used, as defined by standards NF EN 05-015 and DIN EN ISO 4287 of October 1998, corresponding to the arithmetic mean of all the ordinates of the profile within a base length (in our examples, the latter was set at 12.5 mm).

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.

Preferably, the concrete used according to the process of the invention has a surface, after coating with the polymer film, having a roughness Ra of from 0.1 μηη to 5 μηι, preferably from 0.2 to 3 μηι, more preferably from 0.3 to 1 μηη, advantageously from 0.4 to 0.6 μηη. This advantageously makes it possible to obtain a homogeneous coated concrete capable of being covered by a thin photovoltaic layer.

The method according to the invention comprises a step of obtaining a polymer film 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 photoresist.

A composition of unpolymerized reactive monomers and / or prepolymers is applied in whole or in part to the surface of 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 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 tetra-acrylate, are usable according to the invention. Methyl pentanediol diacrylate

(MPDDA) is particularly preferred according to the invention.

a photoinitiator, such as mixtures of benzophenone derivatives and tertiary amines or cationic systems such as triphenylsulphonium hexafluoroantimonate or such as a mixture of oxide acyl phosphines such as Irgacure ™ 819 (BAPO) or Darocur ™ TPO

(Mono acyl phosphine (MAPO)), Darocure ™ 4265 (a mixture of MAPO and 50/50 hydroxyketone) sold by the company Ciba and acetophenone-α-hydroxy-α, β-di-substituted. 2-hydroxy-2-methyl-1-phenylpropan-1-one (Darocure ™ 1173, sold by the company Ciba) and 1-hydroxy-cyclohexyl phenyl ketone (Irgacure ™ 184, sold by the company Ciba) are particularly preferred according to US Pat. 'invention.

One of the preferred compositions according to the invention of monomers and / or unpolymerized reactive prepolymers comprises:

Oligomer of epoxy acrylate

- Methyl pentanediol diacrylate (MPDDA)

- urethane acrylate oligomer

2-hydroxy-2-methyl-1-phenylpropan-1-one or 1-hydroxy-cyclohexyl-phenylketone. The composition of unpolymerized reactive monomers and / or prepolymers used in the process according to the invention may comprise from 1% to 10% by weight of photoinitiator, preferably from 2% to 8% and more preferably from 3% to 6% by weight. %.

Preferably, this composition comprises both monomers and unpolymerized 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 thin and relatively homogeneous in composition thickness on the facing.

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 layers of 20 micrometers with a polymerization between the two applications, instead of the application of a single layer of 40 micrometers.

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 one or more times 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 (as for example silica, carbonate calcium, titanium dioxide, magnesium carbonate, calcium sulphate, magnesium oxide, calcium hydroxide or a powdery solid).

Advantageously, the polymerization step under the action of radiation is implemented 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 applying the composition and polymerization under the action of radiation are implemented as quickly as possible after the end of the demolding step.

Preferably, 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 and scratching, but also a high stability vis-à-vis high temperatures under partial vacuum.

Advantageously, the steps for applying the photovoltaic thin film to the polymer film are in particular by sputtering, chemical vapor deposition, ion deposition, plasma deposition, electron bombardment, laser ablation, and molecular beam epitaxy. by thermal evaporation; the general principle of these techniques is to deposit or condense the covering material (forming the thin layer) under partial vacuum (e.g., using a pressure of 10 ^{^"2-10" 4} Torr) while the carrier material is heated to a constant temperature.

The above method is particularly suitable for treating a high performance concrete having at least one of the above characteristics.

Photovoltaic concrete

The invention also relates to a photovoltaic concrete that can be obtained by the method according to the invention and described above.

The photovoltaic concrete according to the invention is preferably a structural concrete, generally having a compressive strength measured at 28 days greater than or equal to 12 MPa, in particular ranging from 12 MPa to 300 MPa. This concrete can be used in the supporting structure of a structure. A supporting structure is generally all the elements of a structure carrying more than their own weight. As an example of an element that can be a carrier, there may be mentioned poles, floors, walls, beams, lintels, piers, acroteria.

Preferably the photovoltaic concrete according to the invention has a photovoltaic thin film producing electricity thanks to the photovoltaic effect. Preferably, the photovoltaic thin film is based on inorganic compounds, metal compounds, organic compounds or organic-inorganic hybrid compounds (thin layers also called hybrid photovoltaic cells).

It may also be envisaged that the photovoltaic thin film may be composed of photosensitive pigments; we will then speak of dye cell or Graëtzel cell (also called DSSC or DSC).

The inorganic or metallic compounds suitable for producing the photovoltaic thin film may be based on amorphous silicon, liquid silicon, cadmium telluride, copper-indium selenium, copper-indium-gallium selenium, copper-indium, gallium-diselenide-disulphide, gallium arsenide, indium-tin oxide, copper oxide, molybdenum oxide, chalcopyrite oxide or mixtures thereof.

Organic compounds suitable for producing the photovoltaic thin film may be based on two compounds, one electron donor and the other electron acceptor. Among the electron donors, mention may be made of polyarylenes, poly (arylene-vinylene) s, poly (arylene-ethynylene) s or mixtures thereof. By way of example, mention may be made of poly-3-hexylthiophene (also known as P3HT)) or of poly [2-methoxy-5- (3,7-dimethyloctyloxy) -1,4-phenylenevinylene] (also called MDMO-PPV).

Among the electron acceptors there may be mentioned compounds based on fullerene such as methyl [6,6] -phenyl-C61-butanoate (also known as PCBM).

Among the photosensitive pigments constituting photovoltaic cells with dyes or Graëtzel, mention may be made of titanium dioxide.

Preferably the concrete according to the invention generally has a porosity to water of less than 14%, preferably less than 12%, for example less than 10% (determined by the method described in the report Technical Days, PSAC - AFREM, December 1997, pages 121 to 124).

Preferably the photovoltaic concrete according to the invention is an ultra-high performance concrete (BUHP). This high-performance 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 ultra-high performance concrete comprises, in parts by weight: 100 of Portland cement;

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 most coarse 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 μηη;

0.1 to 10 of a water reducing superplasticizer; and

10 to 32 of water, especially 20 to 32 of water.

The ultra-high performance concrete mentioned above 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, especially from 80 to 80 MPa. 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 polymer film and the photovoltaic thin film according to the invention are preferably applied to elements made with ultra-high performance concretes described in patents US6478867 and US6723162 or patent applications EP1958926 and EP2072481.

D90, also D _v 90, is the 90 ^th percentile of the grain size volume distribution, ie 90% of the grains are smaller than D90 and 10% are larger than D90. Similarly, D10, also denoted D _v 10 corresponds to the io ^th percentile of the distribution by volume of grain size, that is to say 10% of the grains have a size smaller than the D10 and 90% have larger than the 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.

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.

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 μηη, and can then aggregate together into aggregates of 20 to 30 μηη. 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. Ground calcium carbonate may, for example, be the Durcal ^® 1 (OMYA, France).

The non-pozzolanic materials preferably have an average particle size of less than 5 μηη, for example from 1 to 4 μηη. Non-pozzolanic materials may be ground quartz, for example C800 which is a substantially non-pozzolanic silica filler supplied by Sifraco, France.

The preferred BET surface (determined by known methods) of calcium carbonate or crushed 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 m ² / 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 μηη. The aggregates themselves form clusters having a size (ternary) greater than 1 μηη.

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 photovoltaic 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 photovoltaic concrete 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 amount of metal fiber expressed in terms of volume of the final hardened concrete is generally less than 4%, for example 0.5 to 3.5%, preferably about 2%. 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.

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 the bundle of multiple filaments is preferably from 10 m to 800 μηη. 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 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.

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 μηη. 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 (S _f ) in the composition is expressed by the formula:

S _f = V _f x L / D

where V _f is the actual volume of the fibers. In the ductile compositions according to the invention S _f 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 S _f can generally be up to about 2 The actual volume can be calculated from the weight and density of the 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.

Cements which are suitable for the concrete according to the invention are Portland cements without fumed silica described in the book "Lea's Chemistry of Cernent 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 book "Concrete Admixtures Handbook, Properties Science and Technology", V.S. Ramachandran, Noyes Publications, 1984:

A water reducer is defined as an additive that reduces the amount of mixing water for a concrete for a given workability typically of 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 used in the process according to the invention, for example an antifoam 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 used in the process 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.

The concrete used in the process according to the invention can be prepared by known methods, in particular the mixing of solid components and water, the shaping (molding, casting, injection, pumping, extrusion, calendering) then hardening.

In order to prepare the concrete used in the process 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 used in the process according to the invention also comprise prestressing reinforcing means, for example, by adhering yarns or by adherent strands, or by posttensioning, by non-adherent strands or by cables or sheaths or bars, the cable comprising a set of wires or comprising strands.

In the mixture of the concrete components used in the process according to the invention, the materials in the form of particles other than cement may be introduced as premixes 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.

Preferably the concrete used in the process according to the invention is a self-compacting concrete, that is to say that it is put in place under the sole effect of gravity without the need to vibrate. In particular, the concrete according to the invention is a self-consolidating concrete as described in documents EP981506 or EP981505.

The invention also relates to a use of a polymer film obtained by polymerization under the action of radiation and a photovoltaic thin layer, to produce electricity on a concrete surface.

The invention also relates to an element for the field of construction comprising a photovoltaic concrete according to the invention as defined above.

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 pillar, a bridge stack, a block, post, staircase, panel (including facade panel), cornice, tile or roof terrace.

The photovoltaic concrete according to the invention could possibly 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 elements.

The invention finally relates to a method of manufacturing the above element, comprising the method described above.

In the present description, including the claims, unless otherwise indicated, the percentages are indicated by weight.

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.

EXAMPLES

The following examples show how the surface of the concrete coated according to the invention withstands the conditions of deposition of photovoltaic thin layers while allowing to obtain suitable surface properties for photovoltaic applications. Ultra High Performance Concrete Formulation (1):

The formulation (1) of ultra-high performance concrete used to carry out the tests is described in Table (1) below:

Table (1)

The components used are available from the following suppliers:

(1) White Portland cement CEM I 52.5 PMES: Lafarge-France Le Teil

(2) DURCAL 1 limestone filler (average particle size of 2.44 μηη): OMYA

(3) Silica fumes MST: SEPR (European Society of Refractory Products) (4) Sand BE01 (D50 at 307 μηι and D10 at 253 μπι): Sibelco France (Career of SIFRACO BEDOIN)

(5) Ductal Adjuvant F2: Chryso

The Portland cement is of the type CEM I 52.5 PMES according to the standard EN 197-1 of February 2001. The 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 with a compressive strength at 28 days greater than 100 MPa.

The ultra high performance concrete according to the formulation (1) was produced using a RAYNERI type kneader. The entire operation was performed at 20 ° C. The method of preparation includes the following steps:

• At T = 0 seconds: put the cement, calcareous filler, silica fumes and sand in the mixing bowl and knead for 7 minutes (15 rpm);

• 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 = 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 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 depositing a coating (1) according to the invention of a composition comprising monomers and / or reactive prepolymers:

The following chemical compounds were used to make the coating (1)

Table (2)

Composition of the coating (1)

Photomer ™ are sold by IGM Resins and Irgacure 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 to the ultra high performance concrete (1) using an applicator roller and 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.

Method for depositing a coating (2) for comparison:

The process was carried out at 20 ° C. and included, after waiting for 14 days after demolding the concrete to be treated, depositing, on the face of the concrete element to be treated, an aqueous emulsion (composed of methacrylate butyl, aliphatic esters, carboxylic acids and ether glycol), corresponding to the PROTECTGUARD ™ Effect Wet Gloss 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).

Method 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, depositing, on the face of the concrete element to be treated, a first layer of a polymer acrylic diluted in an aqueous solvent (corresponding to Solarcir Primer Protec ™ product marketed by Grace-Pieri). The emulsion was pulverized 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 ™ 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.

Durability of the surface visual aspect:

After the surface treatment, plates were stored at 200 ° C for 2 hours under partial vacuum (pressure <0.1 atmosphere) to check the resistance to deformation of the surfaces in a constraining environment, close to that required for the deposition of layers thin photovoltaic. A visual inspection was then performed to examine the plate surfaces and detect possible defects. The results of the visual inspections are presented in the following table (3): Table (3)

The concrete covered with the coating (1) according to the invention has no stain or bubble while the concrete covered with the coating (2) or (3) comparison have at least one of these defects.

Variation of roughness and resistance to deformation:

Mean roughness measurements (Ra parameter) of the treated face of the plates (and uncoated plate) were performed before and after storage at 200 ° C for 2 hours under partial vacuum (pressure <0.1 atmosphere) to verify the resistance to deformation of the surfaces in a constraining environment, close to that required for the deposition of photovoltaic thin layers. The results of the roughness measurements are presented in the following table (4):

Table (4)

The concrete covered with the coating (1) according to the invention does not exhibit a variation of average roughness (Ra) whereas the concretes coated with the coating (2) or (3) of comparison show a greater surface deformation; the concrete covered with the coating (1) is therefore more favorable to photovoltaic thin film deposition. Uncoated concrete has a higher average roughness than coated concrete (1), which is less favorable for photovoltaic thin film deposition.

Hardness and scratch resistance:

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 with parallel and perpendicular incisions in the coating.

After making the incisions, a photograph of the 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)

The concrete covered with the coating (1) has scratch-resistant surface properties, with no incisions having cut through the entire thickness of the coating.

Surface open porosity and liquid permeability

FIG. 1 represents the device 10 used for carrying out a measurement of the permeability of a plate 12, this measurement of water permeability being capable of characterizing the residual porosity of the surface of the concrete (with / without coatings) . 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 end of smaller diameter of the funnel 20 is extended by a graduated pipette 24. A seal 26 covers the contact zone between the funnel 20 and the pipette 24.

The permeability measurement test was performed for each plate after the surface treatment using the test device of Fig. 1 at a temperature of 20 ° C and a relative humidity of 65%. 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 have been presented in the following table (6):

Table (6)

The concrete covered with the coating (1) according to the invention is therefore more impervious than the concrete covered with the coating (2) or (3) of comparison, and also more impervious than the concrete not covered by a coating. The high impermeability of the coated plate (1) according to the invention reflects a very low open surface porosity, which is very favorable to the photovoltaic thin film deposition for forming the photovoltaic concrete according to the invention.

In order to be able to withstand a homogeneous photovoltaic thin film deposition, in particular during partial vacuum deposition (10 ^"4 Torr) and with a concrete temperature brought to about 200 ° C (or more), the concrete should be:

- the smoothest and no surface deformation (Tables 3 and 4),

- be as resistant as possible to scratches (Table 5),

- have the lowest possible surface porosity (Table 6). Upon reading the results, the ultra-high performance concrete formulation (1) coated with the coating (1) is the one that has the best surface characteristics to receive an in-situ deposit of photovoltaic thin film.

After having selected the coating (1) to cover a surface of the ultra high performance concrete formulation (1), tests for depositing a conductive layer to make the rear contact of the photovoltaic thin layers have been made with different materials and according to different processes.

1) 1st test of Molybdenum deposition by sputtering (deposit n ° 1):

The deposition was carried out by cathodic sputtering on two substrates of formulation concrete (1) covered with the coating (1), under a pressure of 2 mTorr and an argon flow of 20 sccm. The Argon plasma was created using radio frequencies (13.56 MHz) with a power of 300 W.

Once these parameters were stabilized, the molybdenum target was exposed to the argon ion flux, resulting in a deposition rate of 22.2 nm / min. The two substrates were mounted on a rotating sample holder which rotates at about 5 rpm, and left 13'30 "under the molybdenum stream to obtain a 300 nm thick layer.

In terms of roughness, the Ra after deposition is 0.03 μηη; the flatness of the No. 1 deposit is well preserved from the profilometer observations and the scanning electron microscope. These two new substrates are therefore able to support a future deposit of CZTS layers in order to obtain the photovoltaic concrete according to the invention.

2) 1 st test of gold deposit by evaporation under vacuum (deposit n ° 2):

The formulation concrete substrate (1) coated with the coating (1) was previously treated for five minutes with a plasma of O ₂ generated at about 0.1 mbar by radio frequencies at 100 W, with a flux of 0 ₂ of 5 sccm.

After this treatment, the chamber was changed to secondary vacuum (from 10 to 2 mbar) and the gold evaporated. The substrate was then placed under the gold source when the sublimation started under heating caused by heating a tungsten filament.

A first deposit of gold by evaporation has been made. Problems with quartz balance calibration and sublimation stability resulted in a 730 nm gold deposit, an unnecessarily high and therefore uneven thickness.

Nevertheless, the measurements by profilometry showed that the deposit n ° 2 was as smooth as that of Molybdenum (Ra = 0.034 μηι) and thus potentially able to support a future deposit of CZTS layers in order to obtain the photovoltaic concrete according to the invention. 3) 2nd and 3rd gold vapor deposition tests (deposits # 3 and # 4) After calibration of the unit, evaporation deposits of finer gold layers, respectively 55 and 150 nm , were carried out according to a process identical to that described above for the deposit No. 2.

Measurement of "resistivity"

By applying a voltage and measuring the current, it was possible to measure the resistance of the metal deposits and thus to go back very closely to their resistivity, in particular by using the Van der Pauw method.

These resistivity measurements are summarized in the table below:

These resistivity measurements showed that the deposits n ° 1 and n ° 3 were conductive but that the deposit n ° 2 was not.

The dull and dark appearance of the first gold evaporation deposit (deposit No. 2) suggests that the polymer coating (1) has degraded during the deposition, and that part of this insulating coating is mixed with pulverized gold, thus making the deposit of gold much more resistive.

The deposits n ° 1 (molybdenum) and n ° 3 and 4 (gold), of smaller thickness than the deposit n ° 2, are better controlled, and present a resistivity correct compatible with applications of thin photovoltaic layers described in the state of the art.

Adhesion test

The adhesion tests carried out according to ASTM D 3359 showed that the molybdenum and gold layers had all adhered well with the formulation concrete substrate (1) covered with the polymer coating (1).

Deposition tests of CZTS layers were then carried out on certain conductive layers described above.

4) Deposition of CZTS layers on concrete substrates (1) coated with the polymer coating (1) previously covered with a layer of molybdenum (deposit No. 1) or a layer of gold (deposit No. 3 ) The layers of CZTS have been deposited in two stages:

4.1. First, co-evaporation of ZnS, Cu2S and SnS was performed. These three metal compounds were heated by conduction in vacuum crucibles, the pressure during the deposition was of the order of 10 ^"6 mbar, it could rise to 5x10 ^{" 5} mbar or more during the deposit but should not . more than 1 x10 ^"5 mbar deposition rates (in nm / s) and metal temperatures (° C) are shown in the table below:

The goal was to obtain Cu2ZnSnS ₄ , the theoretical velocity ratios were that

- the deposit of SnS was 1, 22 times faster than the ZnS, and that

- Cu2S deposition was 1, 2 times faster than ZnS.

4.2. Once the deposit was made, a layer of Cu2-xZnSn1 + yS3 + z was obtained. It was then performed a sulfurization. For this, the samples were placed in an oven with crucibles containing solid sulfur. The furnace atmosphere was a stream of dinitrogen so as to stabilize the pressure at 1 mTorr. The samples were heated for 1 hour at 60 ° C, then 3 minutes at 120 ° C and finally a quarter of an hour at 500 ° C.

Characteristics after deposit:

Measurements of chemical composition by electron spectroscopy of X-rays

(XPS) confirmed that the various layers had been well deposited on the substrates of formulation concrete (1) covered with the polymer coating (1) previously covered with a layer of molybdenum (deposit No. 1) or with a layer of gold (deposit No. 3).

The measurements by profilometry give a final roughness (Ra) after deposit of the

CZTS of 0.35 μηη in both cases.

The CZTS thin film deposition performed can serve as a basis for the realization of a complete photovoltaic cell.

Claims

1. Method of manufacturing a photovoltaic concrete, comprising the following steps:

- have a concrete;

- Polymerize this composition under the action of radiation, so as to obtain a polymer film covering all or part of the concrete surface;

- Sputtering, chemical vapor deposition, ion deposition, plasma deposition, electron bombardment, laser ablation, molecular beam epitaxy, or thermo-evaporation at least one photovoltaic thin film directly onto the film polymer.

The method of claim 1, wherein the temperature of the composition, when applied to the concrete, is less than 35 ° C, preferably less than 30 ° C.

The method of claim 1 or 2, further comprising demolding and / or heat treating the concrete.

Process according to any one of claims 1 to 3, comprising no step of bonding the photovoltaic thin film to the polymer film.

Process according to any one of claims 1 to 4 for which the concrete used has a surface, before coating with the polymer film, having a roughness Ra of from 0.5 μηη to 10 μηι, preferably from 0.5 to 7 μηι, still more preferably from 0.5 to 5 μηι, advantageously from 0.5 to 3 μηι.

Process according to any one of Claims 1 to 5, for which the concrete used has a surface, after coating with the polymer film, having a roughness Ra of from 0.1 m to 5 μηι, preferably of 0.2 at 3 μηη, more preferably from 0.3 to 1 μηη, advantageously from 0.4 to 0.6 μπι.

Photovoltaic concrete obtainable by the process of any one of claims 1 to 6.

8. Concrete according to claim 7 characterized in that it is an ultra high performance concrete.

9. Concrete according to any one of claims 7 to 8, the photovoltaic thin film produces electricity through the photovoltaic effect.

10. Use of a polymer film obtained by polymerization under the action of radiation and a photovoltaic thin film, for producing electricity on a concrete surface.

1 1. Element for the field of construction comprising a photovoltaic concrete according to any one of claims 7 to 9.

A method of manufacturing the element according to claim 1 1, comprising method according to one of claims 1 to 6.