JPH04119805A - Carbon fiber-reinforced cement material and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a sufficient reinforcing effect and a conductivity imparting effect by a small quantity of short fibrous carbon fibers by continuously changing the concentration of carbon fibers along the direction toward the other surface from one surface and forming a concentration gradient, in which concentration near one surface is thinned and concentration near the other surface is thickened. CONSTITUTION:A carbon fiber-reinforced cement group material is manufactured by dispersing carbon fibers in a cement group matrix, and has a shape having at least one pair of opposed surfaces, and a concentration gradient, in which concentration is increased continuously from the surface 1 side with the concentration of carbon fibers is measured along the direction toward a surface 2 from a surface 1 in a cut surface cut by a virtual cutting plane line D-D' when the thickness of a member is comparatively thin is formed. When a distance from the surface 1 to the surface 2 is divided into three equal parts and each part is represented by a first layer, a second layer and a third layer, a reinforcing effect and a conductivity improving effect are displayed remarkably when the quantity of carbon fibers in the third layer is twice or more the quantity of carbon fibers in the second layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carbon fiber-reinforced cement material reinforced by dispersing and blending short fibrous carbon fibers, and a method for producing the same. More specifically, the present invention relates to a carbon fiber-reinforced cement material that can provide sufficient reinforcing effect and conductivity imparting effect with a small amount of carbon fiber, and a method for manufacturing the same.

[Conventional technology]

Cement-based materials such as mortar and concrete are inexpensive,
Moreover, it is a material with excellent durability and fire resistance, and also has excellent physical properties in terms of compressive strength and rigidity. However, when used as a structure, it has low tensile strength and impact strength, has a very low energy absorption ability, and has the disadvantage of being brittle in terms of physical properties.In addition, it has no conductivity at all, so When used for flooring, etc., special measures such as anti-static measures were sometimes required.To solve these problems, a method of using carbon fiber to strengthen the material and make it conductive has been developed. attempted).

In other words, when short fiber carbon fibers are used, they are premixed and blended uniformly, or nonwoven fabrics (dashi mats) are placed in areas where tensile stress is applied. A similar method is used to embed carbon fibers processed into sheets or warped rods in the areas of cement/concrete materials that are subject to tensile stress.

[Problem to be solved by the invention]

However, carbon fiber is generally expensive, and it is difficult to use nonwoven fabrics, sheets, etc. made from carbon fiber.Since it is difficult to insert a cement matrix between nonwoven fabrics or sheets, variations in strength tend to occur and the work becomes complicated. This is not preferable because it increases the cost, but it is preferable to add short carbon fibers into the cement matrix so that a high effect can be obtained simply by dispersing them.

However, when mixing carbon fiber with cement-based materials in a plant that manufactures large quantities of mortar and concrete, the difference in specific gravity between the two is large, and the smaller the fiber diameter, the more easily the fibers become tangled. Carbon fiber has difficulty dispersing into cement-based materials, and it is difficult to mix uniformly as it tends to form pilling called fiber poles in the mixing system, and ordinary carbon fiber has poor adhesion to cement-based matrices. It is difficult to obtain a carbon fiber-reinforced cement-based material with sufficient strength even with a small amount of carbon fiber added, as it is difficult to obtain a carbon fiber-reinforced cement-based material with sufficient strength even with a small amount of carbon fiber added. However, it is not impossible to uniformly disperse carbon fibers using special techniques such as using an omni mixer without considering profitability.However, in thick members such as beams,
The carbon fibers inside are not very useful for reinforcement, and dispersing the carbon fibers uniformly ends up wasting the carbon fibers.

The object of the present invention is to solve the above-mentioned problems, to obtain sufficient reinforcing effect and conductivity imparting effect with a small amount of short fibrous carbon fiber, and to enable carbon fiber reinforcement with simple operation and manufacturing capacity. An object of the present invention is to provide a cement material and a method for producing the same.

[Means to solve the problem]

Invention 1 A carbon fiber-reinforced cementitious material in which carbon fibers are dispersed in a cementitious matrix, which has a shape having at least one pair of opposing surfaces, and basically has -
The concentration gradient changes continuously due to the concentration force of the carbon fiber along the direction from one side of a pair of surfaces to the other, with the concentration being lower near one surface and higher near the other surface. It is a carbon fiber-reinforced cement material characterized by having. Special & Qi If the cement-based material is divided into three equal parts along the above-mentioned direction and the 1st, 2nd and 3rd layers are formed respectively, the amount of carbon fiber in the third layer is the amount of carbon fiber in the second layer. The carbon fiber-reinforced cement material is preferably twice or more.

The present invention also provides the production of a carbon fiber-reinforced cementitious material characterized by dispersing carbon fibers in a cementitious matrix, further precipitating the carbon fibers by subjecting them to vibration treatment in a mold, and then hardening the carbon fibers. It's a method.

Cement matrix refers to a cement-based base material (as opposed to carbon fiber), and includes cement, mortar, and concrete. It also includes various additives (Al1
If cement is considered as a binder, cement is the main binder. The term cement matrix refers to both before and after hardening.

It is particularly preferred that the cement particles used in the cement matrix be fine in order to suppress fiber pull-out.

Specifically, it is preferable to use early strength cement or ultra early strength cement. Further, when using aggregate, fine aggregate such as silica fume or fine silica sand is preferably used to improve the adhesion between the cement hydrate and the fibers.

The length of carbon fibers is usually 0.5 to 2 mm, although milled fibers of less than 0.5 mm can be used if necessary.
Particularly, it is preferable to set the thickness to 1.0 to 6.0 mm because it is highly effective as a reinforcing material. The amount of carbon fibers to be blended is preferably about 1 to 10 vol. %, so that a reinforcing effect can be obtained at a volume ratio of 1 to 20 vol. % to the total volume of the cement matrix containing carbon fibers. If it exceeds 10vol%, the dispersion becomes poor and the reinforcing effect tends to reach a plateau.

In the present invention, carbon fibers having good dispersibility in cement paste and good affinity with cement are used.

Particularly preferred as such carbon fiber is Hawk Tokko 1
It is manufactured by the method disclosed in Publication No. 132832, and the aromatic sulfonic acid-based polymer compound obtained by polymerizing and condensing aromatic sulfonic acids or their salts is dissolved in an aqueous solvent as the main component. Carbon fibers are obtained by dry spinning the resulting spinning solution and carbonizing or further graphitizing it. This is 0.1-2. -C) containing 7% sulfur content and equivalent to 1 to 250 μg per gram of fiber, -
Co()l.

It has a surface acidic group such as -8o3H, and this point is considered to be the reason why it is suitable for the present invention. The carbon fibers produced by this method have a thick fiber diameter of 10 to 100 μm,
It has extremely good dispersibility in cement paste and good affinity with the cementitious matrix, making it an excellent reinforcing material for cementitious materials. The reason why this carbon fiber can be made thicker in fiber diameter than normal carbon fiber is that pitch-based or PAN-based carbon fibers become difficult to make infusible or flame resistant through oxidation when the diameter exceeds 20 μm. When attempting to oxidize to This is because the raw material is essentially an unmeltable resin that does not require infusibility.

The strength of the above preferably used carbon fiber is as follows, and this is approximately twice that of pitch-based carbon fiber.

Diameter (μm) Tensile strength (Kg/mm2) 30
40-100 40 30-60 As carbon fibers for reinforcing cement-based materials, it is effective to reduce the aspect ratio in order to increase the dispersibility of the fibers in the cement-based matrix and the effective fiber coefficient.
A fiber diameter of 15 to 40 μm and a fiber length of 2 to 6 mm is desired. Preferably used carbon fibers (with a maximum fiber diameter of 100 μm and ordinary pitch or PAN fibers)
Compared to other carbon fibers, it is thicker and has a thicker aspect ratio, so there is less entanglement of the fibers when mixed with cement-based materials, resulting in better dispersibility and less damage to the fibers during mixing. Become. Furthermore, since it contains a large amount of acidic functional groups such as sulfone groups, it has good adhesion to the cement matrix, which is alkaline in nature, and can provide a large reinforcing effect.

When the cementitious material of the present invention has a shape as shown in Fig. 1, there are three pairs of opposing surfaces, one of which (
Here, when considering surfaces 1 and 2), the dispersed carbon fibers have the following concentration distribution. In other words, when the thickness of the member is relatively thin (on the cut plane cut along the hypothetical cutting line DD' (the plane surrounded by a, b, c, and d in Figure 1), the direction from plane 1 to plane 2 When the concentration of carbon fibers is measured along the direction, as shown in FIG. 2A, there is a concentration distribution in which the concentration increases continuously from the surface 1 side.
In addition, in the case of the concentration distribution as shown in Figure 2A, the distance from surface 1 to surface 2 is divided into three equal parts as shown by the virtual line (-dotted chain line) in Figure 1, and the distance from surface 1 to surface 2 is divided into three equal parts. When forming the third layer, it is preferable that the amount of carbon fiber in the third layer is at least twice the amount of carbon fiber in the second layer, since the reinforcing effect and the effect of improving conductivity can be achieved significantly.

Also, if the thickness of the member is relatively thick, the thickness of the member that has a concentration distribution where the concentration increases continuously from the surface 1 side as shown in Figure 2B at the cut plane is relatively thin. The end of the second layer of the car is similar to the case (b in Figure 1).
In some cases, there may be a part with a high density near the c and ad sides). Needless to say, in such a case, the carbon fiber concentration distribution and effect are basically the same as in the case where the thickness of the member is relatively thin. Note that the hatched lines in FIGS. 2A and 2B conceptually indicate that the higher the density of the hatched lines, the higher the concentration of carbon fibers.

Hereinafter, for the sake of simplicity, the surface corresponding to surface 1 will be described as an upper surface, and the surface corresponding to surface 2 will be described as a lower surface (bottom surface).

The same applies to drawings.

Although the shape of the cement material of the present invention is plate-like (or prismatic) in FIG. 1, the shape is not particularly limited since the carbon fibers basically have the above concentration distribution.

In producing the cementitious material of the present invention, first, carbon fibers adjusted to an appropriate length are blended and dispersed in a cement paste to which additives such as aggregate and a fluidizing agent are added as necessary. If the above-mentioned preferably used carbon fibers are used, they have extremely good dispersibility in cement paste, so when mixing the short carbon fibers with cement paste, mortar, or concrete, an omni mixer or an iron There is no need to use a special mixer such as a Rich mixer, and by thoroughly mixing with commonly used mixers such as forced mixers, twin-shaft forced mixers, mortar mixers, and tilted-body mixers, cement paste with carbon fibers evenly dispersed. Mortar and concrete can be obtained. Paste, mortar or concrete mixed with fibers can be applied to a base frame of any shape.In the case of paste or mortar, the flow value is 100 to 300 mm, preferably 150 to 250 mm.
degree of fluidity, and in the case of concrete, a slump value of 1
Vibration treatment is performed while maintaining fluidity of about 8 to 21 cm. As a result, in addition to the defoaming effect, the fibers are mainly oriented horizontally and settle, forming a concentration gradient where the concentration is lower at the top and higher at the bottom. This simple vibration treatment allows the carbon fibers to sink through the paste, etc., forming a concentration gradient where the concentration is lower at the top and higher at the bottom. , normal pitch system or P
AN-based carbon fiber, which was not possible, was then molded by press molding, etc. if necessary, and then cured by autoclave curing, steam curing, water curing, air curing, etc. to produce carbon fiber with a carbon fiber concentration gradient. A reinforced cementitious material can be obtained. If autoclave curing or steam curing is not performed,
It is preferable to use a low shrinkage cement. The reinforcing effect can also be enhanced by arranging reinforcing material made of reinforcing bars or other fibers including the carbon fibers in the formwork in advance during molding.

For the vibration treatment, a table vibrator (form vibrator, rod vibrator, etc.) is used.The vibration frequency, HIU vibration time, etc. may be set to appropriate values according to the desired shape. The direction of vibration is preferably vertical.

When adjusting the flow value and slump value, they can be adjusted using a thickener or fluidizing agent such as CMC. Special A: In the case of the carbon fiber-reinforced cement material of the present invention, a naphthalene sulfonic acid condensate-based fluidizing agent or water reducing agent is also effective in improving the strength.

Further, the amount of air may be controlled using an AE agent or an antifoaming agent.

In the cement-based materials manufactured in this way,
Although no sedimentation of the blended carbon fibers was observed, the individual fibers maintained a good dispersion state and exhibited a concentration gradient in which the fibers were thinner near the top and thicker near the bottom. For example, 1f1: 3 vo1% of short fibrous carbon fibers adjusted to a length of 3 mm, and 4 uncured mortar adjusted to a flow value of 250 mm.
0 x 40 x 160mm, vibrator (vertical amplitude 1.5im, 3557 cycles/
The carbon fiber concentration of the 1.2nd and 3rd layers measured from the top by dividing the material into 3 equal parts in the thickness direction after applying vibration for 60 seconds (minutes) was 1.4%, 1.9% and 5.7% on average, respectively.
Next, a sample of 25 x 25 x 160 mm was cut out from the autoclaved and cured sample, and the bending strength was measured by applying loads from the three directions E, F, and G shown in Figure 3. are 260. each. 17
0. It can be seen that the strength particularly in the E direction is significantly enhanced at 90Kg/ca+2. Further, the volume resistivity measured in the major axis direction was 0.65×10 2 Ωcm, which is about 1/2 that of a material in which the same amount of carbon fibers were uniformly dispersed.

In the method of the present invention, carbon fibers with good dispersibility in cement paste and affinity with cement are used, and vibration treatment is applied before hardening to improve the orientation of the fibers and the difference in specific gravity between cement and carbon fibers. A totally unpredictable sedimentation of the fibers occurs, and a carbon fiber-reinforced cementitious material having a carbon fiber concentration gradient where the concentration of carbon fibers is thinner at the top and higher at the bottom can be obtained.

Since the carbon fiber concentration near the lower surface of the carbon fiber reinforced cement material 13 of the present invention is particularly high, the strength is directional and exhibits particularly high strength against forces directed from above to below. This is a much higher strength than when the same amount of carbon fibers are uniformly dispersed. In addition, since electrical resistance is affected by areas with high concentration of carbon fiber,
Compared to the same amount of carbon fibers dispersed uniformly, the volume resistivity is significantly lower and the effect of imparting electrical conductivity is greater.

The carbon fiber reinforced cement material of the present invention can be used as a material for flooring, beams, etc. where the direction of force is constant.
Furthermore, it is particularly suitable as a material for use in locations where antistatic effects and electromagnetic shielding effects are required.

In the carbon fiber-reinforced cement-based material of the present invention, carbon fibers have a concentration distribution, so that the required amount of carbon fibers is present at the required locations, so that the carbon fibers can be used effectively without waste.

〔Example〕

The present invention will be explained in more detail with reference to Examples below. Note that % in the examples represents weight % unless otherwise specified.

Example 1 and Comparative Examples 1 to 3 1280 g of purified naphthalene and 1050 g of 98% sulfuric acid
After sulfonation at 150°C for 3 hours, unreacted naphthalene and water produced by the reaction were distilled off. Next, 200 g of water was added to dilute, and 875 g of 35% formalin was added.
was added and reacted at 105°C for 6 hours to form naphthalene-β-
A methylene-bonded condensate of sulfonic acid was obtained. This condensate was neutralized with aqueous ammonia and the insoluble matter was filtered out. The average molecular weight of the ammonium salt of the condensate was 103·b, and the maximum molecular weight was 1016. To the ammonium salt aqueous solution of the methylene-bonded condensate of naphthalene-β-sulfonic acid, add polyvinyl alcohol in an amount equivalent to 1% of the solid content in the aqueous solution (residue after drying at 110°C for 6 hours) to water. The dissolved material was added and mixed, and the water content was adjusted to 43% to obtain a spinning solution.The viscosity of this spinning solution at 40℃ is 30
At 0 poise, use this spinning solution as L/D=
The obtained yarn was dry-spun at 40°C using 1000-hole gold of 0.3 mm/0.1 mm at a spinning speed of 300 m/min, and was cut into 4.6 mm pieces and loaded on a belt.The inlet temperature was 250°C. The carbon fiber (CF-A) 14 obtained was introduced into a furnace adjusted to an outlet temperature of 1000°C and fired for 20 minutes in a nitrogen stream, with a diameter of 26 μm, a fiber length of approximately 3.0 mm, and an elongation of 2.6%. , tensile strength 89.9Kg
/mrI! 1 The elastic modulus is 3.6 tons/mm2, and the elemental composition (χ) is C: 92.0, H: 0.7, N: 1.
2. S: 0.6.0・5.5, and the acidic functional group measured by neutralization titration method was 25.5 μg equivalent/g. ,
Furthermore, a 2% amount of naphthalene-β-sulfonic acid formalin condensate based water reducing agent was added to the cement, and W/C=0.4.
52, mixed under the condition of S/C = 0.5, 3.0
VO1% carbon fiber (CF-A) was blended and mixed in a mortar mixer for 5 minutes. The resulting carbon fiber blended mortar was poured into a 40 x 40 x 160 mm molding frame and book-bound.
Amplitude 1.5 - Vibration was applied for 30 seconds at a frequency of 3557 cycles/sec. After that, it was cured in an atmosphere of 20°C and 60% relative humidity, and further heated in an autoclave for 150 sec.
Table 1 shows the results of measuring the bending strength and volume resistivity of the specimens cured at ℃ for 10 hours under the following conditions.

In addition, as Comparative Example 1, commercially available pitch-based carbon fiber (CF
-B) Comparative Example 2 Comparative Example 2 Comparative Example 2 Comparative Example 2 Comparative Example 2 Bending test machine with no carbon fiber added as Comparative Example 3 Autograph AG-10TD manufactured by Shimadzu Corporation Loading method 3-point bending Head: R3rm, Ba5e: R3mm Cross head speed 0.5 mm/min span
100 mm Volume resistivity measurement test: Testing machine Atoppantest DC voltage generator TR614
! , digital ammeter TR6851 measurement method 4-terminal method (the following is a blank space) In addition, the distribution of carbon fiber concentration in the vertical direction of the sample of Example 1 (CF-A) is as shown in Table 2; Looking at the carbon fiber concentration distribution from the results shown in Table 2,
When subjected to a simple vibration treatment, the carbon fiber-reinforced cementitious material of the present invention has a unique carbon fiber concentration distribution, whereas no fiber sedimentation is observed in the material to which the same amount of commercially available carbon fiber is added. Physically, it can be seen that the product of the present invention exhibits an excellent reinforcing effect against loads from a specific direction, and also has a large effect of imparting electrical conductivity.

Table 2 [Effects of the Invention] According to the present invention, a carbon fiber-reinforced cement material can be obtained that provides sufficient reinforcing effect and conductivity imparting effect even with a small carbon fiber content. Also provided is a manufacturing method that can easily manufacture such cement-based materials.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the carbon fiber reinforced cement material of the present invention. Fig. 2 is a schematic diagram showing the concentration distribution of carbon fiber in the cement material of the present invention. FIG. 3 is a schematic diagram showing the load direction. Surface 12: Surface 2 3 Virtual cutting plane 11: 1st layer 2nd layer 13: 3rd layer Patent applicant Mitsui Mining Co., Ltd. Representative Patent attorney Tadashi Kuwai

Claims (1)

[Scope of Claims] 1. A carbon fiber-reinforced cementitious material in which carbon fibers are dispersed in a cementitious matrix, which has a shape with at least a pair of opposing surfaces, and is Carbon characterized by having a concentration gradient in which the concentration of carbon fibers changes continuously along the direction toward the other surface, with the concentration being lower near one surface and higher near the other surface. Fiber reinforced cement material. 2. Divide the cement-based material into three equal parts along the direction,
The carbon fiber reinforced cement according to claim 1, wherein the amount of carbon fiber in the third layer is at least twice the amount of carbon fiber in the second layer when the first, second and third layers are respectively formed. system material. 3. Dispersing carbon fibers in a cement matrix,
A method for producing a carbon fiber-reinforced cement material, which comprises precipitating carbon fibers by subjecting them to vibration treatment in a mold and then hardening them.