JP6214393B2 - Multiple fine cracked fiber reinforced cement composites - Google Patents

Description

  The present invention relates to a multiple fine cracked fiber reinforced cement composite (HPFRCC). More specifically, the present invention relates to an improved HPFRCC having improved shear fracture resistance in addition to the excellent tensile performance of conventional HPFRCC.

  Conventionally, as a cement-based composite material, HPFRCC in which strength is improved by randomly blending short fibers in a cement matrix has been developed and is already in widespread use. As conventional HPFRCC, the tensile strength, bending strength and toughness are improved by three-dimensionally orienting polymer fibers 11 for improving the strength of the material in the matrix 10 as in HPFRCC2 shown in FIG. Composite materials are known (see Non-Patent Document 1).

  This HPFRCC absorbs the amount of strain of the entire material by causing a large number of fine cracks (hereinafter also referred to as “multi-crack”) to be dispersed in the cement matrix when a tensile load is applied, and without breaking. It has the property of following tensile deformation and bending deformation. The follow-up performance is 1% or more in terms of tensile strain, and has significantly higher deformability than general cementitious materials.

  In recent years, vinylon short fibers (PVA fibers) are employed as the short fibers for improving the strength, and the properties such as the water / cement ratio of the cement-based composition for forming the matrix are constant. By limiting to the range and optimizing, an HPFRCC that realizes a larger tensile strain capacity and is extremely tough so that the tensile strain reaches several percent has been developed (see Patent Document 1).

  Such excellent deformation performance of HPFRCC exhibits, for example, an excellent effect as a highly durable repair material applied to tunnel spraying in the civil engineering field. Also, in the construction field, it has been confirmed that it is effective in improving earthquake resistance when applied to, for example, a beam member of a super high-rise apartment house.

  However, when applying HPFRCC to a floor slab or a beam, which is a structural member of a bridge, further improvement in characteristics may be desired. Bridge members frequently receive vehicle travel loads. The vehicle running load received by the bridge member always changes the principal stress axis due to the sequential movement of the load application point as the vehicle travels or because the vehicle travel axis varies with each travel. For this reason, the bridge member is subjected to the first principal stress (tensile stress) having the first principal stress axis to generate a fine first crack, and after the load due to the principal stress axis is unloaded, A situation where a second principal stress (tensile stress) having another principal stress axis is applied to the first and second stresses is experienced. In such a situation, the first crack that has already occurred may be liable to cause a shear shift in preference to a new fine second crack that is generated by the second main stress. In this case, the material breaks relatively easily at the first crack portion. In this case, even with HPFRCC, the durability is not always sufficient.

  Therefore, for example, with regard to HPFRCC, a small amount of coarse aggregate is further added to the matrix for the purpose of improving the shear fracture resistance after the occurrence of multi-crack, thereby improving the HPFRCC with improved shear fracture resistance. It has been proposed (see Patent Document 2).

JP 2000-7395 A JP 2011-121832 A

“Concrete Library 127 Multi-cracked Fiber Reinforced Cement Composite Material Design / Construction Guidelines (Draft)” (Concrete Committee Multi-cracked Fiber Reinforced Cement Composite Material Guidelines Subcommittee / Edition: Issued in March 2007)

  Although the HPFRCC described in Patent Document 1 has high deformability as described above, the shear fracture resistance when receiving a shearing force in the direction along each crack after the occurrence of multi-crack is sufficient. I couldn't say that.

  Moreover, although HPFRCC described in Patent Document 2 has improved the shear fracture resistance due to the action of coarse aggregate, the fluidity in the state of ready-mixed concrete is low, and the concrete sufficiently wraps around the gap between the reinforcing bars. In some cases, there were problems in workability.

  In view of the above situation, the present invention has a strength that is favorable for shear fracture resistance after the occurrence of cracks, while maintaining the deformability, which is the original characteristic of HPFRCC, for HPFRCC that is being developed in recent years. It is another object of the present invention to provide a multiple fine crack type fiber reinforced cement composite material (HPFRCC) that is excellent in workability.

  As a result of intensive studies, the inventors of the present invention, in HPFRCC, in addition to the polymer fibers conventionally dispersed and blended randomly in the matrix, the rigid fibers having an aspect ratio of 30 or less are randomly added at a predetermined ratio. It has been found that the above problems can be solved by blending, and the present invention has been completed. More specifically, the present invention provides the following.

(1) A multi-fine crack type fiber reinforced cement composite material in which an average value of ultimate tensile strain obtained by a uniaxial tensile test is 0.5% or more and an average crack width by the uniaxial tensile test is 0.2 mm or less. Te, an aspect ratio of 30 or more and a polymer fiber tensile strength is less than 3000MPa or more 1000 MPa, the aspect ratio is 5 or more and 30 or less, and the elastic coefficient, Tsuyoshi or less 19 7 GPa or more 21 6 GPa Are dispersed and blended randomly in the matrix, the polymer fibers are contained in the matrix at a blending ratio of 1% by volume to 3% by volume, and the rigid fibers are contained in the matrix. A plurality of fine crack type fiber reinforced cement composite materials contained at a blending ratio of 0.1% by volume or more and 2.2% by volume or less.

  According to the invention of (1), it is possible to provide an HPFRCC having a strong shear rupture resistance against a shearing force applied in a direction along the multicrack while maintaining the original deformability of the HPFRCC. .

  (2) The multiple fine crack type fiber reinforced cement composite material according to (1), wherein the rigid fibers are steel fibers.

  According to the invention of (2), the above-mentioned shear fracture resistance can be improved more reliably.

  (3) The multiple fine crack type fiber reinforced cement composite material according to (1) or (2), wherein the polymer fiber is a vinylon short fiber.

  According to the invention of (3), while maintaining the original deformability of HPFRCC, it has a strong shear rupture resistance against a shearing force in the direction along the multi-crack and is economical. It is possible to provide an excellent HPFRCC.

  (4) A bridge member comprising the multiple fine crack type fiber reinforced cement composite material according to any one of (1) to (3).

  According to the invention of (4), it is possible to contribute to improving the durability of bridge members (beams and floor slabs) particularly in road structures and the like in which the stress axis direction changes every moment.

(5) A method for producing a plurality of fine crack type fiber reinforced cement composites, wherein the aspect ratio is 30 or more and the tensile strength is 1000 MPa or more and 3000 MPa or less, and the aspect ratio is 5 or more and 30 or less, In addition, a step of obtaining a kneaded product by mixing a rigid fiber having an elastic modulus of 19 7 GPa or more and 21 6 GPa or less and a cement-based composition, and curing the kneaded product to obtain a cement composite material And the content of the polymer fiber in the kneaded product is 1% by volume or more and 3% by volume or less, and the content of the rigid fiber in the kneaded product is 0.1% by volume or more and 2% by volume. The cementitious composition has a water cement ratio (W / C × 100) of 20% or more and 60% or less and a sand cement ratio (S / C) of 1.0 or less (0 Including several) Manufacturing method of fine crack type fiber reinforced cement composite material.

  According to the invention of (5), it is possible to provide an HPFRCC having a strong shear rupture resistance against a shearing force applied in a direction along the multi-crack while maintaining the original deformability of the HPFRCC. .

  According to the present invention, while maintaining the deformability which is the original characteristic of HPFRCC, it has a desirable strength for shear fracture resistance after the occurrence of cracks, and has excellent workability, and is a multi-fine crack type fiber reinforcement. A cement composite (HPFRCC) can be provided.

It is a conceptual diagram which shows typically the planar structure of HPFRCC (improved type) of this invention. It is a conceptual diagram which shows typically the planar structure which concerns on the multi crack part of HPFRCC (improvement type) of this invention. It is a conceptual diagram which shows typically the arrangement | positioning aspect of the polymer fiber in HPFRCC (improved type) of this invention. It is a conceptual diagram which shows typically the arrangement | positioning aspect of the rigid fiber in HPFRCC (improved type) of this invention. It is a conceptual diagram which shows typically the planar structure of a conventionally well-known general multiple fine crack type | mold fiber reinforced cement composite material (HPFRCC) (improvement type).

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiment.

  In general, a multi-fine cracked fiber reinforced cement composite material (HPFRCC) refers to a composite material in which short fibers for improving strength are blended with a cement-based material, and more specifically, under uniaxial tensile stress. It refers to a high-toughness material that exhibits pseudo-strain hardening characteristics and forms multiple fine cracks (multi-cracks) with high density. In particular, in the present specification, in accordance with the definition described in Non-Patent Document 1, “multiple fine cracked fiber reinforced cement composite material (HPFRCC)” was determined by a predetermined uniaxial tensile test described in Non-Patent Document 1. A cement composite material having an average value of ultimate tensile strain of 0.5% or more and an average crack width obtained by the same test as measured by a predetermined method described in the same document is 0.2 mm or less. Say it. In addition, in the present specification, when the term “tensile strength” is used, the maximum load when the tensile test is performed with the short fiber to be measured sandwiched between the chucks of the tensile tester is processed by the initial cross-sectional area of the short fiber. Let's say the value.

  Among the HPFRCCs defined above, one example of a conventionally known general HPFRCC is a polymer fiber 11 such as vinylon short fibers randomly dispersed in the matrix 10 as shown in FIG. As described above, this conventional HPFRCC 2 is characterized by having tensile strength and high toughness after the occurrence of multi-cracks.

  In contrast to the conventional HPFRCC 2, the improved HPFRCC 1 of the present invention, as shown in FIG. 1, in addition to the above polymer fibers 11, further rigid fibers 12 are randomly dispersed in the matrix 10. In addition, the aspect ratio of the rigid fiber 12 is limited to a range of a low aspect ratio unique to the present application.

  That is, the HPFRCC of the present invention is provided with a rigid fiber that is an additional component specific to the present application among the general HPFRCC in a broad sense according to the above definition in an aspect specific to the present application. The shear fracture resistance against shearing force in the direction along each crack is also greatly improved. About the structural requirements other than the rigid fiber 12 which is an original structural requirement for exhibiting this characteristic, it can manufacture on the same structural requirements as conventionally well-known HPFRCC, such as HPFRCC of patent document 1. FIG.

<Multiple fine crack type fiber reinforced cement composite material (HPFRCC)>
As shown in FIG. 2, in the HPFRCC 1 of the present invention, the tensile strength against the tensile force in the A direction (hereinafter also simply referred to as “A direction”) substantially perpendicular to the direction of the multicrack 100 is It can be provided by stress. This point is the same as HPFRCC2 which is a conventional product. However, the HPFRCC 1 has a strength against a shearing force in a B direction (hereinafter also simply referred to as “B direction”), that is, resistance to shear fracture, by the stress of the rigid fiber 12. The holding point is greatly different from the conventional HPFRCC2.

  The polymer fiber 11 is a high-toughness material made of short fibers containing a polymer resin such as vinylon short fibers (PVA fibers), polypropylene short fibers (PP fibers), polyethylene short fibers (PE fibers), and the like. Among the above-mentioned fibers, the short fibers used for the polymer fibers 11 are preferably vinylon short fibers (PVA fibers) having a good balance of tensile strength, adhesion strength with the matrix, and economy. PVA fibers have a matrix-fiber frictional bond strength of 1-6 MPa and a chemical bond strength of 40 MPa or less. By using the polymer fiber 11 as the PVA fiber, the HPFRCC 1 can be provided with sufficient tensile strength and bending strength while keeping the manufacturing cost relatively low.

  Moreover, the polymer fiber 11 can also use a polyethylene short fiber (PE fiber). As the polyethylene short fibers (PE fibers), in particular, high-strength polyethylene fibers described in "Concrete Engineering Annual Papers, Vol. 34, No. 1, 2012" can be preferably used. By making the polymer fiber 11 a high-strength polyethylene fiber, the manufacturing cost is somewhat increased, but the HPFRCC 1 can have an extremely high tensile strength and bending strength.

  In addition, as the polymer fiber 11, a high-strength polyethylene short fiber (PE fiber) can be preferably used from the viewpoint of high performance. By making the polymer fiber 11 into high-strength polyethylene (PE fiber), the HPFRCC 1 can be further strengthened while maintaining tensile toughness.

  The tensile strength of the polymer fiber 11 is 1000 MPa to 3000 MPa, preferably 1400 MPa to 2600 MPa. Furthermore, the apparent fiber strength is more preferably 1000 MPa or more and 1800 MPa or less. The apparent fiber strength here is the strength at which the PVA fiber breaks in the material of the HPFRCC (standard water curing, age 28 days), which is obtained by conducting a tensile break test on such a cured body. It can be measured.

  Further, when a PVA fiber is employed as the polymer fiber 11, the tensile strength is 1000 MPa or more and 2400 MPa or less, preferably 1400 MPa or more and 2000 MPa or less. Furthermore, the apparent fiber strength is more preferably 1000 MPa or more and 1400 MPa or less.

  By setting the tensile strength of the polymer fiber 11 within the above range, the HPFRCC 1 can be provided with sufficient tensile strength with respect to the tensile force in the A direction. Further, it is more preferable that the tensile strength is appropriately optimized within a more optimal range according to the water / cement ratio of the cement composition forming the matrix. Details of this point will be described later.

  The fiber diameter of the polymer fiber 11 is 30-50 μm, and its aspect ratio is 150 or more, preferably 200 or more and 300 or less. By setting the shape and size of the polymer fiber 11 within this range, characteristics such as high toughness due to the occurrence of multi-cracks can be obtained. The reason is as follows.

In HPFRCC1, the polymer fibers 11 blended in the matrix 10 are arranged mainly for the purpose of resisting the tensile force and bending moment in the A direction. Therefore, it is necessary to resist the pulling out of the matrix 10 by these forces. In order to maintain the resistance to pulling, as shown in FIG. 3, the ratio of the length L ₁ of the maximum embedded portion of the polymer fiber 11 in the matrix 10 to the length L ₀ of the polymer fiber 11 is L ₁ = L _0/2 . At this time, it is efficient that the fiber breaks without being pulled out. Therefore, it is preferable that the aspect ratio of the polymer fiber 11 is equal to or more than a value obtained by grading 0.5 times the apparent fiber strength by the adhesion strength. Since the PVA fiber adhesion strength is about 3 MPa, considering that the apparent fiber strength is 1000 MPa or more, the aspect ratio is preferably at least about 150 or more. For this reason, the aspect ratio of the polymer fiber 11 needs to be a certain level or more. Specifically, the tensile strength required for the HPFRCC 1 can be provided by setting the aspect ratio of the polymer fiber 11 to at least 150 or more. When the aspect ratio is less than 30, it is difficult to obtain the above characteristics due to the occurrence of multi-cracks. On the other hand, when the aspect ratio exceeds 300, it becomes difficult to disperse the fibers randomly (homogeneously) in the three-dimensional direction in the composition in which the water cement ratio and the sand cement ratio are adjusted as described later. It becomes difficult to obtain the above characteristics due to the occurrence of multi-cracks in the blending amount range. A plurality of types of PVA short fibers having different diameters and lengths may be mixed and used, but in this case, the diameter and length of each short fiber satisfy the above-mentioned regulations.

  The blending amount of the polymer fiber 11 in the matrix 10 is 1% by volume to 3% by volume, preferably 1.5% by volume to 2.5% by volume in the matrix 10 of HPFRCC1. . If the content is less than 1% by volume, the effect of improving the tensile strength, which is a crack-dispersed characteristic, is not sufficiently exhibited. Moreover, even if it mix | blends in large quantities exceeding 3 volume%, since an effect is saturated and it becomes uneconomical, it is not preferable.

  The rigid fibers 12 are short fibers made of rigid fibers such as steel fibers and stainless steel. Among the above fibers, the rigid fibers 12 are preferably steel fibers. By using the rigid fibers 12 as steel fibers, the shear resistance of the HPFRCC 1 can be greatly improved while maintaining economic efficiency.

  The rigid fibers 12 may be made of stainless steel fibers from the viewpoint of beauty. By using the rigid fiber 12 as the stainless steel fiber, it is possible to prevent rust from being generated on the surface of the HPFRCC 1 and to realize a member having an excellent aesthetic appearance.

The elastic modulus of the rigid fiber 12 is 19 7 GPa or more and 21 6 GPa or less, preferably 21 1 GPa or more and 21 6 GPa or less. By setting the elastic coefficient of the rigid fiber 12 in the above range, the HPFRCC 1 can be provided with sufficient shear fracture resistance against the shearing force in the B direction.

  The aspect ratio of the rigid fiber 12 is 5 or more and 30 or less, preferably 10 or more and 30 or less. The reason is as follows. The rigid fibers 12 blended in the matrix 10 are arranged mainly for the purpose of resisting the shearing force in the B direction under the rotation of the main stress axis after the occurrence of multi-cracks and suppressing the shear deviation of each crack. Is. Therefore, in order to maintain the resistance to the shearing force, the aspect ratio of the rigid fiber 12 is more important than the length, unlike the polymer fiber 11, as shown in FIG. Therefore, in the conventional HPFRCC, the aspect ratio of the short fibers oriented in the matrix is required to be 30 or more. However, in the improved HPFRCC of the present invention, the rigid fibers 12 are different. As for the aspect ratio, even if it is 30 or less, it works effectively for the above purpose.

  On the other hand, in HPFRCC, it is known that the crack width of the multi-crack 100 can be suppressed to 0.25 mm or less as a general reference value (“Relationship between tensile strain and crack width generated in a high toughness cement composite material). "Experimental study on concrete, Annual report on concrete engineering, Vol. 28, pp 353-358, 2006"). In addition, according to the knowledge of the present inventors, the length of the fiber that is randomly oriented at the place where the crack is generated is more than twice the crack width of the crack, so that the crack can be straddled in the matrix. It has also been found that the fiber proportion can be ½ or more. From the above, the minimum fiber length required for the crack width of 0.25 mm is 0.5 mm. In addition, the general minimum diameter of the rigid fiber which is actually on the market is about 0.1 mm. Therefore, if the aspect ratio of the rigid fiber 12 is 5 or more, it works effectively for the above purpose.

  In addition, the rigid fiber 12 not only improves the shearing force under the main stress rotation after the occurrence of multi-crack, but also generates a new crack in the second direction perpendicular to the main tensile axis direction. The strength performance under the same tensile bending stress can be exhibited.

  The blending amount of the rigid fibers 12 in the matrix 10 is 0.1 vol% to 2.2 vol%, preferably 0.5 vol% to 2.0 vol% in the matrix 10. To. If it is less than 0.1% by volume, the effect of improving the shear fracture resistance is not sufficiently exhibited. Moreover, when it exceeds 2.2 volume%, since a slump flow falls and construction becomes difficult, it is unpreferable. By setting the blending amount of the rigid fibers 12 in the matrix 10 within the above range, the HPFRCC 1 can be provided with sufficient shear fracture resistance.

  The matrix 10 can be obtained by curing a kneaded product obtained by kneading polymer fibers 11 and rigid fibers 12 in a cementitious composition. As a cement-type composition, the cement-type composition currently used for manufacture of the conventional HPFRCC of patent document 1 and 2 can be used suitably. The cement-based composition preferably has a water cement ratio (W / C × 100) of 20% or more and 60% or less and a sand cement ratio (S / C) of 1.0 or less.

  In addition, the water cement ratio (W / C × 100) and the sand cement ratio (S / C) of the matrix 10 may be further optimized by combining with the tensile strength of the polymer fiber 11. preferable. For example, when the water cement ratio (W / C × 100) of the matrix 10 is 30% or more and the sand cement ratio (S / C) is 1.0 or less, the tensile strength of the polymer fiber 11 is The pressure is preferably 1000 MPa or more and less than 1500 MPa. On the other hand, when the water cement ratio (W / C × 100) of the matrix 10 is 30% or more and the sand cement ratio (S / C) is 1.0 or less, the tensile strength of the polymer fiber 11 is It is preferable that it is 1500 MPa or more and 2400 MPa or less. In addition, the specific preparation method of the matrix 10 is not particularly limited. Specific examples include the methods described in Patent Documents 1 and 2, which can be preferably performed.

<Manufacturing method of HPFRCC>
HPFRCC1 is manufactured by kneading the above-mentioned cementitious composition, polymer fiber 11 and rigid fiber 12 at a blending ratio such that the blending ratio in matrix 10 of HPFRCC1 is the blending ratio described above. To obtain a kneaded product. Specifically, the above-mentioned kneading is performed on a cement-based composition having a water cement ratio (W / C × 100) of 20% to 60% and a sand cement ratio (S / C) of 1.0 or less. The content of the polymer fiber 11 in the product is 1% by volume to 3% by volume, and the content of the rigid fiber 12 in the kneaded product is 0.1% by volume to 2.2% by volume, By blending each fiber, the blending ratio of the polymer fiber 11 and the rigid fiber 12 in the matrix 10 in the HPFRCC 1 can be set to the above blending ratio.

  The polymer fiber 11 and the rigid fiber 12 can be randomly dispersed in a three-dimensional direction by kneading. After making such a state, it is placed in a mold and used as a structural material. It can be cast at the construction site or precast at the factory. Depending on the application, reinforcing bars may be present inside.

  The HPFRCC of the present invention obtained by curing the above kneaded material is suitable for structural members such as beams and floor slabs whose main stress axis changes during service, and cracks in multiple directions among existing cementitious structures. It is also suitable for repair / reinforcement of places where cracks occur. It is also suitable as a substitute for concrete when it is desired to improve toughness and prevent peeling of ordinary concrete structures.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

(Example)
As Examples 1 to 4, kneaded materials for producing an improved HPFRCC in which the following polymer fibers and the following rigid fibers were randomly blended in the following matrix were obtained. The blending amount of each fiber into the kneaded product was different from each other as shown in Table 1 in each example.
Polymer fiber: PVA fiber. Fiber diameter = 42 μm, aspect ratio = 286, tensile strength = 1200 MPa.
Hard fiber: Steel fiber. Fiber diameter = 200 [mu] m, aspect ratio = 30, elastic modulus = 21 0 GPa.
Cementitious composition: normal Portland cement is used, and fly ash is blended at a substitution rate of FA / (C + FA) × 100 = 30% as other powder that contributes to hardening, and water cement ratio (W / C × 100) = 46%, sand cement ratio (S / C) = 0.64.
The kneaded product was placed in a mold, and after demolding, 20 ° C., 60% R.D. H. It was set as the HPFRCC of Examples 1 to 4, which was a plate of cement composite material aged about 28 days old, which was cured in an atmospheric environment. The size of these plate-like bodies was 420 × 550 × 20 (mm).

(Comparative example)
As Comparative Example 1, a kneaded product for HPFRCC was obtained by randomly blending the same polymer fiber as in Example 1 into the cement-based composition having the same composition as in Example 1 and without blending the rigid fiber.
As Comparative Example 2, in the cementitious composition having the same composition as in Example 1 above, the same polymer fiber as in Example 1 was randomly blended, the rigid fiber was not blended, and Coarse aggregate was mixed so that the blending amount in the kneaded product was 9% by volume to obtain a kneaded product for HPFRCC.
Coarse aggregate: Commercially available crushed stone 2005 specified in JIS A5005 sieved to 10 mm or less.
The kneaded material was placed in a mold, and after demolding, a plate-like body of a cement composite material having a material age of about 28 days was cured under the same conditions as in Examples, and this was designated as HPFRCC of Comparative Examples 1-2. The size of these plate-like bodies was also the same size as in the examples.

  About each said plate-shaped object, the 1st crack was introduce | transduced by adding the bending deformation to which the long side direction of the board becomes a 1st main stress axis. The cracks were introduced by a “four-point bending test” in which two fulcrum points were provided at intervals of 510 mm in the long side direction, and a load was applied from two action points at intervals of 310 mm. After applying a load from one side so that the maximum tensile strain amount was 40%, the first fine crack was introduced by turning over and applying the same load. Here, the plate-like body into which the first crack is introduced is referred to as “initial crack introduction material”.

  Next, a test material of 250 × long side L × 20 (mm) was cut out from the initial crack introducing material. At that time, the test material was cut out so that the angle θ formed by the long side direction of the initial crack-introducing material (the direction of the first principal stress axis) and the long side direction of the test material was 45 °. The long side L of the test material has secured a dimension of at least 340 mm or more. That is, a state in which a shearing force is applied to each specimen at a 45 ° angle with respect to the main stress axis when the initial crack is introduced was simulated. This is a state in which the B direction in FIG. 2 is a direction of 45 ° with respect to the A direction, whereby a constant shear force is applied in a direction substantially parallel to the multicrack 100 It is.

  About the cut-out sample material, the "four-point bending test" which provided two fulcrums with the space | interval of 340 mm in the long side direction, and applied a load from two action points with the space | interval of 170 mm was implemented. The test material was lowered by a method of lowering the jig pressed against the working point at a constant speed of 0.5 mm / min until the specimen was broken. The amount of displacement at the maximum load until breakage was measured, and the deformability when the shear force was applied to the test material was evaluated. The results are shown in Table 1.

  In addition, the flowability (slump flow) was measured for the kneaded material (raw concrete) as each plate-like body of the above Examples and Comparative Examples in order to use it as an index of workability. The results are shown in Table 1. The slump flow is measured by a concrete slump flow test method (JIS A 1150).

  From Table 1, it can be seen that the conventional HPFRCC (Comparative Example 1) in which only the polymer fiber 11 is randomly blended has insufficient deformability with respect to shear force. Further, it can be seen that HPFRCC (Comparative Example 2) further added with coarse aggregate shows a problem in terms of workability, although the slump flow is low although the improvement of the deformability is seen. In the case of HPFRCC, it is generally preferable that the slump flow is at least 460 mm or more due to the high viscosity. When the slump flow is less than 460 mm, the formability is insufficient, which is not preferable.

  The HPFRCC (Examples 1 to 4) of the present invention in which the appropriate amount and the rigid fibers of the appropriate mode are randomly mixed can maintain excellent deformability. This is because shear deviations in cracks formed in the initial stage are suppressed due to the presence of the low aspect ratio rigid fibers. Accordingly, the HPFRCC of the present invention is expected to exhibit stable and excellent durability in applications where the principal stress axis changes variously such as road decks.

  Moreover, the HPFRCC (Examples 1 to 4) of the present invention is preferable in terms of workability as can be seen from the value of the slump flow. However, when the mixing amount of the rigid fibers greatly exceeds 2.0% by volume, the fluidity is lowered, and there is a possibility that a problem occurs in the workability. From this, HPFRCC is mixed with a low aspect ratio rigid fiber in a content range of 0.1 vol% or more and 2.2 vol% or less. It can be seen that the HPFRCC can sufficiently exhibit the deformability.

  As described above, according to the present invention, a plurality of HPFRCCs that have been developed in recent years have preferable strengths in terms of shear fracture resistance after the occurrence of cracks while maintaining the deformability that is the original characteristic of HPFRCC. It can be seen that a fine cracked fiber reinforced cement composite (HPFRCC) can be provided.

1 HPFRCC
10 matrix 11 polymer fiber 12 rigid fiber 100 multi crack 2 HPFRCC (conventional type)

Claims (5)

An average value of ultimate tensile strain determined by a uniaxial tensile test is 0.5% or more, and an average crack width by the uniaxial tensile test is 0.2 mm or less.
A polymer fiber having an aspect ratio of 30 or more and a tensile strength of 1000 MPa or more and 3000 MPa or less;
Rigid fibers having an aspect ratio of 5 to 30 and an elastic modulus of 19 7 GPa to 21 6 GPa are randomly dispersed and blended in the matrix,
The polymer fiber is contained in the matrix at a blending ratio of 1% by volume to 3% by volume,
A plurality of fine crack type fiber reinforced cement composite materials in which the rigid fibers are contained in the matrix at a blending ratio of 0.1% by volume or more and 2.2% by volume or less.   The multi-fine crack type fiber reinforced cement composite material according to claim 1, wherein the rigid fibers are steel fibers.   The multi-fine crack type fiber reinforced cement composite material according to claim 1 or 2, wherein the polymer fiber is a short vinylon fiber.   The bridge member which consists of multiple fine crack type fiber reinforced cement composite material in any one of Claim 1 to 3. A method for producing a plurality of fine cracked fiber reinforced cement composites,
A polymer fiber having an aspect ratio of 30 or more and a tensile strength of 1000 MPa or more and 3000 MPa or less;
A rigid fiber having an aspect ratio of 5 or more and 30 or less and an elastic modulus of 19 7 GPa or more and 21 6 GPa or less;
Mixing a cement-based composition to obtain a kneaded product;
Curing the kneaded material to obtain a cement composite material,
The content of the polymer fiber in the kneaded material is 1 vol% or more and 3 vol% or less,
The content of the rigid fiber in the kneaded material is 0.1 vol% or more and 2.2 vol% or less,
The cement-based composition has a water cement ratio (W / C × 100) of 20% or more and 60% or less, and a sand cement ratio (S / C) of 1.0 or less (including 0). Manufacturing method of fine crack type fiber reinforced cement composite material.

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