JPH11292582A - Fibrous strand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a fiber reinforced cement good in dispersibility and workability as fresh performance and high in strength as cured body performance. SOLUTION: In the fibrous strand consisting of numerous fibrous single yarns and resins, a compression strength of the resin is 30-300 kgf/cm<2> , an angle of the fibrous single yarn to a longitudinal direction of the fibrous strand is 3-20 deg. and also a proportion of the fibrous single yarn to the fibrous strand is 95-99 wt.%. Preferably, the fiber is a carbon fiber and the fibrous strand is used for compounding cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber strand used for short fiber reinforced concrete excellent in strength, durability and fluidity mainly used in the field of civil engineering and construction.

[0002]

2. Description of the Related Art It is well known to mix fibers with concrete in order to increase the strength of the concrete.
However, in conventional fiber reinforced concrete, long fibers such as rods and meshes are used as fibers, and short fibers are only used in mortar and spray repair materials that do not contain coarse aggregate. . The reason that short fibers are difficult to use as a reinforcing material for concrete is that when fibers are mixed with concrete in a state where fibers are easy to disperse into single yarns, that is, when fiber strands close to an unbunched state are mixed, moisture, cement paste or mortar in the concrete matrix is reduced. This is because the fluid components of the concrete matrix are insufficient due to absorption between the fibers of the fiber strands, and as a result, the fluidity of the concrete during construction is reduced. In addition, if knitted into concrete, fibers in single-filament state or fiber strands in an unbundled state may become fiber balls, and the fibers cannot be dispersed uniformly throughout the matrix. There is also a problem that occurs.

[0003]

In order to prevent a decrease in fluidity and a variation in strength, a method has been proposed in which fibers are bundled with a strong binding force. But, for example,
Japanese Patent Application Laid-Open No. 63-203876 proposes that carbon fibers be cured with an epoxy resin to form an FRP to shorten the fibers and increase the strength. However, since a large amount of resin is used, a concrete matrix and fiber are required. When a load such as bending is applied due to poor adhesion to the strand, the fiber is easily pulled out, and there is a problem that the reinforcing effect is hardly exhibited.

[0004]

The inventors of the present invention have conducted intensive studies to solve such problems. As a result, when kneading with concrete, a strand having a strong convergence force is used. It has been found that fiber strands that are in a thread state and are uniformly dispersed in concrete can solve the above-mentioned problems, and specifically, improve the fluidity of concrete in a fresh state, and provide a fiber ball. In order to prevent this, it is effective to enhance the convergence of the strand. For this purpose, a specific amount of a specific resin is used as an impregnating agent in order to harden the texture of the strand.
Further, in order to make the state close to the single yarn dispersion after kneading, by increasing the number of twists, the impregnated sizing agent is squeezed out so that a large amount of resin accumulates on the surface. By these, it discovered that the fiber strand of this invention which was excellent in the dispersion in concrete and had a high reinforcement effect was obtained, and reached this invention. That is, the gist of the present invention is a fiber strand comprising a large number of fiber single yarns and a resin, wherein the resin has a compressive strength of 30 to 300 kgf / cm ² , and the angle formed by the fiber single yarn with respect to the length direction of the fiber strand is 3 ~ 20 degrees, and
The fiber strand is characterized in that the proportion of the fiber single yarn in the fiber strand is 95 to 99% by weight.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Usually, a fiber strand obtained by bundling a large number of single fibers with a resin called a sizing agent is referred to as a fiber strand. In the present invention, the number of single fiber fibers forming the fiber strand is 1,000 or more, preferably 1,000. The number is at least 50,000 and at most 6,000, particularly preferably at least 6,000. When the number of single fiber fibers forming the fiber strand is 1,000 or less, when the fiber strand is added to the concrete, the fiber strand is easily cut and the reinforcing effect is hardly obtained.
On the other hand, if it exceeds 50,000, the number of fiber strands becomes small even if the addition amount of the fiber single yarn is equal, and it is difficult to obtain a sufficient reinforcing effect. It requires a single fiber fiber and is not economical.

The fiber single yarn used in the present invention has a fiber diameter of usually 3 to 20 μm, preferably 5 to 18 μm, and a tensile strength of usually 200 kgf / mm ² or more, preferably 400 kgf / mm ^2.
As described above, the elongation is usually 1.5% or more, preferably 2.0% or more. Examples of such fibers include aramid fibers and carbon fibers, and carbon fibers are preferably used. As the carbon fiber, a carbon fiber made of coal tar pitch, petroleum pitch, coal liquefaction, polyacrylonitrile, cellulose, or the like can be used. Here, the elongation is a value obtained by dividing the tensile strength of the fiber by its tensile modulus.

[0007] The fiber strand of the present invention can be obtained by bundling a bundle of single fiber yarns with a specific resin as a sizing agent in a state where a predetermined twist is applied. The angle formed by the single fiber yarn with respect to the length direction of the fiber strand is
Also called the degree of twist, 3 to 20 degrees, preferably 5 to 1
0 degrees. The degree of twist of 3 to 20 degrees means that
Expressed in terms of the number of twists per meter, it corresponds to 25 to 200 turns / m. If the degree of twist is less than 3 degrees, the sizing agent penetrates into the strands, and the fiber single yarns are firmly bonded to each other, so that the fiber strands cannot be dispersed into the single yarns in concrete. If it exceeds 20 degrees,
Failure such as damage such as fiber breakage occurs,
The fiber weight per a certain length increases and the concrete cannot be reinforced effectively.

The resin constituting the fiber strand may be any resin which is generally used as a sizing agent, but a resin having a firm texture of the fiber strand obtained when it is attached to the fiber is selected. Has a compressive strength of 30 to 3
The resin is 00 kgf / cm ² , preferably 40 to 100 kgf / cm ² . If the compressive strength is less than 30 kgf / cm ² , the cohesive force for maintaining convergence as a single fiber strand is weak, and if it is 300 kgf / cm ² or more, the cohesive force is too strong and fiber strands do not disperse in concrete. The problem arises. In the present invention, the compressive strength is 5 mm × 5 at the bottom.
A value obtained when a resin cured body having a height of 5 mm and a height of 5 mm was used as a test body and a test body was subjected to a compressive load and measured.

As such a sizing agent, an epoxy resin, a phenol resin, a butyral resin, a nylon resin and the like are usually mentioned. These resins may be dissolved in a solvent or used in the form of a water-dispersed emulsion, but the water-dispersed emulsion is preferable. Examples of the solvent for dissolving the resin in a solvent include alcohol, ketone, methylene chloride, and THF. Particularly, in the case of an epoxy resin, ketones, especially methyl ethyl ketone, are preferred from the viewpoint of the dissolution speed and the boiling point. If necessary, a curing agent may be used for the resin. In the case of an epoxy resin, an amine-based curing agent is particularly preferably used.

[0010] The fiber strand obtained in this manner has a firm texture. The fiber strand having a firm texture has a strong adhesion of the sizing agent existing between the single fiber yarns to the carbon fiber, and the fiber strand in the fiber strand has a strong texture. Since the space between the single yarns is hard to open, excess cement is not absorbed, so that the fluidity of the fresh concrete is hardly reduced. The stiffness of the texture is measured by placing a fiber strand of 50cm length horizontal to the ground and fixing only one end, leaving it to stand for at least 1 minute, and the other end hangs down from its original horizontal position due to its own weight. Those that do not have a firm texture.

The proportion of single fiber fibers in the fiber strand is 95 to 99% by weight, preferably 96 to 98% by weight. When the fiber is a carbon fiber, the proportion of the fiber single yarn in the fiber strand is the proportion occupied by the fiber in the fiber strand composed of the fiber and the sizing agent.
The weight loss at 30 ° C. for 30 minutes is calculated as the weight of the sizing agent. If the proportion of the fiber single yarn in the fiber strand is too high, the amount of the sizing agent is too small, so that the fiber is broken during cutting. On the other hand, if the proportion of the fiber single yarn is too low, that is, if the amount of the sizing agent attached is too large, the performance at the time of cutting is good, but the adhesive force between the concrete and the fiber strand is reduced, and the reinforcing effect is reduced. Before or after impregnating the fiber strand of the present invention with a sizing agent diluted with a solvent, a predetermined number of long filaments of fiber single yarn is twisted,
Thereafter, the sizing agent is obtained by completely evaporating the solvent in which the sizing agent is dispersed and cutting the sizing agent into a predetermined length.

The length of the fiber strand is usually at least 1.5 times, preferably at least 2 times, the maximum dimension of the coarse aggregate mixed with the concrete, and specifically, 30 to 2 times.
00 mm is preferably used. If the length of the fiber strand is less than 30 mm, the reinforcing effect is small because the critical fiber length of the composite material is not reached. In addition, length 30mm
When used in combination with the above fiber strand, a fiber strand having a length of less than 30 mm may be added. Further, under the condition that the fiber strand is two-dimensionally or one-dimensionally oriented, the effect of lengthening the fiber strand becomes remarkable. The diameter of the fiber strand is usually 0.3 to
3 mm.

The fiber strand of the present invention can be made into fiber reinforced concrete by being mixed with concrete. In the fiber strand of the present invention, at the initial stage of kneading with concrete, the fiber strand itself is rigid, so that fiber balls do not occur and are uniformly dispersed. Adhesion with concrete is removed, increasing the reinforcing effect.

Concrete is usually cement, coarse aggregate,
The main ingredients are fine aggregate, admixture and water. As the cement, ordinary Portland, Portland, and Portland are used. The amount of addition is not particularly problematic as long as it is a normal formulation used for civil engineering and construction, and is preferably 250 kg / m ³ or more. As the coarse aggregate (gravel), for example, crushed stone, artificial lightweight coarse aggregate, iron oxide steel or the like is used. Preferably, the average particle size is 30 mm
The following crushed stones are good. The amount of addition is not particularly problematic as long as it is a normal preparation, and is preferably 1000 kg / m ³ or less. As the fine aggregate (sand), for example, sand, silica stone, silica fume, artificial lightweight fine aggregate and the like are used. The amount of addition is not particularly problematic as long as it is a normal formulation used for civil engineering and construction purposes, and is preferably 1500 kg / m ³ or less. The fine aggregate ratio (sand ratio) is not particularly limited as long as it is a normal mixture used for civil engineering and construction purposes, and is preferably 40 to 80.
% Is good.

[0015] The addition amount of the fiber strand is usually at least 0.1 vol%, preferably at least 0.4 vol%, more preferably at least 0.5 vol%. As the amount of addition increases, the bending strength and toughness increase. In addition, since excessive addition causes not only cost but also inefficiency of enhancement of reinforcement effect and decrease of fluidity, it is preferably 0.4 to 1.0% by volume, more preferably 0.5 to 0.7% by volume. %. Examples of the admixture include a water reducing agent, a dispersant, an antifoaming agent, and a foaming agent.
Examples of the water reducing agent include a special surfactant containing a triazine ring-based high condensate salt as a main component, a special sulfonic group-containing carboxyl group-containing multipolymer, an anionic special polymer activator, a naphthalenesulfonic acid condensate ligninsulfonic acid derivative, and oxycarboxylic acid. Acids, ligninsulfonic acid and the like. The amount of addition is usually 1 to 3 parts with respect to 100 parts of cement.

Fiber-reinforced concrete is obtained by kneading cement, coarse aggregate, fine aggregate, carbon fiber strand, water, admixture, etc., pouring it into a mold while vibrating with a vibrator if necessary, and curing at room temperature or steam. And, if necessary, curing by curing in an autoclave. As the mixer to be kneaded, all mixers that are usually used can be used, and paddle type, propeller type, paddle type, turbine type, pan type, ribbon type, screw type, warner type, kneader type,
In the case of a mixer having a stirring blade such as a two-shaft type or an omni type,
After producing ordinary concrete, carbon fiber is added and kneaded again. Fibers may be added from a dry state.

The fiber reinforced concrete thus obtained has a fresh property of JIS A 110
Slump value measured according to 1, usually 5-25cm,
Preferably it is 5 to 20 cm. The dispersion coefficient of the fiber in the concrete determined by the following equation is 0.85 or more. If the dispersion coefficient is less than 0.85, the dispersion of the fibers becomes poor, and the variation in the strength between the test specimens increases, which is not preferable. Dispersion coefficient: α = exp (-ψ)

[0018]

１ (x) = √ (Σ (Xi−X) ² / n) / X where Xi is the number of fiber strands contained in the sample,
n: number of samples, X: average of the number of fiber strands contained in the sample. The dispersion coefficient is a numerical value between 0 and 1, and a value closer to 1 indicates that the fibers are dispersed in the concrete. The bending strength of the cured fiber reinforced concrete measured according to JIS A 1106 is as follows:
It is usually 70 kgf / cm ² or more, preferably 80 kgf / cm ² , and has sufficient strength. If the flexural strength is low, the structure obtained by constructing the fiber reinforced concrete may not have sufficient strength, which is not preferable.

[0019]

The present invention will be described in more detail with reference to the following examples. First, carbon fiber strands used in Examples and Comparative Examples are shown below. <Carbon fiber strand A> As a fiber single yarn, diameter 7μ
m continuous carbon fiber (“T-700S” manufactured by Toray Industries, Inc.) 1
After 2,000 pieces are bundled and twisted at 40 turns / m so that the degree of twist is 5 degrees by a ring twister, the compressive strength when the resin is cured is 60 kgf / cm ² as a sizing agent. Epoxy resin emulsion ("Epilet 3510" manufactured by Yuka Shell Epoxy Co., Ltd.) having a concentration of 3.0% by weight and an amine-based curing agent ("Epicure 8535" manufactured by Yuka Shell Epoxy) being a 1.5% by weight liquid The sizing agent was immersed in a sizing agent solution which had been diluted to 1 mm. Then, after drying at 120 ° C., it was cut into a predetermined length. The diameter of the obtained carbon fiber strand was 0.8 to 1.2 mm. In this example, a small amount of resin adhering to commercially available carbon fibers is not regarded as a sizing agent.

<Carbon fiber strand B> As a sizing agent,
Except that the concentration of the epoxy resin emulsion was changed to 5.0% by weight and the concentration of the amine-based curing agent was changed to 2.5% by weight, and the compressive strength when the sizing agent resin was cured was 60 kgf / cm ^2. Performed similarly to strand A. <Carbon fiber strand C> The same procedure was performed as for carbon fiber strand A, except that the degree of twist was changed to 11 degrees. <Carbon fiber strand D> The same procedure was performed as for carbon fiber strand A, except that the degree of twist was changed to 1.5 degrees. <Carbon fiber strand E> The carbon fiber strand A was manufactured in the same manner as the carbon fiber strand A, except that the twist degree was changed to 39 degrees.

<Carbon Fiber Strand F> As a sizing agent,
Same as fiber strand A, except that the concentration of the epoxy resin emulsion was 5.0% by weight, the amine-based curing agent was not blended, and the compressive strength when the sizing agent resin was cured was 5 kgf / cm ^2. went. <Carbon Fiber Strand G> As a sizing agent, a solvent-based epoxy resin (“Epicoat 828” manufactured by Yuka Shell) having a compressive strength of 500 kgf / cm ² when cured has a concentration of 5.0% by weight, and a solvent-based curing agent (oil). Shell “Epicoat B00”
2 ") Fiber strand A except that a concentration of 2.5% was used.
The same was done. Table 1 shows the properties of the obtained carbon fibers A to G.
Shown in 1

[0022]

[Table 1]

<Example 1> The amount of coarse aggregate, fine aggregate and cement shown in the concrete mixture P was mixed with a biaxial mixer (5
5 liters), and then mixed with water and an admixture, and wet-mixed for 150 seconds to obtain concrete. Next, a carbon fiber strand A having a fiber length of 40 mm was mixed into the concrete at a rate of 9.0 kg / m ³ and wet-kneaded for 1 minute to obtain a kneaded material containing carbon fibers. Here, a part of the obtained kneaded material was fractionated and subjected to JIS A 11
The measurement of the slump value and the degree of fiber dispersion were carried out in accordance with No. 01. The measurement of the degree of fiber dispersion was carried out from the obtained kneaded material by 100%.
One test was to take out the concrete mass of g and count the number of strands. This test was performed 10 times, and the calculation was performed by the following formula using all data. Dispersion coefficient: α = exp (-ψ)

[0024]

２ (x) = √ (Σ (Xi−X) ² / n) / X where Xi: the number of fiber strands contained in the sample,
n: number of samples, X: average of the number of fiber strands contained in the sample. On the other hand, the obtained kneaded material was 10 cm × 10 c
It was poured into a m × 40 cm formwork, demolded after 16 hours to obtain a cured product. After curing for one week at 20 ° C. and 60 RT%, a bending test was performed according to JIS A1106.
The loading speed was 2 mm / min and the number of test pieces was n = 6. The coefficient of variation ψ (x) represents the magnitude of variation in sample intensity, and was calculated by the above equation. The results are summarized in Table-2.

[0025]

[Table 2] In this formulation, W / C = 50% by weight, and the fine aggregate ratio was 50%.
% By volume. The following materials were used as raw materials. Cement: Chichibu Onoda Cement Co., Ltd., early strength Portland cement Fine aggregate: sand (from Hamaoka), maximum dimension 5.0 mm Coarse aggregate: lightweight aggregate mesalite Admixture: Takemoto Yushi Pharmaceutical Co., Ltd., trade name : Tupole HP-11

Examples 2, 3 and Comparative Examples 1-4 Carbon fiber strands B (Example 2), carbon fiber strand C (Example 3), carbon fiber strand D
Comparative Example 1 was performed in the same manner as in Example 1, except that the carbon fiber strand E (Comparative Example 2), the carbon fiber strand F (Comparative Example 3), and the carbon fiber strand G (Comparative Example 4) were used.
Table 2 shows the results.

<Comparative Example 5> The same procedure as in Example 1 was carried out except that no carbon fiber was added. Table 2 shows the results.

[0028]

[Table 3] In addition, the specific gravity of the concrete of Examples 1-3 and Comparative Examples 1-5 was 1.9-2.0.

[0029]

According to the present invention, it is possible to obtain a fiber reinforced concrete which is excellent in dispersibility and workability of fiber strands as a fresh property and has high strength as a cured body performance.

Claims (3)

[Claims] 1. A fiber strand comprising a large number of fiber single yarns and a resin, wherein the resin has a compressive strength of 30 to 300 kgf /
cm ^2, the fiber strands, characterized in that 3 to 20 degrees angle of a fiber single yarn to the length direction of the fiber strand, and the proportion of fiber single yarn occupied in the fiber strand is 95 to 99 wt%. 2. The fiber strand according to claim 1, wherein the fiber is a carbon fiber. 3. The fiber strand according to claim 1, wherein the fiber strand is used for compounding cement.