JP2003128452A - Short-fiber reinforced extrusive cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight and tough short-fiber reinforced extrusive cement preventing a breaking with multiple cracks. SOLUTION: The extrusive cement is broken by causing the multiple cracks in a flexural load test and has a specific gravity of 0.8-1.8. The cement is obtained by extruding a hydraulic cement composition obtained by compounding a PVA short-fiber having 3-15 mm fiber length, 5-200 μm fiber diameter and 150-1,000 aspect ratio to the matrix cement 100 pts.wt., 40-100 pts.wt. silica raw material, 1-80 pts.wt. pulp and 0.1-10 pts.wt. water-soluble cellulose so that the mixing ratio by volume in a compact after hardening may be 2-10%, then hardening the extruded article.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fiber-reinforced cement-based extrusion molding material. More specifically, the present invention relates to a PVA short fiber reinforced cementitious extrusion molding material which is lightweight and has high toughness in which multiple cracks are generated and bending fracture occurs.

[0002]

2. Description of the Related Art Heretofore, attempts have been widely made to improve the performance of hardened cement products by mixing asbestos and synthetic fibers instead of asbestos. However, these conventional improvements by fiber reinforcement have been aimed at improving the fracture strength and elastic modulus within the proportional deformation of the cement hardened body which is a brittle material, and beyond the proportional deformation the cement hardening Without the idea of improving the physical properties of the body,
The means was not known either.

Recently, when the cement first cracked,
Short fibers mixed as a reinforcing material in cement cause the cracks to bridge and share the stress so that the fracture does not immediately occur even after the first crack occurs, and the stress is dispersed by generating multiple cracks. A technique for imparting high toughness by applying large deformation and breaking stress is being researched. This technique adjusts the adhesive force between the matrix and the reinforcing fibers to prevent the reinforcing fibers existing in the cracks from breaking at the same time when the first crack occurs in the cement. Even after that, the stress is shared by the fibers to prevent the cured product from immediately breaking.

As the reinforcing fibers used for this purpose, high strength and high elasticity polyethylene fibers and PVA fibers have been used. For example, Japanese Unexamined Patent Publication No. 2000-264708 describes a high toughness fiber reinforced cement product in which a polyolefin fiber having a tensile strength of 20 g / denier or more and an elastic modulus of 500 g / denier or more is dispersed and blended.
Japanese Patent Laid-Open No. 2000-7395 discloses a high toughness FRC material obtained by randomly blending PVA short fibers in a three-dimensional direction. However, a cement-based fiber composite material which is lightweight and has high fracture toughness extruded and high deformability of multiple crack fracture type is not known.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lightweight, high toughness fiber reinforced cementitious extrusion molding material exhibiting a fracture mechanism that produces multiple cracks.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a cement-based extrusion molding material having a specific gravity of 0.8 to 1.8 which causes multiple cracks and breaks under tensile loading or bending loading. Specifically, the present invention relates to a matrix containing 100 parts by weight of hydraulic cement, 40 to 100 parts by weight of siliceous raw material, 1 to 80 parts by weight of pulp, and 0.1 to 10 parts by weight of water-soluble cellulose, and a fiber length of 3 parts. ~ 15 mm, fiber diameter 5-200
The above cement obtained by extrusion-molding and then hardening a hydraulic cement composition in which PVA short fibers having an aspect ratio of 150 to 1000 and a volume mixing ratio of 2 to 10% in the molded product after curing are blended. System extrusion molding material. Further, the present invention provides a lightweight aggregate 1-1 in the matrix.
The present invention relates to the above cement-based extrusion molding material, which further contains 100 parts by weight. Furthermore, the present invention relates to the cement-based extrusion molding material according to any one of the above, further including 1 to 40 parts by weight of mineral fibers in a matrix.

In the present invention, "multiple cracks" means the following. When stress is applied and the first crack in the hardened cement, stress concentrates on the crack,
In a normal cement hardened body, it will be broken as it is. That is, fracture occurs at the stage of elastic deformation where the stress-strain curve becomes a straight line. Therefore, it has a 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 entire 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 occur, the stress is dispersed, and even after the initial cracking, it withstands an increasing load and does not fracture to a large strain, and exhibits high energy absorption capacity and high toughness.

In the present invention, "PVA fiber" is a polyvinyl alcohol fiber, commonly called vinylon fiber. In the present invention, the "aspect ratio" of PVA short fibers is a value obtained by dividing the fiber length by the diameter of an equivalent circle having the same area as the fiber cross section.

The "volume mixing ratio" of PVA short fibers to the hydraulic cement matrix defined in the present invention means that the hardened cement body is cut in a direction perpendicular to the extrusion direction, and the cut surface is observed by a scanning electron microscope. Use acceleration voltage 2
The backscattered electron image was observed at 5 kV. The fiber mixing ratio V _f in the hardened cement product was obtained as a value obtained by dividing the total cross-sectional area of the PVA short fibers on the observation surface in the field of view of the microscope by the area of the field of view of the electron microscope. As the fiber mixing ratio V _f , an average value of values measured in three different visual fields in the cut surface of the test piece was adopted.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The cement-based extrusion molding material of the present invention is a mixture of PVA short fibers having a specific shape in a cement matrix of a specific formulation at a specific volume mixing ratio, and is lightweight and bendable. It is characterized by the fact that it produces multiple cracks during loading and has high breaking energy and large deformability.

The cement-based extrusion molding material of the present invention having the above-mentioned characteristics is based on 100 parts by weight of hydraulic cement.
40-100 parts by weight of siliceous raw material, 1-80 parts by weight of pulp, 0.1-10 parts by weight of water-soluble cellulose, or a hydraulic cement matrix, or 1-100 parts by weight of lightweight aggregate and mineral fibers. It is obtained by blending PVA short fibers in a matrix in which at least one of 1 to 40 parts by weight is blended. The PVA short fibers used in the present invention have a fiber length of 3 to 15 mm, preferably 6 to 12 mm, a fiber diameter of 5 to 200 μm, preferably 10 to 40 μm, and an aspect ratio of 150 to 1000. Are mixed so that the volume mixing ratio in is 2 to 10%. The PVA short fibers used in the present invention are not particularly limited as long as they correspond to the above fiber length, fiber diameter and aspect ratio.

The cement-based molding material of the present invention thus obtained is a lightweight extrusion molding material having a specific gravity of 0.8 to 1.8.

When the fiber length is shorter, the fiber diameter is larger, or the aspect ratio is smaller than the requirements required for the PVA short fibers of the present invention, cracks are first generated in a state where bending stress is applied. When the fiber occurs, even if the fiber is crosslinked, the fiber cannot bear the stress, and immediately pulls out and breaks before the multiple cracks occur. On the other hand, when the fiber length is longer, the fiber diameter is smaller, or the aspect ratio is larger than the requirements required for the PVA short fiber of the present invention, the fiber pulls out in the state where bending stress is applied. Multiple fissures do not occur because the fiber itself breaks earlier than before.

If the volume mixing ratio of the PVA short fibers is less than 2%, the stress concentrated in the cracks cannot be supported and the crosslinking action cannot be exhibited, and if it exceeds 10%, the fibers contact each other. Since the portion increases and hinders the integration with cement, 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 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.

Examples of siliceous raw materials that can be used in the cement-based extrusion molding material of the present invention include silica stone 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 contributing to the strength improvement and dimensional stability of the molded body,
It is silica stone powder and silica sand. As these siliceous raw materials, those having a specific surface area (according to the method described in JIS R 5201) of 3000 to 15000 cm ² / g are preferably used. The siliceous raw material is mixed in an amount of 40 to 100 parts by weight, preferably 50 to 80 parts by weight, based on 100 parts by weight of hydraulic cement. If the amount of the siliceous raw material is less than 40 parts by weight, the strength of the molded product will be reduced, and moreover, efflorescence will easily occur, and if it is more than 100 parts by weight, the strength of the molded product will be reduced. It is more preferably 50 to 80 parts by weight.

The pulp used in the present invention is preferably natural pulp such as cotton pulp or wood pulp. There is no particular limitation 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, both chemical pulp obtained by chemically removing lignin from the tissue of wood and 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 added in an amount of 1 to 80 parts by weight, preferably 2 to 30 parts by weight, based on 100 parts by weight of hydraulic cement. If it is less than 1 part by weight, the reinforcing effect cannot be exhibited, and if it is more than 80 parts by weight, the dispersion becomes poor and the surface smoothness of the molded product is deteriorated.

The water-soluble cellulose to be blended in the present invention includes alkyl cellulose such as methyl cellulose and ethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyalkyl cellulose such as hydroxyethyl cellulose, hydroxyalkyl alkyl cellulose and carboxymethyl cellulose. Etc. can be illustrated. The water-soluble cellulose imparts viscosity to the kneaded product and improves moldability when the components of the extrusion composition are mixed and extrusion-molded. Water-soluble cellulose is 0.1 to 10 parts by weight with respect to 100 parts by weight of hydraulic cement,
It is preferably blended in a proportion 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. While 10
If the amount is more than the weight part, the cost is increased, and further improvement of the effect cannot be expected.

Examples of the mineral fibers blended in the present invention include sepiolite, wollastonite, talc, attapulgite, rock wool and the like. The mineral fiber is mixed in an amount of 0 to 40 parts by weight, preferably 3 to 25 parts by weight, based on 100 parts by weight of hydraulic cement. If the amount of mineral fibers is more than 40 parts by weight, the strength of the molded product will decrease.

The lightweight aggregates used in the present invention include natural lightweight aggregates such as volcanic gravel, artificial lightweight aggregates such as fired fly ash, ultralight aggregates such as pearlite perlite, obsidian perlite and vermiculite, expanded slag. By-product lightweight aggregates such as can be used. Preferred are pearlite perlite, obsidian perlite, and vermiculite whose specific gravity can be set to 0.06 to 0.5. For example, perlite as described in Japanese Patent No. 3040144 can be exemplified.

In the cement-based extrusion molding material of the present invention, as an additive other than the above, inorganic materials other than silica such as mica, alumina and calcium carbonate, polypropylene fiber, polyethylene fiber, carbon fiber, etc. may be used, if necessary. Other reinforcing fibers, water-reducing agents, surfactants, thickeners and the like can also be added.

The cement-based molding material of the present invention is a molded body formed by extrusion molding. By extrusion molding, a more dense cured product is generally obtained, and since the reinforcing fibers are oriented predominantly in the extrusion direction, tensile stress to the extrusion direction or bending stress from a direction perpendicular to the extrusion direction The reinforcing effect due to the cross-linking action of the fibers can be more effectively exhibited.

[0023]

EXAMPLES The present invention will now be described more specifically and in more detail with reference to Examples. Example 1 100 parts by weight of ordinary Portland cement and 6 m in length
m, fiber diameter 40 μm (aspect ratio 150), PVA short fiber (Kuraray Co., Ltd., trade name “Kuraray Vinylon RKW15
02 ") 5.1 parts by weight, silica stone powder (specific surface area 4000 cm
² / g) 63.5 parts by weight, pulp (hardwood pulp) 5
Parts by weight, 5 parts by weight of sepiolite and 6 parts by weight of methyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd.) were added, and powder-mixed for 3 minutes with a mixer. While continuing to mix the powder, 77.5 parts 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 cylinder type vacuum extrusion molding machine through a mold. The discharge port dimensions of the mold were rectangular with a width of 80 mm and a height of 15 mm. The extrudate discharged from the mold was received by a tray.
The extruded product is wrapped with a plastic film together with the tray,
It was steam-cured in a thermo-hygrostat. Steam curing has a humidity of 98%
It was kept at 70 ° C. for 5 hours under the conditions.

Table 1 shows the bending characteristics (maximum stress, bending at peak, breaking energy, number of cracks), specific gravity and bending stress per specific gravity of the obtained PVA short fiber reinforced cement cured product (cement-based extrusion molding material). did. As shown in Table 1, the hardened cement product caused multiple crack fracture in the bending test and exhibited high physical properties. The volume mixing ratio of PVA fibers in the cured product was 3.0%. Bending properties of the molded body,
The number of cracks and the volume mixing ratio of PVA short fibers were evaluated as follows.

(1) Method for evaluating bending characteristics A test piece for a simple bending test with a width of 40 mm, a length of 200 mm, and a thickness of 15 mm for two-point loading was cut out from a cement hardened body having a width of about 80 mm and a thickness of about 15 mm. The distance between loading points was 50 mm, the distance between fulcrums was 150 mm, and the crosshead speed was 0.5 mm / min. The bending stress σ _b was evaluated by the following formula (1) based on the measured load P: σ _b = PL / bt ² (1) In the formula, b is the width of the test piece and t is the thickness of the test piece. , L represents the distance between fulcrums. Fig. 1 shows the situation of a simple bending test with two points loaded.

(2) Measurement of Number of Cracks Generated The number of cracks generated by the bending test was visually counted on the test piece after fracture. The number of cracks was represented by the average value of three test pieces.

(3) Measurement of Volume Mixing Ratio of PVA Short Fibers A hardened cement material was cut in a direction perpendicular to the extrusion direction, and the cut surface was subjected to an accelerating voltage of 2 using a scanning electron microscope.
The backscattered electron image was observed at 5 kV. The fiber mixing ratio V _f in the hardened cement product was obtained as a value obtained by dividing the total cross-sectional area of the PVA short fibers on the observation surface in the field of view of the microscope by the area of the field of view of the electron microscope. As the fiber mixing ratio V _f , an average value of values measured in three different visual fields in the cut surface of the test piece was adopted.

Examples 2 to 3 A hardened cement product (cement-based extrusion molding material) was prepared in the same manner as in Example 1 except that pearlite was added to the components, and bending properties were obtained. The number of cracks generated and the volume mixing ratio of PVA short fibers were measured. The measurement results are shown in Table 1. The cured products of Examples 2 and 3 also caused multiple crack fracture and exhibited excellent bending properties. Moreover, the stress-deflection curve of the bending test of Examples 1-3 is shown in FIG.

Comparative Example 1 As shown in Table 1, a hardened cement product (cement-based extrusion molding material) was prepared in the same manner as in Example 1 except that the mixing amount of PVA short fibers was set to an amount such that the volume mixing ratio was 1.5%. ) Was produced.
When a bending test was carried out, it broke with a single crack, and the bending characteristics were lower than those of the examples, despite having a higher specific gravity than the cement hardened bodies of the examples.

Comparative Example 2 As shown in Table 1, the volume mixing ratio of PVA short fibers is 3.0%.
A cement hardened product (cement-based extrusion molding material) was prepared in the same manner as in Example 1 except that the amount of lightweight aggregate was increased. When a bending test was carried out, it broke with a single crack, and the bending characteristics were remarkably lower than those of the cement hardened bodies of Examples, and the bending characteristics per specific gravity were also considerably low. The stress-deflection curves of the bending tests of Comparative Examples 1 and 2 are shown in FIG.

[0031]

[Table 1]

[0032]

EFFECT OF THE INVENTION The cement-based extrusion molding material of the present invention in which PVA short fibers having a specific morphology are mixed with a cement matrix at a volume mixing ratio within a specific range produces multiple cracks when stress is applied. Can be broken, and high breaking energy can be expressed.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a two-point loading simple bending test situation of a hardened cement material.

FIG. 2 Bending stress of hardened cement products of Examples 1-3
FIG.

FIG. 3 Bending stress of hardened cement products of Comparative Examples 1 and 2
FIG.

[Explanation of symbols]

1: Example 1, 2: Example 2, 3: Example 3, 4: Comparative example 1, 5: Comparative example 2, 11: hardened cement, 12: fulcrum, 13: Loading point.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C04B 14:04 C04B 16:02 Z 16:02 14:38 C 14:38 16:06 G 16:06) 111: 40 111: 40 (72) Hiroyuki Takashima, 14-5 Shimokita Town, Neyagawa City, Osaka Prefecture F-term in Technical Research Laboratory, Kurashiki Spinning Co., Ltd. (reference) 4G012 PA03 PA04 PA07 PA15 PA22 PE04 4G054 AA01 AA15 BD00

Claims (4)

[Claims] 1. A cement-based extrusion molding material having a specific gravity of 0.8 to 1.8 which causes multiple cracks and breaks during bending loading. 2. A matrix comprising 100 parts by weight of hydraulic cement, 40 to 100 parts by weight of siliceous raw material, 1 to 80 parts by weight of pulp and 0.1 to 10 parts by weight of water-soluble cellulose, and a fiber length of 3 to 15 mm. , Fiber diameter 5 ~ 200μ
2. A extrusion-molded hydraulic cement composition in which PVA short fibers having an m and an aspect ratio of 150 to 1000 are mixed so as to have a volume mixture ratio of 2 to 10% in a molded product after curing, and then cured. The cement-based extrusion-molding material according to. 3. The cementitious extrusion molding material according to claim 2, further comprising 1 to 100 parts by weight of the lightweight aggregate in the matrix. 4. The cement-based extrusion molding material according to claim 2, further comprising 1 to 40 parts by weight of mineral fibers in the matrix.