JPH101341A - Short fiber strand and short fiber reinforced concrete - Google Patents

Abstract

(57) [Summary] [Problem] To obtain carbon fiber reinforced concrete having excellent workability and high strength. [Solution] A short fiber strand is placed in a mortar having a viscosity of 300 cp, and stirring is performed at 200 rpm for 1 minute with a stirring blade having a radius of 3 cm. Strand weight increase A1 when added, viscosity 1
The convergence force is adjusted so that the ratio (A2 / A1) to the increase in strand weight A2 when equivalent stirring is added in a mortar of 000 cp is 1.1 or more and less than 10. Fiber strand and short fiber reinforced concrete using the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to short fiber strands and short fiber reinforced concrete.

[0002]

2. Description of the Related Art Fibers used in fiber-reinforced concrete generally include steel fibers, glass fibers, and organic fibers in order to increase the strength and toughness. However, when using steel fiber,
The fiber reinforced concrete has a problem that the rate of increase in flexural strength relative to non-reinforced concrete is low, about 50%, and the load at the time of initial crack generation is low. Furthermore, when durability problems such as rusting occur or when used for road pavement,
There is a problem that steel fibers protrude into the rut and the tires of automobiles are punctured.

Further, when glass fibers and organic fibers are used, the reinforcing effect is extremely low due to the effects of the alkali resistance of the fibers and the properties of the fibers, such as tensile strength and elastic modulus, and the strength is increased by the degree of suppressing crack progress. Can not hope. On the other hand, when carbon fibers are used, durability such as prevention of fiber deterioration is improved. However, in carbon fiber reinforced concrete, it is performed only with long fibers such as rods and meshes, and short fibers are almost the same as mortar and spray repair materials without coarse aggregate. The reason for being limited to such applications is that when carbon fibers are mixed with short fibers, severe cuts and damages are caused in the presence of coarse aggregate, and the fiber reinforcing effect on the molded body is small. Even when used daringly, it was only a degree of suppression of crack propagation that had already occurred. There was also an attempt to increase the strength by hardening the carbon fiber with epoxy into a rod shape to shorten the fiber, and to increase the strength.However, when a load such as bending is applied, the fiber escapes between the matrix and the fiber, and the reinforcing effect is reduced. Did not appear.

[0004] In addition, when reinforcing fibers are mixed, there is also a serious operational problem that the fluidity of concrete at the time of production is reduced. This is because the fiber components absorb moisture, cement paste or mortar in the matrix, resulting in a shortage of fluid components in the concrete matrix. This phenomenon occurs irrespective of the type of fiber such as steel fiber, carbon fiber, glass fiber, and the like, and technical development has been desired to reduce this problem as much as possible.

[0005] With regard to the bending strength, in the case of SFRC, the bending strength is increased by increasing the amount of fibers. However, since the strength at the time of initial crack generation is almost the same as the bending strength of ordinary concrete, it was not possible to avoid the generation of cracks even if the load was not exceeded even when the load was further increased.

[0006]

Means for Solving the Problems The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, when a strand is formed by a sizing agent in the order of several hundreds to tens of thousands of fibers, concrete Found that by adding fiber strands with low absorption of cement paste in concrete to concrete, it is possible to obtain fiber-reinforced concrete with excellent fluidity with less decrease in fluidity during production compared to before fiber addition. Thus, the present invention has been completed. That is, the gist of the present invention is that (1) a short fiber strand has a viscosity of 300 cp.
200 rpm with a 3 cm radius stirring blade
Strand weight increase A1 when stirring for 1 minute is added,
The ratio (A2 / A1) to the increase in strand weight A2 when equivalent stirring was added in a mortar having a viscosity of 1000 cp was 1.
A short fiber strand characterized in that the convergence force is adjusted so as to be 1 or more and less than 10, and (2) a short fiber reinforced concrete containing the short fiber according to the above (1).

When the value of A2 / A1 is smaller than 1.1, A1
If the value is small, the strength is reduced at the time of producing short fiber reinforced concrete, and if the A1 value is not small, the fluidity at the time of producing short fiber reinforced concrete is deteriorated. A2 / A1 value is 1
When it is 0 or more, the fluidity at the time of producing short fiber reinforced concrete becomes poor. In such short fiber strands and short fiber reinforced concrete, the short fibers are preferably carbon fibers.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As a type of fiber sizing agent, when poured into concrete, it does not readily absorb fluid components such as cement paste and moisture around the fiber strands, that is, in the matrix, and is completely unlike a curable resin. Those other than those that do not absorb, that is, those that cause some absorption are preferred.

As an index for achieving this, a short fiber strand is placed in a mortar having a viscosity of 300 cp containing 300 cc or more in a normal 500 cc beaker, and a stirring blade having a radius of 3 cm (for example, TK Homodisper L manufactured by Tokushu Kika Kogyo Co., Ltd.)
The ratio (A2 / A1) between the strand weight increase A1 when 200 rpm of stirring was added for 1 minute and the strand weight increase A2 when the same stirring was applied in a mortar having a viscosity of 1000 cp was 1 A sizing agent whose convergence can be adjusted so as to be not less than 1 and less than 10 is preferable.
For example, an epoxy-based emulsion is preferably of an epibis type, and preferably has a molecular weight of 800 or more, an anionic or nonionic-based emulsifier, and an emulsifier of less than 20%.

The mortar is prepared by mixing fine aggregate / cement ratio of 0-200 / 100 and water / cement ratio of 35-6.
0/100, the water reducing agent / cement ratio is 1-2 / 2/100, the viscosity is adjusted by the amount of water added, and the measurement is performed by a B-type viscometer. As cement to use,
There is no particular limitation, and examples include ordinary Portland, early-strength Portland, ultra-high-strength Portland, moderate heat cement, and alumina cement.

The fine aggregate (sand) is not particularly restricted but includes river sand, silica sand and the like. 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.

Stirring was performed with a stirring blade having a radius of 3 cm at 200 rpm.
When rotated for 1 minute at a rotation of m, the weight increase is preferably 50 times or less as A1 and 100 times or less as A2 with respect to before input, A2 / A1 is 1.1 or more, and Preferably it is less than 10. For example, a rod-shaped FRP in which A1 is 2.5 times that of A1 is 2.5 because A2 is also 2.5, but A2 / A1 is 1; Even if it is .5 times, since A2 becomes 10 times, A2 / A1 becomes 4.

The weight is measured after the fiber strand is taken out of the mortar and allowed to stand on a 420 μm mesh for 1 minute. In order not to absorb the fibers, it is preferable that the gap between the single yarns in the fiber strand is difficult to be opened. This strength is reflected in the texture of the strand, and the harder the strand, the greater the effect. As an index to measure the hardness, the strand is set to 50c with the ground level.
When only one end of the m-length fiber strand is fixed and allowed to stand for 1 minute or more, it is preferable that the opposite end does not hang down from its original horizontal position due to its own weight.

The fibers used in the present invention include carbon fibers, synthetic fibers such as vinylon and aramid, glass fibers and the like, and carbon fibers are preferred. For example, carbon fiber can be used without particular limitation as long as it has a tensile strength of 100 kgf / mm ² or more, preferably 250 kgf / mm ² and an elongation of 1% or more. For example, coal tar pitch, petroleum pitch, coal Liquefied matter, polyacrylonitrile,
Carbon fibers made of cellulose or the like can be used. Here, the elongation is a value obtained by dividing the tensile strength of the carbon fiber by its tensile modulus.

The shape of the fiber is at least one time, preferably at least two times the maximum dimension of the coarse aggregate used, and the actual length is at least 20 mm, preferably at least 30 mm.
mm or more. If the fiber length is less than 20 mm, the reinforcing effect is small because the critical fiber length as a composite material has not been reached. In addition, if it mixes with the fiber of 20 mm or more, you may add the fiber of less than 20 mm.

The fiber having a yarn diameter of 5 to 30 μm, preferably 6 to 18 μm is used. When the amount of addition is the same, the smaller the number of bundles of fiber strands, the more the reinforcing effect is significant. This is because the number of fiber strands borne during loading simply increases.

The amount of the fiber added is 0.05 vol% or more,
It is preferably at least 0.3 vol%. First, the cement raw material in the present invention is not particularly limited, and is usually Portland, Portland, Portland, Portland,
Moderate heat cement, alumina cement and the like can be mentioned. The amount of addition is not particularly problematic as long as it is a normal preparation used for civil engineering and construction, and is preferably in the range of 200 to 1000 kg / m ³ .

The type and diameter of the coarse aggregate (gravel) are not particularly limited, and include crushed stone, artificial lightweight coarse aggregate, iron oxide stone and the like, and crushed stone having a diameter of 50 mm or less is preferable. The amount of addition is not particularly limited as long as it is a normal preparation used for civil engineering and construction, and is preferably 1500 kg / m ³ or less. Examples of the fine aggregate (sand) include sand, silica stone, gravel, shirasu balloon fly ash, silica fume, and artificial lightweight fine aggregate. The amount of addition is not particularly limited as long as it is a normal preparation used for civil engineering and construction, and is preferably 1500 kg / m ³ or less.

The fine aggregate ratio (sand ratio) is not particularly problematic as long as it is a general formulation used for civil engineering and construction purposes, and is preferably 30 to 70%. As the admixture, it is not particularly necessary to use, but it is preferable to use silica fume having a particle size of 1 μm or less. The addition amount is preferably 1 to 30% based on the cement.

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. , Oxycarboxylic acid, ligninsulfonic acid and the like. The addition amount is preferably 1 to 5 parts with respect to 100 parts of cement.

In addition to the dispersant and the water reducing agent, admixtures 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 mixers that are usually used can be used. In the case of a mixer having a stirring blade such as a paddle type, a propeller type, a paddle type, a turbine type, a pan type, a ribbon type, a screw type, a warner type, a kneader type, a twin-shaft type, an omni type, the fiber and the cement raw material are used. Is first mixed without adding water, and then kneaded by adding water, or kneading raw materials other than fibers with water to produce ordinary concrete, then adding carbon fibers and kneading again.

The vibrator used in the present invention may be any as long as it can be attached to a mixer, but it is preferable to use a vibrator incorporating a high-frequency vibration motor having excellent vibration efficiency.

[0023]

The present invention will be described in more detail with reference to the following examples. In the following examples and comparative examples, 120
A carbon strand consisting of 00 single yarns was used, and a cutter was used for cutting. In addition, TK homodisper L type was used for stirring. Example 1 300 cc mortar having an aggregate / cement ratio of 100/100, a water / cement ratio of 50/100, a water reducing agent / cement ratio of 1/100 and a viscosity of 300 cp (hereinafter referred to as "mortar A") was placed in a 500 cc beaker. , This has a length of 40
5 mm of carbon fiber strands were added, and the mixture was stirred for 1 minute at 200 rpm with a stirring blade having a radius of 3 cm.
00/100, water / cement ratio 45/100, water reducing agent / cement ratio 1/100, viscosity 1000 cp mortar (hereinafter referred to as "mortar B") 300 cc in a 500 cc beaker, and carbon fiber 40 mm in length Add 5 strands, 200 rpm with a 3 cm radius stirring blade
Sizing agent (Epoxy Emulsion KP8 manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) so that the ratio (A2 / A1) to the weight increase A2 of the carbon fiber strand when stirred for 1 minute by rotation of A is 4.4.
The carbon fiber strand (length of the sizing agent: 1.4%) having a length of 40 mm to which (00) was attached was put into concrete and mixed for 60 seconds. The addition amount of the carbon fiber strand was 0.5% based on the total concrete volume.

As for concrete, the cement amount of the early-strength Portland cement is 400 kg / m ³ , W / C 50 wt%, fine aggregate ratio 60 vol% (coarse aggregate has a maximum particle size of 15 mm, fine aggregate is Chichibu sandstone fine sand), Admixture (silica fume, 44 kg / m ³ ),
Mixing agent of 1.5% by weight of admixture (Takemoto Oil & Fat Tupole HP11), 2-axis mixer (55 liters) as a mixer
It was used. First, coarse aggregate, fine aggregate and cement are charged and dry-mixed for 60 seconds. Then, a mixed solution of water and an admixture is charged, and
What was wet-mixed for 50 seconds was used as concrete.

The kneaded mixture obtained by mixing the carbon fibers was poured into a mold and demolded after 16 hours. Curing of the strength test specimen is 20
The test was conducted at 60 ° C. and 60% RT, and after curing for 2 weeks, a bending test was performed in accordance with JIS A 1106. The loading speed is 2mm / m
In, the test log was performed with n = 6. Table 2 shows the results. Comparative Example 1 300 cc of mortar A was placed in a 500 cc beaker, 5 carbon fiber strands having a length of 40 mm were added thereto, and the weight increase of carbon fiber strands A1 when the mixture was stirred for 1 minute at 200 rpm with a stirring blade having a radius of 3 cm was added. , Mortar B, 300 cc in a 500 cc beaker, 5 carbon fiber strands having a length of 40 mm were added thereto, and a radius of 3 cm
The sizing agent (Takemoto Yushi Co., Ltd. Epoxy Emulsion MCS1094) was adjusted so that the ratio (A2 / A1) to the weight increase A2 (A2 / A1) of the carbon fiber strands when the mixture was stirred at 200 rpm for 1 minute with the stirring blade of No. 1 was used. Length attached 4
0 mm carbon fiber strand (impregnated amount of sizing agent:
(1.3%) was put into concrete and mixed for 60 seconds.
The addition amount of the carbon fiber strand was 0.5% based on the total concrete volume.

As for concrete, the cement strength of the early-strength Portland cement is 400 kg / m ³ , W / C 50 wt%, fine aggregate ratio 60 vol% (coarse aggregate has a maximum particle size of 15 mm, fine aggregate is Chichibu sandstone fine sand), Admixture (silica fume, 44 kg / m ³ ),
Mixing agent of 1.5% by weight of admixture (Takemoto Oil & Fat Tupole HP11), 2-axis mixer (55 liters) as a mixer
It was used. First, coarse aggregate, fine aggregate and cement are charged and dry-mixed for 60 seconds, then a mixture of water and an admixture is charged,
What was wet-mixed for 150 seconds was used as concrete.

The kneaded product obtained by mixing the carbon fibers was poured into a mold and demolded after 16 hours. Curing of the strength test specimen is 20
The test was conducted at 60 ° C. and 60% RT, and after curing for 2 weeks, a bending test was performed in accordance with JIS A 1106. The loading speed is 2mm / m
In, the test log was performed with n = 6. Table 2 shows the results. Comparative Example 2 300 cc of mortar A was put into a 500 cc beaker, 5 carbon fiber strands having a length of 40 mm were added thereto, and the weight increase A1 of the carbon fiber strands was obtained when stirring was performed at 200 rpm for 1 minute with a stirring blade having a radius of 3 cm. , Mortar B, 300 cc in a 500 cc beaker, 5 carbon fiber strands having a length of 40 mm were added thereto, and a radius of 3 cm
A sizing agent (Dynippon Resin Co., Ltd. Dynamic Resin B910) such that the ratio (A2 / A1) to the weight increase A2 (A2 / A1) of the carbon fiber strands when stirring at 300 rpm for 1 minute with a stirring blade of No. A carbon fiber strand having a length of 40 mm (amount of the sizing agent attached: 50%) to which was diluted twice with epoxy thinner) was added to concrete and mixed for 60 seconds. The amount added was 0.5% of the total concrete volume.

As for concrete, the cement amount of early-strength Portland cement is 400 kg / m ³ , W / C is 50 wt%, fine aggregate ratio is 60 vol% (coarse aggregate has a maximum particle size of 15 mm, fine aggregate is Chichibu sandstone fine sand), Admixture (silica fume, 60 kg / m ³ ),
Mixing agent of 1.5% by weight of admixture (Takemoto Oil & Fat Tupole HP11), 2-axis mixer (55 liters) as a mixer
It was used. First, coarse aggregate, fine aggregate and cement are charged and dry-mixed for 60 seconds. Then, a mixed solution of water and an admixture is charged, and
What was wet-mixed for 50 seconds was used as concrete.

The kneaded product obtained by mixing the carbon fibers was poured into a mold and demolded after 16 hours. Curing of the strength test specimen is 20
The test was conducted at 60 ° C. and 60% RT, and after curing for 2 weeks, a bending test was performed in accordance with JIS A 1106. The loading speed is 2mm / m
In, the test log was performed with n = 6. Table 2 shows the results.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

As described above, by kneading the short fiber strand and the concrete mixed with the short fiber strand according to the present invention, a carbon fiber reinforced concrete excellent in workability and high in strength can be obtained.

Claims (3)

[Claims] 1. A short fiber strand is placed in a mortar having a viscosity of 300 cp and a stirring blade having a radius of 3 cm is agitated at 200 rpm for 1 minute.
The convergence force is adjusted so that the ratio (A2 / A1) to the increase in strand weight A2 when equivalent stirring is added in a mortar of 000 cp is 1.1 or more and less than 10. Textile strand. 2. The short fiber strand according to claim 1, wherein the short fiber is a carbon fiber. 3. A staple fiber reinforced concrete comprising the staple fiber according to claim 1 or 2.