USE OF COMPOSITE FIBERS FOR CONCRETE REINFORCEMENT

Abstract

The present invention relates to the use, for improving the alkali resistance of a composite based on at least one reinforcing element, of a resin composition comprising at least one photocurable resin and a crosslinking system comprising at least one photoinitiator, the resin composition not comprising any crosslinking agent other than the photoinitiator or comprising less than 4% by weight relative to the total weight of the resin composition. Figure 2

Description

Title of the invention: USE OF COMPOSITE FIBERS FOR REINFORCING CONCRETE

[0001] The present invention relates to improving the alkali resistance of composites based on at least one reinforcing element and a resin composition. It finds applications in particular for the reinforcement of concrete.

[0002] Concrete is probably the most widely used construction material today due to its high compressive strength, durability, longevity and resilience. Its properties make it a material of choice, particularly in the fields of construction, roads and civil engineering.

[0003] Concrete is mainly composed of aggregates held together by a binder, most often Portland cement. To improve the properties of concrete, it is known to use additives such as ultrafine particles (silica fume for example), superplasticizers also called water reducers or metallic, synthetic or mineral fibers.

[0004] Although very resistant to compression, concrete has low tensile strength, often accompanied by the appearance of cracks. To combat this problem, it is known to use reinforcing fibers, due to their interesting mechanical properties. Reinforcing fibers are thus widely used to make concrete more ductile and improve its resistance to cracking.

[0005] However, metal fibers have the disadvantage of being sensitive to corrosion, which can be detrimental to the longevity of concrete comprising such fibers. Furthermore, they often have densities greater than 7.7 and are therefore not distributed homogeneously in concrete having a lower density (metal fibers tend to flow under the effect of gravity, or even under the effect of vibrations when the concrete is vibrated to evacuate air bubbles that may have been entrained during pouring).

[0006] To solve this problem it has been proposed to replace the metal fibers with synthetic fibers. However, the mechanical resistance (Young's Modulus, tensile strength for example) of these fibers is not as good as that of metal fibers. Furthermore, their operating temperature (generally between 100°C and 160°C) is much lower than that of metal fibers (between approximately 600°C and 900°C), which may limit their use for certain applications.

[0007] Document WO2022129747Al proposes synthetic fibers which are resistant to corrosion, to improve the service life of concrete, and which have improved mechanical properties, to improve resistance to cracking. Furthermore, in Due to their density and reinforcing capacity, these fibers make it possible to significantly reduce overall CO2 emissions compared to the use of metal fibers, at a constant level of reinforcement. These fibers are made of a glass-resin composite comprising glass filaments embedded in a crosslinked resin, the crosslinked resin being based on a curable vinyl ester resin, a photoinitiator and a crosslinking agent.

[0008] Concrete being a very alkaline environment, it remains interesting to have such fibers which, in addition to the aforementioned properties, have good resistance to alkalis.

[0009] Continuing its research, the Applicant unexpectedly discovered that reducing the level of the crosslinking agent, known to improve the crosslinking of photocrosslinkable resins, or even eliminating it, makes it possible to improve the alkali resistance of these glass-resin composite fibers.

[0010] Thus, the subject of the invention is the use of a resin composition comprising: - at least one photocrosslinkable resin, and - a crosslinking system comprising at least one photoinitiating agent, the resin composition not comprising a crosslinking agent other than the photoinitiator agent or comprising less than 4% by weight relative to the total weight of the resin composition, to improve the alkali resistance of a composite based on at least one reinforcing element. I- DEFINITIONS

[0011] In this document, unless expressly indicated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0012] By the expression "composition based on", it is meant a composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacture of the composition; the composition thus being able to be in the totally or partially crosslinked state or in the non-crosslinked state.

[0013] The expression "based on at least one reinforcing element embedded in a composition" means a composite comprising the reinforcing element and said composition, the composition having been able to react with the surface of the reinforcing element during the different phases of manufacturing the composite, in particular during the crosslinking of the composition or during the making of the composite before crosslinking of the composition.

[0014] By "embedded" is meant that the reinforcing element is in direct contact with the resin composition over its entire surface, with the possible exception of the cutting zones of the composite.

[0015] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., excluding limits a and b), while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In the present document, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also and preferably designated. II- BRIEF DESCRIPTION OF THE FIGURES

[0016] [Fig-1] [Fig.l] represents a diagram of the process of synthesis of a composite comprising at least one reinforcing element.

[0017] [Fig.2] [Fig.2], not shown to scale to facilitate understanding, is a drawing showing a cross-section of a composite comprising at least one reinforcing element which is a single strand of fiber-resin composite. III- DESCRIPTION OF THE INVENTION

[0018] According to the invention, the resin composition comprises: - at least one photocrosslinkable resin, and - a crosslinking system comprising at least one photoinitiating agent, the resin composition not comprising any crosslinking agent other than the photoinitiating agent or comprising less than 4% by weight relative to the total weight of the resin composition.

[0019] By "resin composition" is meant here the resin as such or any composition based on this resin and comprising at least one additive (i.e. one or more additives) before crosslinking.

[0020] By "crosslinked" resin, we understand of course that the resin is hardened (photocured and / or thermoset), in other words in the form of a network of three-dimensional bonds, in a state specific to so-called thermosetting polymers (as opposed to so-called thermoplastic polymers).

[0021] The photocrosslinkable resin may be any resin capable of crosslinking in the presence of a photoinitiating agent under the action of light radiation, in particular ultraviolet or visible radiation. Preferably, the photocrosslinkable resin is a UV crosslinkable resin.

[0022] The photocrosslinkable resin is advantageously chosen from the group consisting of vinylester, epoxy, polyester, novolac resins and their mixtures, preferably from the group consisting of vinylester, epoxy resins and their mixtures, more preferably from the group consisting of vinylester resins and their mixtures. In a manner known to those skilled in the art, these photocrosslinkable resins may contain a diluent, such as styrene at a content of up to approximately 40% by weight of the photocrosslinkable resin. The photocrosslinkable resins sold in the trade are often marketed diluted.

[0023] By "polyester" resin is meant, in a known manner, a resin of the unsaturated polyester type. "Vinylester" resins are well known in the field of composite materials.

[0024] Without this definition being limiting, the vinylester resin is preferably of the epoxyvinylester type. More preferably, a vinylester resin is used, in particular of the epoxy type, which at least in part is based on (i.e. grafted onto a structure of the type) novolac (also called phenoplast) and / or bisphenolic, or preferably a vinylester resin based on novolac, bisphenolic, or novolac and bisphenolic.

[0025] A novolac-based epoxyvinylester resin (part in brackets in formula I below) corresponds, for example, in a known manner, to the following formula (I): -3 if

[0026] A bisphenol A-based epoxyvinylester resin (part in brackets of formula (II) below) corresponds, for example, to the formula (the "A" reminding us that the product is manufactured using acetone): H

[0027] An epoxy vinyl ester resin of the novolac and bisphenolic type has shown excellent results. As an example of such a resin, mention may be made in particular of the vinyl ester resins “ATLAC 590” and “ATLAC E-Nova FW 2045” from the company AOC (diluted with approximately 40% styrene) described in the aforementioned applications EP-A-1 074 369 and EP-A-1 174 250.

[0028] The level of photocrosslinkable resin in the resin composition may be in a range from more than 93% to 99.5% by weight, preferably from more than 94.5% to 99% by weight, preferably from more than 96% to 99% by weight, relative to the total weight of the resin composition. When the photocrosslinkable resin comprises a diluent, the aforementioned levels of photocrosslinkable resin include said diluent.

[0029] As is known, a photoinitiating agent is a molecule that creates reactive species such as free radicals, cations or anions, when exposed to ultraviolet or visible radiation. Particularly advantageously, the photocrosslinkable resin is a UV-crosslinkable resin and the photoinitiating agent is a photoinitiating agent reactive to UV above 300 nm, preferably between 300 and 450 nm.

[0030] For the purposes of the invention, in particular when the photocrosslinkable resin is chosen from the group consisting of vinylester, epoxy, polyester, novolac resins and their mixtures, the photoinitiating agent is preferably chosen from the group consisting of type I photoinitiators and their mixtures. The photoinitiating agent may also be a photoinitiator which is not a type I photoinitiator, for example a type II photoinitiator or the like, but this is not preferred.

[0031] Type I photoinitiators are selected from the group consisting of benzoin ethers, benzil ketals, alpha-dialkoxy-aceto-phenones, alpha-hydrody-alkyl-phenones, alpha-amino-alkyl-phenones, phosphine oxides and mixtures thereof. Preferably, the photoinitiating agent is selected from the group consisting of phosphine oxides and mixtures thereof. The phosphine oxide may advantageously be a bis(acyl)phosphine oxide.

[0032] As an example of a photoinitiating agent that can be used in the context of the present invention, mention may be made of bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (“Omnirad 819” from the company IGM or “speedcureBPO” from the company Lambson) or a mono(acyl)phosphine oxide (for example “Esacure TPO” from the company IGM), such phosphine compounds being able to be used in a mixture with other photoinitiators, for example photoinitiators of the alpha-hydroxy-ketone type such as for example dimethylhydroxy-acetophenone (eg “Omnirad 1173” from IGM) or 1-hydroxy-cyclohexyl-phenyl-ketone (eg “Omnirad 184” from IGM), benzo-phenones such as 2,4,6-trimethylbenzophenone (eg “Esacure TZT” from IGM) and / or thioxanthone derivatives such as isopropylthioxanthone (eg “Esacure Omnirad ITX” from IGM).

[0033] The level of photoinitiating agent is advantageously within a range from 0.5% to 3% by weight, preferably from 1% to 2.5% by weight, preferably from 1% to 2% by weight, relative to the total weight of the resin composition.

[0034] For the purposes of the invention, the resin composition does not comprise any crosslinking agent other than the photoinitiator agent or comprises less than 4% by weight relative to the total weight of the resin composition. It is thanks to this low level of this compound, or even its absence, that it is possible to improve the alkali resistance of the composite based on at least one reinforcing element. Usually, these compounds are used at levels greater than 5% by weight relative to the total weight of the resin composition to be crosslinked.

[0035] Preferably, the resin composition does not comprise a crosslinking agent other than the photoinitiating agent or comprises less than 3% by weight, preferably less than 2% by weight, preferably less than 1% by weight, relative to the total weight of the resin composition. More preferably, the resin composition does not comprise a crosslinking agent other than the photoinitiating agent.

[0036] As an example of a crosslinking agent other than the photoinitiator agent, mention may be made of multifunctional acrylate or methacrylate derivatives and peroxides well known to those skilled in the art.

[0037] The crosslinking agent other than the photoinitiator agent may be chosen from the group consisting of multifunctional (meth)acrylates, and their mixtures, preferably from the group consisting of tri(meth)acrylates and their mixtures. In particular, the crosslinking agent may be chosen from the group consisting of the triacrylate family.

[0038] The resin composition is used to improve the alkali resistance of a composite based on at least one reinforcing element, in particular compared to a composite comprising a reinforcing element and a resin composition which would comprise more than 4% by weight of a crosslinking agent other than a photoinitiating agent compared to the resin composition.

[0039] The invention is applicable to any type of reinforcing element or any composite based on at least one reinforcing element, in particular composites which are also based on photocrosslinkable resins.

[0040] By "reinforcing element" is meant an element allowing the mechanical reinforcement of a matrix in which this reinforcing element is intended to be embedded. The reinforcing element may be a wire element.

[0041] The wire element may be metallic or textile. By "wire element" is meant an element having a length at least 10 times greater than the largest dimension of its section regardless of the shape of the latter: circular, elliptical, oblong, polygonal, in particular rectangular or square or oval. In the case of a rectangular section, the wire element has the shape of a strip.

[0042] The invention is particularly interesting when applied to reinforcing elements or composites based on at least one reinforcing element which has sensitivity to alkalis. It finds applications in particular in the field of concrete reinforcing fibers.

[0043] Thus, preferably, the reinforcing element is a reinforcing fiber. The reinforcing fiber may be chosen from the group consisting of glass, basalt, carbon, aramid, polyester, polyethylene, boron, ceramic fibers and combinations thereof, preferably the reinforcing fiber is chosen from the group consisting of glass fibers.

[0044] The composite comprising a reinforcing element is preferably a single strand (or fiber, the two terms being able to be used equivalently) in fiber-resin composite (abbreviated "CFR") comprising filaments embedded in said resin composition, said resin composition being crosslinked (i.e. a resin hardened after crosslinking). In other words, the composite comprising a reinforcing element is preferably a CFR monostrand comprising filaments embedded in a resin crosslinked from the resin composition useful for the purposes of the invention.

[0045] The filaments of the fiber-resin composite monofilament can be chosen from the group consisting of glass, basalt, carbon, aramid, polyester, polyethylene, boron, ceramic filaments and combinations thereof, preferably the filaments are chosen from the group consisting of glass filaments.

[0046] As examples of fibers that can be used in the context of the present invention, mention may be made of the glass fibers “R25H” or “SE1200” from the company Owens Corning, the alkali-resistant glass fibers “AR320S-920S”, “AR640S-920S” or “AR1200S-920S” from the company Nippon Electric Glass or “Cem-fil” from the company Owens Corning, the basalt fibers “KVT400TEX14LKV41” from the company Basaltex, “Filva™” from the company Isomatex, the carbon fibers* HTS40” from the company Teijin or “ZOLTEK PX35” from the company Zoltek. The person skilled in the art knows very well how to adapt the sizing to the surface of the filaments to improve the compatibility of the filaments with the resin used in the mineral-resin composite, in particular using a silane-type compatibilizing agent.

[0047] The single strand of fiber-resin composite advantageously has an average diameter in a range from 0.2 to 2.5 mm, preferably from 0.3 to 1.3 mm, preferably from 0.5 to 1.2 mm.

[0048] The average diameter covers both single strands of essentially cylindrical shape (with a circular cross-section) and single strands of different shapes, for example oblong single strands (of more or less flattened shape) or rectangular cross-section. In the case of a non-circular cross-section and unless otherwise specifically indicated, the average diameter is by convention the so-called overall diameter, i.e. the diameter of the imaginary cylinder of revolution surrounding the single strand, in other words the diameter of the circumscribed circle surrounding its cross-section.

[0049] The single strand of fiber-resin composite advantageously has a length in a range from 5 to 85 mm, preferably from 10 to 80 mm.

[0050] The single strand of fiber-resin composite advantageously has a length / diameter ratio ranging from 10 to 110, preferably from 20 to 90, more preferably from 25 to less than 80.

[0051] The filaments advantageously represent from 60% to 85%, preferably from 70% to 80%, by weight of the single strand in fiber-resin composite and the resin composition represents from 15% to 40%, preferably from 20% to 30%, by weight, of the single strand in fiber-resin composite.

[0052] The weight ratio of the filaments is calculated by calculating the ratio of the initial fiber count to the final single-strand count. The count (or linear density) is determined on at least three samples, each corresponding to a length of 50 m, by weighing this length; the count is given in tex (weight in grams of 1000 m of product - as a reminder, 0.111 tex is equivalent to 1 denier). The percentage by weight of crosslinked resin can be obtained by calculating the difference between the final single-strand count and the initial fiber count.

[0053] Typically, the filaments are present in the form of a single multifilament fiber or several multifilament fibers associated with each other. In the latter case, the multifilament fibers are preferably essentially unidirectional. Each of the multifilament fibers may comprise several tens, hundreds or even thousands of unit glass filaments. These very fine unit filaments generally and preferably have an average diameter of the order of 5 to 30 μm, more preferably 10 to 20 μm.

[0054] The glass transition temperature (Tg) of the crosslinked resin is preferably greater than 190°C, preferably greater than 195°C, in particular greater than 200°C. It is measured in a known manner by DSC (Differential Scanning Calorimetry), on the second pass, for example and unless otherwise specified in the present application, according to the ASTM D3418 standard of 1999 (Mettler Toledo "822-2" DSC apparatus; nitrogen atmosphere; samples previously brought from room temperature (23°C) to 250°C (10°C / min), then rapidly cooled to 23°C, before final recording of the DSC curve from 23°C to 250°C, according to a ramp of 10°C / min).

[0055] The composite based on at least one reinforcing element can be manufactured by any method known to those skilled in the art depending on the object to be produced.

[0056] A non-limiting example of a method for manufacturing a composite comprising at least one reinforcing element which is a single strand of glass-resin composite (abbreviated as "GRC") comprising filaments embedded in a resin crosslinked from said resin composition is described below. This method may comprise the following successive steps: - make a rectilinear arrangement of filaments and drive this arrangement in a direction of advancement, - in a vacuum chamber, degas the arrangement of filaments by the action of the vacuum, - at the outlet of the vacuum chamber, after degassing, pass through a vacuum impregnation chamber so as to impregnate said arrangement of filaments with the resin composition useful for the purposes of the invention, in the liquid state, called “impregnation resin”, to obtain an impregnation containing the filaments and the composition of resin, - passing said impregnated material through a calibration die having a predefined surface section and shape, to impose a single-strand shape on it, - downstream of the die, in a UV irradiation chamber, polymerize the resin composition under the action of UV, the irradiation chamber comprising a tube transparent to UV, called an irradiation tube, through which the monostrand being formed circulates, traversed by a current of inert gas, the speed (denoted Vir) of passage of the monostrand in the irradiation chamber being greater than 50 m / min, the irradiation time (denoted Dir) of the monostrand in the irradiation chamber being equal to or greater than 1.5 s, step at the end of which a CVR monostrand is obtained comprising filaments embedded in a crosslinked resin, step at the end of which a CVR monostrand is obtained comprising filaments embedded in a crosslinked resin - optionally, cut the single strand to a desired length, for example to a length in the range from 5 to 85 mm.

[0057] In a particularly advantageous manner, the method for manufacturing the CVR single strand of the invention comprises the following essential steps: - the speed (Vir) of passage of the single strand in the irradiation chamber is greater than 50 m / min; - the duration (Dir) of passage of the single strand in the irradiation chamber is equal to or greater than 1.5 s and equal to or less than 10 s; - the irradiation chamber comprises a UV-transparent tube (such as a quartz tube or preferably a glass tube), called an irradiation tube, through which the single strand being formed circulates, this tube being traversed by a current of inert gas, preferably nitrogen.

[0058] All the steps (arrangement, degassing, impregnation, calibration, polymerization, optional winding and cutting) of the process of the invention are, independently of one another, steps known to those skilled in the art, as are the materials (multifilament fibers and resin compositions) used; they have for example been described in one and / or the other of applications EP1074369A1 and EP1174250A1.

[0059] The attached [Fig.l] very simply diagrams an example of a device 10 allowing the production of single strands in CVR.

[0060] There is shown a reel 11a containing, in the example illustrated, glass fibers 11b (in the form of multifilaments). The reel is continuously unwound by driving, so as to produce a rectilinear arrangement 12 of these fibers 11b. In general, the reinforcing fibers are delivered in "rovings", that is to say already in groups of fibers wound in parallel on a reel; for example, fibers marketed by Owens Corning under the designation "Advantex" fiber are used, with a count equal to 1200 tex (as a reminder, 1 tex = 1 g / 1000 m of fiber). This is for example the traction exercised by the rotating reception 26 which will allow the advancement of the fibers in parallel and of the single strand in CVR along the entire length of the installation 1.

[0061] This arrangement 12 then passes through a vacuum chamber 13 (connected to a vacuum pump not shown), arranged between an inlet pipe 13a and an outlet pipe 13b opening onto an impregnation chamber 14, the two pipes preferably with rigid walls having for example a minimum section greater (typically twice as much) than the total section of fibers and a length much greater (typically 50 times as much) than said minimum section.

[0062] As already taught by application EPI 174250A1, the use of rigid-walled tubing, both for the inlet orifice in the vacuum chamber and for the outlet orifice of the vacuum chamber and the transfer from the vacuum chamber to the impregnation chamber, proves to be compatible both with high rates of passage of the fibers through the orifices without breaking the fibers, but also makes it possible to ensure sufficient sealing. It is sufficient, if necessary experimentally, to search for the largest passage section, taking into account the total section of the fibers to be treated, still making it possible to provide sufficient sealing, taking into account the speed of advancement of the fibers and the length of the tubing. Typically, the vacuum inside the chamber 13 is for example of the order of 0.1 bar, the length of the vacuum chamber is approximately 1 meter.

[0063] At the outlet of the vacuum chamber 13 and the outlet pipe 13b, the arrangement 12 of fibers 11b passes through an impregnation chamber 14 comprising a supply tank 15 (connected to a metering pump not shown) and a sealed impregnation tank 16 completely filled with impregnation composition 17 based on a curable resin of the vinylester type (e.g., "ALTAC® E-Nova FW 2045" from AOC). For example, the composition 17 also comprises (at a weight rate of 1 to 2%) a photoinitiating agent suitable for UV and / or UV-visible radiation with which the composition will subsequently be treated, for example bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide ("Omnirad 819" from the company IGM). Of course, the impregnation composition 17 is in the liquid state.

[0064] Preferably, the length of the impregnation chamber is several meters, for example between 2 and 10 m, in particular between 3 and 5 m.

[0065] Thus, an impregnation which comprises, for example (% by weight) 65% to 75% of solid fibers 11b, the remainder (25 to 35%) being constituted by the liquid impregnation matrix 17, emerges from the impregnation chamber 14, in a sealed outlet pipe 18 (still under primary vacuum).

[0066] The impregnated material then passes through calibration means 19 comprising at least one calibration die 20 whose channel (not shown here), for example circular, rectangular or even conical in shape, is adapted to the particular conditions of realization. The calibration die allows, thanks to a cross section of determined dimensions, generally and preferably circular or rectangular, to adjust the proportion of resin in relation to the fibers, while imposing on the impregnated the shape and thickness targeted for the single strand. For example, this channel has a minimum cross section of circular shape whose downstream orifice has a diameter slightly greater than that of the targeted single strand. Said die has a length which is typically greater than at least 100 times the minimum dimension of the minimum section. Its function is to ensure high dimensional precision of the finished product, it can also play a role in dosing the rate of fiber in relation to the resin. According to a possible variant embodiment, the die 20 can be directly integrated into the impregnation chamber 14, which avoids for example the use of the outlet pipe 18.

[0067] Preferably, the length of the calibration zone is several centimeters, for example between 5 and 50 cm, in particular between 5 and 20 cm.

[0068] Thanks to the calibration means (19, 20) a "liquid" composite monostrand 21 is obtained at this stage (liquid in the sense that its impregnation resin is always liquid) whose cross-sectional shape is preferably essentially circular.

[0069] At the outlet of the calibration means (19, 20), the liquid composite monostrand 21 thus obtained is then polymerized by passing through a UV irradiation chamber (22) comprising a sealed glass tube (23) through which the composite monostrand circulates; said tube, the diameter of which is typically a few cm (for example 2 to 3 cm), is irradiated by a plurality (here, for example 4) of in-line UV irradiators (24) ("UVAprint" lamps from the company Dr. Hônle, with a wavelength of 200 to 600 nm) arranged at a short distance (a few cm) from the glass tube.

[0070] The polymerization or UV irradiation chamber then has the function of polymerizing and crosslinking the resin under the action of UV rays.

[0071] The UV irradiation chamber may comprise one or more UV irradiators (or radiators). Advantageously, the irradiation chamber comprises a plurality of UV irradiators, i.e. at least two (two or more than two) which are arranged in a line around the irradiation tube. Each UV irradiator typically comprises one (at least one) UV lamp (preferably emitting in a spectrum of 200 to 600 nm) and a parabolic reflector at the focus of which is the center of the irradiation tube; it delivers a linear power preferably between 2,000 and 14,000 watts per meter. Even more preferably, the irradiation chamber comprises at least three, in particular at least four UV irradiators in a line.

[0072] Even more preferably, the linear power delivered by each UV irradiator is between 2,500 and 12,000 watts per meter, in particular within a range of 3,000 to 10,000 watts per meter.

[0073] UV radiators suitable for the process are well known to those skilled in the art, e.g. example those marketed by the company Dr. Hônle AG (Germany) under the reference "1055 LCP AM UK", equipped with "UVAPRINT" lamps (iron-doped high-pressure mercury lamps). The nominal (maximum) power of each radiator of this type is approximately 13,000 Watts, the power actually delivered being able to be adjusted with a potentiometer between 30 and 100% of the nominal power.

[0074] The diameter of the irradiation tube (preferably made of glass) is preferably between 10 and 80 mm, more preferably between 20 and 60 mm.

[0075] Preferably, the length of the irradiation chamber is several meters, for example between 2 and 15 m, in particular between 3 and 10 m.

[0076] In this example, the irradiation tube (23) is traversed by a stream of nitrogen.

[0077] The irradiation conditions are preferably adjusted in such a way that, at the outlet of the impregnation chamber, the temperature of the CVR single strand, measured at the surface of the latter (for example using a thermocouple), is higher than the Tg of the crosslinked resin (in other words higher than 190°C), and more preferably lower than 270°C.

[0078] Once the resin has polymerized (hardened), the CVR single strand (25), this time in the solid state, driven in the direction of arrow F, then arrives on its final receiving reel (26).

[0079] Between the calibration die and the final receiving support, it is preferable to maintain the tensions undergone by the mineral fibers at a moderate level, preferably between 0.2 and 2.0 cN / tex, more preferably between 0.3 and 1.5 cN / tex; to control this, it will be possible, for example, to measure these tensions directly at the outlet of the irradiation chamber, using appropriate tensiometers well known to those skilled in the art.

[0080] We finally obtain a finished composite block of manufacture as shown very simply in [Fig.2], in the form of a continuous CVR monostrand (25), of very great length, whose unitary glass filaments (251) are distributed homogeneously throughout the volume of hardened resin (252). Its diameter is for example equal to approximately 1 mm.

[0081] The continuous CVR single strand (25) can be cut to a determined length (not shown in [Fig.l]), for example 45 mm by any means known to those skilled in the art, for example using a hydraulic guillotine, such as the “SH-5214” from Baileigh. This step can be carried out directly at the outlet of the irradiation chamber (23). It can also be carried out after being packaged on a final receiving reel (26). In this case, it is preferable to unwind the single strand from the reel from the end of the single strand which is located the most axially external of the reel, in order to avoid helically deforming the single strand. Indeed, if the single strand is unwound from the reel from the end of the single strand which is located the most axially inside the coil, this helically deforms the single strand which can be detrimental to the breaking stress. IV- EXAMPLES IV-1 Measurements and tests used Mechanical properties

[0082] The mechanical properties in extension of the CVR single strand (breaking stress Cr and elongation at break Ar) were measured using an “INSTRON” tensile machine of the 5944 type (BLUEHILL® UNIVERSAL software supplied with the tensile machine), according to the ASTM D2343 standard, at a temperature of 23°C.

[0083] The measurements were carried out on CVR single strands with or without crosslinking agent and with or without aging in an alkaline medium. The aging in an alkaline medium consisted of immersing the CVR single strands in a solution of NaOH and KOH (pH = 13.1) at a temperature of 60°C for 72 hours.

[0084] Before measurement, these single strands (aged or not) were subjected to prior conditioning (storage of the single strands for at least 24 hours in a standard atmosphere according to the European standard DIN EN 20139 (temperature of 23 ± 2°C; humidity of 50 ± 5%)). The aged CVR single strands were previously dried on absorbent paper.

[0085] The 240 mm samples tested were subjected to traction at a nominal speed of 50 m / min, under a pre-test preload of 0.5 MPa (distance between the jaws: 150 mm). All results given are an average of 10 measurements. Concrete aging protocol

[0086] A fresh commercial concrete of the Ductal brand is prepared by following the supplier's recommendations and then adding 3% by volume of CVR monostrands at the end of the mixing cycle. The fresh fiber-reinforced concrete is poured into a large bakelized film-coated plywood panel of 745x540x15mm. Filling is done by pouring onto the edge of the mold, favoring the orientation of the fibers in the direction of pouring. After preparation, the large plate is kept at the manufacturing site under normal conditions of temperature, pressure and humidity. The plate is removed from the mold after 24 hours and then placed in a room regulated at 20°C ± 2 and humidity at 100% RH for 14 days.

[0087] The plate is then cut into mini-plates (called plates) of 325x50x15 mm in the longitudinal direction, corresponding to the direction of pouring of the fiber-reinforced concrete and therefore to the preferential orientation of the fibers.

[0088] Four plates are kept in a humid room (temperature at 20°C ± 2 and humidity at 100% RH) for an additional 14 days and then are mechanically tested in 4-point bending corresponding to a test deadline t28humid-

[0089] Four other plates are kept immersed in hot water 60°C ± 2 in a climatic chamber for 42 additional days then are mechanically tested in 4-point bending corresponding to a test deadline t56hot.

[0090] The specimens are tested in four-point bending according to standard EN 1170-5. The results presented below correspond to the average of the individual results of these four tests.

[0091] Two characteristics are noted:

[0092] (i) The limit of proportionality LOP, as being the average value of the end of the Stress / deflection linearity during the bending test. For each single strand (Ml, M3), the LOP results at t56 are presented on a base of 100 relative to the LOP result at t28 of the single strand considered. A result greater than 100 indicates an improvement in the bending strength of the concrete matrix at low deformation.

[0093] (ii) The maximum breaking stress MOR, as being the average maximum value of the stress during the bending test. For each single strand (M1, M3), the MOR results at t56 are presented on the basis of 100 relative to the MOR result at t28 of the single strand considered. A result lower than 100 reflects a degradation in the strength of the reinforcing fibers intended to improve the bending strength at higher deformation. IV-2 Tests on single strands

[0094] The examples presented below aim to compare the breaking stress with or without aging in an alkaline medium of composites in accordance with the invention with composites not in accordance with the invention in that they comprise more than 4% by mass of crosslinking agent.

[0095] Single strands (M1 to M4) in CVR were manufactured according to the method described previously with a speed Vir of passage of the single strand in the irradiation chamber of 100 m / min, an irradiation time Dir of the single strand in the irradiation chamber of 2.4 s, the length of the irradiation chamber being 4 m.

[0096] The resin composition used for the control single strands (M1 and M2) was based on vinylester resin (“ATLAC E-NOVA FW2045” from the company), a triacrylate hardener (“SR 368” from the company Sartomer), as a crosslinking agent, at a rate of 15% by weight relative to the total weight of the resin composition, and a photoinitiator (“Omnirad 819” from the company IGM). The resin composition used for the single strands in accordance with the invention (M3 and M4) differed from the resin composition of the control single strands only in that it did not comprise a crosslinking agent.

[0097] The glass filaments of the single strands M1 to M4 were “R25H” filaments from Owens Corning. Their diameter was 0.54 mm, the tex of the glass fibers was 300 g / km and the mass ratio of the glass fibers to the crosslinked resin was 70 / 30. The mechanical properties of the single strands M1 to M4 are presented in Table 1 below.

[0098] The results are expressed in (Mpa) as well as in percentage base 100 relative to the control single strand M1 for the single strand M3 and in percentage base 100 relative to the control single strand M2 for the single strand M4.

[0099] [Tables 1] Ml M2 M3 M4 Crosslinking agent With With Without Without Alkaline aging No Yes No Yes Stress at break (MPa) 1388 768 1327 1047 Stress at break (base 100) 100 100 96 136

[0100] The results presented above show that the removal of the crosslinking agent makes it possible to improve the breaking stress of the composite after aging in alkaline media, without affecting the breaking stress before aging. Thus, the use of a resin composition in accordance with the invention makes it possible to improve the alkali resistance of a composite based on at least one reinforcing element and a resin composition.

[0101] Single strands (M1 and M3) as described above were subjected to the aforementioned aging protocol in concrete. The properties of these single strands are presented in Table 2 below.

[0102] [Tables2] Ml (with crosslinking agent) M3 (without crosslinking agent) Aging protocol in concrete, LOP at t28wet 100 100 Aging protocol in concrete LOP at t56Hot 107 109 Aging protocol in concrete MOR at t28wet 100 100 Aging protocol in concrete MOR at t28hot 50 75 Aging protocol in concrete MOR at t56hot 30 54

[0103] As expected, the base 100 results of LOP at t56 compared to t28 show an improvement in the flexural strength of the low-strain concrete matrix during the aging of concrete. The single strands according to the invention do not degrade this improvement. On the other hand, the single strands according to the invention (M3) greatly limit the degradation of the strength of the reinforcing fibers intended to improve the flexural strength at higher deformation (MOR). Thus, the use of a resin composition according to the invention in CVR single strands makes it possible to further strengthen the concrete over time.

[0104] Due to their high breaking stress, the monostrands using a resin composition in accordance with the invention therefore make it possible to improve the cracking resistance of the concrete. It has thus been found that these monostrands present an improved compromise of performance between in particular mechanical strength, corrosion resistance, processability (in particular dispersibility during mixing, the implementation temperature and the maintenance of homogeneity during drying of the concrete).

Claims

Claims

1. Use of a resin composition comprising: - at least one photoretic resin, and - a crosslinking system comprising at least one photoinitiator agent, characterized in that the resin composition does not comprise a crosslinking agent other than the photoinitiator agent or comprises less than 4% by weight relative to the total weight of the resin composition, for improving the alkali resistance of a composite based on at least one reinforcing element.

2. Use according to claim 1, wherein the photocrosslinkable resin is selected from the group consisting of vinylester, epoxy, polyester, novolac resins and their mixtures, preferably from the group consisting of vinylester, epoxy resins and their mixtures, more preferably from the group consisting of vinylester resins and their mixtures.

3. Use according to any one of the preceding claims, wherein the level of photocrosslinkable resin in the resin composition is within a range of more than 93% to 99.5% by weight, preferably more than 94.5% to 99% by weight, preferably more than 96% to 99% by weight, relative to the total weight of the resin composition.

4. Use according to any one of the preceding claims, wherein the photoinitiating agent is selected from the group consisting of type I photoinitiators and mixtures thereof, preferably from the group consisting of phosphine oxides and mixtures thereof.

5. Use according to any one of the preceding claims, wherein the level of photoinitiating agent is within a range of from 0.5% to 3% by weight, preferably from 1% to 2.5% by weight, preferably from 1% to 2% by weight, relative to the total weight of the resin composition.

6. Use according to any one of the preceding claims, in which the crosslinking agent other than the photoinitiating agent is chosen from the group consisting of multifunctional (meth)acrylates, and mixtures thereof, preferably from the group consisting of tri(meth)acrylates and their mixtures.

7. Use according to any one of the preceding claims, wherein the resin composition does not comprise a crosslinking agent other than the photoinitiating agent or comprises less than 3% by weight, preferably less than 2% by weight, preferably less than 1% by weight, relative to the total weight of the resin composition.

8. Use according to any one of claims 1 to 6, wherein the resin composition does not comprise a crosslinking agent other than the photoinitiating agent.

9. Use according to any one of the preceding claims, wherein the photocrosslinkable resin is a UV crosslinkable resin and the photoinitiating agent is a photoinitiating agent reactive to UV above 300 nm.

10. Use according to any one of the preceding claims, wherein the reinforcing element is a reinforcing fiber.

11. Use according to claim 10, wherein the reinforcing fiber is selected from the group consisting of glass, basalt, carbon, aramid, polyester, polyethylene, boron, ceramic fibers and combinations thereof, preferably the reinforcing fiber is selected from the group consisting of glass fibers.

12. Use according to any one of the preceding claims, in which the composite based on at least one reinforcing element is a single strand of fiber-resin composite comprising filaments embedded in said response composition, said resin composition being crosslinked.

13. Use according to claim 12, wherein the fiber-resin composite monostrand has an average diameter in a range from 0.2 to 2.5 mm, preferably from 0.3 to 1.3 mm, preferably from 0.5 to 1.2 mm.

14. Use according to any one of claims 12 to 13, in which the single strand of fiber-resin composite has a length in a range from 5 to 85 mm, preferably from 10 to 80 mm.

15. Use according to any one of claims 12 to 14, wherein the filaments represent from 60% to 85%, preferably from 70% to 80%, by weight of the fiber-resin composite monostrand and the resin composition represents from 15% to 40%, preferably from 20% to 30%, by weight, of the fiber-resin composite monostrand.

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