Fiber Reinforced Structures

Abstract

A fiber-reinforced structure, in particular a fiber-reinforced concrete structure, comprises a multiplicity of composite fibers distributed in a matrix of a construction material, in particular a matrix of a mineral binder-based construction material, where each composite fiber comprises non-metallic load-bearing fibers bound by and / or embedded in an organic synthetic material, and where each composite fiber has a linear density of 25-500 tex, in particular 50-350 tex.

Description

[Technical field]

[0001] The present invention relates to a fiber-reinforced structure, in particular a fiber-reinforced concrete structure, comprising a multitude of composite fibers dispersed in a matrix of a construction material. Furthermore, the present invention also relates to a method for producing the fiber-reinforced structure, as well as to the use of the composite fibers as reinforcement in construction materials, in particular concrete. [Background technology]

[0002] Conventionally, to increase the tensile strength of structures made from construction materials such as concrete or mortar, the structures are reinforced with steel rebars.

[0003] Alternatively, structural reinforcement can be achieved with relatively short fibers randomly distributed in the construction material. For this purpose, fibers of different materials can also be used, for example steel fibers, polymeric materials or composite fibers. In comparison with reinforcement with steel fibers, such composite and polymeric fibers are usually non-corrosive, lighter than steel, easier to apply and cause less wear on the mixing and feeding equipment.

[0004] For example, US Patent Application Publication No. 2021 / 0245456 A1 (USB I, LLC) describes improved composite fibers and structural materials incorporating these composite fibers. The fibers are produced by an improved process in which resin is vertically textured and impregnated into the fibers without introducing a substantial amount of microbubbles into the resin. The use of vertical impregnation and twisting of fiber strands with specific viscosity control produces stronger composite fibers with substantially no trapped microbubbles, which have improved tensile strength and low tensile strength variability for use in reinforcing structural concrete and other structural materials.

[0005] However, the production of such composite fibers requires a rather complicated multi-step process, in particular, the core fibers must be independently textured by a rotating texturizer, and then twisted into a fiber strand in a resin impregnation device while a resin having a predetermined viscosity is injected into the resin impregnation device.

[0006] Furthermore, for example, in the case of concrete structures, there are regulations regarding the type and performance of reinforcement. One of them is the FIB Model Code 2010, which describes the crack opening / force reduction after the first crack in a brittle concrete matrix. The residual force should not be less than 40% of the maximum load before cracking (f R1 / f LK >0.4).

[0007] Although it is possible to produce concrete structures that meet the requirements of the FIB Model Code 2010 using conventional rebars and certain steel fibers, no satisfactory solutions based on non-metallic reinforcement are known so far.

[0008] Thus, there remains a need for new and improved solutions which, to the extent possible, overcome the aforementioned shortcomings. Summary of the Invention [Means for solving the problem]

[0009] The object of the present invention is to provide an improved solution for the production of reinforced structures, in particular fiber-reinforced structures based on mineral binder compositions, especially fiber-reinforced concrete structures. In particular, said solution should allow the production of concrete structures that meet the requirements of the FIB Model Code 2010 regarding crack opening. At the same time, the reinforced structures should be as easy to produce as possible.

[0010] Surprisingly, it has been found that these objects can be achieved by the fibre-reinforced structures, methods and uses as described in independent claims 1, 14 and 15.

[0011] In particular, according to the invention, composite fibres comprising non-metallic load-bearing fibres bound by and / or embedded in an organic synthetic material and having a linear density of 25-500 tex, in particular 50-350 tex, are used as reinforcement in fibre-reinforced structures, in particular fibre-reinforced structures based on mineral binder compositions, especially reinforced concrete structures.

[0012] Consequently, composite fibres comprising non-metallic load-bearing fibres bound together by organic synthetic materials and having a linear density of 25-500 tex, in particular 50-350 tex, are very useful reinforcements for fibre-reinforced structures, in particular for mineral binder-based construction materials, such as fibre-reinforced concrete.

[0013] A linear density of 25-500 tex, especially 50-350 tex, allows the production of sufficiently strong composite fibers with a relatively short length and high modulus of elasticity. Nevertheless, the composite fibers can be grouped together and / or embedded in the matrix of the construction material such that a sufficiently high pull-out force occurs. This allows the provision of a fiber-reinforced structure in which, under sufficiently high loads, the reinforcing composite fibers themselves or the matrix around the reinforcing composite fibers break, rather than the reinforcing composite fibers being pulled out of the matrix.

[0014] In particular, concrete structures that meet the requirements of the FIB Model Code 2010 regarding crack opening can be obtained without the need for metal components. Specifically, when using the composite fibers of the present invention, the residual force is at least 40% of the maximum load before cracking, i.e., f R1 / f LK >0.4. As a result, the composite fibers of the present invention can be used in place of conventional metal rebar or metal fibers.

[0015] After selecting the type of construction material, e.g. the type of concrete, and the type of composite fiber, in particular with respect to modulus of elasticity, toughness, length, surface structure and / or pull-out force, the minimum dosage of the composite fiber is determined according to the requirements: R1 / f LK >0.4 can be used as a basis for the determination.

[0016] The special structure of the composite fibers allows for effective reinforcement to be achieved with an amount of composite fiber that does not significantly affect the processing of the construction material during the manufacturing process of the fiber-reinforced structure, and yet complete fracture of the composite fibers connecting the cracks can be effectively prevented under normal loads.

[0017] Furthermore, the composite fibers can be easily added to and intimately mixed with mineral binder-based construction materials when producing fiber-reinforced structures. In certain embodiments, the organic-based synthetic material that forms the casing for the non-metallic load-bearing fibers minimizes wear on the feeding and mixing equipment.

[0018] Additionally, composite fibers can be designed without any metal components, which is beneficial with regard to corrosion.

[0019] Particularly preferred embodiments are outlined throughout the description and dependent claims.

[0020] 1 shows drawings used to explain an embodiment; [Brief description of the drawings]

[0021] [Figure 1] 1 is a graph showing the post-crack flexural strength at various prescribed values ​​of preformed crack opening (CMOD), namely 0.5, 1.5, 2.5 and 3.5 mm, for various concrete specimens with and without composite fibers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A first aspect of the invention relates to a fibre-reinforced structure, in particular a fibre-reinforced structure based on a mineral binder composition, especially a fibre-reinforced concrete structure, comprising a multiplicity of composite fibres distributed in a matrix of a construction material, in particular a matrix of a mineral binder composition, in particular a matrix of concrete, each composite fibre comprising non-metallic load-bearing fibres held together by and / or embedded in an organic synthetic material, each composite fibre having a linear density of 25 to 500 tex, in particular 50 to 350 tex.

[0023] By "fiber-reinforced structure" is intended a rigid structure. The shape of the structure may be as desired. For example, the structure may be part of a building and / or an infrastructure construction, such as a road, a bridge, or a tunnel. For example, the structure may be a ceiling, a wall, a roof, a floor, a support beam, and / or a column.

[0024] The unit "tex" is a measure of the linear density of a fiber and is defined as the mass in grams per 1000 meters of length.

[0025] The construction material is intended in particular to be a binder-based composition, which can be cured and / or hardened, in particular with water. In the fiber-reinforced structure, the binder-based composition is present in the cured and / or hardened state. The binder can be selected from mineral binders and / or organic binders.

[0026] The term "mineral binder" refers to a binder that reacts in the presence of water, for example in a hydration reaction, to form a solid hydrate or hydrate phase. Mineral binders are, for example, hydraulic binders, such as cement and / or hydraulic lime; latent hydraulic binders, such as slag; pozzolanic binders, such as fly ash; or non-hydraulic binders, such as gypsum and / or white lime. Organic binders may be, for example, synthetic resin dispersions and / or one- or two-part reactive resins that harden, for example, by polymerization.

[0027] A fiber-reinforced structure includes a multitude of individual composite fibers, whereby the composite fibers are distributed in a construction material forming a continuous matrix, in particular, the composite fibers are randomly distributed in the matrix of the construction material.

[0028] Each composite fiber comprises at least two non-metallic load-bearing fibers, which are bound together by an organic synthetic material. In a preferred embodiment, the non-metallic load-bearing fibers are fully embedded in the organic synthetic material, although this is not mandatory. For example, the non-metallic load-bearing fibers can be joined together while being partially embedded in the surface of a common central core made of an organic synthetic material. Another preferred embodiment is described further below.

[0029] In particular, the elastic modulus of the composite fibers is at least as large as the elastic modulus of the matrix of the construction material. The elastic modulus of the matrix of the construction material is thereby intended to be the elastic modulus without the composite fibers. In the case of mineral binder-based construction materials, the elastic modulus is preferably measured according to standard DIN EN 12390-13:2021-09 after 28 days from the production of the construction material. The elastic modulus of the composite fibers can be measured according to standard ISO 527-3:2018.

[0030] By adjusting the modulus of the composite fibers to that of the construction material, as mentioned above, it is possible to reduce the elongation of the fibers just after matrix fracture and before the onset of fiber pull-out of the reinforced fiber structure, thereby effectively reducing crack opening in the concrete structure, in contrast to known synthetic reinforcing fibers.

[0031] In particular, the modulus of elasticity of the composite fibres is equal to at least 1.1 times, in particular at least 1.5 times and in particular at least 2 times the modulus of elasticity of the construction material.

[0032] In particular, the modulus of elasticity of the composite fibre is >40 GPa, in particular >50 GPa or more, for example >60 GPa.

[0033] This is particularly appropriate when the construction material is a mineral binder-based composition, such as a concrete composition, for example, the construction material has an elastic modulus of 5 to 80 GPa, in particular 10 to 70 GPa, for example 15 to 60 GPa.

[0034] The non-metallic load-bearing fibers may be selected from natural fibers, inorganic fibers and / or synthetic fibers.

[0035] For example, the non-metallic load-bearing fibers are selected from carbon fibers, glass fibers, igneous rock fibers, basalt fibers, polyolefin fibers, aramid fibers, Vectran fibers, polyhydroquinone-diimidazopyridine fibers (PIPD fibers; M5 fibers), poly(p-phenylene-2,6-benzobisoxazole) fibers (PBO fibers; Zylon).

[0036] Preferably, the load-bearing fibers comprise or consist of carbon and / or synthetic fibers. Thus, preferably, the synthetic fibers are selected from polyhydroquinone-diimidazopyridine fibers and / or poly(p-phenylene-2,6-benzobisoxazole) fibers. It has been found that the above types of fibers are very stable under the alkaline conditions prevailing in the mineral binder composition, resulting in a long-term and reliable reinforcement of the fiber-reinforced structure.

[0037] Particularly preferably, the load-bearing fibres comprise or consist of carbon fibres, which have been found to be optimal in terms of chemical stability, mechanical properties and compatibility with organic-based synthetic materials for embedding.

[0038] Preferably, in the composite fibres, the non-metallic load-bearing fibres run parallel and / or in one direction, which has been found to be optimal for load-bearing properties, in particular the non-metallic load-bearing fibres are not twisted, in particular not helically twisted.

[0039] In particular, each composite fiber comprises at least 5, in particular at least 10, preferably at least 25, for example at least 50, especially at least 100, particularly preferably at least 500, advantageously at least 800 non-metallic load-bearing fibers, for example, each composite fiber comprises from 100 to 3000, in particular from 500 to 1500 non-metallic load-bearing fibers.

[0040] In particular, the organic synthetic material is a thermosetting resin and / or a thermoplastic resin.

[0041] In particular, the organic-based composite material may comprise a single material or a mixture of two or more materials.

[0042] For example, the organic synthetic material is selected from epoxy resins, polyurethane resins, polyester resins, vinyl ester resins, epoxy vinyl ester resins, polyolefins, vinyl polymers, polyamides, polyvinyl alcohols, polyesters, polyoxymethylene, polycarbonates, thermoplastic polyurethanes, and / or ionomers.

[0043] Preferably, the organic synthetic material is selected from epoxy resins, epoxy vinyl ester resins, polyamides, polyvinyl alcohols, polyolefins, polyethylene terephthalate and / or poly(ethylene vinyl acetate). These materials have been found to be very suitable in the context of the present invention. Particularly preferred are epoxy resins, epoxy vinyl ester resins, polyolefins and / or polyethylene terephthalate.

[0044] In particular, the epoxy resins and / or epoxy vinyl ester resins are one-part or two-part curable resins. For example, one-part resins contain a latent curing agent, such as dicyanamide. Curing can be initiated by heating the resin to a predetermined temperature.

[0045] According to a preferred embodiment, the organic synthetic material is selected from polyolefins and / or polyethylene terephthalate, preferably polypropylene and / or polyethylene terephthalate glycol (PET-G), more preferably polypropylene.

[0046] Preferably, based on the total weight of the composite fiber, the composite fiber comprises 20 to 99 wt.%, preferably 40 to 99 wt.%, in particular 50 to 95 wt.% of non-metallic load-bearing fibers and 1 to 80 wt.%, preferably 1 to 60 wt.%, in particular 5 to 50 wt.% of organic synthetic material.

[0047] In particular, the non-metallic load-bearing fibers are grouped together in a shear-resistant manner, which specifically means that the non-metallic load-bearing fibers cannot move relative to each other.

[0048] In particular, the non-metallic load-bearing fibers are completely impregnated and embedded in an organic synthetic material, which allows the production of fairly stiff composite fibers, especially when a thermosetting resin, for example an epoxy resin, is used as the organic synthetic material for embedding the load-bearing fibers and curing the thermosetting resin.

[0049] According to another preferred embodiment, the composite fiber is configured as a core-shell structure, comprising non-metallic load-bearing fibers forming the core of the composite fiber and an organic synthetic material forming a casing around the core, in particular so that the non-metallic load-bearing fibers are only partially impregnated with the organic synthetic material and are therefore able to move relative to each other within the composite fiber.

[0050] In the direction perpendicular to the longitudinal direction, the composite fibers preferably have a circular, oval, elliptical, rectangular and / or square cross section. In particular, the composite fibers have an oval, elliptical and / or rectangular cross section. More preferably, the aspect ratio of the height to the width of the cross section is >1.5, in particular >2, especially >4. In particular, in the case of a non-rectangular cross section, the height refers to the maximum Feret diameter of the cross section and the width refers to the minimum Feret diameter of the cross section.

[0051] In particular, the length of the bicomponent fibres is <75mm, in particular <30mm and / or >2.5mm, in particular >5mm. In particular, the bicomponent fibres have a length of 2.5 to 75mm, in particular 5 to 40mm or 20 to 35mm.

[0052] The diameter of the composite fibers, in particular the equivalent diameter of the composite fibers determined according to the EN 14889-2:2006 standard, is for example 0.05 to 2 mm, in particular 0.1 to 1 mm.

[0053] Composite fibers having these lengths and / or diameters are particularly advantageous because they can be easily mixed with the mineral binder composition so that the composite fibers are homogeneously distributed and embedded in the mineral binder composition. Due to their relatively short length, the composite fibers hardly protrude from the surface of the matrix of the construction material (protrusion is usually undesirable). Furthermore, fiber aggregation is suppressed compared to longer fibers. Nevertheless, despite their rather short length, the composite fibers of the present invention can be embedded in the matrix of the construction material, thereby achieving sufficiently high pull-out force and structural reinforcement. Other lengths and / or diameters may also be suitable for certain applications.

[0054] According to a particularly preferred embodiment, the bicomponent fiber is constructed as follows: the load-bearing fibers comprise carbon fibers, basalt fibers, glass fibers and / or synthetic fibers, where the synthetic fibers are selected from aramid fibers, polyhydroquinone-diimidazopyridine fibers and / or poly(p-phenylene-2,6-benzobisoxazole) fibers; the organic synthetic material is selected from epoxy resins, polyamides, ethylene-vinyl acetate and / or epoxy vinyl ester resins; - the composite fibre comprises 40-99 wt.%, in particular 50-95 wt.%, of load-bearing fibres and 1-60 wt.%, in particular 5-50 wt.%, of organic synthetic material; - the composite fibre has a length between 2.5 and 75 mm; the aspect ratio of the height to the width of the cross section is >1.5, preferably >2; the elastic modulus of the composite fibres is preferably >40 GPa, in particular >50 GPa, for example >60 GPa; In a further preferred embodiment: the load-bearing fibres comprise or consist of carbon fibres; the organic synthetic material is an epoxy resin and / or an epoxy vinyl ester resin; - the composite fibre comprises 40-99 wt.%, in particular 50-95 wt.%, of load-bearing fibres and 1-60 wt.%, in particular 5-50 wt.%, of organic synthetic material; - the composite fibre has a length between 2.5 and 75 mm; the aspect ratio of the height to the width of the cross section is >1.5, preferably >2; The modulus of elasticity of the composite fibres is preferably >40 GPa, in particular >50 GPa, for example >60 GPa.

[0055] These particular configurations result in highly advantageous bicomponent fibers, particularly those characterized by high chemical stability, advantageous mechanical properties and high durability in mineral binder compositions, but other configurations may be suitable as well, especially for specialized applications.

[0056] Preferably, the composite fiber forms a surface structure on its outer surface. In particular, the composite fiber is provided with indentations and / or embossments on its outer surface and / or the outer surface of the composite fiber is coated with particles, e.g. sand particles. This can be achieved, for example, by embossing, polishing, sandblasting, crimping and / or coating, e.g. coating with sand particles.

[0057] Specifically, the root mean square roughness Rq (λ=800 μm, magnification 50 times) of the surface is 1 to 80 μm, in particular 3 to 60 μm or 5 to 40 μm. Rq is measured according to ISO 4287:1997.

[0058] In particular, the surface structure satisfies the following conditions: Wq 2 / WSm=0.001 to 0.5 μm, in particular 0.005 to 0.20 μm, where Wq is the root mean square waviness Wq (λ=250 μm, magnification 10 times) and WSm is the waviness spacing. Wq and WSm are measured according to ISO 4287:1997.

[0059] In particular, the surface structures are configured to increase the pull-out force of the embedded composite fibers as compared to unstructured composite fibers.

[0060] In particular, the composite fibers do not include metallic materials, especially steel, and more particularly steel fibers.

[0061] Bicomponent fibers can be produced, for example, by pultrusion, whereby, for example, non-metallic load-bearing fibers are impregnated and / or coated with a die or bath of organic synthetic material used for embedding, from which the non-metallic load-bearing fibers are drawn horizontally and / or vertically. Pultrusion methods for producing fibers are well known to those skilled in the art.

[0062] In particular, the composite fibers are provided in the form of one or more fiber bundles, with each bundle preferably having a number of composite fibers held together by a wrapping, most preferably a water-soluble wrapping, which allows the composite fibers to be added to and mixed with construction materials in a highly controlled and efficient manner, facilitating the manufacture of fiber-reinforced structures.

[0063] For example, in a bundle, the bicomponent fibers are grouped together in a parallel arrangement.

[0064] In particular, the bundle may contain, for example, 100 to 15,000, in particular 1,000 to 10,000 bicomponent fibers.

[0065] The water-soluble wrapping material may be, for example, a water-soluble foil made of polyvinyl alcohol. If the wrapping material is made of a water-soluble foil, when it comes into contact with the mixed water of the construction material, the wrapping material dissolves in the water and releases the individual composite fibers, which can then be homogenously mixed with the construction material.

[0066] Preferably, the content of the composite fibers in the matrix of the construction material is between 0.1 and 10 kg / m 3 , especially 0.5 to 5 kg / m 3 Therefore, m 3 The unit volumes refer to the volume of the construction material without fibre or before the addition of fibre, respectively.

[0067] In particular, the density of the fibers in the matrix of the construction material should be between 50,000 and 2,000,000 composite fibers / m 3 , especially 100,000 to 1,000,000 composite fibers / m 3 , 100,000-700,000 composite fibers / m 3 Therefore, m 3 The unit volumes refer to the volume of the construction material without fibre or before the addition of fibre, respectively.

[0068] These contents and densities have been found to be optimal for reinforcing construction materials, especially mineral binder-based construction materials, especially concrete, however, depending on the requirements, other densities may be suitable as well.

[0069] In a particular embodiment, the fiber-reinforced structure comprises at least one further fiber that is chemically and / or physically different from the composite fiber of the invention, said further fiber being selected from metal fibers and / or synthetic fibers, in particular synthetic fibers, which allows further tuning of the desired properties of the fiber-reinforced structure.

[0070] In a preferred embodiment, the further fibres are synthetic fibres, preferably having a linear density of 100 to 800 tex, in particular 250 to 750 tex and / or a length of up to 75 mm, in particular 20 to 65 mm.

[0071] In particular, the content of further fibres in the matrix of the construction material, in particular the content of synthetic fibres, is between 0.1 and 10 kg / m 3 , especially 0.5 to 6 kg / m 3 It is.

[0072] The synthetic fibres are for example selected from polyethylene and / or polypropylene fibres, however in certain embodiments the fibre reinforced structure does not comprise further fibres in the form of metal fibres.

[0073] In particular, the construction material comprises or consists of a mineral binder composition, in particular a cement-based mineral binder, especially a concrete or mortar composition.

[0074] In particular, with respect to the total weight of the mineral binder, the mineral binder comprises a proportion of at least 5 wt.%, at least 20 wt.%, at least 35 wt.%, or at least 65 wt.% hydraulic binder, for example cement. According to an exemplary embodiment, the mineral binder consists of at least 95 wt.% hydraulic binder, for example cement. For example, the cement is of type CEM I, CEM II, CEM III, CEM IV or CEM V (according to standard EN 197-1).

[0075] However, the mineral binder may also contain or consist of other binders. They are, for example, latent hydraulic binders and / or pozzolanic binders. Suitable latent hydraulic binders and / or pozzolanic binders are, for example, slag, fly ash and / or silica dust. Similarly, the construction material may contain inert substances such as, for example, limestone, quartz powder and / or pigments. In an exemplary embodiment, the mineral binder comprises 5-95 wt.%, for example 5-65 wt.%, for example 15-35 wt.% latent hydraulic and / or pozzolanic binder. Advantageous latent hydraulic and / or pozzolanic binders are slag and / or fly ash.

[0076] In an exemplary embodiment, the mineral binder comprises a hydraulic binder, in particular cement, and a latent hydraulic binder and / or pozzolanic binder, preferably slag and / or fly ash. The proportion of latent hydraulic and / or pozzolanic binder may be 5-65 wt.%, in particular 15-35 wt.%, and at least 35 wt.%, in particular at least 65 wt.% hydraulic binder, such as cement.

[0077] In further exemplary embodiments, the construction material, in particular the mineral binder composition, comprises additional solid aggregates, such as gravel, sand and / or rock aggregates. The corresponding compositions can be formulated, for example, as mortar or concrete compositions.

[0078] In particular, in the unhardened state, the mineral binder composition further comprises water, and the weight ratio of water to mineral binder may be in the range of 0.25 to 0.8, such as 0.3 to 0.6, for example 0.35 to 0.5. Such binder compositions can be directly processed into mortar or concrete compositions.

[0079] Furthermore, the mineral binder composition may contain at least one additive, such as a concrete additive and / or a mortar additive. The at least one additive may, for example, include an antifoaming agent, a dye, a preservative, a plasticizer, a set retarder, a pore former, a shrinkage reducer and / or a corrosion inhibitor, or a combination thereof. Typically, such additives are present in a proportion of 0.0001 to 10 wt.% relative to the total weight of the mineral binder composition.

[0080] A second aspect of the invention relates to a method for producing a fibre-reinforced structure as described above, in which composite fibres, in particular in the form of one or more fibre bundles as described above, are mixed with a construction material, in particular a mineral binder-based construction material, especially concrete, in which each composite fibre comprises non-metallic load-bearing fibres held by and / or embedded in an organic synthetic material, and in which each composite fibre has a linear density of 25 to 500 tex, in particular 50 to 350 tex.

[0081] In the method of the present invention, the construction material, the non-metallic load-bearing fibres, the organic-based synthetic material for embedding the non-metallic load-bearing fibres, the composite fibres, the density, length and diameter of the composite fibres in the construction material, and in particular any further characteristics, are as defined and configured as described above in relation to the first aspect.

[0082] In particular, when the composite fibers are mixed with a construction material, the construction material is in a processable state. Specifically, when the construction material is a mineral binder composition, the mineral binder composition is in an unhardened and processable state.

[0083] In particular, the bicomponent fibres are homogeneously distributed in the construction material, in particular randomly distributed.

[0084] The content of composite fibers in the construction material is specifically 0.1 to 10 kg / m 3 , especially 0.5 to 5 kg / m 3 It is.

[0085] In particular, the fiber dosage is selected depending on the desired flexural strength of the construction material, e.g., concrete composition, and / or fiber tensile strength. For construction materials with a higher desired flexural strength, the fiber dosage is increased, whereas for fibers with a higher tensile strength, the dosage is decreased.

[0086] A third aspect of the invention relates to the use of composite fibres as reinforcement in a construction material, in particular a mineral binder based construction material, especially concrete, wherein the composite fibres comprise non-metallic load-bearing fibres held by and / or embedded in an organic based synthetic material, and each composite fibre has a linear density of 25 to 500 tex, in particular 50 to 350 tex.

[0087] In the use of the present invention, the construction material, the non-metallic load-bearing fibres, the organic-based synthetic material for holding and / or embedding the non-metallic load-bearing fibres, the composite fibres, the density, diameter and any other characteristics, and in particular the fibre-reinforced structure and the manufacturing method are defined, configured and / or implemented as described above in relation to the first and second aspects.

[0088] The composite fibers are used in particular for preparing fiber-reinforced structures, in particular fiber-reinforced structures based on mineral binder compositions, particularly preferred fiber-reinforced concrete structures, whereby preferably the fiber-reinforced concrete structures meet the requirements of the FIB Model Code 2010 regarding crack opening.

[0089] Further advantageous embodiments of the invention are evident from the exemplary embodiments. EXAMPLES

[0090] material The following fibers were used in the experiments, as listed in Table 1:

[0091] [Table 1]

[0092] Composite fibres F2, F3, F6 and F7 were produced by standard pultrusion process using carbon fibre and epoxy / EVA, whereas fibres R, F1, F4 and F5 were purchased from Suprem SA (Switzerland; composite fibres F1 and F5), Suter-Kunststoffe AG ​​(Switzerland; composite fibre F4; fibres from van Dijk Pultrusion Products) and Krampe Harex GmbH & Co.KG (Germany; fibre R).

[0093] Sample preparation The reference fibre R and the composite fibres F1-F7 were tested in a standard concrete composition with a compressive strength of 60 MPa. To this end, each fibre was added together with a standard polymer fibre (SikaFiber Force-40; available from Sika, Switzerland) during the preparation of the concrete composition and mixed with the other components of the composition. The proportion of the composite fibres F1-F7 was m 3 The ratio of steel fibers R was chosen to obtain 400,000 composite fibers per m. 3 The standard polymer fibre rate was 5 kg / m for all concrete compositions. 3 Therefore, the standard polymer fibers in all compositions have the same effect and do not affect comparisons between different concrete compositions.

[0094] Beam test specimens according to EN 14651:2005 were produced from the concrete compositions thus produced.

[0095] Test Method The flexural tensile strength of beam specimens was measured under centre line load according to EN 14651:2005. This test determines the residual (post-crack initiation) flexural strength (MPa) at different specified values ​​of preformed crack opening (CMOD), i.e. 0.5 mm, 1.5 mm, 2.5 mm and 3.5 mm, thus defining the descending region of the load-deflection curve.

[0096] FIG. 1 shows the results obtained for fibers R and F1 to F7. The dashed curves show the results for a standard polymer fiber (SikaFiber Force-40; 5 kg / m 3 ) and no other fibers are used.

[0097] As is clear from FIG. 1, when the composite fibers F4 and F5 of 350 tex and 300 tex are added, f R1 / f LKThe ratio of f increased from 26% (reference without composite fiber) to 81% (F4) or 64% (F5), respectively. For composite fibers F1, F2, F3, F6 and F7 with linear density of 100 tex, the ratio f R1 / f LK is still above the standard limit of 40%. In contrast, for steel fibre R, the ratio f R1 / f LK was well below 40%.

[0098] The composite fibres according to the invention are therefore highly suitable for the manufacture of concrete structures which meet the requirements of the FIB Model Code 2010.

[0099] It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics, and therefore the implementations and embodiments disclosed herein are considered in all respects to be illustrative and not restrictive.

Claims

1. A fiber-reinforced structure, in particular a fiber-reinforced concrete structure, comprising a multitude of composite fibers distributed in a matrix of a construction material, in particular in a matrix of a mineral binder-based construction material, each composite fiber comprising non-metallic load-bearing fibers held together by an organic synthetic material, each composite fiber having a linear density of 25 to 500 tex, in particular 50 to 350 tex.

2. 2. A fiber-reinforced structure according to claim 1, wherein the elastic modulus of the composite fibers, measured according to ISO 527-3:2018, is at least as large as the elastic modulus of the matrix of the construction material, in particular the elastic modulus of the composite fibers is at least equal to 1.1 times, in particular at least 1.5 times, and in particular at least 2 times the elastic modulus of the matrix of the construction material, the elastic modulus of the matrix of the construction material being measured according to EN 12390-13:2013.

3. f Ｒ１ / f ＬＫ >0.4 requirement, as specified in the FIB Model Code 2010. Ｒ１ is the residual force after the first crack, and f ＬＫ 3. The fiber-reinforced structure according to claim 1, wherein σ is the maximum load before cracking.

4. 3. The fiber-reinforced structure of claim 1 or 2, wherein the load-bearing fibers comprise carbon fibers, basalt fibers, glass fibers, and / or synthetic fibers, the synthetic fibers being selected from aramid fibers, polyhydroquinone-diimidazopyridine fibers, and / or poly(p-phenylene-2,6-benzobisoxazole) fibers.

5. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the load-bearing fibers consist of carbon fibers.

6. 3. A fiber-reinforced structure according to claim 1 or 2, wherein said organic synthetic material is a thermosetting resin and / or a thermoplastic resin.

7. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the organic synthetic material is selected from epoxy resins, epoxy vinyl ester resins, polyamides, polyvinyl alcohols, polyolefins, polyethylene terephthalates and / or poly(ethylene vinyl acetate).

8. 3. A fiber reinforced structure according to claim 1 or 2, wherein said organic synthetic material is selected from polyolefins and / or polyethylene terephthalate, preferably polypropylene and / or polyethylene terephthalate glycol, more preferably polypropylene.

9. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the composite fiber comprises 20 to 99 wt. %, preferably 40 to 99 wt. %, in particular 50 to 95 wt. % of non-metallic load-bearing fibers and 1 to 80 wt. %, preferably 1 to 60 wt. %, in particular 5 to 50 wt. % of said organic synthetic material, based on the total weight of the composite fiber.

10. 3. A fiber reinforced structure according to claim 1 or 2, wherein in said composite fabric, said non-metallic load-bearing fibers are fully impregnated with and embedded in said organic-based synthetic material.

11. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the composite fiber is configured as a core-shell structure, with the non-metallic load-bearing fibers forming the core of the composite fiber and the organic synthetic material forming a casing around the core.

12. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the composite fibers have a circular, oval, elliptical, rectangular and / or square cross section perpendicular to the longitudinal direction, preferably the composite fibers have an oval, elliptical and / or rectangular cross section with an aspect ratio of height to width of the cross section >1.5, in particular >2, especially >4.

13. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the length of the composite fibers is <75 mm, in particular <30 mm, and the length is >2.5 mm, in particular >5 mm.

14. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the composite fibers form a surface structure on their outer surface, in particular such that the surface has a root-mean-square roughness Rq (λ=800 μm, magnification 50x) of 1 to 80 μm, in particular 3 to 60 μm or 5 to 40 μm, Rq being measured according to ISO 4287:1997.

15. The content of the composite fiber in the matrix of the construction material is 0.1 to 10 kg / m ３ , especially 0.5 to 5 kg / m ３ 3. The fiber-reinforced structure according to claim 1 or 2, wherein:

16. 3. A fiber-reinforced structure according to claim 1 or 2, further comprising at least one further fiber which is chemically and / or physically different from the composite fiber, said further fiber being selected from metal fibers, glass fibers, basalt fibers and / or synthetic fibers, in particular synthetic fibers.

17. 17. A fiber-reinforced structure according to claim 16, wherein the further fibers are synthetic fibers, preferably having a linear density of 100 to 800 tex, in particular 250 to 750 tex, and / or a length of up to 75 mm, in particular 20 to 65 mm.

18. The content of the further fibers in the matrix of the construction material is between 0.1 and 10 kg / m ３ , especially 0.5 to 6 kg / m ３ 17. The fiber-reinforced structure of claim 16, wherein:

19. 3. A fiber-reinforced structure according to claim 1 or 2, wherein the construction material is a concrete composition.

20. 3. A method for producing a fiber-reinforced structure according to claim 1 or 2, comprising mixing a plurality of composite fibers, in particular a plurality of composite fibers according to claim 1 or 2, in particular in the form of one or more fiber bundles each comprising a plurality of composite fibers held together by a water-soluble wrapping, with a construction material, in particular a mineral binder-based construction material, wherein each composite fiber comprises non-metallic load-bearing fibers held in and / or embedded in an organic synthetic material, and each composite fiber has a linear density of 25 to 500 tex, in particular 50 to 350 tex.

21. Use of bicomponent fibers as reinforcement for construction materials, in particular for mineral binder-based construction materials, in particular the use of bicomponent fibers according to claim 1 or 2, Use in which the composite fibers comprise non-metallic load-bearing fibers held in and / or embedded in an organic synthetic material, each composite fiber having a linear density of 25 to 500 tex, in particular 50 to 350 tex.

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