Polymer fibers for concrete reinforcement

Abstract

The invention relates to a coarse synthetic fiber consisting of three or more partially fused filaments made of a polymer composition comprising at least one polypropylene, wherein the fiber has a multi-lobed cross-sectional shape with three or more lobes. The invention further relates to a method of producing a coarse synthetic fiber, to a cementitious material comprising a binder and the coarse synthetic fiber of the invention, and to a method of forming a concrete surface using a concrete mixture modified with the coarse synthetic fiber of the invention.

Description

Technical Field

[0001] This invention relates to polymer fibers for use in building materials, particularly for use in cement compositions. Specifically, this invention relates to coarse synthetic fibers that undergo gradual fibrillation when mechanically stirred within a matrix material to be reinforced. Background Technology

[0002] Concrete is the most common man-made building material used in structural applications worldwide. Typically, concrete is a brittle material with high compressive strength but low tensile strength (crack resistance). The tensile strength of concrete can be increased by using modifying additives such as steel bars and reinforcing mesh. Polymers, metals, glass, and natural fibers have also been used to improve the tensile strength (strength before the first crack occurs) and toughness (crack resistance) of concrete.

[0003] Different types of fibers can be used to improve specific properties of concrete. Synthetic microfibers (microfibers) with a linear density not exceeding 580 denier are typically used to prevent plastic shrinkage cracking during concrete setting, i.e., preventing microcracking of concrete during the first 24 to 48 hours after pouring. Coarse synthetic fibers (coarse fibers) with a linear density greater than 580 denier and a diameter equal to or greater than 0.3 mm are added to the concrete composition to improve the overall toughness, quantified by measuring residual strength after the first fracture. Coarse fibers are typically added at a rate of 1.8 to 8.9 kg / m³. 3 The dosage of fibers is added to the concrete mixture. Coarse fibers can be obtained in various shapes, such as ropes, strips, or rods, and they can be twisted, serrated, or embossed to enhance the mechanical bond with the concrete. The concrete reinforcing properties of synthetic fibers depend on both the strength of the fibers and the adhesion between the fibers and the concrete matrix.

[0004] The benefits of fiber-reinforced concrete have led to the widespread use of fibers in many applications, including slabs on the ground, replacing conventional temperature and shrinkage reinforcements as well as toughness enhancers. Common plastic materials used for reinforcing concrete fibers include polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), aramid fibers (e.g., Kevlar), polyamides, and polyvinyl alcohol fibers. All of these have one or more disadvantages, such as high cost, low alkali resistance, low toughness, or poor interfacial bonding between the concrete matrix and the fibers. Polypropylene and polyethylene have been widely used as raw materials for both microfibers and coarse fibers. Their advantages include ease of processing into fibers via melt spinning (extrusion), low cost, and high tolerance to alkaline environments. However, due to their low density and hydrophobicity, fibers tend to bloom on the surface during finishing, meaning the fibers tend to protrude from the concrete surface before curing is complete. Furthermore, polypropylene and polyethylene do not bond well to concrete; therefore, these types of coarse fibers are often crimped or embossed to enable mechanical bonding to the matrix. The interfacial bonding between the fiber and concrete can be controlled by using a coating applied to the fiber surface or by chemical modification of the fiber surface. However, these methods typically lead to increased costs and complexity in fiber production processes.

[0005] In terms of fiber aspect ratio, larger fibers are generally better suited for improving the toughness of concrete than smaller fibers. Coarser fibers have higher breaking strength, but they also offer less interfacial bonding with concrete due to their reduced surface area. The bonding properties of fibers can often be improved by using longer and finer fibers. However, longer and finer fibers tend to clump together when added to concrete, forming hard-to-break spheres (spheroidization). Anti-spheroidization can be improved by using fibers pre-packaged in “discs” and / or by using fibers that fibrillate into many smaller fibers when mechanically mixed within a matrix material to be reinforced with the fiber. Fibrillation increases the surface area of ​​the fibers, leading to improved interfacial bonding with concrete. However, excessive fibrillation can cause problems with workability, fiber distribution, and mixing, and reduce the toughness-reinforcing properties of larger fibers.

[0006] Surface finishing requirements in slab applications vary depending on traffic, texture, indoor or outdoor, or decorative appeal. For most indoor concrete and composite metal decking, a smoother, hard steel finish is desired. These smooth finishes are important for various reasons, such as reduced surface abrasion, ease of cleaning, and long-term durability. In hard steel finish applications, coarse fiber-reinforced concrete may leave numerous fibers on the surface, which is an undesirable result for the user due to its appearance. Therefore, concrete reinforcing fibers with a low tendency to protrude from the concrete surface before full curing, enabling a smooth surface finish, are highly valuable in slab applications.

[0007] Therefore, it is desirable to provide a low-cost coarse synthetic fiber that is suitable for improving specific properties of concrete, particularly the overall toughness and durability of concrete, without negatively impacting other properties such as surface finish and / or aesthetic appeal. Invention Overview

[0009] The purpose of this invention is to provide coarse synthetic concrete reinforcing fibers that solve one or more problems of existing coarse synthetic fibers.

[0010] Another object of the present invention is to provide low-cost coarse synthetic fibers that are highly effective in improving the toughness and durability of concrete, exhibiting good dispersibility and good surface finishing properties in concrete mixtures.

[0011] Surprisingly, it has been found that coarse synthetic fibers consisting of three or more partially fused filaments (wherein the filaments are made of a polymer composition containing at least one polypropylene) can solve or at least alleviate many of the problems associated with coarse synthetic fibers using existing technologies.

[0012] The subject of this invention is crude synthetic fiber as defined in claim 1.

[0013] One advantage of the coarse synthetic fibers of this invention is that the fibers possess consistent self-fibrillation properties. Once introduced into a concrete mixture, the fibers break down into predetermined portions (filaments) during the mixing process. This breaking down increases the contact area between the concrete matrix and the fibers, and further randomizes the orientation of the fibers. Due to these consistent self-fibrillation properties, the fibers can be readily incorporated into fluidized concrete mixtures with a low aspect ratio of <100, avoiding problems associated with dispersion (spheroidization), while still achieving improved concrete properties, particularly concrete toughness, through the higher aspect ratio of the individual filaments that separate from the fibers during the mixing process.

[0014] Another advantage of the coarse synthetic fibers of this invention is that the fibers can be incorporated into concrete compositions to improve toughness without negatively impacting the surface finish properties in slab applications. By using the fibers of this invention, the amount of fibers remaining on the surface of concrete slabs in hard steel coating applications can be significantly reduced or even eliminated.

[0015] Other aspects of the invention are set forth in the other independent claims. Preferred aspects of the invention are set forth in the dependent claims.

[0016] Brief description of the attached figures

[0017] Figure 1 A possible cross-sectional shape of the coarse synthetic fiber according to the invention is illustrated schematically.

[0018] Figure 2A schematic diagram of a possible method for producing the crude synthetic fibers of the present invention is shown. Invention Details

[0020] The subject of this invention is a coarse synthetic fiber composed of three or more partially fused filaments, said filaments being made of a polymer composition containing at least one polypropylene, wherein said fiber has a multi-leaf cross-sectional shape with three or more blades.

[0021] The term "polymer" refers to a collection of chemically homogeneous macromolecules produced by a polymerization reaction (polymerization, addition polymerization, condensation polymerization), wherein the macromolecules differ in their degree of polymerization, molecular weight, and chain length. The term also includes derivatives of the collection of said macromolecules produced by polymerization reactions, i.e., compounds obtained by reactions (e.g., addition or substitution) of functional groups in a predetermined macromolecule, and which may be chemically homogeneous or chemically heterogeneous.

[0022] The term "propylene copolymer" refers to a copolymer containing at least 50% by weight, more preferably at least 60% by weight, propylene-derived units based on the weight of the copolymer, while the term "ethylene copolymer" refers to a copolymer containing at least 50% by weight, more preferably at least 60% by weight, ethylene-derived units based on the weight of the copolymer.

[0023] The term "melting temperature" refers to the temperature at which a material undergoes a transition from a solid to a liquid state. Melting temperature (T0) m The temperature (T) is preferably determined by differential scanning calorimetry (DSC) according to ISO 11357 using a heating rate of 2 °C / min. It can be measured using a Mettler Toledo DSC 3+ apparatus, and T can be determined from the measured DSC curves with the aid of DSC software. m Value. When the measured DSC curve shows several peak temperatures, the first peak temperature from the lower temperature side of the thermogram is taken as the melting temperature (T). m ).

[0024] The term "amount or content of at least one component X" in a composition, such as "amount of at least one thermoplastic polymer P1," refers to the sum of the individual amounts of all thermoplastic polymers P1 contained in the composition. For example, if the composition contains 20% by weight of at least one thermoplastic polymer P1, the sum of the amounts of all thermoplastic polymers P1 contained in the composition equals 20% by weight.

[0025] The term "normal room temperature" refers to a temperature of 23°C.

[0026] The coarse synthetic fiber of the present invention comprises three or more partially fused filaments, said filaments being made of a polymer composition containing at least one polypropylene. The term "partially fused" in the context of this invention should be understood to mean that the coarse synthetic fiber is obtained by using a method comprising extruding a molten polymer composition to provide extruded filaments, said extruded filaments being allowed to contact and partially fuse with each other on a portion of their primary outer surface to form unstretched fibers. The term "primary outer surface" of a filament refers to the longitudinally extending surface of said filament.

[0027] Fibers composed of partially fused filaments are significantly different from fibers composed of single filaments (monofilament fibers) and significantly different from multifilament fibers in which the filaments are bonded together or mechanically joined together.

[0028] According to one or more embodiments, coarse synthetic fibers are obtained by a method comprising extruding a molten polymer composition through an extruder die comprising a plurality of orifices to provide undrawn fibers, wherein at least a portion of the orifices comprises an assembly of three or more holes closely arranged but not overlapping each other, such that when the molten polymer composition is extruded through the orifices, the resulting extruded filaments are partially fused to form undrawn fibers. The expression “overlapping each other” should be understood to mean that the distance between adjacent holes in the assembly is such that the edges of the holes do not intersect each other.

[0029] Due to the partially fused filament structure, the fibers of this invention can undergo gradual fibrillation when mechanically stirred within a matrix reinforced with the fibers to be used. The first portion of fibrillation occurs in the early stages of mixing, which gives the fibers additional time to disperse within the matrix. The second portion of fibrillation occurs after a considerable amount of mixing, at which point a significant portion of the fibers have been distributed into the matrix, which reduces the tendency for individual filaments separated from the fibers to clump together into spheres.

[0030] Existing multifilament fibers are generally found to have unfavorable fibrillation properties. Some multifilament fibers have been found to exhibit incomplete fibrillation and fiber end abrasion during in-concrete mixing, leading to increased fiber entanglement and thus fiber balling. In other cases, separation of the filament from the fiber center and / or fiber end abrasion before the first stage of mixing have been observed, also contributing to increased fiber entanglement and balling problems during in-concrete mixing. Furthermore, monofilament fibers with multi-lobed cross-sections have been found to exhibit insufficient fibrillation when mixed in concrete.

[0031] Preferably, at least one polypropylene accounts for at least 70% by weight of the polymer composition, more preferably at least 75% by weight. According to one or more embodiments, at least one polypropylene accounts for 70-95% by weight of the total weight of the polymer composition, preferably 75-90% by weight, more preferably 80-90% by weight.

[0032] The types of at least one polypropylene and at least one polyethylene are not particularly limited in this invention.

[0033] Suitable polypropylenes include polypropylene homopolymers (hPP), such as isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP), and propylene copolymers, such as multiphase propylene copolymers, random propylene copolymers, and block propylene copolymers.

[0034] Multiphase propylene copolymers are multiphase polymer systems comprising a highly crystalline base polyolefin and a low-crystalline or amorphous polyolefin modifier. The multiphase morphology consists of a matrix phase primarily composed of the base polyolefin and a dispersed phase primarily composed of the polyolefin modifier. Suitable commercially available multiphase propylene copolymers include reactor blends of the base polyolefin and the polyolefin modifier, also known as “in-situ TPO”, “reactor TPO”, or “impact copolymer (ICP)”, which are typically prepared in a sequential polymerization process, wherein the matrix phase component is prepared in a first reactor and transferred to a second reactor, in which the dispersed phase component is prepared and incorporated into the matrix phase as a phase region. Multiphase propylene copolymers comprising polypropylene homopolymers as the base polymer are generally referred to as “multiphase propylene copolymers (HECO)”, while multiphase propylene copolymers comprising polypropylene random copolymers as the base polymer are generally referred to as “multiphase propylene random copolymers (RAHECO)”. The term “multiphase propylene copolymer” in this disclosure includes both HECO and RAHECO type multiphase propylene copolymers.

[0035] According to one or more embodiments, the at least one polypropylene has

[0036] - A flexural modulus of at least 1000 MPa, preferably at least 1100 MPa, more preferably at least 1200 MPa, as determined according to ISO 178:2019, and / or

[0037] The melting temperature (T0) determined by differential scanning calorimetry (DSC) at a heating rate of 2°C / min, according to ISO 11357-3:20 18, is -115°C and above, preferably 125°C and above, more preferably 135°C and above, even more preferably 145°C and above, and still more preferably 155°C and above. m ), and / or

[0038] - A melt flow index (230°C / 2.16 kg) measured according to ISO 1133 standard, not greater than 100 g / 10 min, preferably not greater than 50 g / 10 min, more preferably not greater than 35 g / 10 min, even more preferably not greater than 15 g / 10 min, for example 0.5-15 g / 10 min, preferably 1-10 g / 10 min, more preferably 1-5 g / 10 min.

[0039] According to one or more embodiments, the at least one polypropylene comprises or is composed of a polypropylene homopolymer, preferably isotactic polypropylene, and preferably has at least 80%, preferably at least 85%, more preferably at least 90% by means of... 13 Isosteric index determined by C-NMR spectroscopy.

[0040] According to one or more embodiments, based on the total weight of the polymer composition, the polymer composition further comprises at least 1 wt%, preferably at least 5 wt%, more preferably at least 7.5 wt% of at least one type of polyethylene. Without being bound by any theory, it is believed that because the polymer composition of the filaments contains both polypropylene and polyethylene, the boundaries between partially fused filaments are more prone to tearing than in the case of filaments composed solely of polyethylene or polypropylene. It is believed that this enhances the ability of the fibers to undergo gradual fibrillation when mechanically stirred within the fiber-reinforced matrix. According to one or more embodiments, at least one type of polyethylene comprises 1-30 wt%, preferably 5-25 wt%, more preferably 10-20 wt% of the total weight of the polymer composition.

[0041] Suitable polyethylenes include ethylene homopolymers and ethylene copolymers.

[0042] According to one or more embodiments, the at least one polyethylene has

[0043] The melting temperature (T0) measured by differential scanning calorimetry (DSC) at a heating rate of 2°C / min, according to ISO 11357-3, is -90°C and above, preferably 100°C and above, more preferably 105°C and above, for example 90-140°C, preferably 100-135°C, more preferably 105-125°C. m ), and / or

[0044] - A melt flow index (190°C / 2.16 kg) measured according to ISO 1133 standard, not greater than 100 g / 10 min, preferably not greater than 50 g / 10 min, more preferably not greater than 35 g / 10 min, even more preferably not greater than 15 g / 10 min, for example 0.5-15 g / 10 min, preferably 1-10 g / 10 min, more preferably 1-5 g / 10 min.

[0045] According to one or more embodiments, the at least one polyethylene comprises or is composed of: low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE), or high-density polyethylene (HDPE), preferably linear low-density polyethylene (LLDPE).

[0046] The coarse synthetic fibers have a multi-leaf cross-sectional shape with three or more lobes. The term "fiber cross-section" in this disclosure refers to a fiber cross-section that has been cut into a plane perpendicular to the longitudinal direction of the fiber. Similarly, the term "cross-sectional shape" of the fiber refers to the cross-sectional shape that has been cut into a plane perpendicular to the longitudinal direction of the fiber.

[0047] Preferably, the coarse synthetic fiber has a multi-leaf cross-sectional shape, having three or more leaves and axially extending through the central portion of the fiber.

[0048] The central portion of the fiber is preferably solid, i.e., it does not include axial holes or voids. According to one or more embodiments, at least two of the blades extend outwards, preferably radially from the central portion. According to one or more embodiments, at least two of the blades are connected to each other through the central portion.

[0049] Preferably, each blade has a tip portion and a base portion located towards the center of the fiber. Furthermore, the tip portion of each blade is preferably curved, more preferably convexly curved. Figure 1 The cross-sectional shape of a coarse synthetic fiber according to one embodiment of the invention is schematically shown. The coarse synthetic fiber consists of four partially fused filaments, wherein the fiber (1) has a four-leaf cross-sectional shape, wherein four leaves (2) extend outward from the central portion (3) of the fiber.

[0050] According to one or more embodiments, the basal portion of each blade has a width (D2) smaller than the maximum width (D1) of the tip portion. The term "maximum width of the tip portion" refers to the length of the longest line extending perpendicular to the longitudinal line connecting the central portion of the fiber and the tip portion of the blade, wherein the longitudinal line extends toward the profile of the blade. The term "width of the basal portion" refers to the length of the line connecting the two endpoints of the basal portions of two adjacent blades. Figure 1 In the diagram, the maximum width of the tip portion of the blade (2) is represented by the letter "D1", the width of the base portion of the blade (2) is represented by the letter "D2", and the longitudinal line connecting the central portion (3) of the fiber and the tip portion of the blade (2) is represented by the letter "L". Widths D1 and D2 can be determined by a micrograph of the fiber cross-section.

[0051] According to one or more embodiments, in each blade, the ratio (D1:D2) between the maximum width of the tip portion and the width of the base portion is 1.1:1 to 3:1, preferably 1.2:1 to 2.7:1, and more preferably 1.3:1 to 2.5:1. It has been found that coarse synthetic fibers with a ratio between the maximum width of the tip portion (D1) and the width of the base portion (D2) within the above range are advantageous because the blades, and therefore the partially fused filaments of the fibers, tend to peel or separate from the base portion by shear force, thus enabling gradual fibrillation when the fibers are mechanically stirred within the matrix material to be reinforced.

[0052] According to one or more embodiments, the coarse synthetic fiber consists of four partially fused filaments. In these embodiments, the coarse synthetic fiber preferably has a tetralobed cross-sectional shape with four blades, wherein preferably at least two of the blades extend outward, more preferably radially from the central portion of the fiber. Such coarse synthetic fibers have been found to be very effective in improving the toughness of concrete and exhibit good dispersibility and good surface finishing properties in concrete mixtures. According to one or more embodiments, the coarse synthetic fiber has a tetralobed cross-sectional shape with four blades extending outward, preferably radially, from the central portion of the fiber.

[0053] Preferably, the linear density of the coarse synthetic fiber is at least 1000 denier, more preferably at least 1200 denier, even more preferably at least 1300 denier, and still more preferably at least 1500 denier. The term "denier" is an abbreviation for "denier," which in this disclosure refers to a unit of measurement for the linear mass density of a fiber, i.e., the mass in grams per 9000 meters of fiber.

[0054] Preferably, the coarse synthetic fiber has a length of at least 15 mm, more preferably at least 20 mm, even more preferably at least 25 mm, and still more preferably at least 30 mm, and / or an aspect ratio (l / d) of not more than 85, more preferably not more than 80, even more preferably not more than 75, and still more preferably not more than 70, and / or a fiber diameter of at least 0.25 mm, more preferably at least 0.35 mm, even more preferably at least 0.45 mm, and still more preferably at least 0.5 mm. The term "aspect ratio" in this disclosure refers to the ratio of the fiber's length to its diameter. The term "fiber diameter" in this disclosure refers to the equivalent diameter of the fiber as measured according to EN14889-2:20 06.

[0055] According to one or more embodiments, the crude synthetic fiber has:

[0056] A linear density of -1000-5000 densities, preferably 1500-4500 densities, more preferably 2000-4000 densities, and even more preferably 2500-3500 densities.

[0057] -15-100mm, preferably 20-85mm, more preferably 25-75mm, even more preferably 25-65mm, and even more preferably 30-60mm in length, and / or

[0058] -15-85, preferably 25-80, more preferably 35-75, even more preferably 40-70, and still more preferably 45-70 in length-to-diameter ratio (l / d) and / or

[0059] The fiber diameter is -0.25-1.5mm, preferably 0.35-1.25mm, more preferably 0.45-1.0mm, even more preferably 0.5-0.9mm, and even more preferably 0.55-0.8mm.

[0060] Preferably, the crude synthetic fiber has the following characteristics:

[0061] - An elastic modulus of at least 5 MPa, preferably at least 7 MPa, measured according to EN 14889-2:2006 at 23°C and a strain rate of 5% / min, and / or

[0062] - Elongation at break of not more than 15%, preferably not more than 10%, as determined according to EN 10002-1:2001 at 23°C, and / or

[0063] - Tensile strength of at least 250 MPa, preferably at least 350 MPa, determined according to EN 14889-2:20 06 at 23°C and a strain rate of 5% / min.

[0064] Coarse synthetic fibers with physical properties falling within the above range have been found to be particularly suitable as concrete reinforcing fibers.

[0065] The coarse synthetic fibers are preferably drawn at a draw ratio of at least 5:1, more preferably 10:1. Drawing causes the polymer chains to align in the longitudinal direction of the fiber, which increases tensile strength and reduces fiber elongation. Furthermore, drawn fibers generally have lower stretchability in the width direction. Finally, drawing also weakens the bonding regions between partially fused filaments, resulting in more efficient fibrillation during mixing with the concrete matrix.

[0066] According to one or more embodiments, the coarse synthetic fibers are uniaxially stretched at a draw ratio of 7.5:1 to 25:1, preferably 10:1 to 20:1, more preferably 10:1 to 17.5:1, and even more preferably 12:1 to 15:1.

[0067] Preferably, the coarse synthetic fiber can be separated into monofilaments with a linear density of no more than 1250 den, preferably no more than 1000 den, more preferably no more than 900 den and / or an aspect ratio (l / d) of at least 100, preferably at least 105, more preferably at least 110, and even more preferably at least 115.

[0068] According to one or more embodiments, the crude synthetic fiber can be separated into monofilaments, said monofilaments having:

[0069] A linear density of -150-1250 densities, preferably 250-1150 densities, more preferably 350-1000 densities, and even more preferably 400-950 densities, and / or

[0070] A length-to-diameter ratio (l / d) of -100-250, preferably 105-200, more preferably 110-175, and even more preferably 115-150, is preferred.

[0071] The filament diameter is -0.1-1.0 mm, preferably 0.15-0.85 mm, more preferably 0.2-0.7 mm, even more preferably 0.2-0.55 mm, and even more preferably 0.25-0.5 mm.

[0072] The coarse synthetic fibers can be further crimped or embossed, preferably crimped, to include one or more deformations along the fiber length. It has been found that crimping reduces fiber stiffness and improves fibrillation properties. There is no particular limitation on the number of crimps along the fiber length. Generally, the number of crimps should be high enough to provide fibers with improved fibrillation properties without negatively impacting other properties such as fiber dispersion. According to one or more embodiments, the coarse synthetic fibers include deformations formed along the fiber length, wherein the deformations include at least one crimp along the fiber length, preferably at least three crimps.

[0073] Unless otherwise stated, the preferred embodiments of at least one polypropylene and at least one polyethylene given above apply to all subjects of the present invention.

[0074] Another subject of the present invention is a method for producing crude synthetic fibers, comprising the following steps:

[0075] I) Extruding a molten polymer composition containing at least one polypropylene through an extruder die to provide undrawn fibers consisting of three or more partially fused filaments.

[0076] II) The unstretched fibers prepared in step I) of uniaxial stretching are used to provide stretched fibers.

[0077] III) Optionally crimp the stretched fibers prepared in step II) to provide crimped fibers, and

[0078] IV) Cut the fibers prepared in step II) or III) to a predetermined length.

[0079] Preferably, at least one polypropylene comprises at least 70% by weight of the melt polymer composition, more preferably at least 75% by weight.

[0080] According to one or more embodiments, based on the total weight of the molten polymer composition, the molten polymer composition further comprises at least 1% by weight, preferably at least 5% by weight, of at least one type of polyethylene.

[0081] According to one or more embodiments, the at least one polypropylene accounts for 70-95% by weight, preferably 75-90% by weight, more preferably 80-90% by weight, of the melt polymer composition, and the at least one polyethylene accounts for 1-30% by weight, preferably 5-25% by weight, more preferably 10-20% by weight, of the melt polymer composition.

[0082] The melt polymer composition is preferably obtained by melt blending a starting composition containing the components of the melt polymer composition using a suitable mixing apparatus. The term "melt blending" in this disclosure refers to a method in which at least one melt polymer component is closely mixed with at least one other component (which may be another melt polymer component or a solid component, such as a filler) until a melt blend is obtained, i.e., a mixture of one or more polymer components with other components in a substantially homogeneous manner.

[0083] Melt blending of the starting composition can be carried out in an intermittent manner using any conventional mixer (e.g., Brabender, Banbury, or roller mixer) or in a continuous manner using a continuous mixer (preferably an extruder, such as a single-screw or twin-screw extruder or planetary roller extruder). It is preferred to use a conventional feeding system including a hopper and a feed extruder to feed the components of the starting composition into the mixer. Alternatively, some or all of the components of the starting composition can be fed directly into the mixer as a separate stream, as a premix, or as a masterbatch. Furthermore, the components of the starting composition can first be processed into granules or pellets in a compounding extruder before being fed into the mixer.

[0084] In the first step (I) of this method, the molten polymer composition is extruded as a filament through an extruder die to provide undrawn fibers consisting of three or more partially fused filaments. The extruder die is preferably a spinneret comprising a plurality of spinneret orifices through which the molten polymer composition is extruded.

[0085] According to one or more implementation schemes, step I) of the method includes the following steps:

[0086] i) Extruding the molten polymer composition through a spinneret comprising multiple spinneret orifices to provide unstretched fibers, and

[0087] ii) The unstretched fibers prepared in step i) are guided into the cooling bath via an air gap.

[0088] At least a portion of the spinneret, preferably each spinneret, comprises an assembly of three or more holes, said three or more holes being arranged closely such that when the molten polymer composition is extruded through said holes, the resulting extruded filaments are partially fused to form unstretched fibers. The term "air gap" here refers to the gap between the spinneret and the cooling bath.

[0089] In the second step II) of the method, the unstretched fibers prepared in step I) are uniaxially stretched to provide stretched fibers. According to one or more embodiments, the extruded unstretched fibers are uniaxially stretched at a draw ratio of 7.5:1 to 25:1, preferably 10:1 to 20:1, more preferably 10:1 to 17.5:1, and even more preferably 12:1 to 15:1. The stretching of the fibers can be performed using a conventional hot stretching machine, such as a machine of the hot roller, hot plate, or hot air oven type.

[0090] Stretching causes the polymer chains to align in the longitudinal direction of the fiber, which increases tensile strength and reduces the elongation of unstretched fibers. Furthermore, stretched fibers typically have less stretchability in the width direction. Finally, stretching also weakens the bonding regions between partially fused filaments, leading to more efficient fibrillation during mixing with the concrete matrix.

[0091] According to one or more embodiments, step III) of the method includes subjecting the stretched fibers prepared in step II) to crimping to provide crimped fibers. The crimping of the fibers can be performed using any conventional crimping apparatus, such as a crimping box, or a tow crimping machine. In the case of a crimping box, the stretched fibers are loaded into the crimping box, which fills and bends the crimped portion into the fibers. The stretched fibers can also be mechanically crimped to provide crimp in the fibers by running the fibers through gears or gear sets. According to one or more embodiments, the stretched fibers prepared in step II) are crimped by running the fibers through a gear set.

[0092] In the fourth step (IV) of the method, the stretched and optionally crimped fibers prepared in step (II) or (III) are cut into sheets of predetermined length. According to one or more embodiments, the stretched and optionally crimped fibers have:

[0093] -15-100mm, preferably 20-85mm, more preferably 25-75mm, even more preferably 25-65mm, and even more preferably 30-60mm in length, and / or

[0094] -15-85, preferably 25-80, more preferably 35-75, even more preferably 40-70, and still more preferably 45-70 in length-to-diameter ratio (l / d), and / or

[0095] Fiber diameter of -0.25-1.5mm, preferably 0.35-1.25mm, more preferably 0.45-1.0mm, even more preferably 0.5-0.9mm, and still more preferably 0.55-0.8mm, and / or

[0096] - An elastic modulus of at least 5 MPa, preferably at least 7 MPa, measured according to EN 14889-2:2006 at 23°C and a strain rate of 5% / min, and / or

[0097] - Elongation at break of not more than 15%, preferably not more than 10%, as determined according to EN 10002-1:2001 at 23°C, and / or

[0098] - Tensile strength of at least 250 MPa, preferably at least 350 MPa, determined according to EN 14889-2:20 06 at 23°C and a strain rate of 5% / min.

[0099] Figure 2 A schematic diagram of one embodiment of the method for producing the coarse synthetic fibers of the present invention is shown. In this embodiment, the components of the starting composition are fed into an extruder unit (5) using a metering and feeding device (4), wherein the starting material is melt-processed into a molten polymer composition. The melt-processed starting composition is extruded through a spinneret (6) comprising a plurality of spinneret orifices. The extruded fibers are then guided through an air gap into a water bath (7). The cooled fibers are conveyed from the water bath (7) to a first (stretching) oven (9) using a powered take-off roller comprising a first roller frame (8). The unstretched fibers are oriented in the first (stretching) oven (9), stretched using a second roller frame (10), and further processed in a second (annealing) oven (11). Heating in the first oven (9) and the second oven (11) is preferably achieved using forced hot air at a controlled temperature.

[0100] The stretched fibers passing through the second oven (11) are passed through a mechanical crimping machine (12), which consists of two mating rollers that are partially joined to deform the stretched fibers. The crimped fibers are fed from the crimping machine using a third roller frame (13), wound by a winding machine (14), and cut to a predetermined length. Figure 2 (Not shown in the image).

[0101] According to one or more embodiments, the unstretched fiber consists of three to six partially fused filaments. In these embodiments, at least a portion of the spinneret orifice consists of an assembly of three to six closely spaced holes.

[0102] There are no particular restrictions on the shape of the hole in the component. The cross-section of the hole can be circular, elliptical, trefoil-shaped, triangular, Y-shaped, or star-shaped, with a circular shape being preferred.

[0103] The holes in the component can have the same diameter or different diameters, preferably the same diameter. Preferably, the diameter of the hole is no greater than 5.0 mm, more preferably no greater than 4.0 mm, and even more preferably no greater than 3.0 mm. According to one or more embodiments, the diameter of the hole in the component is 0.35-2.5 mm, preferably 0.5-2.0 mm, more preferably 0.75-2.0 mm, even more preferably 0.85-1.75 mm, and still more preferably 0.95-1.75 mm.

[0104] Preferably, the holes of the component are arranged closely together but do not overlap, that is, the distance between adjacent holes of the component is arranged such that the edges of the holes do not intersect each other.

[0105] On the other hand, the distance between the centers of two adjacent holes should not be too high to prevent the extruded filaments from contacting and partially fusing with each other. According to one or more embodiments, the holes of the component are configured such that the distance between the edges of any two holes that are closest to each other, measured along a line connecting the centers of the two holes, is no greater than 1.0 mm, preferably no greater than 0.85 mm, and more preferably no greater than 0.75 mm.

[0106] According to one or more preferred embodiments, the unstretched fiber consists of four partially fused filaments. In these embodiments, at least a portion of the spinneret orifice is composed of an assembly of four adjacent orifices.

[0107] According to one or more preferred embodiments, the four holes of the component are arranged in a quadrilateral shape, preferably a group of free trapezoids, kite shapes, parallelograms, rhombuses, rectangles, or squares. The statement "arranged in a quadrilateral shape" should be understood to mean that the center of the hole of the component is located at the intersection of the sides of the quadrilateral.

[0108] The spinneret orifices can be positioned in any conventional manner, such as in multiple parallel rows or concentric circles. According to one or more preferred embodiments, all spinneret orifices of the spinneret consist of the same orifice assembly in terms of the number, geometric arrangement, shape, and size of the holes.

[0109] According to one or more embodiments, the method for producing crude synthetic fibers further includes the following steps:

[0110] V) Package the fibers prepared in any one of steps II) to IV) into tight bundles, each containing thousands of fibers, and

[0111] VI) Wrap the bundle prepared in step V) in a water-soluble plastic film.

[0112] If the bundled fibers in step V) are not cut to a predetermined length, the method may include another step VII) to cut the bundled fibers prepared in step VI) to a predetermined length.

[0113] Another subject of the present invention is crude synthetic fiber obtained by using the method of the present invention for producing crude synthetic fiber.

[0114] Another subject of the present invention is the use of the coarse synthetic fibers of the present invention to improve the properties of hardened cement compositions, preferably toughness.

[0115] The term "cement composition" in this disclosure refers to concrete, shotcrete, grout, mortar, paste, or a combination thereof. The terms "paste," "mortar," "concrete," "shotcrete," and "grout" are well-known to those skilled in the art. A paste is a mixture containing a hydrated cementitious binder, typically Portland cement, masonry cement, or mortar cement. Mortar is a paste that additionally contains fine aggregate (e.g., sand). Concrete is a mortar that additionally contains coarse aggregate, such as crushed stone or stone. Shotcrete is concrete (or sometimes mortar) delivered via hose and pneumatically projected onto a surface at high speed. Grout is a particularly flowable form of concrete used to fill gaps. A cement composition can be formed by mixing desired amounts of certain components (e.g., Portland cement, water, and fine and / or coarse aggregate) to produce a specific cement composition.

[0116] According to one or more embodiments, the cement composition is selected from concrete, shotcrete, grouting and mortar, preferably concrete and shotcrete, more preferably concrete.

[0117] According to one or more embodiments, coarse synthetic fibers are added to the cement composition in an amount of 0.1-3.0% by volume, preferably 0.2-2.0% by volume, more preferably 0.2-1.0% by volume, based on the total volume of the hardened cement composition.

[0118] According to one or more embodiments, the toughness of the hardened cement composition, as a measure of residual strength after the first fracture, is improved by at least 5%, preferably at least 10%, and more preferably at least 15%, compared to the toughness of a hardened cement composition that does not contain the coarse synthetic fibers of the present invention.

[0119] Another subject of the present invention is a cementitious material comprising:

[0120] a) Adhesive,

[0121] b) Based on the total volume of cementitious material, 0.1-3.0 vol%, preferably 0.2-2.0 vol%, more preferably 0.2-1.0 vol% of the coarse synthetic fiber according to the invention,

[0122] c) Aggregates, and

[0123] d) Water.

[0124] According to one or more embodiments, the adhesive a) is selected from hydraulic adhesives, non-hydraulic adhesives, potential hydraulic adhesives, and volcanic ash adhesives.

[0125] The term "hydraulic binder" refers to a substance that reacts with water in a hydration reaction to form a solid mineral hydrate or hydrate phase, which is insoluble in water or has low water solubility. Therefore, hydraulic binders (such as Portland cement) can harden and maintain their strength even when exposed to water (e.g., underwater or under high humidity conditions). Conversely, the term "non-hydraulic binder" refers to a substance that hardens by reacting with carbon dioxide and therefore does not harden under humid conditions or underwater.

[0126] Examples of suitable hydraulic binders include hydraulic cement and hydraulic lime. The term "hydraulic cement" here refers to a mixture of silicates and oxides, including allit, belite, tricalcium aluminate, and calcium aluminoferrite ores.

[0127] According to DIN EN 197-1, commercially available hydraulic cements can be classified into five main types: Portland cement (CEM I), Portland composite cement (CEM II), blast furnace cement (CEM III), pozzolanic cement (CEM IV), and composite cement (CEM V). These five main types of hydraulic cement are further subdivided into another 27 cement types, which are known to those skilled in the art and are listed in DIN EN 197-1. Of course, all other hydraulic cements produced according to another standard, such as ASTM standards or Indian standards, are also appropriate.

[0128] Examples of suitable non-hydraulic binders include air-hydrated lime (non-hydraulic lime) and gypsum. The term "gypsum" in this disclosure refers to any known form of gypsum, particularly dehydrated calcium sulfate, α-hemihydrate calcium sulfate, β-hemihydrate calcium sulfate, or anhydrous calcium sulfate, or mixtures thereof.

[0129] In this invention, the term "potentially hydraulic binder" refers to a Type II concrete additive that exhibits "potential hydraulicity" as defined in DIN EN 206-1:2000. These types of mineral binders are calcium aluminosilicates, which, when mixed with water, do not harden directly or harden too slowly. The hardening process is accelerated in the presence of an alkaline activator, which breaks the chemical bonds in the amorphous (or glassy) phase of the binder and promotes the dissolution of ionic substances and the formation of a calcium aluminosilicate hydrate phase.

[0130] Examples of suitable potential hydraulic binders include ground granulated blast furnace slag. Ground granulated blast furnace slag is typically obtained by quenching molten iron slag from a blast furnace in water or steam to form a glassy granular product, followed by drying and grinding the glassy material into a fine powder.

[0131] The term "volcanic ash binder" in this disclosure refers to a Type II concrete additive having the "volcanic ash characteristics" as defined in DIN EN 206-1:2000. These types of mineral binders are silicate or aluminosilicate compounds that react with water and calcium hydroxide to form calcium silicate hydrate or calcium aluminosilicate hydrate phases.

[0132] Examples of suitable volcanic ash binders include natural volcanic ash, such as volcanic soil, and artificial volcanic ash, such as fly ash and silica fume. The term "fly ash" in this disclosure refers to the fine ash residue produced by the combustion of pulverized coal, which is carried away along with gases emitted from a coal-fired furnace. The term "silica fume" in this disclosure refers to finely particulate silica in an amorphous form. Silica fume is typically obtained as a byproduct of silica ore processing, such as the melting of quartz in a silica furnace, which results in the formation of silica gas, which further oxidizes upon exposure to air to produce small particles of amorphous silica.

[0133] According to one or more embodiments, the binder is a hydraulic binder, preferably a hydraulic cement, such as Portland cement.

[0134] Suitable aggregates for cementitious materials include coarse and fine aggregates (sand) as well as pebbles and rocks of various sizes, typically in the range of 10-20 mm (3 / 8”-3 / 4”). According to one or more embodiments, the cementitious material is a fiber-reinforced concrete composition.

[0135] According to one or more embodiments, the weight ratio of water to adhesive is in the range of 0.2:1 to 0.7:1, preferably 0.3:1 to 0.6:1, more preferably 0.4:1 to 0.6:1, and even more preferably 0.45:1 to 0.55:1.

[0136] Another subject of the present invention is a method for forming a concrete surface, comprising the following steps:

[0137] I. Coarse synthetic fibers according to the invention are added to a fluidized concrete mixture under the action of a rotating mixer to provide a modified concrete mixture.

[0138] II. Pour the modified concrete mixture prepared in step I to provide the cast concrete body.

[0139] III. Smooth the surface of the cast concrete prepared in step II., and

[0140] IV. Curing the modified concrete mixture.

[0141] According to one or more embodiments, the fluidized concrete mixture comprises binder, aggregate and water.

[0142] The weight ratio of water to adhesive is preferably in the range of 0.2:1 to 0.7:1, more preferably 0.3:1 to 0.6:1, even more preferably 0.4:1 to 0.6:1, and even more preferably 0.45:1 to 0.55:1.

[0143] Preferred binders and aggregates have been discussed above in relation to the cementitious materials of the present invention.

[0144] According to one or more embodiments, the modified concrete mixture contains 0.1-3.0 vol% (preferably 0.2-2.0 vol%), more preferably 0.2-1.0 vol% (based on the total volume of the hardened cement composition), of coarse synthetic fibers.

[0145] The surface of the poured concrete can be smoothed, for example, by using a tray or trowel. Example

[0146] The following compounds, as shown in Table 1, were used in the examples:

[0147] Table 1

[0148]

[0149] Preparation of crude synthetic fibers

[0150] The crude synthetic fiber and reference crude synthetic fiber of the present invention Figure 2 The method of production is illustrated in the diagram.

[0151] The raw material of coarse synthetic fibers is fed into an extruder (5) using a metering and feeding device (4), the extruder (5) comprising a 110 mm single-screw extruder with an L / D ratio of 32:1 and two melt pumps feeding two circular dies. The melt-processed composition is extruded through an extruder die (6) comprising a plurality of spinnerets consisting of a cavity assembly, and the extruded fibers are guided through an air gap into a water bath (7). The downstream device is a powered take-off roll, which comprises a first roll frame (8) equipped with five rolls and rolls on the exit roll.

[0152] The unstretched fibers obtained from the exit roll are oriented in a first (stretching) oven (9), stretched using a second roll frame (10) consisting of seven rolls, and further processed in a second (annealing) oven (11) to obtain stretched fibers. Heating in the first and second ovens (9, 11) is achieved with forced hot air at controlled temperatures.

[0153] In some cases, the stretched fibers obtained from the second oven (11) are passed through a mechanical crimping machine (12) consisting of two matched rollers that are partially engaged to deform the stretched fibers. After leaving the crimping machine (12), the fibers are further processed through a third roller frame (13) consisting of seven rollers, with the exit roller having a roll. Finally, the stretched and crimped fibers are wound and cut to a predetermined length using a winding machine (14).

[0154] The coarse synthetic fiber of Embodiment Ex-1 of the present invention is produced using an extruder die with multiple spinnerets, each spinneret consisting of a component of four non-intersecting circular holes arranged in a quadrilateral configuration. The produced fiber has a multi-leaf cross-sectional shape, wherein four leaves extend radially from the center of the fiber, as shown below. Figure 1 As shown schematically in the diagram.

[0155] The coarse synthetic fiber of Reference Example Ref-1 is produced using an extruder die with multiple spinnerets, each spinneret consisting of a component of three intersecting circular holes arranged in a triangular pattern. The fiber has a multi-lobed cross-section, with three lobes extending radially from the center of the fiber. A single fiber is not composed of "fused filaments" because there is no space between the edges of the spinneret holes. Therefore, each fiber is extruded as a single filament. The extruded fiber is mechanically fibrillated but not crimped.

[0156] The coarse synthetic fiber of Reference Example Ref-2 is produced using an extruder die with multiple spinnerets, each spinneret consisting of an assembly of four circular holes connected by cleaving lines arranged in a straight line. Individual fibers are not composed of “fused filaments” because there is no space between the edges of the spinneret holes. Therefore, each fiber is extruded as a single filament. The extruded fibers are mechanically fibrillated but not crimped.

[0157] The coarse synthetic fiber of Reference Example Ref-3 is produced using an extruder die with multiple spinneret orifices, each orifice consisting of a single circular cavity. A single fiber is not composed of "fused filaments" because the spinneret orifice consists of a single cavity. Therefore, each fiber is extruded as a single filament.

[0158] Elastic modulus, tensile strength, elongation at break

[0159] The elastic modulus and tensile strength at break were determined according to EN 14889-2:2006 at 23°C and a strain rate of 5% / min. Elongation at break was determined according to EN 10002-1:2001 at 23°C.

[0160] Application of fibers in cementitious materials

[0161] The aim was to test the effect of adding different doses of coarse synthetic fiber to a typical concrete mixture with a compressive strength of 24-31 MPa after 7 days of aging.

[0162] Concrete was batched and mixed according to the standard implementation procedure for preparing and curing concrete test specimens in the laboratory, ASTM C192-19. Fibers were added at the beginning of the batch sequence, and the concrete was mixed with rock and sand for 1 minute before the addition of cementitious materials. The concrete was then mixed for 3 minutes, allowed to stand for 3 minutes, mixed for another 2 minutes, and poured into molds. Plasticity properties were then determined and recorded according to applicable ASTM standards. Hardening properties after 7 days were tested using cylinders measuring 6”×12” (150×300mm) and beams measuring 6”×6”×20” (150×150×500mm) according to ASTM C1609-19a. Mixing ratios, plasticity, and hardening properties are shown in Tables 3 and 4. Hardening property values ​​were calculated as the average of measurements obtained using six beams.

[0163] For 6”×6”×20” beam samples, concrete was poured directly from a wheeled truck into the mold, filling it to a height of approximately 1–2 inches above the edges. For 6”×12” cylinder samples, concrete was poured using a scoop, filling it to a height of approximately 1–2 inches above the mold edges. The beam and cylinder samples were then consolidated at a frequency of 60 Hz using an external vibration table. Consolidation was determined to be adequate once the mortar had reached all the inner edges and corners of the mold and no voids larger than 1 / 8” diameter were observed. Care was taken to ensure all samples were vibrated for the same duration and simultaneously. The samples were then smoothed with an aluminum trowel and moved to a horizontal surface. The samples were covered with damp burlap and plastic in a manner that did not interfere with the surface finish and prevented moisture loss. After curing in the mold for 24 hours, the hardened samples were removed from the mold and placed in a saturated lime bath at 23±2°C until the test time.

[0164] Six beam samples from each mix were tested using roller supports that met the requirements of the ASTM C1812-15 standard implementation specification for journal bearing support design for testing fiber-reinforced concrete beams, with a span length of 18” (450 mm). The testing machine used was a Satec Model 5590-HVL closed-loop, dynamic servo hydraulic testing machine that met the requirements of the ASTM E4-20 standard implementation specification for testing machine force verification. Load and deflection data were electronically collected at a frequency of 5 Hertz. The load was applied perpendicular to the molded surface after the edges were ground with a grinding stone. Net deflection values ​​were obtained at the mid-span and mid-height of the beam for data acquisition and rate control. The rate was kept constant throughout the entire duration of each test at an average net deflection value of 0.002 in / min.

[0165]

[0166]

[0167]

Claims

1. A coarse synthetic fiber comprising three or more partially fused filaments, said filaments being made of a polymer composition comprising at least one polypropylene and at least one polyethylene, said at least one polypropylene comprising at least 70% by weight of said polymer composition and said at least one polyethylene comprising at least 5% by weight of said polymer composition based on the total weight of said polymer composition, wherein said fiber has a multi-bladed cross-sectional shape with three or more blades, wherein each blade has a curved tip portion and a base portion located toward the center portion of said fiber, the ratio (D1:D2) between the maximum width (D1) of said tip portion and the width (D2) of said base portion is 1.2:1 to 2.7:1, said coarse synthetic fiber is drawn at a draw ratio of at least 5:1, said coarse synthetic fiber has a fiber length of at least 20 mm, and / or an aspect ratio (l / d) not greater than 85, and / or a fiber diameter of at least 0.25 mm. mm, the central portion of the fiber is solid, the coarse synthetic fiber is obtained by using a method comprising extruding a molten polymer composition through an extruder die comprising a plurality of holes to provide unstretched fibers, wherein at least a portion of the holes consists of a component of three or more holes closely arranged but not overlapping each other.

2. The crude synthetic fiber according to claim 1, wherein the crude synthetic fiber can undergo gradual fibrillation when mechanically stirred within a matrix material reinforced with the fiber to be used.

3. The coarse synthetic fiber according to claim 1, having a multi-leaf cross-sectional shape, the multi-leaf cross-sectional shape having three or more leaves extending axially through the central portion of the fiber.

4. The coarse synthetic fiber according to claim 1 or 2, which is composed of four partially fused filaments.

5. The coarse synthetic fiber according to claim 1 or 2, wherein the linear density is at least 1000 den, and / or the fiber length is at least 20 mm, and / or the aspect ratio (l / d) is not greater than 85, and / or the fiber diameter is at least 0.25 mm.

6. The coarse synthetic fiber according to claim 1 or 2, wherein the linear density is at least 1200 den, and / or the fiber length is at least 25 mm, and / or the aspect ratio (l / d) is not greater than 75, and / or the fiber diameter is at least 0.35 mm.

7. A method for producing crude synthetic fibers, comprising the following steps: I) Extruding a melt polymer composition comprising at least one polypropylene and at least one polyethylene to provide undrawn fibers consisting of three or more partially fused filaments, wherein the at least one polypropylene comprises 70-90% by weight of the polymer composition and the at least one polyethylene comprises 5-25% by weight of the polymer composition. II) Uniaxial stretching of the unstretched fibers prepared in step I) to provide stretched fibers. III) Optionally crimp the stretched fibers prepared in step II) to provide crimped fibers, and IV) Cut the fibers prepared in step II) or III) into predetermined lengths; The fiber has a multi-bladed cross-sectional shape with three or more blades, wherein each blade has a curved tip portion and a base portion located toward the central portion of the fiber, the ratio (D1:D2) between the maximum width (D1) of the tip portion and the width (D2) of the base portion is 1.2:1 to 2.7:1, the coarse synthetic fiber is stretched at a draw ratio of at least 5:1, the fiber length of the coarse synthetic fiber is at least 20 mm, and / or the aspect ratio (l / d) is not greater than 85, and / or the fiber diameter is at least 0.25 mm, the central portion of the fiber is solid, and the coarse synthetic fiber is obtained by means of extruding a molten polymer composition through an extruder die comprising a plurality of holes to provide unstretched fibers, wherein at least a portion of the holes consists of an assembly of three or more holes closely arranged but not overlapping each other.

8. The method according to claim 7, wherein, Step I) includes the following steps: i) Extruding the molten polymer composition through a spinneret comprising a plurality of spinneret orifices to provide unstretched fibers. ii) The unstretched fibers prepared in step i) are guided into the cooling bath through an air gap. The spinneret orifice is at least a portion of an assembly of three or more holes arranged adjacent to each other, such that when the molten polymer composition is extruded through the holes, the resulting extruded filaments are partially fused together to form unstretched fibers.

9. The method according to claim 8, wherein, The distance between adjacent holes in the component is arranged such that the edges of the holes do not intersect each other.

10. The method according to claim 8, wherein, The component consists of four adjacent holes arranged in a quadrilateral shape.

11. Crude synthetic fibers obtained by using the method according to any one of claims 7-10.

12. Use of the coarse synthetic fiber according to any one of claims 1-6 or the coarse synthetic fiber according to claim 11 for improving the toughness of a hardened cement composition.

13. Cementitious materials, including: a) Adhesive, b) Based on the total volume of cementitious materials, 0.1-3.0 vol% of the crude synthetic fiber according to any one of claims 1-6 or the crude synthetic fiber according to claim 11, c) Aggregates, and d) Water.

14. The cementitious material according to claim 13, wherein b) 0.2-2.0 vol% of the coarse synthetic fiber according to any one of claims 1-6 or the coarse synthetic fiber according to claim 11, based on the total volume of the cementitious material.

15. A method for forming a concrete surface, comprising the following steps: I. Adding coarse synthetic fibers according to any one of claims 1-6 or according to claim 11 to a fluidized concrete mixture while the mixer is rotating to provide a modified concrete mixture. II. Pour the modified concrete mixture prepared in step I to provide the poured concrete body. III. Smooth the surface of the poured concrete prepared in step II., and IV. Curing the modified concrete mixture.

Images