JPS63247008A - Manufacture of fiber-reinforced concrete - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing fiber-reinforced concrete in which short fibers are mixed into concrete in order to improve various properties such as tensile strength and bending strength of concrete. It depends.

[Conventional technology]

Conventionally, fiber-reinforced concrete is produced by mixing short fibers such as steel fibers, glass fibers, carbon fibers, and polymer fibers into an unhardened cement matrix, and by kneading the mixed short fibers with the unhardened cement matrix. It is produced by dispersing it in an uncured cement matrix and then curing the uncured cement matrix. Regarding fiber-reinforced concrete, see 81 of the Abstracts of Academic Lectures at the Architectural Institute of Japan (Architectural Institute of Japan, published in July 1986).
There are reports on steel fiber reinforced concrete on pages 82 to 82, aramid fiber reinforced concrete on pages 87 to 88, and carbon fiber reinforced concrete on pages 601 to 602.

[Problem that the invention seeks to solve]

The conventional method for producing fiber-reinforced concrete includes mixing elongated and bulky short fibers such as steel fibers, glass fibers, carbon fibers, and polymer fibers into an unhardened cement matrix;
Since the mixed short fibers are dispersed in the unhardened cement matrix by kneading the unhardened cement matrix, a large amount of air is entrained into the unhardened cement matrix during kneading. In this way, the mixed short fibers are uniformly dispersed, but if a large amount of air is entrained in the uncured cement matrix and the uncured cement matrix hardens, the cement matrix after hardening will be sparse. However, there was a problem in that the reinforcing effect of the fibers was reduced, and the tensile strength and bending strength of the fiber-reinforced concrete were reduced.

It is an object of the present invention to eliminate these conventional disadvantages.

[Means for solving problems]

The present invention provides a method for producing concrete mixed with fibers, in which the raw materials are kneaded without vacuum deaeration, and then vacuum deaeration is performed and further kneading is performed under vacuum. This is a method for producing reinforced concrete.

In the production method of the present invention, after kneading without vacuum deaeration, vacuum deaeration is performed and further kneading is performed under vacuum. Air is no longer entrained in the uncured cement matrix, and the cement matrix after hardening becomes dense, but the short fibers mixed in are not dispersed uniformly, and the reinforcing effect of the fibers decreases. This is because it was discovered that this causes the disadvantage that the tensile strength and bending strength of fiber-reinforced concrete decrease.

Vacuum deaeration as used in the present invention means to bring the inside of the kneading container to a pressure equal to or lower than atmospheric pressure. In order to make the cement matrix particularly dense, it is optimal to degas to a vacuum level of 60 uHg or less.

The kneading used in the present invention does not require any particular means, but in order to more uniformly disperse the fibers, it may be oscillating kneading.

In other words, it is a device that does not use stirring blades, but has a rubber ball that can freely move up to 5 m on a disk-shaped oscillating plate. It is optimal to knead by shaking a rubber ball filled with the ingredients to accelerate the contents, varying the speed and direction to scatter them in random directions, and an omni mixer can be used.

The kneading time in the present invention is 1 to 60 minutes for both cases of non-vacuum degassing and vacuum degassing, but in order to achieve better uniform dispersion of fibers and better density of the cement matrix. After kneading for 5 to 45 minutes without vacuum degassing, perform X air degassing, and then knead for 1 to 45 minutes under vacuum.
Kneading for 10 minutes is optimal.

The fibers referred to in the present invention include steel fibers and glass fibers.

Refers to carbon fiber, polymer fiber, etc.

Concrete as used in the present invention refers to Daltland cement, blast furnace cement, fly ash cement, alumina cement, colloid cement, oil well cement, etc. and coarse aggregate,
In addition to concrete consisting of fine aggregate, admixtures, and water, mortar and coarse aggregate that do not contain coarse aggregate as components,
In the present invention, pastes containing no fine aggregate are collectively referred to as concrete.

〔Example〕

Example! A. Materials used: Cement: Early strength Portland cement mixture, TO agent: Methyl cellulose Hi-Metrose 90
8H-4000 Water: Tap water Carbon range @: PAN-based carbon carbon fiber chopped fibers (Table 1 shows the physical properties of the fibers used.

Table-1 Physical properties of fibers used B, 1iI11 go Table 2 shows the formulation in this example.

Table 2 Preparation 0, Kneading method Each component shown in Table 2 was put into an omni mixer capable of vacuum treatment, kneaded at high speed for 6 minutes without vacuum degassing, and vacuum degassing was performed. Kneading was further performed for 5 minutes under a vacuum degree of .

The flow value of the kneaded product obtained by K in this manner is 124, and the unit volume weight is 1. 9/1 in 89,
The amount of entrained air, which is a measure of compactness, was 3.

D. Molding method and curing method Molding was carried out using a metal mold (4 x 4 x 16 cm) by pouring into this.

After casting, the mold was left standing in a constant temperature and humidity room at 20°C and relative humidity of 80% for 1 day, then removed from the mold and autoclaved for 5 hours at 180°C and 10 atm. After being removed from the autoclave, the temperature was 20°C and the relative humidity was 659°C until it was subjected to a bending strength test on the 7th day after pouring.
It was left standing in a constant temperature and humidity room of 6.

83 Bending strength test The bending strength test is conducted at 5 t T with the distance between the supporting points being LOm.
It was carried out using an OM-5000 test machine.

The test results are shown in Table 3.

From Table 3, the average bending strength was 485 KVc11.

Furthermore, when the fractured surface of the specimen after the bending strength test was polished and the dispersion distribution of the fibers was analyzed by image analysis, uniform dispersion of the fibers was observed.

Comparative Example 1 The components of Example 1 and the konji preparation were put into the same mixer as in Example 1, and kneaded at high speed for K11 minutes without vacuum degassing.

The flow value of the kneaded product thus obtained, which was not set yet, was 126, and the unit volume weight was 1.60V'l. Further, the amount of entrained air was 17, which was about 5.7 times that of Example 1.

The molding method, curing method, and bending strength test method were the same as in Example 1.

The bending strength test results are as shown in Table 3, and the average value was 297 S/-.

Comparative Example 2 Each component of the same formulation as in Example 1 was put into the same mixer as in Example 1, vacuum deaerated from the beginning, and kneaded for 11 minutes under a vacuum of 30 u+Hg.

The flow value of the kneaded product thus obtained, which has not solidified yet, is 121. The unit volume weight was 1.90Q/l.

Further, the amount of entrained air was 1%, which was about 178 in Comparative Example 1.

The molding method, curing method, and bending strength test method were the same as in Example 1.

The bending strength test results are shown in Table 3, and the average value was 27LK9/cd.

Furthermore, when the fractured surface of the specimen after the bending strength test was polished and the dispersion distribution of the fibers was analyzed by image analysis, no uniform dispersion of the fibers was observed.

Example 2 Each component of the same formulation as in Example 1 was put into the same mixer as in Example 1, and kneaded for 10 minutes without vacuum degassing.
After kneading for 25 minutes and 40 minutes, vacuum deaeration was performed for each, and kneading was continued for an additional 5 minutes under a vacuum degree of 30 mHH.

The flow values of the uncured kneaded products thus obtained were 120, 135, and 144, respectively, and the unit volume weight was 1.
ti soleso h 1.9 oKvl, 9 to 1.91
/l # 1.92KSI/V.

The entrained air amount was 19%, LSI, 1.3%.

The molding method, curing method, and curve strength test method are as in Example 1.
The same as

The bending strength test results are as shown in Table 3, with average values of 500, 574, 5+/d, and 6, respectively.
It was 15Kjl/-.

Furthermore, when the fractured surface of the specimen after the bending strength test was polished and the dispersion distribution of the fibers was analyzed by image analysis, uniform dispersion of the fibers was observed.

Table-3 Bending strength test result table [Effects of the invention] As described above, according to the present invention, steel fiber, glass fiber,
Long, slender, bulky short fibers such as carbon fibers and polymer fibers can be uniformly dispersed in the cement matrix, and a dense cement matrix can be obtained. This improves the reinforcing effect of the mixed fibers, making it possible to produce fiber-reinforced concrete with extremely high tensile strength and 2 bending strengths.

Claims (1)

[Claims] A method for producing fiber-reinforced concrete characterized in that when kneading the raw materials in the method for producing concrete mixed with fibers, the raw materials are kneaded without vacuum deaeration, and then vacuum deaeration is performed and further kneading is performed under vacuum.