WO2012111474A1 - 繊維補強セメント系混合材料 - Google Patents
繊維補強セメント系混合材料 Download PDFInfo
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- WO2012111474A1 WO2012111474A1 PCT/JP2012/052682 JP2012052682W WO2012111474A1 WO 2012111474 A1 WO2012111474 A1 WO 2012111474A1 JP 2012052682 W JP2012052682 W JP 2012052682W WO 2012111474 A1 WO2012111474 A1 WO 2012111474A1
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B16/00—Use of organic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of organic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B16/04—Macromolecular compounds
- C04B16/06—Macromolecular compounds fibrous
- C04B16/0616—Macromolecular compounds fibrous from polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C04B16/0625—Polyalkenes, e.g. polyethylene
- C04B16/0633—Polypropylene
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
- C04B2111/2038—Resistance against physical degradation
- C04B2111/2053—Earthquake- or hurricane-resistant materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/34—Non-shrinking or non-cracking materials
Definitions
- the present invention relates to a fiber-reinforced cement-based mixed material having a high strength produced by mixing fibers in a cement-based matrix that does not contain coarse aggregates.
- Ultra high-strength fiber reinforced concrete in which reinforcing fibers such as metal fibers and organic fibers are mixed in a cement-based matrix in which cement particles and pozzolanic reactive particles (pozzolanic material) are mixed with aggregate particles with a maximum aggregate particle size of 1-2 mm Is known (see Patent Documents 1-3).
- Such ultra-high-strength fiber reinforced concrete is able to secure a certain level of tensile strength and toughness even after cracking by combining high-strength fibers with a dense, ultra-high-strength cement matrix. It has characteristics. That is, it is considered to be due to a so-called cross-linking effect in which, when tensile stress acts on the material and cracks occur in the cement matrix, the fiber bears a tensile force instead of the cement matrix.
- such an ultra-high-strength fiber reinforced concrete does not require reinforcement by a reinforcing bar.
- assembled using such an ultra-high-strength fiber reinforced concrete can make a member thin and lightweight.
- ultra high strength fiber reinforced concrete is formed into a denser hydrated structure during the hydration reaction process when the cementitious matrix is heat-cured, which can greatly improve the durability. it can.
- Patent Documents 1 and 2 are inventions in which a dense and ultra-high strength cement-based matrix material is reinforced with steel fibers. Regarding the adhesion between the cement-based matrix and the fibers, the steel fibers By showing the relationship between the length and the diameter, only the minimum required adhesion length is presented.
- a method of increasing the adhesion area by increasing the fiber length and a method of increasing the adhesion area by increasing the fiber diameter can be easily considered.
- the fiber length is increased, the dispersion of the fibers in the cementitious matrix is deteriorated, and the probability that the fibers are entangled with each other increases, so that the risk of separation of the fibers in the cementitious matrix increases.
- the flowability of ultra-high strength fiber reinforced concrete containing long fibers decreases, so there is a limit to increasing the fiber length.
- the fiber cross-sectional area related to the fiber strength is proportional to the square of the diameter
- the adhesion area related to the adhesion strength is proportional to the square of the diameter.
- Patent Document 3 discloses a case where the reinforcing fiber is an organic fiber or a combination of an organic fiber and a metal fiber, but the adhesive force between the cementitious matrix and the fiber is described above. Similar to Patent Documents 1 and 2, only the relationship between the length and diameter of the fiber is presented.
- the fiber comes out (or slips between the cementitious matrix and the fiber) with a tensile force lower than the tensile strength of the fiber, and the mixed fiber is The original tensile strength could not be fully utilized.
- Patent Document 4 the surface of the fiber is made uneven by embossing, and by applying a surface treatment agent to the fiber surface, the adhesion and hydrophilicity are improved to improve the chemical properties of concrete and fiber.
- a technique for increasing the adhesive force is disclosed.
- Patent Document 5 discloses a technique for increasing the adhesion force by making the fiber itself a corrugated shape instead of a straight line.
- the concrete material which is fiber-reinforced in Patent Document 4 or 5 is conventional concrete in which coarse aggregate is blended.
- the main purpose is to improve the initial adhesion between the fiber and the concrete, and the adhesion between the fiber and the concrete is recovered once the adhesion is broken. Since it is not something that can be expected, a significant improvement in toughness cannot be expected.
- Conventional concrete includes normal fluid, high-fluidity concrete, mass concrete, underwater concrete, etc. that are applied to civil engineering and building structures depending on the purpose of use. It is the assumed material.
- FRC Fiber Reinforced Concrete
- Aggregate particles in these concrete blends are composed of fine aggregate and coarse aggregate.
- the most commonly used concrete is 400-700%, and even powder-based high-fluidity concrete that contains many powders Is about 250-300%.
- the maximum particle size of coarse aggregate used in conventional concrete is most often limited to 20mm and 25mm when applied to general structures, and limited to 40mm and 80mm when applied to dams, etc. . Therefore, the adhesion mechanism between fibers and concrete in conventional fiber reinforced reinforced concrete is not expected for the mechanical adhesion force through the aggregate mixed in the concrete, but between concrete hydrate (cement paste) and fibers. This is expected for chemical adhesion and friction.
- concrete hydrate is filled so as to cover the periphery of the fiber, and the chemical adhesion is mainly expected. Is.
- an object of the present invention is to provide a fiber-reinforced cement-based mixed material that can ensure high tensile strength and high toughness even after the occurrence of cracks.
- the fiber reinforced cementitious mixed material of the present invention includes a cement (weight C), an admixture (weight A), water, an admixture, and a total weight of the cement and the admixture.
- the fiber is formed into a concavo-convex fiber having a concavo-convex formed on the surface, and the ratio h (H / H) of the concavo-convex depth h of the concavo-convex fiber to the minimum cross-sectional diameter H is 0.05-0.8. It is characterized by being molded as follows.
- the thus configured fiber-reinforced cement-based mixed material of the present invention is a material in which fibers having high tensile strength are combined with a dense and ultra-high-strength cement-based matrix. And at least one part of the fiber mixed is made into the uneven fiber by which the unevenness
- a structure constructed using a fiber-reinforced cement-based mixed material that can exhibit performance with excellent toughness with little decrease in yield strength even when deformed greatly can be expected to increase final yield strength.
- seismic energy can be absorbed significantly compared to conventional reinforced concrete, making it ideal as a material for seismic structures.
- FIG. 6 is a cross-sectional view for explaining an adhesion resistance experiment of Example 2.
- 6 is a graph for explaining the results of an adhesion resistance experiment of Example 2 (Examples 1 to 3 and Comparative Examples 1 to 3).
- 6 is a graph illustrating the results of an adhesion resistance experiment of Example 2 (Examples 1 to 3 and Comparative Examples 4 to 6).
- 7 is a graph illustrating the results of a bending toughness experiment of Example 2 (Example-T1, Example-T2, Comparative Example-T1, Comparative Example-T7, Comparative Example-T8).
- 6 is a graph for explaining the results of a bending toughness experiment of Example 2 (Example-T3 to Example-T6, Comparative Example-T2 to Comparative Example-T4).
- 7 is a graph illustrating the results of a bending toughness experiment of Example 2 (Example-T7, Comparative Example-T5, Comparative Example-T6).
- the ultra-high-strength fiber reinforced concrete as the fiber-reinforced cement-based mixed material of the present embodiment contains cement, an admixture, water, an admixture, aggregate particles, and fibers.
- Portland cement ordinary Portland cement, early strong Portland cement, super early strong Portland cement, moderately hot Portland cement, low heat Portland cement, sulfate resistant Portland cement, etc.
- Admixtures include silica fume, precipitated silica, ground granulated blast furnace slag (blast furnace slag fine powder), ground granulated blast furnace slag, fly ash, classified fly ash, coal gasification fly ash, volcanic ash, diatomaceous earth, silicic acid Etchingite-forming admixtures such as clay, truss, expansion material, limestone fine powder, anhydrous gypsum, polymer dispersions and re-emulsifying resin powdered from them can be used.
- the admixture is a material that chemically reacts in the presence of cement.
- the chemical reaction can be broadly classified into a mutual chemical reaction between the admixture and the cement constituent compound and a chemical reaction of the admixture itself.
- these admixtures can be used alone or in combination.
- the admixture is an additive used for many purposes such as improvement of fluidity and strength development, setting control, and improvement of durability, and at least one kind is used.
- This admixture includes high-performance water reducing agents, high-performance AE water reducing agents, fluidizing agents, antifoaming agents, setting accelerators, setting retarders, thickeners, shrinkage reducing agents, quick setting agents, foaming agents, and rust prevention
- a single agent or the like can be used alone or in combination.
- aggregate particles for concrete particles such as crushed sand, river sand, sea sand, quartz sand, limestone crushed sand, recycled aggregate sand, bauxite crushed material, iron ore crushed material, slag crushed material Anything possible can be used.
- the average particle diameter phi A of the aggregate particles is preferably in the 0.2-0.8 mm.
- the average particle diameter phi A of the aggregate particles, in the particle size accumulation curve of the aggregate particles, the weight ratio of the passage weight percentage (or passage rate) is the particle diameter corresponding to 50% (diameter), so-called It corresponds to the average particle diameter D 50.
- organic fibers for example, polypropylene (PP) fibers, polyvinyl alcohol (PVA) fibers, aramid fibers, polyethylene fibers, ultra high strength polyethylene fibers, polyethylene terrestrial fibers
- PP polypropylene
- PVA polyvinyl alcohol
- aramid fibers polyethylene fibers
- ultra high strength polyethylene fibers polyethylene terrestrial fibers
- PET Talat
- rayon fiber rayon fiber
- nylon fiber PVC fiber
- polyester fiber acrylic fiber
- alkali-resistant glass fiber etc.
- inorganic fiber steel fiber, high-tensile steel fiber, stainless steel fiber, titanium fiber, aluminum
- Fiber carbon fiber, basalt fiber, mineral fiber, and the like.
- not only one type of fiber but also a plurality of types may be combined.
- the cross-sectional shape of the fiber may be any shape such as a flat ellipse, a circle, and a rectangle as shown in FIG.
- the circular cross section has the smallest adhesion area for the same cross sectional area.
- the flat cross section has an adhesion area larger than that of the circular cross section with respect to the same cross sectional area. Therefore, the flat elliptic cross section and the rectangular cross section are more advantageous for the adhesion.
- the total volume of the mixed fibers is preferably 0.7-8% of the total volume. That is, if there is a fiber mixing rate of 0.7%, it is an amount that can be expected although the cross-linking effect of the fiber is small as ultra-high strength fiber reinforced concrete. On the other hand, the fiber mixing rate of 8% is an amount that can sufficiently expect the fiber cross-linking effect. However, if a larger amount of fiber is mixed in the cement matrix, the fresh properties of the kneaded material cannot be maintained and self-filling is difficult. Therefore, there is a possibility that it cannot be applied substantially as a structural material.
- the total amount of fibers to be mixed can more preferably be 1.0-5.5% of the total volume.
- the uneven fiber 1 having an uneven surface as shown in FIG.
- a plurality of concave portions 11 are arranged in a staggered manner at intervals on the fiber surface, and a convex portion 12 is formed between the concave portions 11, 11.
- This uneven shape can be formed by embossing the fiber surface, for example.
- the convex part 12 should just protrude with respect to the bottom face of the recessed part 11, even if the space
- the recess 11 is formed into a rhombus in plan view having a depth of h.
- the depth h of the concave portion 11 refers to a distance from the highest height of the convex portion 12 to the lowest height (bottom surface) of the concave portion 11 as shown in FIG.
- the maximum section diameter B is the maximum diameter passing through the center of gravity G
- the minimum section diameter H is the minimum diameter passing through the center of gravity G.
- the minimum cross-sectional diameter H is measured by making the bottom face of the recessed part 11 into an outer peripheral surface as shown in FIG.
- the depth h of the concave / convex concave portion 11 is formed such that the ratio h / H to the minimum cross-sectional diameter H of the concave / convex fiber 1 is 0.05-0.8.
- the pitch p of the concave / convex concave portions 11 in the length direction of the concave / convex fibers 1 is a ratio p / B to the maximum cross-sectional diameter B of the concave / convex fibers 1. It is adjusted to be 0.3-10.0.
- the length Li of the concavo-convex fiber 1 is 1 mm or more.
- the ultra high strength fiber reinforced concrete of the present embodiment configured as described above is a material in which a fiber having high tensile strength is combined with a dense and ultra high strength cement matrix.
- FIG. 2 is a diagram schematically showing an enlarged upper half section of the uneven fiber 1 and aggregate particles 2,... And cement hydrate 4 contained in the cementitious matrix.
- the cementitious matrix formed along the concave portions 11 and the convex portions 12 of the concavo-convex fiber 1 is dotted with aggregate particles 2,. 2,... Enter the recess 11 of the uneven fiber 1.
- the cement-based matrix containing ⁇ ⁇ becomes an anchor portion for the uneven fiber 1.
- the convex part 12 between the concave part 11 and the concave part 11 of the concavo-convex fiber 1 becomes an anchor part for the cementitious matrix.
- the cementitious matrix of the ultra-high-strength fiber reinforced concrete according to the present embodiment includes aggregate particles 2 of appropriate size and amount, the conventional ultra-high-strength fiber reinforcement Compared to concrete, the mutual shear transmission resistance inside the cementitious matrix is increased by the meshing of the aggregate particles 2.
- blended aggregate particles generally have higher elastic modulus and compressive strength than cement hydrate 4 excluding the aggregate particles in the cementitious matrix. It is considered that high shear resistance can be expected.
- the parameters related to the uneven shape of the surface of the uneven fiber 1 and the amount of aggregate particles are defined.
- WR is less than 50%
- the aggregate particle 2 contained in the cementitious matrix of the concave portion 11 of the concave-convex fiber 1 is too small, and the aggregate particle 2 meshes with the concave portion 11.
- the weight ratio WR exceeds 95%
- the depth h of the concave portions 11 of the concavo-convex fibers 1 is a ratio h / H to the minimum cross-sectional diameter H of the concavo-convex fibers 1 as a parameter. It is set. When the ratio h / H is reduced, the depth h of the concave portion 11 becomes shallow, so that the mechanical adhesion (mechanical bond) tends to decrease.
- the ratio h / H in the range of 0.05 to 0.8, it is expected that the mechanical adhesion force (mechanical bond) generated by an appropriate amount of aggregate particles engaged with the concave and convex portions of the concave and convex fiber 1 will be greatly improved. In addition, the possibility of fiber breakage and a decrease in fiber rigidity can be minimized.
- the ratio h / H is less than 0.05, in the relative depth of the concave portion 11 of the concavo-convex fiber 1 is small, even if the average particle diameter phi A of the aggregate particles 2 small combination, the recess of the uneven fiber 1
- the aggregate particle 2 in 11 is too large, and the probability that the aggregate particle 2 is effectively meshed with the recess 11 decreases, and high shear rigidity and high shear resistance cannot be expected.
- the ratio h / H exceeds 0.8, the effect of meshing with the aggregate particles 2 is considered to increase, but since the cross-sectional defect of the uneven fiber 1 is increased, the aggregate particles 2 are interposed.
- the parameter of the ratio h / H related to the depth h of the concave portion 11 of the concave-convex fiber 1 is more preferably in the range of 0.05-0.5.
- the average particle diameter phi A of the aggregate particles 2 in the range of 0.2-0.8mm is preferred.
- the average particle diameter phi A of the aggregate particles 2 is less than 0.2mm, the probability that aggregate particles 2 is too small to aggregate the particles 2 in the recess 11 of the uneven fiber 1 is engaged directly into the recess 11 As a result, the effect of high stiffness or high shear resistance around the concave portion 11 of the uneven fiber 1 is reduced. Further, if the average particle diameter phi A is small, the deviation shear force resistance of one per aggregate particles 2 is reduced in proportion to the square of the diameter. However, when the average particle diameter phi A is large on the contrary increases in proportion to the square of the diameter.
- the average particle diameter phi A is exceeding 0.8mm, although deviations shear force resistance of one per aggregate particles 2 increases, the size aggregate particles 2 in the recess 11 of the uneven fiber 1 Since the probability that the aggregate particles 2 are directly meshed with the concave portion 11 is reduced, the high shear rigidity and the high shear resistance are eventually reduced. That is, it is possible to increase the probability of engaging the average particle diameter phi A of the aggregate particles 2 by a 0.2-0.8 mm, the aggregate particles 2 into the recess 11 and the protrusion 12 of the uneven fiber 1.
- the average particle diameter ⁇ A of the aggregate particles 2 is more preferably in the range of 0.2-0.6 mm.
- the ratio p / B to the maximum cross-sectional diameter B of the uneven fiber 1 is set to 0.3-10.0.
- this ratio p / B is less than 0.3, the pitch p of the projections and depressions in the length direction is shortened, that is, the length of the projections 12 is shortened.
- the resistance length of the anchor portion of the concavo-convex fiber 1 described above decreases, so that the convex portion 12 of the concavo-convex fiber 1 against the shear shear force generated between the concavo-convex fiber 1 and the cementitious matrix.
- a decrease in shear shear rigidity results in an increase in crack width and a decrease in toughness of ultra high strength fiber reinforced concrete, and a decrease in shear shear strength results in a decrease in tensile strength of ultra high strength fiber reinforced concrete.
- the ratio p / B related to the pitch p of the concave and convex portions 11 in the length direction of the concave and convex fibers 1 is more preferably in the range of 0.5 to 7.0.
- the ultra-high-strength fiber reinforced concrete according to the present embodiment has the irregularities defined in the range in which the unevenness of the fiber surface is present in the cement matrix in which the aggregate particles of the formulation weight defined in a certain range are blended.
- the fibers 1 By mixing and combining the fibers 1, it is possible to obtain the adhesion effect between the concavo-convex fibers 1 and the cementitious matrix and the crosslinking effect as fiber reinforced concrete, which could not be obtained individually. That is, by the synergistic effect of the combination of the uneven shape of the uneven fiber 1 and the blended weight of the aggregate particles, high tensile strength and high toughness after occurrence of cracks, which were not obtained with conventional ultrahigh strength fiber reinforced concrete, are obtained. I was able to do it.
- the ratio AR is less than 10, when satisfying the average particle diameter phi A and formulation weight of the combination condition of irregular shape and aggregate particles 2 of uneven fiber 1 according to this embodiment also, adhesion area is too small Sufficient adhesion performance cannot be ensured.
- the ratio AR exceeds 500, sufficient adhesion performance can be secured between the uneven fiber 1 and the cementitious matrix.
- the length of the fiber becomes too long, the fibers become entangled when mixed with the cement-based matrix, and the risk of forming a fiber ball increases rapidly. For this reason, it becomes difficult to disperse
- the aspect ratio AR of the ultra-high-strength fiber reinforced concrete of the present embodiment has a width depending on the flow performance of the fiber material and the cementitious matrix, but the conventional ultra-high strength can be improved because the adhesion performance can be improved. Compared with fiber reinforced concrete, the aspect ratio AR can be set small, and the amount of the mixed fibers 1 can be increased.
- This ratio DR is set to 2-20.
- the maximum particle diameter Dmax of the aggregate particle 2 is a particle diameter (diameter) in which the weight ratio of the passing weight percentage (or passing ratio) is 100% in the aggregate particle diameter curve of the aggregate particle 2. Is the minimum value.
- the ratio DR is less than 2
- the average length Lm of the concavo-convex fibers 1 is less than twice the maximum particle diameter Dmax, and therefore, the crosslinking effect by the fibers in the vicinity of the aggregate cannot be expected.
- the aggregate particles 2 generally have higher strength and rigidity than the cement-based matrix, and the matrix around the aggregate particles 2 in the cement-based matrix is in a state of being easily peeled off.
- the ratio DR exceeds 20
- the cross-linking effect by the fibers can be expected sufficiently, but the fiber length becomes too long and the fibers are entangled when the fibers are mixed into the cement matrix. Therefore, the risk of fiber ball generation increases rapidly. Therefore, the function as ultra high strength fiber reinforced concrete cannot be performed.
- the amount of mixed fibers it is possible to obtain ultra high strength fiber reinforced concrete in which the dispersibility and fresh properties of the fibers are adjusted to desired characteristics. Furthermore, by controlling the length and diameter of the concavo-convex fiber 1, the fresh properties such as the dispersibility and fluidity of the fiber can be adjusted to desired characteristics.
- the cross-sectional shape of the uneven fiber 1A-1E may be any of a circle, an ellipse, a crushed circle, a rectangle, a polygon, and the like.
- embossing is generally used, but is not limited to this, and any processing method such as cutting and folding may be used.
- any processing method such as cutting and folding may be used.
- the uneven shape is provided, for example, on both opposing surfaces (upper surface and lower surface) of the fiber, the uneven shape provided mainly on the upper surface of the fiber will be described below.
- the shape of the recesses 11A-11E, 13A, and 13B is not limited, and may be any shape such as a rhombus in plan view, a triangle in plan view, a circle in plan view, an ellipse in plan view, a polygon in plan view, and a slit shape. May be. Moreover, it may be formed not only on the bottom having a flat shape but also on an inclined surface such as a mortar shape or a pyramid shape.
- the concavo-convex fiber 1A shown in FIG. 3 matches the concavo-convex fiber 1 described in the above embodiment in that it has a flat elliptical cross section.
- concave portions 11A having a rhombic shape in a plan view are formed in a row at intervals in the length direction. Further, on both sides where the recesses 11A,... Are formed, recesses 13A,.
- the pitch p between the concave portions 11A and 13A sandwiching the convex portion 12A of the concavo-convex fiber 1A is the distance in the length direction between the concave portion 11A and the concave portion 13A adjacent thereto as shown in FIG.
- the concave-convex fiber 1A is displaced from the position of the concave portion 11A at the center of the lower surface and the position of the concave portion 13A at the side of the upper surface. This is a value obtained by subtracting the depth (h + h) of the recess 11A and the recess 13A from the thickness of 1A.
- the concavo-convex fiber 1B shown in FIG. 4 has a rectangular cross section, and linear concave portions 11B, 13B,.
- the concave portions 11B and 13B may not be linear, but may be curved or continuous sinusoidal.
- the recesses 11B and 13B are formed into a square cross section having a depth h by embossing or cutting.
- the cross sections of the recesses 11B and 13B are not limited to a quadrangle, and may be a semicircle or an inverted triangle.
- the recess 11B is a groove that inclines in the first direction and crosses the fiber surface
- the recess 13B is a groove that inclines in the direction opposite to the first direction from the end of the recess 11B and crosses the fiber surface.
- a convex portion 12B having an isosceles triangle shape in plan view is formed between the concave portion 11B and the concave portion 13B.
- the pitch p of the concave and convex portions 11B and 13B of the concave and convex fiber 1B is the distance in the length direction between the end portion of the concave portion 11B and the end portion of the concave portion 13B on the same side as shown in FIG.
- the maximum cross-sectional diameter B of the concavo-convex fiber 1B is the maximum diagonal length of the cross section passing through the center of gravity G as shown in the cross section of FIG.
- the minimum cross-sectional diameter H is a value obtained by subtracting the depth (h + h) of the concave portion 11B on the upper surface and the concave portion 13B on the lower surface from the length of the short side of the rectangle passing through the center of gravity G.
- the uneven fiber 1C shown in FIG. 5 has a rectangular cross section, and linear recesses 11C crossing the fiber surface are formed at intervals in the length direction.
- the recess 11C may not be linear, but may be a curve or a waveform.
- the recess 11C is formed into an inverted triangular cross section having a depth (height) h by embossing or cutting.
- the cross section of the recess 11C is not limited to an inverted triangle, and may be a semicircle or a rectangle.
- corrugated recessed part 11C of the uneven fiber 1C becomes the distance of the length direction between the valleys of the recessed parts 11C and 11C, as shown in FIG.
- a convex portion 12C having a rectangular shape in plan view is formed between the concave portions 11C and 11C.
- the maximum cross-sectional diameter B of the concavo-convex fiber 1C is a diagonal length of a rectangle passing through the center of gravity G where the concave portion 11C does not appear in the cross section as shown in FIG.
- the minimum cross-sectional diameter H is a value obtained by subtracting the depth h of the concave portion 11C from the thickness of the concave / convex fiber 1C.
- the uneven fiber 1D shown in FIG. 6 has a rectangular cross section in which the diagonal of the rectangle has the maximum cross-sectional diameter B and the short side has the minimum cross-sectional diameter H, and has a saw blade shape on both sides of the fiber.
- the concave portions 11D and the convex portions 12D are alternately formed.
- the convex part 12D is shape
- the cross-sectional area is always constant in the length direction.
- this blade shape may not be formed with a plane, but may be formed with a curved surface.
- this recessed part 11D is shape
- recessed part 11D when recessed part 11D is formed in a curved surface, it becomes a dome shape in planar view.
- corrugation of the uneven fiber 1D becomes the distance of the length direction between the valleys of the recessed parts 11D and 11D, as shown in FIG.
- a convex portion 12D having an isosceles triangle shape in plan view is formed between the concave portions 11D and 11D.
- the uneven fiber 1E shown in FIG. 7 has a rectangular cross section, and a plurality of rectangular columnar recesses 11E,... Are formed in a lattice shape at regular intervals in the length and width directions on the fiber surface.
- the recess 11E may not be a quadrangular prism, but may be a cylinder or a polygonal column.
- the recess 11E is formed to a certain depth h by embossing or cutting.
- the recessed part 11E may not be a column shape of the fixed depth h, but may be a mortar shape or a pyramid shape.
- the pitch p of the concave and convex portions 11E of the concave and convex fiber 1E is the distance between the concave portion 11E and the concave portion 11E adjacent to it in the length direction, as shown in FIG. Further, a convex portion 12E having a square shape in plan view is formed between the concave portions 11E and 11E.
- the maximum cross-sectional diameter B of the uneven fiber 1E is the maximum diagonal length of the cross-section passing through the center of gravity G as shown in the cross-section of FIG. Furthermore, since the position of the concave portion 11E on the upper surface and the position of the concave portion 11E on the lower surface of the concave / convex fiber 1E is shifted, the minimum cross-sectional diameter H is a value obtained by subtracting the depth h of the concave portion 11E from the thickness of the concave / convex fiber 1E. Become.
- Example 2 the results of experiments conducted to confirm the performance of the ultra-high-strength fiber-reinforced concrete described in the above embodiment or Example 1 will be described.
- the description of the same or equivalent parts as those described in the above embodiment or Example 1 will be given the same reference numerals.
- the mechanical properties of the above ultra-high-strength fiber reinforced concrete depend on the material and surface shape of the concavo-convex fibers 1 and 1A-1E to be mixed as shown below, even when a cement-based matrix having the same composition is used. A certain amount of width occurs with respect to strength characteristics.
- the ultra-high-strength fiber reinforced concrete of this embodiment has a compressive strength (test result of a cylindrical specimen of ⁇ 10 ⁇ 20 cm) of 100-250 N / mm 2 and a bending tensile strength (4 ⁇ 4 ⁇ 16 cm). Bending specimen test result) is 20-80 N / mm 2 , tensile strength at which initial cracking occurs (split test result with ⁇ 10 ⁇ 20 cm cylindrical specimen) is 5-20 N / mm 2 , fracture energy for bending tension Has a mechanical property such that is 5 to 150 N / mm.
- the cement-based matrix has a very low water-cement ratio of 20-26%, and the close-packing technology is applied to the mixing of admixtures and aggregate particles other than cement. It becomes a reactant and becomes a material that maintains durability on the order of 100 years.
- the close-packing technique is a technique for obtaining the particle size distribution and the mixing volume (weight) ratio of each material so that the material mixed in the cement-based matrix has the maximum density.
- this is a technique for packing a material so as to obtain the maximum density. For example, by blending admixtures such as silica fume and blast furnace slag fine powder having a particle size smaller than that of cement particles, these fine particles are packed in the gaps between the cement particles, and the density increases.
- the durability is greatly improved.
- the salinity diffusion coefficient is 1.0 ⁇ 10 ⁇ 3 ⁇ 5.0 ⁇ 10 ⁇ 3 cm 2 / year
- the hydraulic conductivity is 2 ⁇ 10 ⁇ 17 ⁇ 8 ⁇ 10 -17 cm / sec.
- no decrease in the relative dynamic elastic modulus is observed even after 500 or more freeze-thaw cycles in the freeze-thaw test (JIS A 1148 underwater freeze-thaw test method).
- the resistance to neutralization is such that the neutralization depth after 500 years is 2 mm or less and does not require verification for neutralization.
- the cement matrix mixed by close-packing is expected to have a filler effect and a bearing effect by mixing an admixture with a particle size smaller than cement particles and by mixing the aggregate of aggregate particles 2 with adjusted particle size.
- the fluidity of the cementitious matrix is greatly increased.
- a high-performance water reducing agent or the like is applied as an admixture, self-fillability can be realized even with a small water cement ratio (W / C ratio).
- W / C ratio water cement ratio
- Factors affecting the tensile properties of the ultra-high-strength fiber reinforced concrete of the present embodiment or Example 1 include (1) cracking strength of the cement matrix, and (2) tensile strength (adhesion strength) of the cement matrix. (3) Tensile rigidity of fibers mixed for reinforcement including uneven fibers 1, 1A-1E, (4) Tensile strength of the fibers, (5) Adhesive strength between the fibers and the cementitious matrix, etc. .
- (1) to (4) are directly influenced by the characteristics of the cementitious matrix material and the fiber material, but the “adhesion strength between the fiber and the cementitious matrix” in (5) The combination of these materials is considered to have an effect, leading to the present invention.
- adhesion resistance experiment conducted to prove the performance of the ultra-high-strength fiber-reinforced concrete according to an embodiment of the present invention will be described.
- This specimen 3 is a rectangular parallelepiped of 12 cm ⁇ 12 cm ⁇ 2 cm, and a cylindrical portion 3 a of ⁇ 20 mm is provided at the bottom so that the thickness of the central portion of the rectangular parallelepiped is 6 mm, and the uneven fiber 1 is vertically embedded in the center. Created.
- the cement-based matrix specimen 3 in which the concavo-convex fibers 1 are embedded is thermally cured in a predetermined temperature environment and time, both ends of the specimen 3 are fixed to a loading tester (Instron tester is used in this experiment). It fixed to the tools 35 and 35, and it pulled out and loaded with respect to the uneven fiber 1 which protruded from the upper part of the test body 3.
- FIG. Therefore, the adhesion length of the uneven fiber 1 is 6 mm (the thickness of the central portion of the specimen 3 above the cylindrical portion 3a) in all the experimental examples described below.
- a measurement hole 36 is provided immediately below the cylindrical portion 3 a, and the lower end of the concavo-convex fiber 1 hanging down therein is used as a reflector 32 as a target. Attached. And the laser displacement meter 33 was installed just under the reflecting plate 32, and the displacement amount of the reflecting plate 32 which irradiates a laser was measured. Simultaneously with the measurement of the pull-out amount of the uneven fiber 1, the pull-out load of the uneven fiber 1 was also measured.
- the pulling speed of the upper end of the concavo-convex fiber 1 by an Instron testing machine was 1.0 mm / min. Further, since it is difficult to hold the uneven fiber 1 directly with the steel air chuck 34 when pulling up the tip of the uneven fiber 1, the periphery of the upper end of the uneven fiber 1 is reinforced with an epoxy resin and held. A portion 31 was formed, and the gripping portion 31 was sandwiched between air chucks 34 to apply a pulling load. [Specifications of each example] Table 1 shows specifications such as characteristics of the cementitious matrix used in the adhesion resistance experiment.
- the strength characteristics of the cementitious matrix shown in Table 1 are those in a state where 100% strength is exhibited by heat curing at 90 ° C. for 30 hours. That is, after heat curing, there is no tendency to increase in strength, and shrinkage due to drying shrinkage does not occur.
- the compressive strength shown in Table 1 is the compressive strength of only a cement-based matrix that does not mix fibers using a cylindrical specimen of ⁇ 5 ⁇ 10 cm.
- the bending strength is a bending strength obtained by a bending test (JIS A 1106) using a 4 ⁇ 4 ⁇ 16 cm square column specimen made of a cement-based matrix in which fibers are not mixed. This bending strength shows a strong positive correlation with the tensile strength of the cementitious matrix.
- Table 2 shows specifications such as the characteristics of the fibers used in the adhesion resistance experiment.
- the fibers used in the experiment are polypropylene fibers (PP fibers) and polyvinyl alcohol fibers (PVA fibers).
- PP fibers polypropylene fibers
- PVA fibers polyvinyl alcohol fibers
- the tensile strength of the fiber can be obtained from the product of the cross-sectional area of the fiber and the tensile strength of the fiber.
- Comparative Examples f-1 and f-2 are comparative examples when there is no unevenness, and therefore, when FIGS. 1 and 3 are used as reference diagrams, they are referred to as having no recesses 11 and 11A.
- Table 3 shows combinations of the cementitious matrix shown in Table 1 and the fibers shown in Table 2.
- Examples-1 to 3 are included in the fiber-reinforced cementitious mixed material of one embodiment of the present invention, and are comparative examples.
- -1 to Comparative Example-6 are comparative examples for confirming the effect of one embodiment of the present invention.
- Results of adhesion resistance experiment 9 and 10 show the results of the adhesion resistance experiment using the combinations shown in Table 3.
- FIG. 9 shows the result of comparing Example-1 to Example-3 with Comparative Example-1 to Comparative Example-3.
- the graph shown in FIG. 9 is a graph showing the relationship between the adhesion stress shown on the vertical axis and the fiber pull-out amount shown on the horizontal axis.
- Example-1, Example-2, Example-3 the adhesion stresses of the examples (Example-1, Example-2, Example-3) are the same as in any of the Comparative Examples (Comparative Example-1, Comparative Example-2, Comparative Example-3). It can be seen that the adhesion stress is clearly higher than that.
- Example-1 and Example-2 the type of cementitious matrix is different, but the uneven fibers 1 to be mixed are of the same shape and the same material.
- Example-1 and Example-3 the type of cementitious matrix is the same, but the concavo-convex fibers 1 to be mixed have different shapes (the materials are the same).
- the example can generate a larger adhesion stress than the comparative example because the aggregated particles having an appropriate particle size contained in an appropriate amount in the cementitious matrix are provided on the surface of the uneven fiber 1. It is considered that the result is that the adhesion characteristics are improved by meshing with the moderate uneven shape (the concave portion 11 and the convex portion 12), and the mechanical adhesion (mechanical bond) is excellent. Even when the pull-out amount further increases, a resistance force due to mechanical meshing is newly generated between the unevenness imparted to the fiber surface and the aggregate particles in the cementitious matrix, and a sustainable adhesive force (sustainable) This is thought to be the result of the continuous bond).
- Comparative Example-1 and Comparative Example-2 are the same type of cementitious matrix as Example-1 or Example-2, but the fibers to be mixed are PP fibers of the same material as each Example. However, there is no uneven shape on the fiber surface of the comparative example.
- the adhesion stress of Comparative Example-1 and Comparative Example-2 shown in FIG. 9 is considerably smaller than the adhesion stress of Example-1 and Example-2.
- the reason for this is that even if an appropriate amount of aggregate particles having an appropriate particle size is mixed in the cementitious matrix, if the surface shape of the PP fiber is flat (smooth surface), the mechanical adhesive force (mechanical bond) is effective. It can be expected that only the adhesion stress due to the adhesion strength and frictional resistance of the cementitious matrix itself can be expected.
- Comparative Example-3 shows a behavior that fluctuates as the pull-out amount increases, and is similar to Examples (Example-1, Example-2, Example-3).
- Comparative Example-3 applies PP fiber having the uneven shape of Example f-2 as the fiber to be mixed, but the cementitious matrix is Comparative Example m-1, so that the blended aggregate The average particle diameter of the particles is outside the numerical limit range of one embodiment of the present invention.
- Comparative Example-3 like this shows a lower adhesion stress than the Examples (Example-1, Example-2, Example-3).
- Comparative Example-3 uses a fiber having a concavo-convex shape on the fiber surface
- mechanical adhesive strength can be expected from Comparative Example-1 and Comparative Example-2. Since the average particle size of the aggregate particles contained in the cement matrix is small, it becomes difficult to strongly mesh the aggregate particles of the cement matrix and the uneven shape of the fiber surface, and the desired mechanical adhesion ( It is thought that the mechanical bond could not be obtained.
- Example-3 and Comparative Example-3 the same type of PP fiber having the concavo-convex shape of Example f-2 is applied as the fiber to be mixed, but the cementitious matrix of Example-3 is an example.
- the cementitious matrix of Comparative Example-3 is Comparative Example m-1, and the average particle diameter of the blended aggregate particles is outside the numerical limit range of one embodiment of the present invention. ing. Therefore, in Comparative Example-3, it was difficult to strongly mesh the aggregate particles of the cementitious matrix and the uneven shape of the fiber surface, and as a result, the adhesion stress was lower than that of Example-3.
- the graph shown in FIG. 10 shows a comparison between the examples (Example-1, Example-2, Example-3) and the comparative examples (Comparative Example-4, Comparative Example-5, Comparative Example-6).
- the fibers of the comparative examples are all PVA fibers that are not provided with an uneven shape. Therefore, as can be seen from the results of the comparative example, once the adhesion between the cementitious matrix and the fibers is broken, the adhesion stress rapidly decreases with an increase in the amount of pull-out.
- the cement matrix was Example m-1 and Example m-2, and the initial adhesion stress was larger than that in Example. This is presumably because the hydrophilicity of the PVA fibers worked and a chemical bond with the cementitious matrix acted.
- the ultra-high strength fiber reinforced concrete of the present embodiment or Example 1 has improved adhesion strength due to the combination of the cement-based matrix and the concavo-convex shape of the fiber, and the concavo-convex fiber 1 and the cement-based matrix. It was confirmed that even when the initial adhesion with the sag was once reduced and the concavo-convex fiber 1 slipped out of the cementitious matrix, the adhesion stress was maintained without significantly decreasing.
- the ultra high strength fiber reinforced concrete of the present embodiment or example 1 shows high tensile strength and high toughness (stickiness strength) in comparison with the example and the comparative example.
- the bending toughness experiment was carried out according to the Japan Society of Civil Engineers standard "Bending strength and bending toughness test method of steel fiber reinforced concrete" (JSCE-G 552-2010). Specifically, this is an experimental method in which a 10 ⁇ 10 ⁇ 40 cm square column specimen is loaded with a trisection load and the deflection of the center point and the load are measured. Further, the bending stress f b was determined from the load Q by the following formula.
- f b QL / bh 2
- Q is the loaded load (N)
- the load load speed was adjusted so that the rate of increase in bending stress was 0.06 ⁇ 0.04 N / mm 2 per second.
- the flexural toughness coefficient was determined according to the Japan Society of Civil Engineers' standard "Bending strength and bending toughness test method for steel fiber reinforced concrete" (JSCE-G 552-2010).
- the strength characteristics of the cementitious matrix shown in Table 4 are the results obtained by conducting experiments on specimens manufactured under the same curing conditions.
- the compressive strength is a compressive strength obtained by a compressive strength test (JIS A 1108) using a cylindrical specimen of ⁇ 10 ⁇ 20 cm manufactured using a cement-based matrix in which fibers are not mixed.
- the bending strength is a bending strength obtained by a bending test (JIS A 1106) using a 4 ⁇ 4 ⁇ 16 cm square column specimen made of a cement-based matrix in which fibers are not mixed. This bending strength shows a strong positive correlation with the tensile strength and adhesion strength of the cementitious matrix.
- Table 5 shows specifications such as the characteristics of the fibers used in the bending toughness experiment.
- Example F-4 and Example F-5 are blends in which two types of fibers, ie, the uneven fiber 1 and a fiber without unevenness (here, steel fiber) are mixed.
- Table 6 shows the bending toughness test performed on specimens manufactured under the same curing conditions by placing ultrahigh-strength fiber reinforced concrete combining the cementitious matrix of Table 4 and the fibers of Table 5. The results were shown.
- FIG. 11 to FIG. 13 plot the results of the bending toughness experiment in a graph in which the vertical axis indicates the bending stress and the horizontal axis indicates the deflection of the center point. The following can be mentioned as a common behavior of the bending toughness curve drawn by the result of this bending toughness experiment.
- the bending toughness curve has a behavior in which the bending stress increases linearly with respect to the deflection of the center point at the initial stage of the loaded load, and then the bending stress rapidly decreases.
- a zone exhibiting this behavior is referred to as a “first zone”.
- the first peak is referred to as “first peak”.
- the bending stress tends to increase again.
- the magnitude of the increase may or may not be greater than the first first peak.
- the increased bending stress tends to gradually decrease again as the deflection at the center point increases.
- a zone exhibiting this behavior is referred to as a “second zone”.
- the second peak is referred to as “second peak”.
- the specimen In the first zone, in the behavior process in which the deflection of the center point increases linearly with the initial load increase, the specimen is not cracked and is considered to be elastic. In addition, the bending stress decreases at the first peak, and this is considered to be because the bending stress sharply decreases because bending cracks occurred at the lower end near the center of the specimen.
- the bending stress at the first peak is considered to have a positive correlation with the crack initiation strength of the cement matrix obtained by the split test.
- the bending stress sharply decreases after the first peak because bending cracks are generated at the lower end of the specimen, and thereafter, a behavior in which the bending stress increases again is observed. This is a behavior due to the tensile force being applied to the fibers where the crack surfaces where the cracks are generated are cross-linked.
- the degree of decrease in bending stress after the first peak tends to decrease as the rigidity of the fiber increases, the amount of mixed fibers increases, and the initial adhesion resistance between the cementitious matrix and the fibers increases. Show.
- the bending stress tends to increase again.
- the increased second peak may or may not be larger than the first peak.
- the reason why the bending stress is increased is that the fibers cross-linked with each other bear the tensile force.
- This tensile strength is the maximum tensile stress when a pure tensile force is applied to ultrahigh strength fiber reinforced concrete.
- Two methods are used as a method for obtaining the tensile strength of the ultra-high-strength fiber reinforced concrete material by a test.
- One is a method of obtaining directly from the peak of tensile strength by a direct tensile loading test.
- the test control method of the direct tensile loading test itself is difficult, and there is a problem that the test results vary.
- the other is to perform a bending load test, obtain the relationship between tensile stress and crack width by inverse analysis from the load-notch crack width curve or load-deflection curve obtained by the test, and calculate the tensile strength from it.
- a notch may or may not be put in the center of the bending specimen.
- this method has an advantage that the bending test method is easy and there are few variations due to the test, but time and cost are required for the reverse analysis.
- the area of the portion surrounded by the bending toughness curve indicates the fracture energy of the material, and it can be said that the larger the area, the higher the toughness (or stickiness).
- FIG. 11 is a comparison under the same conditions in which the fiber mixing ratio is all 3.0%, and is a comparison result excluding the influence factor that the bending strength increases as the fiber mixing amount (mixing ratio) increases.
- Example-T1 and Example-T2 consist of the uneven fiber 1 of Example F-1 shown in Table 5 and the cementitious matrix of Example M-2 and Example M-5 shown in Table 4. It is a combination.
- the fibers of Comparative Example-T7 and Comparative Example-T8 are all fibers of Comparative Example F-1 shown in Table 5, and no irregularities are formed on the fiber surface.
- the material of the fiber is PVA fiber rich in hydrophilicity, it is considered that the adhesive force with the cementitious matrix is high.
- Example-T1 and Example-T2 show higher bending stress and higher toughness than Comparative Example-T1, Comparative Example-T7 and Comparative Example-T8. Yes.
- Example-T1 and Example-T2 show clearly higher values than the other three comparative examples, and any second peak is much higher than the first peak. The value is shown. This indicates that the two examples have high tensile strength.
- Example-T1 and Example-T2 show that the bending stress gradually decreases after the second peak, and the bending resistance does not decrease until large deformation, that is, shows high toughness performance. Recognize.
- Table 6 described above shows the tensile strength estimated from the second peak in each experiment and the fracture energy obtained from the area of the bending toughness curve. As is apparent from the numerical values shown in Table 6, it can be seen that the tensile strength of the example is 1.6 to 2.0 times that of the comparative example, and the fracture energy is 2.5 to 3.6 times.
- the combination of materials of Comparative Example T7 in the bending toughness experiment is similar to the combination of materials of Comparative Example 6 of the adhesion resistance experiment.
- the second peak is smaller than the first peak, and the bending stress rapidly decreases after the second peak.
- Comparative Example-6 of the adhesion resistance experiment the initial adhesion stress is low, and the fiber comes out when the pull-out amount is about 0.5 mm. This is consistent with the fact that Comparative Example-T7 rapidly decreases the bending stress after the second peak in the bending toughness experiment.
- Example F-4 the results of Example F-4 in Table 5 in which the fiber surface is a hybrid mixed fiber of PP fiber having a concavo-convex shape and steel fiber having no concavo-convex shape.
- the fiber shown in Example F-5 was used.
- the mixing rate of the entire fiber is 2.8%
- the breakdown of the amount of fibers is that the PP fiber which is the uneven fiber 1 has a mixing rate of 2.7. %
- Steel fiber without irregularities on the fiber surface is 0.1%.
- the second peak in each example is larger than that in the comparative example, and the area of the bending toughness curve is also large.
- the 2nd peak of an Example is larger than a 1st peak
- the 2nd peak is smaller than a 1st peak in a comparative example.
- Table 6 the numerical values of the tensile strength and the fracture energy are also larger in the example than in the comparative example.
- Example-T7 and Comparative Example-T5 show that the fiber mixing rate is 2.8%, and one type of fiber is used for each.
- the same fiber as Example F-2 shown in Table 5 is mixed.
- Example-T7 and Comparative Example-T5 draw different bending toughness curves even though the same type of uneven fiber 1 is used. That is, in Example-T7, the second peak was larger than the first peak, but in Comparative Example-T5, the first peak was large, but the second peak was small.
- Example-T7 has clearly higher tensile strength and higher toughness than Comparative Example-T5 and Comparative Example-T6.
- the ultra-high-strength fiber reinforced concrete of the present embodiment has not been obtained so far due to the combination of the cement-based matrix aggregate particles and the uneven shape of the surface of the uneven fiber 1. It was found that such a high tensile strength and high toughness can be achieved.
- the feature of the ultra-high-strength fiber reinforced concrete according to the present embodiment is not limited to a specific material for any material of the cement-based matrix and the concavo-convex fiber 1, but the average of aggregate particles is not limited to the cement-based matrix.
- the particle size and the weight ratio represented by aggregate / (cement + admixture) are specified, and the uneven fiber 1 is not specified the material but only the uneven shape of the surface.
- the reason why the tensile strength of the ultra-high-strength fiber reinforced concrete is increased is that the adhesion resistance stress between the uneven fiber 1 and the cementitious matrix is greatly improved. Further, the toughness is increased because the adhesion resistance stress between the concavo-convex fiber 1 and the cementitious matrix does not decrease even if the fiber pull-out increases, It can be said that these results can be obtained by combining the combination of aggregate particles contained in an appropriate cementitious matrix.
- the organic fiber is the uneven fiber 1
- the present invention is not limited to this, and an inorganic fiber such as a steel fiber can also be an uneven fiber.
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Abstract
Description
そして、凹凸繊維1Dの凹凸の凹部11Dのピッチpは、図6に示すように、凹部11D,11Dの谷間の長さ方向の距離になる。また、凹部11D,11D間には、平面視二等辺三角形状の凸部12Dが成形される。
[付着抵抗実験]
本実施の形態又は実施例1の超高強度繊維補強コンクリートの引張特性に影響を与える要因としては、(1)セメント系マトリックスのひび割れ発生強度、(2)セメント系マトリックスの引張強度(付着強度)、(3)凹凸繊維1,1A-1Eを含む補強用に混入する繊維の引張剛性、(4)同繊維の引張強度、(5)同繊維とセメント系マトリックスとの付着強度、などが考えられる。
[付着抵抗実験の実験方法]
セメント系マトリックスと凹凸繊維1,1A-1E(以下、「1」の符号で代表して説明する。)との付着抵抗を調べるために、図8に示すように対象とする凹凸繊維1を埋め込んだセメント系マトリックスの供試体3を作成して、繊維の引抜き載荷実験を行った。
[実施例の各諸元について]
表1に、付着抵抗実験に使用したセメント系マトリックスの特性などの諸元を示す。
この表1に示したセメント系マトリックスの強度特性は、90℃で30時間の熱養生を行い、強度を100%発現させた状態のものである。すなわち熱養生後は、強度増加の傾向はなく、また乾燥収縮による収縮も発生しない。
この表2に示したように、実験に使用した繊維の材質は、ポリプロピレン繊維(PP繊維)とポリビニールアルコール繊維(PVA繊維)である。また、繊維の断面積と繊維の引張強度との積により、繊維の引張耐力を求めることができる。また、繊維の周長と付着長(=6mm)との積により付着面積を求めることができる。なお、比較例f-1,f-2は、凹凸が無い場合の比較例であるため、図1,3を参考図とする場合は凹部11,11Aが無いものとして参照する。
この表3に示したセメント系マトリックスと繊維との組み合せにおいて、実施例-1から実施例-3が、本発明の一実施形態の繊維補強セメント系混合材料に含まれるものであって、比較例-1から比較例-6は、本発明の一実施形態の効果を確認するための比較例である。
[付着抵抗実験の結果]
図9及び図10に、表3に示した組み合せによる付着抵抗実験の結果を示す。ここで、図9には、実施例-1から実施例-3を、比較例-1から比較例-3までと比較した結果を示す。
[曲げタフネス実験]
上述した付着抵抗実験により、本実施の形態又は実施例1の超高強度繊維補強コンクリートは、セメント系マトリックスと繊維の凹凸形状との組み合せにより付着強度が向上し、さらに凹凸繊維1とセメント系マトリックスとの初期付着が一旦低下して凹凸繊維1がセメント系マトリックスから抜け出した場合でも、付着応力は大幅に低下することなく保持されることが確認できた。
[曲げタフネス実験の実験方法]
曲げタフネス実験は、土木学会規準の「鋼繊維補強コンクリートの曲げ強度および曲げタフネス試験方法」(JSCE-G 552-2010)に従って実施した。具体的には、10×10×40cmの四角柱供試体に対して3等分点荷重で載荷をおこない、中央点のたわみと載荷荷重を計測する実験方法である。また、載荷荷重Qから曲げ応力fbを以下の式により求めた。
ここで、fbは曲げ応力(N/mm2)、Qは載荷荷重(N)、Lは供試体の支点間距離(スパン)(=300 mm)、bは供試体の幅(=100 mm)、hは供試体の高さ(=100 mm)を示す。また、載荷荷重の速度は、曲げ応力の増加率が毎秒0.06±0.04 N/mm2になるように調整した。
[実施例の各諸元について]
表4に、曲げタフネス実験に使用したセメント系マトリックスの特性などの諸元を示す。
この表4に示したセメント系マトリックスの強度特性は、すべて同じ養生条件により製作された供試体に対して実験をおこなって求めた結果である。ここで、圧縮強度は、繊維を混入させないセメント系マトリックスにより製作したφ10×20cmの円柱供試体による圧縮強度試験(JIS A 1108)により求められた圧縮強度である。
この表5には、凹凸形状のパラメータの他に、繊維の材質、繊維の容積混入率(混入率)、繊維の引張強度、弾性係数、繊維一本あたりの断面積、繊維の長さなど、超高強度繊維補強コンクリートの曲げタフネス実験の結果に影響を与える繊維の物性値を示した。ここで、実施例F-4と実施例F-5は、凹凸繊維1と凹凸の無い繊維(ここでは鋼繊維)との2種類の繊維を混合した配合である。
[曲げタフネス曲線について]
図11-図13は、曲げタフネス実験の結果を、縦軸を曲げ応力、横軸を中央点のたわみとしたグラフにプロットしたものである。この曲げタフネス実験の結果によって描かれる曲げタフネス曲線の共通した挙動として、以下のことが言及できる。
[曲げタフネス実験の結果]
図11は、繊維の混入率がすべて3.0%となる同一条件下での比較であり、繊維混入量(混入率)が多いほど、曲げ強度が高くなるという影響要因を除いた比較結果である。
本出願は、2011年2月18日に日本国特許庁に出願された特願2011-33090に基づいて優先権を主張し、その全ての開示は完全に本明細書で参照により組み込まれる。
11 凹部
11A-11E 凹部
13A,13B 凹部
12 凸部
12A-12E 凸部
2 骨材粒子
h 深さ
H 最小断面径
p ピッチ
B 最大断面径
C セメント重量
A 混和材重量
S 骨材粒子重量
WR 重量比率
φA 骨材粒子の平均粒径
Claims (5)
- セメントと、混和材と、水と、混和剤と、前記セメントと前記混和材の合計重量に対する重量比率で50-95%の割合で含まれる骨材粒子と、繊維とを含有する繊維補強セメント系混合材料であって、
前記繊維の少なくとも一部を表面に凹凸が形成された凹凸繊維にするとともに、その凹凸繊維の凹凸の凹部の深さhを最小断面径Hに対する比率(h/H)が0.05-0.8となるように成形したことを特徴とする繊維補強セメント系混合材料。 - 前記骨材粒子の平均粒径を0.2-0.8mmとしたことを特徴とする請求項1に記載の繊維補強セメント系混合材料。
- 前記凹凸繊維の長さ方向における凹凸の凹部のピッチpを最大断面径Bに対する比率(p/B)が0.3-10.0となるように成形したことを特徴とする請求項1又は2に記載の繊維補強セメント系混合材料。
- 前記繊維の長さLiは、1mm以上、かつ平均断面径dに対する比率(Li/d)が10-500であり、前記繊維の合計容積量が全容積の0.7-8%であることを特徴とする請求項1乃至3のいずれか一項に記載の繊維補強セメント系混合材料。
- 前記凹凸繊維の平均長さLmは、前記骨材粒子の最大粒径Dmaxに対する比率(Lm/Dmax)が2-20であることを特徴とする請求項1乃至4のいずれか一項に記載の繊維補強セメント系混合材料。
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