Resin concrete composition, hardened resin concrete, fiber-reinforced plastic composite pipe

Abstract

Resin concrete compositions containing fillers coated with silane coupling agents have been shown to improve flexural strength. However, coating the resin mortar layer with a coupling agent complicates the molding of fiber-reinforced plastic composite pipes. The present invention has been made in view of the above circumstances and provides a resin concrete composition that can further increase strength. [Solution] The material comprises an aggregate containing silica sand, specific fibers having a fiber length of 100 to 20,000 μm, and a thermosetting resin, wherein the content of the specific fibers relative to the total of the aggregate and the specific fibers is 0.1 to 3.0% by mass.

Description

Technical Field

[0001] The present invention relates to a resin concrete composition, a cured product of resin concrete, and a fiber reinforced plastic composite pipe.

Background Art

[0002] A fiber reinforced plastic composite pipe generally has a resin mortar layer formed by molding and curing a resin concrete composition, and a fiber reinforced resin layer located on at least one of its inner peripheral surface and outer peripheral surface. A resin concrete composition is a composition containing a synthetic resin as a binder and an aggregate. As the synthetic resin, a thermosetting resin such as an unsaturated polyester, an acrylic resin, an epoxy resin or a phenolic resin is used.

[0003] The resin mortar layer made of the resin concrete composition affects the strength of the fiber reinforced plastic composite pipe. For example, Patent Document 1 proposes a resin concrete composition containing a filler coated with a silane coupling agent. According to the invention described in Patent Document 1, improvement in flexural strength is intended.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, coating the resin mortar layer with a coupling agent complicates the molding of the fiber reinforced plastic composite pipe. Therefore, an object of the present invention is a resin concrete composition capable of further enhancing strength.

Means for Solving the Problems

[0006] It is known that the addition of fibers to particulate materials contributes to improved strength and toughness. In other words, adding fibers to resin concrete can be expected to have a reinforcing effect. However, it is known that as the fiber length of the fibers used in the mixture increases, the filler (fibers, aggregates, etc.) becomes bulkier, and the packing efficiency decreases. In particle-fiber composites, the addition of long fibers (e.g., fiber length of 50 mm or more) to the already orderly particle packing structure disrupts the arrangement. This can potentially reduce the packing efficiency. Since a decrease in packing efficiency means an increase in void ratio, there are concerns that adding long fibers to resin concrete may lead to a decrease in strength. The inventors of this invention discovered that strength can be increased by combining silica sand with fibers of a specific fiber length, leading to the present invention.

[0007] The present invention has the following aspects. <1> It contains aggregate containing silica sand, specific fibers with a fiber length of 100 to 20,000 μm, and a thermosetting resin. A resin concrete composition in which the content of the specific fibers relative to the total amount of the aggregate and the specific fibers is 0.1 to 3.0% by mass. <2> The resin concrete composition according to claim 1, wherein the fibers include glass fibers. <3> The resin concrete composition according to claim 1, wherein the silica sand comprises two or more groups of particles with different average particle sizes. <4> The resin concrete composition according to claim 1, wherein the content of silica sand relative to the total mass of the aggregate is 95% by mass or more. <5> A cured resin concrete product comprising a cured resin concrete composition according to any one of claims 1 to 4. <6> A fiber-reinforced plastic composite tube having a resin mortar layer and a fiber-reinforced resin layer located on at least one of the inner and outer surfaces of the resin mortar layer, The resin mortar layer is made of a cured product of the resin concrete composition described in any one of claims 1 to 4. The fiber-reinforced resin layer is made of fiber-reinforced resin, forming a fiber-reinforced plastic composite tube.

[0008] <7> The process includes a mixing step of mixing aggregate containing silica sand, specific fibers having a fiber length of 100 to 20,000 μm, and a thermosetting resin. The mixing step is a method for producing a resin concrete composition, wherein the content of the specific fibers relative to the total amount of the aggregate and the specific fibers is 0.1 to 3.0% by mass. <8> The process includes a crushing step to obtain a crushed material containing specific fibers, which are fibers with a fiber length of 100 to 20,000 μm, The mixing step involves mixing the pulverized material, the aggregate, and the thermosetting resin. <7> A method for producing the resin concrete composition described above. <9> The ratio of the pulverized material, expressed as [mass of specific fibers]:[mass of non-specific fibers], is 3:7 to 0.5:9.5. <8> A method for producing the resin concrete composition described above. <10> <7> ~ <9> A step of obtaining a resin concrete composition by a method for producing a resin concrete composition described in any of the above, A step of curing the resin concrete composition, A method for producing a hardened resin concrete product having the following characteristics. <11> A method for manufacturing a fiber-reinforced plastic composite pipe having a resin mortar layer and a fiber-reinforced resin layer located on at least one of the inner and outer surfaces of the resin mortar layer, <7> ~ <9> A step of obtaining a resin concrete composition by a method for producing a resin concrete composition described in any of the above, The process involves curing the obtained resin concrete composition to form the resin mortar layer, A step of providing the fiber reinforced resin layer on at least one of the inner peripheral surface and the outer peripheral surface of the resin mortar layer; A method for manufacturing a fiber reinforced plastic composite pipe having the same.

Effects of the Invention

[0009] According to the resin concrete composition of the present invention, the strength can be further increased.

Brief Description of the Drawings

[0010] [Figure 1] It is a perspective view showing a fiber reinforced plastic composite pipe according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0011] In this specification, the numerical range represented by "~" includes the numerical values at both ends of the numerical range.

[0012] [Resin Concrete Composition] The resin concrete composition of the present invention includes silica sand, fibers, and a thermosetting resin. The resin concrete composition of this embodiment includes compositions called resin concrete, resin mortar, and resin mortar described in JIS A 1181 "Test Methods for Resin Concrete".

[0013] "Aggregate" By including an aggregate, the resin concrete composition reduces the content of the thermosetting resin. Thereby, the amount of heat generated during the curing of the thermosetting resin is reduced, the temperature difference between the surface and the inside when the resin concrete composition cures is alleviated, and the occurrence of cracks is suppressed. In addition, the amount of shrinkage when the thermosetting resin cures is reduced, and the shrinkage when the resin concrete composition cures is decreased. Furthermore, the amount of use of the thermosetting resin is reduced, and the cost of the resin concrete composition can be reduced. In addition, by including an aggregate and specific fibers described later, the strength of the cured resin concrete can be further increased.

[0014] The aggregate contains silica sand. The silica sand may be natural silica sand, artificial silica sand, or a mixture of natural and artificial silica sand.

[0015] The average particle size of silica sand is preferably 10 to 2000 μm, more preferably 100 to 1500 μm, and even more preferably 150 to 1300 μm. If the average particle size is above the lower limit, it exceeds the so-called critical particle size, thus further reducing voids. If the average particle size is below the upper limit, the increase in void size due to the so-called wall effect, where particles are arranged along the walls of the filling container, can be suppressed, thereby further reducing voids.

[0016] Silica sand can be used alone or in combination of two or more types. For example, silica sand may consist of a single group of particles with a different average particle size, or a combination of two or more groups of particles with different average particle sizes, with a combination of two or more groups of particles with different average particle sizes being preferable. By using two or more groups of particles with different average particle sizes, the strength of the resin concrete molded body can be further increased. When using two or more particle groups with different average particle sizes, the difference in average particle size between the two groups is preferably 500 to 1500 μm. If the difference in average particle size is greater than or equal to the lower limit, the so-called loosening effect can be suppressed, further reducing voids. If the difference in average particle size is less than or equal to the upper limit, the increase in void size due to the so-called wall effect, where particles are aligned along the coarser particles, can be suppressed, further reducing voids. The average particle size of the silica sand was measured using a sieve shaker with sieves (mesh openings of 30 μm, 45 μm, 53 μm, 75 μm, 90 μm, 106 μm, 125 μm, 150 μm, 180 μm, 212 μm, 250 μm, 300 μm, 600 μm, 850 μm, 1180 μm, 1700 μm, and 2360 μm, sieves conforming to JIS Z 8801 "Test sieves - Part 1: Metal wire mesh sieves"), and is the cumulative 50% particle size (D50) by mass.

[0017] Examples of commercially available silica sand include, but are not limited to, Silica Sand No. 3 (average particle size 1,180 mm: manufactured by Sankyu Kaiun Co., Ltd.), Silica Sand No. 6 (average particle size 0.3 mm: manufactured by Sankyu Kaiun Co., Ltd.), and Silica Sand No. 7 (average particle size 0.180 mm: manufactured by Sankyu Kaiun Co., Ltd.).

[0018] The resin concrete composition may contain aggregates other than silica sand (optional aggregates). The type of aggregate is not particularly limited, but aggregates that have been conventionally incorporated into resin concrete compositions, such as gravel, crushed stone, pebbles, blast furnace slag aggregate, or artificial lightweight aggregate, can be used. The optional aggregate may be used individually or in combination of two or more types.

[0019] The aggregate content is not particularly limited, but it is preferably 60 to 90% by mass relative to the total mass (100% by mass) of the resin concrete composition.

[0020] In resin concrete compositions, the total volume of aggregate is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more, of the total volume of the resin concrete composition. When the total volume of silica sand is above the lower limit mentioned above, the frequency of contact between particles increases, and the desired filling structure can be more reliably achieved. In resin concrete compositions, the total volume of silica sand is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less, relative to the total volume of the resin concrete composition. When the total volume of silica sand is below the above upper limit, the amount of resin required for molding can be reduced, thereby improving the efficiency of material costs.

[0021] The silica sand content relative to the total mass of aggregate is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably substantially 100% by mass. When the silica sand content is above the lower limit mentioned above, the strength of the hardened resin concrete composition can be further increased.

[0022] "fiber" The resin concrete composition contains fibers with a fiber length of 100 to 20,000 μm (hereinafter sometimes referred to as "specific fibers"). By including aggregate containing silica sand and specific fibers, the strength of the hardened resin concrete can be further increased.

[0023] The type of specific fiber is not particularly limited, and examples include glass fiber, carbon fiber, and resin fiber. From the viewpoint of further increasing the strength of the hardened resin concrete, glass fiber is preferred as the specific fiber.

[0024] The specified fibers may be long fibers cut to the desired fiber length, or they may be selected from crushed resin concrete hardened material (recycled material). In the case of recycled material, only the specified fibers may be used, or the specified fibers with resin attached may be used as the raw material for the specified fibers.

[0025] The length of the specific fibers (fiber length) is 100 to 20,000 μm, preferably 200 to 1,000 μm, and more preferably 300 to 500 μm. When the fiber length of the specific fibers is within the above range, the strength of the hardened resin concrete can be further increased. Fiber length is a value measured by image analysis of microscopic observation images.

[0026] The thickness (fiber diameter) of the specific fiber is preferably 10 to 1000 μm, and more preferably 20 to 500 μm. When the fiber diameter of the specific fiber is within the above range, the reinforcing effect of the specific fiber can be further enhanced. Fiber diameter is a value measured by image analysis of microscopic observation images. Furthermore, if the cross-section of a particular fiber is perfectly circular, its diameter is the fiber diameter. If the cross-section of a particular fiber is not perfectly circular, the diameter of the circumscribed circle of that cross-section is the fiber diameter.

[0027] The content of specific fibers is 0.1 to 3.0% by mass, preferably 0.2 to 2.5% by mass, and more preferably 0.3 to 1.0% by mass, relative to the total amount of specific fibers and aggregate. If the content of specific fibers is above the lower limit, the strength of the resin concrete composition can be further increased. If the content of specific fibers is below the upper limit, voids can be further reduced.

[0028] "Thermosetting resin" Examples of thermosetting resins include unsaturated polyester resins, vinyl ester resins, epoxy resins, acrylic resins, phenolic resins, polyimide resins, melamine resins, and urethane resins. Among these, unsaturated polyester resins are preferred from the viewpoint of cost and moldability.

[0029] <Unsaturated polyester resin> The unsaturated polyester resin comprises an unsaturated polyester (a) and a polymerizable unsaturated monomer (b).

[0030] For the unsaturated polyester (a), it is preferable to use a saturated dibasic acid (a1), an unsaturated dibasic acid (a2), and a glycol (a3) ​​as raw materials.

[0031] A saturated dibasic acid (a1) is a dibasic acid that does not contain a non-conjugated double bond between carbon atoms in a single molecule, such as orthophthalic acid, isophthalic acid, terephthalic acid, or adipic acid. A saturated dibasic acid (a1) may be used alone or in combination of two or more types, as needed. An unsaturated dibasic acid (a2) is a dibasic acid that contains one or more non-conjugated double bonds between carbon atoms in one molecule, such as maleic anhydride or fumaric acid. An unsaturated dibasic acid (a2) may be used alone or in combination of two or more types, as needed.

[0032] Glycol (a3) ​​is a diol containing two hydroxyl groups in one molecule, such as alkylene glycols like ethylene glycol or propylene glycol, polyoxyalkylene glycols like dialkylene glycol or trialkylene glycol, or bisphenols like bisphenol A or bisphenol F. Glycol (a3) ​​may be used alone or in combination of two or more types, as needed.

[0033] The unsaturated polyester (a) can also be made from monomers (a4) having one or two non-conjugated double bonds between carbon atoms in a single molecule, which are not included in either the unsaturated dibasic acid (a2) or the glycol (a3). Examples of such monomers (a4) include, but are not limited to, styrene, propylene, dicyclopentadiene, and alkyl (meth)acrylates. Monomers (a4) may be used individually or in combination of two or more types, as needed.

[0034] Methods for synthesizing unsaturated polyester (a) include, but are not limited to, a synthesis method in which a saturated dibasic acid (a1), an unsaturated dibasic acid (a2), and a glycol (a3), and optionally a monomer (a4), are charged and condensed simultaneously.

[0035] Unsaturated polyester resins can be classified into ortho-unsaturated polyester resins, iso-unsaturated polyester resins, tere-unsaturated ester resins, and bis-unsaturated polyester resins depending on the type of saturated dibasic acid (a1) or glycol (a3).

[0036] The polymerizable unsaturated monomer (b) is not particularly limited, and any monomer conventionally used in unsaturated polyester resins can be used. Examples of polymerizable unsaturated monomers (b) include styrene, α-methylstyrene, chlorostyrene, dichlorostyrene, divinylbenzene, t-butylstyrene, vinyltoluene, vinyl acetate, diarylphthalate, triarylcyanurate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate. Stearyl methacrylate, tridecyl methacrylate, dicyclopentenyloxyethyl methacrylate, ethylene glycol monomethyl ether methacrylate, ethylene glycol monoethyl ether methacrylate, ethylene glycol monobutyl ether methacrylate, ethylene glycol monohexyl ether methacrylate, ethylene glycol mono-2-ethylhexyl ether methacrylate, diethylene glycol monomethyl ether methacrylate, diethylene glycol monoethyl ether methacrylate, diethylene glycol monobutyl ether methacrylate, diethylene glycol monohexyl ether methacrylate, diethylene glycol mono-2-ethylhexyl ether methacrylate, dipropylene glycol monomethyl ether methacrylate, dipropylene glycol monoethyl ether methacrylate, dipropylene glycol monobutyl ether methacrylate, dipropylene glycol monohexyl ether methacrylate Crylate, dipropylene glycol mono-2-ethylhexyl ether (meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polytetramethylene glycol dimethacrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 2-hydroxy-1,3-dimethacryloxypropane, 2,2-bis[4-(methacryloxyethoxy)phenyl]propane, 2,Examples include, but are not limited to, 2-bis[4-(methacryloxydiethoxy)phenyl]propane, 2,2-bis[4-(methacryloxypolyethoxy)phenyl]propane, tetraethylene glycol diacrylate, bisphenol A ethylene oxide-added (n=2) diacrylate, isocyanurate ethylene oxide-added (n=3) diacrylate, and pentaerythritol diacrylate monostearate. Polymerizable unsaturated monomer (b) may be used alone or in combination of two or more types, as needed.

[0037] The number-average molecular weight of the unsaturated polyester (a) is not particularly limited, but is preferably 400 to 1500, more preferably 400 to 1200, and even more preferably 400 to 1000. When the number-average molecular weight of the unsaturated polyester (a) is within this range, the fluidity of the unsaturated polyester resin is good, and the moldability is better.

[0038] The content of unsaturated polyester (a) and polymerizable unsaturated monomer (b) in the unsaturated polyester resin is not particularly limited, but it is preferable that, with a total amount of unsaturated polyester (a) and polymerizable unsaturated monomer (b) of 100 parts by mass, the unsaturated polyester (a) is 80 to 60 parts by mass and the polymerizable unsaturated monomer (b) is the remainder. Within this range, the shrinkability, physical properties, and moldability of the polyester resin are improved.

[0039] The unsaturated polyester resin may be mixed with compounds other than the compounds used in the synthesis of the unsaturated polyester (a) and the polymerizable unsaturated monomer (b), to the extent that the effects of the present invention are not lost.

[0040] Examples of commercially available unsaturated polyester resins include iso-type unsaturated polyester resins (manufactured by Nippon Yupika Co., Ltd.).

[0041] The content of unsaturated polyester resin in the resin concrete composition of this embodiment is not particularly limited, but is preferably 10 to 30% by mass, more preferably 10 to 20% by mass, and even more preferably 10 to 15% by mass, based on the total mass (100% by mass) of the resin concrete composition. Furthermore, in the resin concrete composition of this embodiment, thermosetting resins other than unsaturated polyester may be used in combination as a binder, but the content of unsaturated polyester resin is preferably more than 50 parts by mass and 100 parts by mass or less, more preferably 65 to 100 parts by mass, even more preferably 80 to 100 parts by mass, and particularly preferably 95 to 100 parts by mass, per 100 parts by mass of binder.

[0042] "Fibers other than specified fibers" The resin concrete composition may include fibers other than the specified fibers (it may also include arbitrary fibers). Examples of arbitrary fibers include short fibers with a fiber length of less than 100 μm and long fibers with a fiber length of more than 20,000 μm. The type of arbitrary fiber may be the same as or different from the type of specific fiber.

[0043] The total amount of specific fibers and arbitrary fibers (total fiber amount) is preferably 0.1 to 3.0% by mass, more preferably 0.2 to 2.5% by mass, and even more preferably 0.3 to 1.0% by mass, relative to the total amount of fiber amount and aggregate (100% by mass). The content of specific fibers relative to the total fiber content (100% by mass) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may also be 100% by mass. If the content of specific fibers is above the lower limit mentioned above, the strength of the hardened resin concrete can be further increased.

[0044] "Filling material" The resin concrete composition may further include a filler. When a resin concrete composition contains a filler, it can penetrate the gaps between silica sand particles, enabling dense filling. This improves workability by enhancing the moldability of the resin concrete composition and improves the physical properties of the hardened resin concrete, such as toughness.

[0045] The filler is not particularly limited, but preferably at least one selected from the group consisting of calcium carbonate, silica, clay, mica, talc, wollastonite, alumina, aluminum hydroxide, and kaolin, with calcium carbonate being more preferred. The filler material may be used alone or in combination of two or more types, as needed.

[0046] The average particle size of the filler is not particularly limited, but is preferably 100 μm or less, more preferably 0.05 to 50 μm, and even more preferably 0.1 to 10 μm. Here, the average particle size of the filler is the average of 10 measurements taken using an optical microscope and an electron microscope.

[0047] Examples of commercially available products using calcium carbonate as a filler include, but are not limited to, Whiteon (particle size 3 μm; manufactured by Shiraishi Kogyo Co., Ltd.).

[0048] When the resin concrete composition contains fillers, the amount of fillers is not particularly limited, but the total amount of aggregate and fillers is preferably 60 to 90% by mass of the total mass (100% by mass) of the resin concrete composition.

[0049] Polymerization inhibitors The resin concrete composition may further contain a polymerization inhibitor. The inclusion of a polymerization inhibitor suppresses the reaction between unsaturated polyesters and polymerizable unsaturated monomers, thereby increasing safety. Polymerization inhibitors are not particularly limited, but hydroquinone, toluhydroquinone, trimethylhydroquinone, tert-butylhydroquinone, ditert-butylhydroquinone, tert-butylcatechol, methoxyhydroquinone, benzoquinone, tert-butylquinone, and phenothiazines may be used. Polymerization inhibitors may be used individually or in combination of two or more types. When a resin concrete composition contains a polymerization inhibitor, the amount of polymerization inhibitor it contains is not particularly limited, but it is preferably 0.0001 to 0.1% by mass relative to the total mass (100% by mass) of the resin concrete composition.

[0050] "Hardening agents and curing accelerators" To cure the resin concrete composition, it is preferable to add a hardening agent and heat it. A hardening accelerator may also be used in combination with the hardening agent.

[0051] (Hardening agent) The curing agent is not particularly limited, but an organic peroxide catalyst is preferred, and organic peroxides such as methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, diisopropyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyn-3,3-isopropyl hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, dicumyl hydroperoxide, acetyl peroxide, bis(4-t-butylcyclohexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, isobutyl peroxide, 3,3,5-trimethylhexanoyl peroxide and lauryl peroxide can be used, as well as azo polymerization initiators such as azobisisobutyronitrile and azobiscarbonamide. The hardening agent may be used alone or in combination of two or more types.

[0052] When adding a hardening agent to a resin concrete composition, the amount to be added is not particularly limited, but it is preferably 0.1 to 4% by mass, and more preferably 0.3 to 3% by mass, relative to the total mass (100% by mass) of the resin concrete composition. It is preferable to add the hardening agent before molding the resin concrete composition. After molding the resin concrete composition, a hardened resin concrete product with a defined shape can be obtained by heating and curing it.

[0053] (Curing accelerator) The curing accelerator is not particularly limited, but may include metal soaps such as vanadyl octenoate, copper naphthenate, barium naphthenate, cobalt naphthenate and cobalt octenoate, Li3[Co(NO2)6], Li3[Co(NO2)5Cl], Li3[Co(NO2)5Br], Li3[Co(NO2)4Cl2], Li3[Co(NO2)4Br2], Na3[Co(NO2)6], Na3 Cobalt compounds such as [Co(NO2)5Cl], Na3[Co(NO2)5Br], Na3[Co(NO2)4Cl2], Na3[Co(NO2)4Br2], K3[Co(NO2)6], K3[Co(NO2)5Cl], K3[Co(NO2)5Br], K3[Co(NO2)4Cl2] and K3[Co(NO2)4Br2], vanadylacetyl acetate, cobalt acetate Metal chelate compounds such as iron acetate and iron acetylacetonate, as well as amines such as N,N-dimethylamino-p-benzaldehyde, N,N-dimethylaniline, N,N-diethylaniline, methylhydroxyethylaniline, N,N-dimethyl-p-toluidine, N,N-bis(2-hydroxyethyl)-p-toluidine, 4-N,N-dimethylaminobenzaldehyde, 4-N,N-bis(2-hydroxyethyl)aminobenzaldehyde, 4-methylhydroxyethylaminobenzaldehyde, N,N-bis(2-hydroxypropyl)-p-toluidine, N-ethyl-m-toluidine, triethanolamine, m-toluidine, diethylenetriamine, pyridine, phenylmorpholine, piperidine, and diethanolaniline can be used. The hardening accelerator may be used alone or in combination of two or more types.

[0054] When a resin concrete composition contains a hardening accelerator, the amount of the hardening accelerator is not particularly limited, but it is preferably 0.001 to 5% by mass relative to the total mass (100% by mass) of the resin concrete composition. The hardening accelerator may be added to the resin concrete composition of this embodiment before adding the hardening agent, or it may be added to the resin concrete composition at the same time as the hardening agent.

[0055] "Other ingredients" In addition to the components described above, additives such as UV absorbers, pigments, viscosity reducers, antioxidants, plasticizers, flame retardants, stabilizers, or reinforcing agents may be included, to the extent that they do not interfere with the effects of this embodiment.

[0056] "Method for manufacturing resin concrete composition" The method for producing the resin concrete composition is not particularly limited, but examples include the following: The silica sand, specific fibers, thermosetting resin, and other components as needed are mixed in a mixer (mixing step). When mixing the silica sand and thermosetting resin, one or more types selected from fillers, additives, and curing accelerators may be mixed together as desired. Various modifications are possible, such as adding the curing accelerator and curing agent immediately before manufacturing the cured product.

[0057] The method for producing a resin concrete composition may include a crushing step when recycled materials are used as a source of specific fibers. The crushing step involves crushing the hardened resin concrete containing fibers. After crushing the hardened resin concrete, the crushing step may involve a sorting operation (e.g., sieving) to obtain crushed material containing specific fibers. The crushing operation is carried out, for example, by crushing using various types of crushers. In the crushed material, the ratio of [mass of specific fibers] to [mass of other (non-specific fibers)] is preferably 3:7 to 0.5:9.5, and more preferably 2:8 to 1:9. If the mass of specific fibers is above the lower limit, the reinforcing effect can be further enhanced. If the mass of specific fibers is below the upper limit, productivity in the sorting process can be increased.

[0058] [Resin concrete hardened product] The cured resin concrete product of the present invention consists of a cured product of the resin concrete composition described above.

[0059] Specific examples of hardened resin concrete include the resin mortar portion of fiber-reinforced plastic composite pipes, manholes, drainage pits, building material blocks, pavement blocks, covers, pipe materials, repair materials, and other molded products for civil engineering and construction, as well as molded products made of artificial marble, molded products for landscape use, chairs, benches, CC (information and communication power underground burial) boxes, information-related molded products, and power-related molded products.

[0060] "Method for manufacturing hardened resin concrete" The method for producing the resin concrete composition is not particularly limited, but examples include casting, centrifugal molding, compression molding, and continuous molding. In the casting method, the resin concrete composition is poured into a mold and then heated to cure it. In centrifugal molding, the resin concrete composition is poured into a cylindrical mold, then the mold is rotated, and the centrifugal force molds the resin concrete composition to a uniform thickness, followed by heat curing. In the compression molding method, the resin concrete composition is poured into a mold, then compressed with a press and heat-cured. In the continuous molding method, the resin concrete composition is wrapped around a mandrel while it is rotated and fed forward at a constant speed, then passed through a curing furnace for heating and curing.

[0061] The curing temperature of the resin concrete composition of this embodiment is not particularly limited, but is preferably 50°C or higher, more preferably 50-60°C, and even more preferably 55-65°C. The curing time of the resin concrete composition of this embodiment is not particularly limited, but is preferably 6 hours or more, more preferably 12 hours or more, and even more preferably 24 to 48 hours.

[0062] [Fiber-reinforced plastic composite pipe] The following describes a fiber-reinforced plastic composite tube (hereinafter sometimes abbreviated as "FRPM tube") according to one embodiment of the present invention, with reference to Figure 1. The FRPM pipe 1 of this embodiment has an annular or cylindrical resin mortar layer 4, an inner fiber-reinforced resin layer 3 located on the inner circumferential surface of the resin mortar layer 4, an outer fiber-reinforced resin layer 5 located on the outer circumferential surface of the resin mortar layer 4, an inner protective layer 2 located on the inner circumferential surface of the inner fiber-reinforced resin layer 3, and an outer protective layer 6 located on the outer circumferential surface of the outer fiber-reinforced resin layer 5. In other words, the FRPM pipe 1 has the following layers positioned in order from the inner circumference: an inner protective layer 2, an inner fiber-reinforced resin layer 3, a resin mortar layer 4, an outer fiber-reinforced resin layer 5, and an outer protective layer 6. Either the inner fiber-reinforced resin layer 3 or the outer fiber-reinforced resin layer 5 is sufficient, but both are preferable. The inner protective layer 2 and the outer protective layer 6 are not required, but one or both are preferable.

[0063] In this embodiment, the FRPM pipe 1 has a resin mortar layer 4 made of a cured resin concrete composition of this embodiment. The inner fiber-reinforced resin layer 3 and the outer fiber-reinforced resin layer 5 are made of fiber-reinforced resin.

[0064] "Manufacturing method for FRPM pipes" The method for manufacturing the FRPM tube 1 is not particularly limited, and examples include conventionally known manufacturing methods such as filament winding, centrifugal molding, pultrusion, or hand lay-up. The filament winding method is a manufacturing method in which FRPM pipes are continuously produced by sequentially winding the materials of the inner protective layer 2, inner fiber-reinforced resin layer 3, resin mortar layer 4, outer fiber-reinforced resin layer 5, and outer protective layer 6 onto a core tube while it is rotated and fed at a constant speed, and then sequentially heating and curing them. By changing the size of the core tube, FRPM pipes of various sizes can be manufactured. Furthermore, other methods for manufacturing the FRPM pipe 1 include the method for manufacturing the FRPM pipe described in

[0016] to

[0019] of Japanese Patent Application Publication No. 2001-205711, the method for manufacturing the FRPM pipe described in

[0020] to

[0028] of Japanese Patent Application Publication No. 2001-205712, or the method for manufacturing the FRPM pipe described in

[0009] to

[0019] of Japanese Patent Application Publication No. Hei 10-193467.

[0065] [Other embodiments] The resin concrete cured product of the present invention may be used in composites other than FRPM pipes. In this paper, a composite is an article in which a resin concrete cured product member and a member other than resin concrete cured product are joined together. Examples of composites other than FRPM pipes include glass fiber reinforced plastic (GFRP), carbon fiber reinforced plastic (CFRP), glass fiber reinforced thermoplastic resin (GFRTP), and carbon fiber reinforced thermoplastic resin (CFRTP). [Examples]

[0066] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0067] [Raw materials used] • Silica sand A: No. 3 silica sand (average particle size 1,180 mm: manufactured by Sunnet Co., Ltd.). ·Silica sand B: No. 7 silica sand (average particle size: 0.180mm: manufactured by Miku Kaiun). • Specific fibers: The pulverized material produced in Manufacturing Example 1 below was used as the source of specific fibers. • Thermosetting resin: Unsaturated polyester resin (5503, manufactured by Nippon Yupika Co., Ltd.). • Hardener: Methyl ethyl ketone peroxide (Permec S, manufactured by NOF Corporation). • Heavy calcium carbonate: Heavy calcium carbonate (product name: SS#80, manufactured by Nitto Funka Co., Ltd.).

[0068] "Manufacturing Example 1" Method for manufacturing pulverized material The FRPM pipes were crushed into plates. The plates of FRPM pipes were then crushed using a crusher, and the crushed material containing specific fibers was obtained by passing it through a sieve and sorting machine. Of the total mass of the obtained pulverized material, specific fibers accounted for 10% by mass, resin for 16% by mass, silica sand (No. 3 silica sand: No. 7 silica sand = 2:1 (mass ratio)) for 71% by mass, and calcium carbonate for 4% by mass.

[0069] [Evaluation Method] "Porosity" The void ratio of the hardened resin concrete in each example was measured according to the following formula. Porosity (%) = (Volume measurement result - Theoretical volume) / Volume measurement result Here, the theoretical volume = [volume of filler added] / [volume of resin added]. The filler is a mixture of silica sand, crushed material, and heavy calcium carbonate.

[0070] "Bending strength" A test specimen measuring 40mm x 40mm x 150mm was cut from the cured resin concrete in each example. The flexural modulus (MPa) and flexural strength (MPa) of the obtained test specimens were measured at 23°C in accordance with JCI-S-001-2003. The bending strength (MPa) was measured for each of the five test specimens.

[0071] [Examples 1-3, Comparative Examples 1-2] A filler mixture was prepared by mixing silica sand, crushed material, and heavy calcium carbonate according to the formulation shown in Table 1. A resin concrete composition was obtained by mixing 159 parts by mass of a filler mixture, 20 parts by mass of a thermosetting resin, 0.2 parts by mass of a hardening agent, and 0.2 parts by mass of another hardening agent using a mixer (product name: 2P-1 type, manufactured by Primix Corporation). The composition of the obtained resin concrete composition is shown in Table 2. The obtained resin concrete composition was placed in a mold (a square pipe-shaped mold with an inner dimension of 40 mm square), and the resin concrete composition was cured to obtain a hardened resin concrete product. The specific fiber content, void ratio, and flexural strength of the obtained hardened resin concrete were determined, and the results are shown in Table 2.

[0072] [Table 1]

[0073] [Table 2]

[0074] As shown in Table 2, Examples 1 to 3 to which the present invention was applied had a bending strength of 11.0 MPa or higher. Comparative Examples 1 and 2, in which the content of specific fibers relative to the total amount of aggregate and specific fibers was 3.45 to 5.37% by mass, had a bending strength of 6.7 to 8.2 MPa. These results confirm that the strength of hardened resin concrete can be increased by applying the present invention. [Explanation of Symbols]

[0075] 1. Fiber-reinforced plastic composite tube 2. Inner protective layer 3. Inner fiber-reinforced resin layer 3a Inner fiber-reinforced resin layer (circumferential direction) 3b Inner fiber-reinforced resin layer (axial direction) 4. Resin mortar layer 5. Outer fiber-reinforced resin layer 5a Outer fiber-reinforced resin layer (axial direction) 5b Outer fiber-reinforced resin layer (circumferential direction) 6 Outer protective layer

Claims

1. It comprises an aggregate containing silica sand, specific fibers having a fiber length of 100 to 20,000 μm, and a thermosetting resin. A resin concrete composition in which the content of the specific fibers relative to the total amount of the aggregate and the specific fibers is 0.1 to 3.0% by mass.

2. The resin concrete composition according to claim 1, wherein the fibers include glass fibers.

3. The resin concrete composition according to claim 1, wherein the silica sand comprises two or more groups of particles with different average particle sizes.

4. The resin concrete composition according to claim 1, wherein the content of silica sand relative to the total mass of the aggregate is 95% by mass or more.

5. A cured resin concrete product comprising a cured resin concrete composition according to any one of claims 1 to 4.

6. A fiber-reinforced plastic composite tube having a resin mortar layer and a fiber-reinforced resin layer located on at least one of the inner and outer surfaces of the resin mortar layer, The resin mortar layer is made of a cured product of the resin concrete composition described in any one of claims 1 to 4. The fiber-reinforced resin layer is made of fiber-reinforced resin, forming a fiber-reinforced plastic composite tube.

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