JP2002020144A - Admixture and concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an admixture capable of reducing excess water in a concrete production process, thereby producing concrete having high strength and a dense structure. SOLUTION: An admixture 1 is formed by coating the surface of special lightweight artificial aggregate 2 with a water-soluble polymer 3 to be dissolved by an alkaline component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an admixture which is mixed with cement together with water, aggregates and the like at the time of concrete production, and which has a special countermeasure against excess water, and concrete using the admixture.

[0002]

2. Description of the Related Art In order to build a durable concrete building, a high quality aggregate and an AE water reducing agent are used at the time of concrete production, and fresh concrete is produced in a unit water amount as small as possible within a range where casting is easy. Have been.
Also, recently, since high-quality aggregates have decreased and the unit water volume has exceeded the specified value, high performance AEs have been used to reduce the unit water volume.
Water reducing agents are increasingly used.

[0003] On the other hand, when pouring fresh concrete, a method of attaching a water-permeable sheet to the inside of a formwork and removing excess water in excess concrete is also used. Further, it is preferable that fresh concrete having a low water-cement ratio is densely cast into the formwork. Furthermore, it is known as a measure for improving durability that sufficient water retention curing is performed so as not to dry when the concrete hardens.

[0004]

However, even if concrete is manufactured using high-quality aggregate and a high-performance AE water reducing agent, it is required for the cement hydration to maintain the fluidity of fresh concrete. The amount of water used is about 1.5 to 2 times the amount of water used. Therefore, after casting, excess water other than the water necessary for the hydration reaction bleeds inside the concrete due to the difference in density between the cement and the aggregate, and rises to the concrete surface. As a result, the surplus water that has moved inside the concrete forms a water supply (Mizumichi) and, after drying, becomes a capillary cavity and the structure of the concrete becomes dense.

[0005] As a result, when the concrete becomes coarse and dense, not only does the long-term compressive strength of the concrete decrease, but also cracks due to drying shrinkage, an increase in the neutralization speed due to the penetration of carbon dioxide gas in the air, and an acidity due to a decrease in water tightness. There is a problem that it becomes a factor that impairs durability, such as intrusion of rain and deterioration of frost damage resistance in cold regions. The admixture and concrete according to the present invention are proposed to solve such problems.

[0006]

The gist of the present invention for solving the above-mentioned problems of the admixture according to the present invention is that a special lightweight artificial aggregate is formed by coating a surface of a water-soluble polymer which is soluble with an alkaline component. It is that you are.

The gist of the concrete of the present invention is that the above-mentioned admixture is kneaded and produced by substituting 5 to 15% of the fine aggregate in the aggregate volume ratio of the concrete.

In the admixture according to the present invention, the water-soluble polymer coated on the surface of the special lightweight artificial aggregate does not dissolve even if it is exposed to moisture in the air or rain during storage. Also, even if it is kneaded during the production of concrete, it is not immediately dissolved by the alkali component of fresh concrete, but after kneading, it is transported to the site and gradually dissolved according to the time of completion of casting. Yes, it melts at the time when bleeding starts, and the special lightweight artificial aggregate gradually absorbs excess water.

According to the admixture and concrete according to the present invention, in fresh concrete poured into a formwork, a water-soluble polymer gradually dissolves due to an increase in alkalinity (OH-) due to a hydration reaction, and the coating material disappears. By doing so, surplus water is absorbed by air bubbles in the special lightweight artificial aggregate of the admixture. Thereby, bleeding is suppressed. In addition, the water-cement ratio is reduced, resulting in high-strength concrete.

The water-soluble polymer as the coating material is dispersed on the surface of the special lightweight artificial aggregate in the admixture, and a part of the water-soluble polymer is absorbed by the bubbles of the special lightweight artificial aggregate together with excess water. During the curing period during hardening of the concrete, the excess water absorbed by the air bubbles is supplied to the surroundings and substitutes for the curing water, and the water-soluble polymer dissolved in the excess water during the drying is used as the surface of the special lightweight artificial aggregate. It hardens in the air bubbles and restricts the movement of moisture in the concrete to reduce drying shrinkage.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an admixture according to the present invention and concrete using the same will be described with reference to the drawings. As shown in FIG. 1, the admixture 1 of the present invention is formed by coating the surface of a special lightweight artificial aggregate 2 with a water-soluble polymer 3 that is soluble in an alkaline component.

The special lightweight artificial aggregate 2 is obtained by sintering and granulating raw materials such as expanded shale, expanded clay, and fly ash, and has a particle size of about 1 mm to 2 mm.
It is. The special lightweight artificial aggregate 2 coated with a water-soluble polymer is in a completely dry state and has a water absorption of 1%.
It is about 0 to 20% by weight.

The special lightweight artificial aggregate 2 has fine bubbles of about 50 to 300 microns inside the particle diameter. There are the air bubbles, and the strength of the special lightweight artificial aggregate is also strong.

The water-soluble polymer 3 is usually a fine granular powder which is dissolved in water when used. The water-soluble polymer 3 is difficult to dissolve in water at normal temperature.
It dissolves easily in warm water of about 0 ° C to 80 ° C. It can be adjusted to an aqueous solution having appropriate viscosity with water. In addition, the water-soluble polymer 3 dissolves in normal temperature water if it is an alkaline solution. For example, polymer polyvinyl alcohol and the like are used. Further, the water-soluble polymer 3 cures when dried, and has an appropriate strength.

In order to form this admixture, after the special lightweight artificial aggregate is sintered, it is cooled to, for example, about 50 ° C. to 80 ° C., and then the aggregate is introduced from the upper hopper of the dropping type stirring and spraying apparatus. While passing through the apparatus, the sprayed water-soluble polymer 3 is sprayed. When the water-soluble polymer 3 is sprayed, the temperature of the special lightweight artificial aggregate is relatively high, so that the water-soluble polymer instantaneously adheres to the aggregate and hardens.

Thereafter, the water-soluble polymer 3 coated on the surface of the special lightweight artificial aggregate is dried by a drying device installed in the device. When the admixture arrives at the hopper at the bottom of the device, the coated water-soluble polymer 3 is completely dry.

In the coating of the admixture 1, the time from the production of fresh concrete to the casting of the formwork and the time of bleeding occur,
It adjusts the solubility with respect to the alkali concentration and the coating thickness.

The concrete of the present invention comprises cement, water,
Coarse aggregate, fine aggregate, and the admixture replaced with 5 to 15% of the fine aggregate in the volume ratio of concrete, and other admixtures are kneaded to produce fresh concrete,
After that, it is cast into a mold and cured.

After the fresh concrete is poured into the formwork, the concrete becomes more alkaline due to the progress of the hydration reaction, and the water-soluble polymer 3
Gradually dissolves, and excess water 4 that is necessary for the fluidity (workability) of the concrete but unnecessary for the hydration reaction is
It is absorbed by the bubbles 5 of the special lightweight artificial aggregate 2.

[0020] Since the admixture is properly dispersed in the concrete, the surplus water can move only a small amount in the concrete.
Bleeding is prevented without making a water supply with excess water, and concrete with a dense structure free of water and air bubbles can be produced. Further, since the admixture absorbs excess water before the concrete hardens, the water-cement ratio can be reduced and the strength becomes high.

Further, after the concrete is hardened, the excess water absorbed by the admixture gradually diffuses into the concrete and becomes curing water, which contributes to an increase in strength and a reduction in drying shrinkage.

[0022]

As described above, the admixture according to the present invention is formed by coating the surface of a special lightweight artificial aggregate with a water-soluble polymer which is soluble in an alkali component. Excess water can be absorbed during the reaction, and the concrete structure can be densified.

The concrete of the present invention comprises the admixture
5-15% of fine aggregate in concrete aggregate volume ratio
It becomes a dense concrete because it is replaced and kneaded and produced, it reduces drying shrinkage, delays neutralization, improves frost damage resistance and water tightness, and improves the durability of the entire concrete It has the effect that it has.

[Brief description of the drawings]

FIG. 1 is a sectional view of a concrete according to the present invention.

FIG. 2 is an explanatory view showing that the admixture according to the present invention absorbs excess water into bubbles of a special lightweight artificial aggregate by dissolving the coating with an alkaline component.

[Explanation of symbols]

1 admixture, 2 special lightweight artificial aggregate, 3 water-soluble polymer, 4 excess water, 5 bubbles.

Continuing from the front page (72) Inventor Toshiro Itaya 1-7-1 Kyobashi, Chuo-ku, Tokyo Toda Construction Co., Ltd. (72) Inventor Munehiro 1-7-1 Kyobashi, Chuo-ku, Tokyo Toda Construction Co., Ltd. (72) Inventor Naoto Hata 1-7-1 Kyobashi, Chuo-ku, Tokyo F-term in Toda Construction Co., Ltd. (reference) 4G012 LA15 PA06 PA27 PA27 PB29

Claims (2)

[Claims] 1. An admixture characterized by being formed by coating a surface of a special lightweight artificial aggregate with a water-soluble polymer soluble in an alkaline component. 2. An admixture formed by coating the surface of a special lightweight artificial aggregate with a water-soluble polymer that dissolves in an alkaline component is reduced to 5 to 15% of the fine aggregate in the aggregate volume ratio of concrete. Concrete produced by mixing and kneading and producing.