JP2002338319A - Short fiber reinforced cement type extrusion forming material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tough fiber reinforced cement type extrusion material which exhibits a fracture mechanism due to multiple cracking. SOLUTION: This polypropylene short fiber reinforced cement type extrusion forming material generates multiple cracking and is fractured by tension. This cement type extrusion forming material is made by compounding polypropylene short fiber of fiber length 3-15 mm, fiber diameter 5-20 μm and aspect ratio 150-1000 to hydraulic cement matrix by 3-10% in volume ratio of incorporation. Further, in this cement type extrusion forming material, the matrix is made by compounding silica raw material of 40-100 wt.%, pulp of 1-40 wt.% and water soluble cellulose of 0.1-10 wt.% with respect to the hydraulic cement of 100 wt.%. In this cement type extrusion forming material, the matrix, furthermore, contains mineral fiber of 1-40 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene short fiber reinforced cement-based extruded material. For more information,
The present invention relates to a high-toughness polypropylene short fiber reinforced cement-based extruded material which generates multiple cracks and causes tensile fracture.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to improve the performance of hardened cement by mixing asbestos and synthetic fibers instead of asbestos. However, the conventional improvement by these fiber reinforcements has been directed to improving the breaking strength and the elastic modulus within the proportional deformation of the hardened cementitious material, which is a brittle material. If there is no idea to improve the physical properties of the body,
The means were not known.

Recently, when the first cracks occurred in cement,
Short fibers incorporated in cement as a reinforcing material create a bridge in the crack and share the stress, so that it does not immediately break even after the first crack occurs, dispersing the stress by generating multiple cracks Techniques for imparting high toughness by applying large deformation and breaking stress are being studied. This technology adjusts the adhesion between the matrix and the reinforcing fibers to prevent the first fiber from cracking at the same time as the first crack in the cement, thereby preventing the first fibers from cracking. Even after that, the stress is shared by the fibers to prevent the cured body from breaking immediately.

As the reinforcing fibers used for this purpose, only high-strength high-elasticity polyethylene fibers and vinylon fibers have been found. The reason is that vinylon has a sufficiently high modulus and strength and has a moderate adhesion to the cement matrix. A short fiber reinforced cement composite material having improved toughness using a polyolefin short fiber having a low affinity for cement such as polypropylene fiber and a low tensile modulus as a reinforcing material has not been obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reinforcing fiber suitable for a high-toughness cementitious composite material because the tensile modulus is not particularly high and the affinity for cement is low. An object of the present invention is to provide a fiber-reinforced cement-based extruded material having excellent toughness by using a polypropylene short fiber that has not come as a reinforcing material. In particular, it is an object of the present invention to provide a high-toughness fiber-reinforced cementitious extruded material exhibiting a fracture mechanism that generates multiple cracks.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a polypropylene short fiber reinforced cementitious extruded material which forms multiple cracks and breaks in tension. The present invention also relates to a cement-based extruded material reinforced with short polypropylene fibers such that the interfacial shear strength of the fibers at the interface between the hydraulic cement and the reinforcing fibers is from 0.2 MPa to 1.4 MPa.
Specifically, the present invention relates to a hydraulic cement matrix in which polypropylene short fibers having a fiber length of 3 to 15 mm, a fiber diameter of 5 to 20 μm, and an aspect ratio of 150 to 1000 are mixed at a volume ratio of 3 to 10% in a molded product after curing. The present invention relates to the cement-based extruded material according to any one of the above, which is blended so as to be: More specifically, the present invention relates to a hydraulic cement matrix comprising 100 to 100 parts by weight of hydraulic cement, 40 to 100 parts by weight of a siliceous raw material,
The present invention relates to the above-mentioned cement-based extruded material, which comprises 40 parts by weight and 0.1 to 10 parts by weight of water-soluble cellulose. Still further, in the present invention, the hydraulic cement matrix may contain 1 to 4 mineral fibers per 100 parts by weight of hydraulic cement.
The present invention relates to the above-mentioned cement-based extruded material further containing 0 parts by weight. More specifically, the present invention relates to a hydraulic cement 1
A matrix comprising 00 parts by weight, 40 to 100 parts by weight of a siliceous raw material, 1 to 40 parts by weight of pulp, 1 to 40 parts by weight of mineral fibers, 0.1 to 10 parts by weight of water-soluble cellulose, and 40 to 90 parts by weight of water. Ingredients, fiber length 3-15mm,
Extrusion molding of a hydraulic cement composition in which polypropylene short fibers having a fiber diameter of 5 to 20 μm and an aspect ratio of 150 to 1000 are blended so as to have a volumetric mixing ratio of 3 to 10% in the molded article after curing, followed by curing. The present invention relates to a cement-based extruded material according to any one of the above.

In the present invention, “multiple cracks” means the following. At the stage where the first crack is formed in the hardened cement body by the application of the tensile stress, the stress is concentrated on the crack portion, and the normal hardened cement body is directly broken. That is, fracture occurs at the stage of elastic deformation where the stress-strain curve becomes a straight line. Therefore, it has low energy absorption capacity and exhibits brittle fracture. On the other hand, even after the first crack is formed, there is a phenomenon that the whole material is not immediately broken, and a plurality of cracks are generated following the first crack. This is called a multiple crack.
When multiple cracks are generated, the stress is dispersed, so that even after the initial crack generation, the structure does not break down to a large strain withstanding an increased load, and exhibits high energy absorption capacity and high toughness.

In the present invention, the interfacial shear strength of a fiber means a strength at which a fiber existing as a reinforcing material in a cement matrix breaks at an interface with the cement matrix in a shearing manner, and the fiber parameters (V _f , d) _f , _Lf )
Via the following equation (1)

(Equation 1) By a value to be associated with fracture energy G _b required for fibers pulled out from the cement matrix of the extrudate. Where τ is the interfacial shear strength of the fiber, V _f
Volume mixing ratio of the fibers, is d _f fiber diameter, the L _f is the fiber length. A large interfacial shear strength τ means that the affinity between the cement matrix and the fiber is high.

In the present invention, the "aspect ratio" of the polypropylene short fiber is a value obtained by dividing the fiber length by the diameter of an equivalent circle having the same area as the area of the fiber cross-sectional area.

In the present invention, the terms "cement-based extruded material" and "hydraulic cement matrix" mean hardened materials, while "hydraulic cement composition" refers to a mixture of various raw materials. Means an uncured state in which water is mixed with the obtained cement composition.

The "volume mixing ratio" of polypropylene short fibers with respect to the hydraulic cement matrix as defined in the present invention means that the cured cement is cut in a direction perpendicular to the extrusion direction, and the cut surface is measured with a scanning electron microscope. A reflected electron image was observed at an acceleration voltage of 25 kV. The fiber mixing ratio _Vf in the cured cement body was determined as a value obtained by dividing the total cross-sectional area of the polypropylene fibers on the observation surface in the visual field of the microscope by the area of the visual field of the electron microscope. As the fiber mixing ratio _Vf , an average value of values measured for three different visual fields in a cut surface of the test piece was adopted.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a polypropylene short fiber reinforced cementitious extrusion material which is reinforced with polypropylene short fiber reinforcement and generates multiple cracks and breaks in tension. The present invention also provides a cement-based extruded material reinforced with short polypropylene fibers such that the interfacial shear strength of the fibers at the interface between the hydraulic cement and the reinforcing fibers is from 0.2 MPa to 1.4 MPa. . When the interfacial shear strength τ is less than 0.2 MPa, the fiber is easily pulled out even if cross-linked to a crack. Therefore, a sufficient reinforcing effect cannot be obtained. Since the frictional force applied to the interface exceeds the tensile breaking strength of the fiber, the fiber breaks and does not crosslink into cracks, and the fiber reinforcing effect cannot be obtained.

The extruded cementitious material of the present invention having the above characteristics has a fiber length of 3 to 15 mm and a fiber diameter of 5 to 20 μm.
m, polypropylene short fibers having an aspect ratio of 150 to 1000 can be produced by blending with a hydraulic cement matrix at a volume mixing ratio of 3 to 10%. The polypropylene short fiber used in the present invention is not particularly limited as long as it corresponds to the above fiber length, fiber diameter and aspect ratio, and a polypropylene fiber as a cement reinforcing fiber currently used can be used. For example, a polypropylene fiber as described in Japanese Patent No. 2521101 can be exemplified.

If the fiber length is shorter, the fiber diameter is larger, or the aspect ratio is smaller than the requirements required for the polypropylene short fiber of the present invention, cracks are initially formed under tensile stress. When the fibers are cross-linked, the fibers cannot bear the stress even if they are cross-linked, and are quickly pulled out and broken before generating multiple cracks. On the other hand, if the fiber length is longer, the fiber diameter is smaller, or the aspect ratio is larger than the requirements required for the polypropylene short fiber of the present invention, the fiber is pulled out under a tensile stress. Prior to this, multiple cracks do not occur because the fibers themselves break.

[0015] The volume mixing ratio of polypropylene short fiber is 3%
If it is smaller, it cannot support the stress concentrated in the crack when it is cracked, cannot exert a crosslinking effect, and has a 10%
If it is larger, the contact portion between the fibers increases, and the integration with the cement is hindered, so that a sufficient reinforcing effect cannot be obtained.

In the present invention, the term "hydraulic cement" refers to a cement capable of forming a hardened body by reaction with water or a hardened body obtained by hardening such a cement.
The hydraulic cement used in the present invention is not particularly limited, and includes all kinds of Portland cement, blast furnace cement, fly ash cement, alumina cement, silica cement, magnesia cement, sulfate cement and the like.

The siliceous raw material that can be used for the cement-based extrusion molding material of the present invention includes silica powder, blast furnace slag, silica sand, fly ash, diatomaceous earth, silica fume,
Amorphous silica or the like can be used. Preferably,
From the point of improving the strength of the molded body and contributing to dimensional stability,
Silica powder and silica sand. As these siliceous raw materials, those having a specific surface area (according to the method described in JIS R5201) of preferably 3000 to 15000 cm ² / g are used. The siliceous raw material is blended in an amount of 40 to 100 parts by weight, preferably 50 to 80 parts by weight, based on 100 parts by weight of the hydraulic cement. If the amount of the siliceous raw material is less than 40 parts by weight, the strength of the molded body is reduced, and efflorescence tends to occur. If the amount is more than 100 parts by weight, the strength of the molded body is reduced. More preferably, it is 50 to 80 parts by weight.

The pulp blended in the present invention is preferably a natural pulp such as cotton pulp or wood pulp. It is not particularly limited as long as it is a natural pulp, and not only virgin pulp but also recycled pulp from waste paper can be used. In the case of wood pulp, either chemical pulp obtained by chemically removing lignin from wood tissue or mechanical pulp obtained by mechanically treating wood can be used. The pulp preferably has a fiber length of 0.05 to 10 mm. The pulp is blended at a ratio of 1 to 40 parts by weight, preferably 2 to 30 parts by weight, based on 100 parts by weight of the hydraulic cement. If the amount is less than 1 part by weight, the reinforcing effect cannot be exerted. If the amount is more than 40 parts by weight, dispersion becomes poor, and the surface smoothness of the molded article is deteriorated.

Examples of the water-soluble cellulose compounded in the present invention include alkyl cellulose such as methyl cellulose and ethyl cellulose, hydroxyalkyl cellulose such as hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose and hydroxyethyl cellulose, hydroxyalkyl alkyl cellulose, and carboxymethyl cellulose. And the like. The water-soluble cellulose imparts viscosity to the kneaded product and improves moldability when mixing and extruding the components of the extrusion composition. Water-soluble cellulose is 0.1 to 10 parts by weight based on 100 parts by weight of hydraulic cement,
Preferably, it is blended at a ratio of 2 to 7 parts by weight. If the amount is less than 0.1 part by weight, there is no plasticity and molding cannot be performed. On the other hand 10
When the amount is more than the weight part, the cost only increases, and no further improvement in the effect can be expected.

Examples of the mineral fibers blended in the present invention include sepiolite, wollastonite, talc, attapulgite, rock wool and the like. The mineral fibers are blended in a proportion of 1 to 40 parts by weight, preferably 3 to 25 parts by weight, based on 100 parts by weight of the hydraulic cement. 1
If it is less than 10 parts by weight, it does not contribute to fluidity, while if it is more than 40 parts by weight, the strength of the molded article is reduced.

The cement-based extruded molding material of the present invention may further contain, as necessary, additives other than the above, such as inorganic materials other than silica such as mica, alumina and calcium carbonate, lightweight aggregates such as pearlite, vinylon fiber, Other reinforcing fibers such as polyethylene fiber and carbon fiber, water reducing agent, surfactant,
Thickeners and the like may be added.

It is particularly preferred that the composite material of the present invention is formed by extrusion. By extrusion molding, a denser cured product is generally obtained, and the reinforcing fibers are more dominantly oriented in the extrusion direction, so that tensile stress in the extrusion direction or bending stress in the direction perpendicular to the extrusion direction is reduced. Reinforcement hardening by the cross-linking action of the fibers can be more effectively exerted.

Preferred examples of the hydraulic cement composition for producing the polypropylene short fiber reinforced cement-based extrusion molding material of the present invention by extrusion molding include 100 parts by weight of hydraulic cement, 40 to 100 parts by weight of siliceous raw material, A matrix component comprising 1 to 40 parts by weight of pulp, 1 to 40 parts by weight of mineral fibers, 0.1 to 10 parts by weight of water-soluble cellulose and 40 to 90 parts by weight of water has a fiber length of 3 to 15 m.
m, fiber diameter 5-20 μm, aspect ratio 150-100
No. 0 polypropylene short fiber is contained at a volume mixing ratio of 3 to 10% in the molded article after curing.

[0024]

EXAMPLES The present invention will be described below more specifically and in detail with reference to examples. Example 1 100 m parts of ordinary Portland cement, 6 m in length
m, fiber diameter 18 μm, specific gravity 0.91 and Young's modulus 3.7 GP
a, polypropylene short fiber having a tensile strength of 295 MPa 9.
0 parts by weight, silica powder (specific surface area: 4000 cm ² / g) 64
Then, 5 parts by weight of pulp (hardwood pulp), 5 parts by weight of sepiolite, and 6 parts by weight of water-soluble cellulose (manufactured by Shin-Etsu Chemical Co., Ltd.) were added and powder-mixed with a mixer for 3 minutes. While continuing powder mixing, 77 parts by weight of water (42% by weight of water) was added little by little and mixed for 2 minutes, then transferred to a kneader and kneaded for 3 minutes to knead the cement paste. The obtained cement paste was extruded from a cylindrical vacuum extruder through a mold. The discharge port size of the mold used was a rectangular shape having a width of 80 mm and a height of 15 mm. The extrudate discharged from the mold was received in a tray. The extruded body was wrapped with a plastic film together with the tray, and was steam-cured in a thermo-hygrostat. The steam curing was maintained at 70 ° C. for 5 hours under a condition of a humidity of 98%.

The tensile properties, bending properties, interfacial shear strength of the fibers and the volumetric mixing ratio of the polypropylene fibers of the obtained cured polypropylene short fiber reinforced cement (cement-based extruded material) were evaluated as follows. (1) Method of evaluating tensile properties A test specimen having a width of 40 mm, a length of 230 mm, and a thickness of 15 mm was cut out from a hardened cement body having a width of about 80 mm and a thickness of about 15 mm. The crosshead speed is 0.2 mm / min.
, And the displacement was measured using a differential transformer-type intergage extensometer with a 50 mm intergap distance. The chuck portion was reinforced by bonding an aluminum plate having a width of 40 mm, a length of 60 mm, and a thickness of 2 mm to the test piece with an epoxy resin. Based on the measured load P, the tensile stress σ was evaluated by the following equation (2): σ = P / bt (2) In the equation, b represents the width of the test piece and t represents the thickness of the test piece. FIG.
Shows the state of the tensile test.

(2) Evaluation Method of Bending Characteristics From a hardened cement material having a width of about 80 mm and a thickness of about 15 mm, a test specimen for a two-point simple bending test having a width of 40 mm, a length of 200 mm and a thickness of 15 mm was cut out. Loading point distance is 5
The measurement was performed at 0 mm, the distance between fulcrums was 150 mm, and the crosshead speed was 0.2 mm / min. Based on the measured load P, the bending stress σ _b was evaluated by the following equation (3): σ _b = PL / bt ² (3) where b is the width of the test piece and t is the thickness of the test piece. , L represent the distance between fulcrums. FIG. 2 shows the situation of the two-point loading simple bending test.

(3) Volumetric mixing ratio of polypropylene fiber
Measurement Cut the hardened cement in the direction perpendicular to the extrusion direction
Then, the cut surface was subjected to an acceleration voltage of 2 using a scanning electron microscope.
The reflected electron image was observed at 5 kV. Fiber in hardened cement
Fiber mixing rate V_fIs the protocol of the observation surface in the field of the microscope.
The total cross-sectional area of the pyrene fiber is calculated as the area of the field of view of the electron microscope.
It was calculated as the value divided by. Fiber mixing rate V _fOf the specimen
Average of the values measured for three different fields of view in the cut plane
The value was adopted.

(4) Measurement of the number of cracks generated The number of cracks generated by the tensile test was visually counted for the test piece after the tensile fracture. The number of cracks was represented by the average value of three specimens.

(5) Calculation of interfacial shear strength τ of polypropylene short fiber The fracture energy _Gb was determined from the stress-strain curve in the tensile test, and this was substituted into the above equation (1) to obtain a polypropylene short fiber. The interfacial shear strength τ of the fiber was calculated: FIG.
(A) shows the load (vertical axis) -displacement (horizontal axis) relationship at the time of fracture with multiple cracks of the test specimen in the tensile test.
BCD schematically shows a general load-displacement curve. In this figure, a straight line parallel to AB, which is a straight line portion indicating an elastic deformation portion, is drawn from the maximum load point C, and the intersection with the horizontal axis is A '. Calculating the enclosed area S in A'CDA 'from the figure, the equation _{G b = S / bt (4} ) ( wherein, b and t has the same meaning as in the formula (3))
_Gb can be calculated from the relationship FIG. 3B schematically shows a load-displacement relationship in the case of breaking with a single crack as a comparison. Flexural properties (maximum stress, peak deflection, number of cracks), tensile properties (maximum stress, peak strain, number of cracks, interfacial shear strength) and polypropylene measured for the cured polypropylene short fiber reinforced cement obtained in this example Table 1 shows the volume mixing ratio of the fibers.

[0030] Examples 2-5, Examples 2-5 and Comparative Examples 1 to 4 the mixing amount of Comparative Examples 1 to 4 Polypropylene staple fibers in the same manner except for changing as shown in Table 1 as in Example 1 A hardened cement body (cement-based extruded material) was prepared, and the tensile properties, bending properties, volume mixing ratio of polypropylene fibers, and the number of generated cracks were measured. Table 1 shows the measurement results. FIG. 4 shows the stress-strain curves of the tensile tests of Examples 1 and 2 and Comparative Example 2, and FIG. 5 shows the stress-strain curves of Comparative Example 1.

[0031]

[Table 1]

[0032]

The cement-based extruded material of the present invention in which polypropylene short fibers having a specific form are blended with a cement matrix in a specific range of a volume mixing ratio generates multiple cracks when tensile stress is applied. As a result, it is possible to exhibit high breaking energy.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a tensile test state of a hardened cement body.

FIG. 2 is an explanatory view showing a two-point loading simple bending test situation of a hardened cement body.

[Figure 3] bending load for calculating the fracture energy G _b - displacement schematic view: (a) a load in the case of breaking a multiple Crack - displacement schematic,
(B) Schematic diagram of load-displacement in the case of breaking with a single crack.

FIG. 4 is a view showing a relation between tensile stress and strain of the cement hardened bodies of Examples 1 and 2 and Comparative Example 2.

FIG. 5 is a diagram showing a relationship between tensile stress and strain of a cured cement body of Comparative Example 1.

[Explanation of symbols]

 1: Example 1 2: Example 2 3: Comparative example 14 4: Comparative example 2 11: Cement hardened body 12: Strain gauge 13: Aluminum plate of grasping part 14: Support point 15: Loading point.

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Claims (6)

[Claims] An extruded polypropylene short fiber reinforced cementitious material which generates multiple cracks and breaks in tension. 2. A cement-based extruded material reinforced with polypropylene short fibers such that the interfacial shear strength of the fibers at the interface between the hydraulic cement and the reinforcing fibers is from 0.2 MPa to 1.4 MPa. 3. A hydraulic cement matrix having a fiber length of 3 to 15 mm, a fiber diameter of 5 to 20 μm, and an aspect ratio of 1.
The cement-based extruded material according to claim 1 or 2, wherein 50 to 1000 polypropylene short fibers are blended so as to have a volumetric mixing ratio of 3 to 10% in the cured product. 4. A hydraulic cement matrix comprising 100 to 100 parts by weight of hydraulic cement and 40 to 1 of siliceous raw material.
The cement-based extruded material according to claim 3, wherein the cement-based extrusion molding material is mixed with 00 parts by weight, 1 to 40 parts by weight of pulp, and 0.1 to 10 parts by weight of water-soluble cellulose. 5. The cement-based extruded material according to claim 4, wherein the hydraulic cement matrix further contains 1 to 40 parts by weight of mineral fibers based on 100 parts by weight of hydraulic cement. 6. Hydraulic cement 100 parts by weight, siliceous raw material 40 to 100 parts by weight, pulp 1 to 40 parts by weight, mineral fiber 1 to 40 parts by weight, water-soluble cellulose 0.1 to 10 parts by weight and water 40 to 100 parts by weight. A matrix component comprising 90 parts by weight has a fiber length of 3 to 15 mm, a fiber diameter of 5 to 20 μm,
An extrusion molding of a hydraulic cement composition comprising polypropylene short fibers having an aspect ratio of 150 to 1000 blended so as to have a volumetric mixing ratio of 3 to 10% in a molded article after curing, followed by curing. The cement-based extruded material according to any one of the above.