JPH07233591A - Hydraulic compound material of carbon short fiber-chopped strand reinforced with carbon short fibers - Google Patents

Abstract

PURPOSE:To bring out the strength, by combining chopped strands in which silica with a specified size is stuck, boundby a water soluble binder, on producing a fiber reinforced concrete mortar. CONSTITUTION:A carbon short fiber in which silica having 5mum or smaller particle sides is added by 0.5-3wt.% is bundled by a polyvinyl alcohol water-soluble hinder to form a carbon short fiber chopped strand. It is preferable that fine particles (silica) of 0.02-0.5mum in sizes to be dispersed in the binder are added by 1-1.5wt.% in the carbon fibers. Next, aggregates, a dispersing agent, a water reducing agent, and the cart>on short fiber chopped strand are mixed with a low-contraction cement or high-early-strength portland cement, etc. And after that, water is added and kneaded further to increase the wettability and and adhesion of the carbon fibers and the cement matrix. In this way, the strength can be brought out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber reinforced hydraulic composite material excellent in strength development, which is mainly used in the fields of civil engineering and construction.

[0002]

2. Description of the Related Art A carbon fiber reinforced hydraulic composite material was developed in order to make up for the lack of strength of ordinary mortar and the like by utilizing the tensile strength and elastic modulus of carbon fiber. Excellent strength and toughness. A method is known in which the carbon fibers for the carbon fiber-reinforced hydraulic composite material are bundled using a water-soluble polymer, and the carbon fibers are dispersed in a single yarn during kneading. (For example, JP-A-63-162559.
However, when such a water-soluble sizing agent is used,
There was a problem that the flexural strength was poorly expressed, the fiber and cement were not well compatible, and the strength as a composite material was not sufficient.

Further, since the average particle size of the cement particles is large and often the maximum particle size is about 100 μm, the cement particles cannot sufficiently wrap around between the carbon fibers, and the carbon fibers and the cement are bonded together. There is also a problem in that it is likely to be insufficient. Furthermore, particle size 0.02 to 0.5
Although it has been reported that the strength is increased by adding silica having a particle diameter of μm to the cement, the weight% of the silica relative to the cement (hereinafter,% means% by weight unless otherwise specified).
And If it is added in an amount of 10% or more, the fluidity decreases and the work becomes difficult. Then, in order to maintain the fluidity, it is considered to increase the water-cement ratio, but there arises a problem that the strength is significantly reduced. On the other hand, when the content of the silica is 10% or less, the probability that the silica is present in the vicinity of the carbon fiber is lowered, so that there are problems that the adhesion of the carbon fiber and cement cannot be increased by utilizing the microfiller effect.

There is also a method (Japanese Patent Publication No. 2715/1992) of impregnating carbon fibers with a two-pack type epoxy emulsion sizing agent in which silica is dispersed at a high ratio. There is a problem in that short carbon fibers become difficult to disperse into single yarns and the reinforcing effect on cement becomes small. On the other hand, if the amount of silica impregnated is 3% or more, the amount of silica around the carbon fibers is too large and the bond between the carbon fibers and the matrix is weakened.
There arises a problem that the strength of FRC) weakens.

[0005]

DISCLOSURE OF THE INVENTION As a result of various investigations to solve the above-mentioned problems, the present inventors have found that by attaching silica to a carbon fiber together with a water-soluble sizing agent, the adhesion between the two is increased and high strength is achieved. The present invention has been completed by finding that a short carbon fiber reinforced hydraulic composite material is produced.

[0006]

That is, an object of the present invention is to provide a short carbon fiber chopped strand for reinforcement, which has good compatibility with cement and can sufficiently exert the strength of the carbon fiber. To provide a short carbon fiber reinforced hydraulic composite material that fully utilizes the strength of the above and a method for producing the same, and an object thereof is to provide a short carbon fiber in which 0.5 to 3% by weight of fine particles having a particle diameter of 5 μm or less are impregnated. , Easily achieved by chopped strands of short carbon fibers formed by bundling with a water-soluble sizing agent.

The present invention will be described in detail below. First, the cement used in the present invention is not particularly limited, and may be any of ordinary Portland cement, early-strength Portland cement, blast furnace cement, alumina cement and low-shrink cement, but preferably low-shrink cement and early-strength Portland cement. Use a component. As the carbon fiber used in the present invention, known carbon fibers can be used without particular limitation, for example, coal tar pitch, petroleum pitch, coal liquefaction, polyacrylonitrile,
Carbon fiber made of cellulose or the like can be used. The fiber diameter of the carbon fiber is preferably 5 to 20 μm because the effect of silica can be brought out greatly. As the fiber length of the carbon fiber, one having an aspect ratio of 500 to 4000 is usually used. A suitable carbon fiber diameter is 5 to 20 microns, so the maximum length is 80 mm. Also,
The tensile strength of carbon fiber is 100-750 Kg / mm
^Two are used. The mixing ratio of carbon fibers in the short carbon fiber reinforced hydraulic composite material is preferably 0.5 to 2% in terms of volume fraction.

The sizing agent used for the chopped strands of the present invention is a water-soluble sizing agent since it is necessary that the strand-like carbon fibers can disperse in a single yarn when mixed with water in cement. Specifically, as the polyvinyl alcohol type, there are unsaponified polyvinyl acetate, partially saponified polyvinyl alcohol, and fully saponified polyvinyl alcohol. Further, cellulose derivatives such as methyl cellulose, ethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose and starch derivatives such as soluble starch are also used. And a polyvinyl alcohol type is preferably used. The concentration of the sizing agent is preferably 0.5 to 2%.

The fine particles to be dispersed in the sizing agent have a particle size of 5 μm or less, preferably 0.02 to 0.5 μm, and the amount of attachment to the carbon fiber is 0.5 to 3%, preferably 1 to 1. 5% is effective. In the present invention, the particle size of 0.02 to 0.5 μm means that 70% or more of all particles have a particle size of 0.02 to 0.5 μm. The types of the fine particles may be water-insoluble ones such as carbon black and various metal powders, with silica being particularly preferred. As the method of impregnation, usually, a sizing agent is mixed in water in which fine particles are dispersed so as to have a prescribed concentration, and the solution is impregnated with carbon fibers as long fibers through a pulley. The carbon fiber after impregnation is dried and cut at 100 to 120 ° C. The fiber length is preferably 5 to 20 mm.

When the amount of fine particles impregnated is 0.1% or less, there is almost no change from the case of no impregnation, and when it is 3% or more, the amount of fine particles around the carbon fibers is too large and the bond between the carbon fibers and the matrix is weak. Therefore, the strength of CFRC decreases. Therefore, the amount of the fine particles impregnated is set to 0.5 to 3% to obtain a sufficient effect. Usually, various additives such as aggregates, dispersants, and water-reducing materials that are usually mixed with CFRC are added to cement to obtain a hydraulic composite material.

As the aggregate, sand, silica stone, gravel, crushed stone,
Examples include shirasu balloon and fly ash.
A fine aggregate having an average particle size of about 6 mm, preferably silica sand No. 5, and a lightweight aggregate of hollow silica having an average particle size of about 40 μm are mixed in a total amount of 20 to 30 parts with respect to 100 parts of cement. Is preferred. As the fiber dispersant, those generally used may be used, and examples thereof include cellulose derivatives such as methyl cellulose and hydroxyethyl cellulose, polyamide type, polyamine type, alkylpicolinium salt type, and alkylamine water-soluble acid. Type cationic surfactant, alkylamine oxide type nonionic surfactant, alkylalanine type,
Any one kind or a mixture of two or more kinds of amphoteric surfactants such as an alkylamine oxide type nonionic surfactant, an alkylglycine type, an alkylalanine type, an alkylbetaine type and an alkylimidazoline type is used.

As the water-reducing agent, a special surfactant containing a triazine ring-based high condensation product salt as a main component, a special polymer having a special sulfone group and a carboxyl group, an anionic special polymer surfactant, a naphthalenesulfonic acid condensate ligninsulfonic acid derivative Etc. The addition amount is 1 to 4 parts with respect to 100 parts of cement. Further, in addition to the dispersant and the water reducing agent, an admixture such as an antifoaming agent and a foaming agent can be appropriately added.

As a mixer for kneading the cement raw material, carbon fiber, water and other auxiliaries, all commonly used mixers can be used, including paddle type, propeller type, paddle type, turbine type, pan type and ribbon type. In the case of a mixer having a stirring blade such as a screw type, a warner type, or a kneader type, the carbon fiber and the cement raw material are first mixed without adding water, and then water is added and kneaded.

[0014]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. The composition of the short carbon fiber reinforced hydraulic composite material was obtained by kneading and curing 50 parts of water, 25 parts of aggregate, and 5 parts of admixture with 100 parts of cement, and the volume ratio of carbon fiber to the entire composition was There are two types, 1% and 2%. The chopped strand length of the carbon fiber was 18 mm, and the main impregnation conditions are shown below.

Examples 1 to 8 Silica having a particle size of 0.02 to 0.5 μm (Elkem,
A sizing agent polyvinyl alcohol (“GOHSENOL” KH-20, manufactured by Nippon Gosei Co., Ltd.) 1.5 in which “Micro Silica”, grade 980) was sufficiently dispersed by stirring.
% Aqueous solution with carbon fiber having a tensile strength of 238 kg / mm ² by passing it through a long fiber as it is using a pulley,
The amount of silica impregnated is 0.5%, 0.6%, 0.8%, 1
%, 1.5%, 2%, 2.5% or 3%, and dried at 120 ° C. for 30 minutes, and then cut into 18 mm long chopped strands. This short carbon fiber chopped strand was added to a mortar mixer with an internal volume of 5 liters so that the volume ratio to the short carbon fiber reinforced hydraulic composite was 1% and 2%, and 100 parts by weight of low-shrinkage cement and silica sand 12 0.5 parts by weight, lightweight aggregate 12.5 parts by weight, and methylcellulose 0.25 parts by weight were added and dry mixed for 30 seconds to obtain a mixture in which short fibers were sufficiently dispersed, and then 50 parts by weight of water was added and kneaded for 30 seconds. After doing, 4x4x16c
The short carbon fiber reinforced hydraulic composite material molded body was manufactured by pouring into a m frame. The next day, the mold was removed, and the temperature was 20 ° C and the humidity was 6
0R. A bending test was performed after curing for 4 weeks in the T% state. The loading speed was 2 mm / mim, and the logarithm of the test was n = 6. The results are shown in Table-1.

Comparative Examples 1 to 3 Carbon short fiber reinforced hydraulic composite material moldings were produced and bent in the same manner as in Example 1 except that the silica loading was 0%, 0.1% or 5%. The test was conducted. The results are shown in Table 1.

Comparative Example 4 A two-pack type epoxy emulsion as a sizing agent was mixed with silica having the same particle diameter of 0.02 to 0.5 μm as used in Example 1 and diluted with water to prepare an emulsion of silica. Cut the carbon fiber so that the impregnated amount becomes 2 wt%, and
It was a carbon short fiber chopped strand of 8 mm. Using this short carbon fiber chopped strand, a carbon fiber reinforced hydraulic composite material molded body was produced by the same composition as in Example 1, and a bending test was performed. The results are shown in Table 1.

[0018]

[Table 1]

[0019]

As described above, according to the present invention, that is, by wetting carbon fibers with a slurry in which fine particles having a particle size of 0.02 to 0.5 μm are dispersed in a water-soluble sizing agent, the wettability with a cement matrix is improved. Further, by improving the adhesiveness and making better use of the characteristics of the carbon fiber, it is possible to manufacture a carbon short fiber reinforced hydraulic composite material having high strength and high reliability.

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Claims (7)

[Claims] 1. A short carbon fiber chopped strand obtained by bundling short carbon fibers having 0.5 to 3% by weight of fine particles having a particle diameter of 5 μm or less with a water-soluble sizing agent. 2. The short carbon fiber chopped strand according to claim 1, wherein the fine particles are silica. 3. The fine particles have a diameter of 0.02 to 0.5 μm.
The short carbon fiber chopped strand according to claim 1. 4. The short carbon fiber chopped strand according to claim 1, wherein the amount of the fine particles impregnated is 0.6 to 2.5% by weight. 5. The short carbon fiber chopped strand according to claim 1, wherein the water-soluble sizing agent is polyvinyl alcohol. 6. A short carbon fiber-reinforced hydraulic composite in which short carbon fibers impregnated with 0.5 to 3% by weight of fine particles having a particle size of 5 μm or less are mixed as a short carbon fiber chopped strand by bundling with a water-soluble sizing agent. material. 7. A carbon fiber is passed through a slurry containing fine particles having a particle size of 5 μm or less and a water-soluble sizing agent, and the focused carbon fibers are cut, so that the amount of the fine particles attached is 0.5 to 3% by weight. A short carbon fiber reinforced hydraulic composite material that is made into short carbon fiber chopped strands and is mixed with cement.