JP3477252B2 - Carbon fiber for cement reinforcement and method for producing concrete using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbon fibers suitable for reinforcing cement materials.

[0002]

2. Description of the Related Art Cement-based matrices used as raw materials for building civil engineering materials have brittle properties and lack reliability as structural materials by themselves. Reinforcing bars have been conventionally used for the purpose of reinforcing and supplementing them, and in recent years, further improvement of the characteristics (mainly strength) of structural materials by reinforcing fibers has been studied. For example, by mixing an appropriate amount of carbon fibers, it is possible to impart strength properties, deformation properties, elasticity properties, etc., which were not possible with conventional cement concrete, and there are great expectations as new structural materials. .

With respect to carbon fibers, various measures have been taken to improve the adhesiveness and dispersibility in a cement matrix and to increase the strength of the resulting carbon fiber reinforced concrete. For example, JP-A-62-108755 discloses that a cationic styrene-butadiene rubber latex is attached to the surface of carbon fiber. Further, in JP-A-60-81052, a nonionic polymer flocculant such as polyacrylamide is formed on the fiber surface when a reinforced cement material is produced by the Hatschek papermaking method,
Alternatively, a method of attaching a modified polyacrylamide Mannich is disclosed.

[0004]

However, in the above prior art, the treating agent itself used for improving the physical and chemical state of the carbon fiber surface is an ionic treating agent. There is no example in which the electrical state of the carbon fiber surface after treatment with, that is, the zeta potential is directly measured and controlled.

As a result of intensive studies by the present inventors, the zeta potential of the surface of the carbon fiber which has been subjected to a surface treatment such as electrolytic oxidation which is usually carried out at the carbon fiber production stage is found to be at a total pH of 2-12.
It was found that the region has a large negative value. Even if such a carbon fiber surface is treated with a nonionic or cationic treating agent as disclosed in the prior art, in the high pH range of pH 11 to 13 such as in cement kneading water, the carbon fiber surface It was found that the zeta potential was much smaller than -10 mV. It was also found that the magnitude of the zeta potential depends not only on the surface treatment conditions such as electrolytic oxidation usually performed in the carbon fiber production stage but also on the concentration of the treating agent.

According to the results of studies by the present inventors, the pH of the water in which the cement is dispersed is 11 to 13, and the zeta potential of the cement particles in the water is −10 mV to −several mV. Therefore, when the surface zeta potential of the carbon fiber is negative and has a large value, the dispersibility of the carbon fiber in the cement matrix is deteriorated and the adhesive force with the matrix is weakened.

In view of such a situation, the present inventors have controlled the zeta potential in cement kneading water, which has not been achieved by the prior art, and have improved the adhesiveness and dispersibility of the carbon fiber in the matrix. The present invention has been completed for the purpose of obtaining a carbon fiber reinforced concrete having excellent strength.

[0008]

According to the present invention, the surface zeta potential measured by the streaming potential method has the same pH 11 as that of cement.
Cement-reinforcing carbon fiber and the carbon fiber, wherein the carbon fiber is -10 mV or more (excluding carbon fiber treated with a liquid in which silicone rubber fine particles are dispersed in a cationic surfactant) in an aqueous solution of -13. A method for producing a carbon fiber reinforced concrete characterized by dispersing in a cement matrix.

In the present invention, the zeta potential indicates a value measured by a streaming potential method using a Shimadzu streaming potential meter (ZP-10B). Specifically, the carbon fiber treated with various treatment agents was loaded into the measuring cell in the state of long fiber, and the streaming potential generated when the flowing liquid of each pH adjusted to have the same ionic strength was passed through the cell was measured. The zeta potential was determined by measurement and calculation.

FIG. 1 shows the results of measurement of the zeta potential of a fluid having various pH values for carbon fiber which has been subjected only to ordinary electrolytic oxidation treatment.
It was shown to. In this case, total pH from low pH side to high pH side
The zeta potential became negative in the region. Since the pH of ordinary cement kneading water is usually 11 to 13, in the present invention, p
It was performed by measuring the zeta potential at H12.

The zeta potential measured by the streaming potential method specified in the present invention is -10 mV in an aqueous solution of pH 11-13.
The carbon fiber having the above is obtained by treating a carbon fiber that has been subjected to the usual electrolytic oxidation treatment with a cationic polymer or a cationic surfactant.

Examples of the cationic polymer include polydimethylaminoethyl acrylate-methyl chloride quaternary salt, polydimethylaminoethyl acrylate-methyl chloride quaternary salt, polydimethylaminoethyl methacrylate sulfate and other polyalkylaminoalkyl methacrylates. Or a quaternary salt of polyalkylaminoalkyl acrylate, a copolymer of acrylamide and a quaternary salt of alkylaminoalkyl methacrylate, or a quaternary salt of alkylaminoalkyl acrylate,
Quaternary salt of alkylaminoalkyl acrylate, or copolymer of alkylaminoalkylmethacrylate, acrylamide and acrylic acid, chitosan, amine-halide polycondensate, amine-formalin polycondensate, amine-epoxy polycondensate, polyamide polyamine , Polyester polyamine can be mentioned.

Examples of the cationic surfactants include quaternary ammonium salts such as lauryl trimethyl ammonium chloride, lauryl dimethyl benzyl ammonium chloride, cetyl dimethyl ethyl ammonium bromide and lauryl dimethyl chloro benzyl ammonium chloride.

[0014]

Among these treatment agents, from the viewpoints of alkali resistance, ionic strength and adhesion to carbon fiber, polyalkylaminoalkyl acrylate quaternary salt type and polyalkylaminoalkyl methacrylate quaternary salt type and acrylamide type are used. Those of the copolymer type are particularly preferable.

The amount of treatment agent adhered to the carbon fiber is 0.0
It is 1 to 5% by weight, preferably 0.1 to 1% by weight. When the amount of adhesion is small within this range, a sufficient zeta potential cannot be imparted, and as a result, the adhesive force between the cement matrix and the carbon fiber becomes weak. On the other hand, if the adhered amount is larger than this range, the carbon fibers are adhered to each other and the dispersibility of the fibers in the cement matrix is lowered, which is not preferable.

As a method of attaching the above-mentioned treating agent to the carbon fiber, the electrolytically treated carbon fiber is immersed in an aqueous solution or dispersion of the treating agent or continuously passed through to deposit a prescribed amount of the treating agent. It is achieved by drying at room temperature or under heating.

The zeta potential defined in the present invention is -10 mV or more, preferably -10 mV to +40 mV, in an aqueous solution having the same pH as that of cement.
If the zeta potential is smaller than this range, the dispersibility and adhesive strength of the carbon fiber in the cement matrix will be weakened, and the strength of the carbon fiber reinforced cement material will be reduced. Also,
If it is more than this range, the interaction between the carbon fiber and the matrix becomes too large, which adversely affects the dispersibility of the carbon fiber and causes a decrease in strength.

The carbon fiber that can be used in the present invention is not particularly limited as long as it is a known carbon fiber. However, since the main purpose of the present invention is to increase the strength of the reinforcing cement material, carbon which is a reinforcing material is particularly used. It is desirable that the fibers have higher strength. Therefore, a polyacrylonitrile-based carbon fiber that is versatile and easily obtains high strength characteristics is preferable.

There is no limitation on the usage form of the carbon fiber, and it may be a long fiber or a short fiber. Further, it can be used in the form of a strand, a sheet, a non-woven fabric, a woven fabric, a knitted fabric or a braided form, and has an advantage that it can be carried out by various methods such as a direct spray method, a premix method, an impregnation method, a hand layup method and a papermaking method.

The cement material reinforced with carbon fibers according to the present invention, if the carbon fibers are dispersed in the cement matrix, the presence or absence of aggregates such as sand and gravel,
It excels in strength properties regardless of the amount, the amount of reinforcing bars, various additives and admixtures, or the type of cement.

The carbon fiber reinforced cement material according to the present invention can be used to form molded products in various shapes such as plate, tube, and column.

[0023]

EXAMPLES Next, the present invention will be described more specifically by way of examples. Examples 1 to 5 Diameter 7 μm, Specific gravity 1.80, Tensile strength 450 kgf / mm ² , Elastic coefficient 24 tonf / mm
² , 1 in a 5% aqueous solution of ammonium bicarbonate, pH 7.5
After passing the polyacrylonitrile-based carbon fiber bundle having the number of filaments of 12,000, which has been subjected to electrolytic oxidation treatment at an electric quantity of 100 coulomb per gram, through each treatment liquid shown in Table 1, 1
An adhesion treatment was performed by drying at 20 ° C. for 2 minutes. The treatment liquid was prepared to be an aqueous solution or dispersion of 0.2% of the active ingredient. PH 1 of carbon fiber obtained by treatment
Table 1 also shows the values obtained by measuring the zeta potential in Example 2 by the streaming potential method.

[0024]

[Table 1]

The carbon fiber bundle treated as described above was cut into a length of 3 mm, and a carbon fiber reinforced concrete specimen was prepared with the composition shown in Table 2. For kneading, a 10 liter omni mixer was used with the volume fraction of carbon fiber being 0.5%.

[0026]

[Table 2]

After molding, the first curing (1 day in a humidity chamber),
Further, after demolding in 1 day of age, a second curing (7 days in water at 30 ° C.) was performed. The bending strength of the carbon fiber reinforced cement material was evaluated according to JIS-R5 using a specimen of 4 × 4 × 16 cm.
It carried out according to 201. The results are shown in Table 1.

[Comparative Examples 1 and 2] Carbon fibers were treated only with electrolytic oxidation and no other treatment (Comparative Example 1) and the treating agents shown in Table 1 (Comparative Examples 2 and 3) were used. In the same manner as in Example 1, the zeta potential was measured and the bending strength of the carbon fiber reinforced cement material was measured. The results are also shown in Table 1.
It was shown to.

[0029]

The carbon fiber reinforced cement material produced by using the carbon fiber of the present invention exhibits a large bending strength and a high reinforcing effect is achieved. Therefore, it is extremely useful in the production of various concrete products.

[Brief description of drawings]

FIG. 1 is a diagram showing the pH dependence of the zeta potential of electrolytically oxidized carbon fibers.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshikazu Takei 2-19-1 Tobita-yari, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Laboratory (72) Inventor Migameo Kobayashi 2-2-1, Tobita, Chofu-shi, Tokyo Number 1 Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Tatsuo Suenaga 192-1 Tobita, Chofu City, Tokyo Metropolitan Government Kashima Construction Co., Ltd. Technical Research Center (72) Inventor Koji Satoyama Tobita Shoji, Chofu City, Tokyo No. 19-1 Kashima Construction Co., Ltd. Technical Research Institute (56) Reference JP-A-3-150242 (JP, A) JP-A-7-48155 (JP, A) (58) Fields investigated (Int.Cl . ⁷ , DB name) C04B 2/00-32/02

Claims (2)

(57) [Claims] 1. A surface zeta potential measured by a streaming potential method is -10 m in an aqueous solution of pH 11 to 13 which is the same as that of cement.
Carbon fiber for cement reinforcement, which is V or more (excluding carbon fiber treated with a liquid in which silicone rubber fine particles are dispersed in a cationic surfactant). 2. A surface zeta potential measured by a streaming potential method is -10 m in an aqueous solution having the same pH 11 to 13 as cement.
A method for producing a carbon fiber reinforced concrete, which comprises dispersing carbon fibers of V or more (excluding carbon fibers treated with a liquid in which silicone rubber fine particles are dispersed in a cationic surfactant) in a cement matrix.