JPH10121730A - Reduction construction method for crack due to temperature of concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the cracks due to temperature of concrete, by mixing synthetic resin powder dissolved by the hydration heat of concrete into concrete for forming a mass concrete. SOLUTION: Cement A, coarse aggregate B, fine aggregate C, various chemical admixtures D, water E, and synthetic resin powder F are charged in a kneaded 10 and kneaded together. And the concrete mixture is placed to construct a mass concrete structure. The powder F mixed in the concrete is dissolved by the hydration heat. The temperature increase of the concrete is reduced by the dissolution heat. After the powder F has been dispersed in fine pores in the curing concrete, it is hardened to increase the toughness, the tensile strength, and the resistance against cracks of the concrete. In this way, the thermal stress is reduced and the resistance against cracks is improved and cracks of the mass concrete structure resulting from the temperature can be reduced by these synergistic effects.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing temperature cracks in concrete, and more particularly to a method for reducing temperature cracks in mass concrete structures.

[0002]

2. Description of the Related Art A mass concrete structure having a large member cross section accumulates heat of hydration reaction of cement and considerably raises the internal temperature. The structure expands and contracts in the process of such an increase in the internal temperature and a subsequent temperature decrease associated with cooling, and such a change in volume is constrained by external factors, or the internal temperature is not uniform. Therefore, it is known that stress is generated inside and temperature cracks easily occur.

[0003] Such temperature cracks naturally affect the durability and function of the structure. Therefore, a number of methods for reducing this kind of cracks have been proposed in the past, for example, a pre-cooling method of directly cooling concrete constituent materials such as aggregates and concrete with ice or liquefied nitrogen, or a method after casting. Cooling methods such as post cooling method (pipe cooling) for cooling concrete,
There is a constraint reduction method (after-bond rebar, slot method) that reduces the constraint when the volume changes (shrinks).

[0004] However, such a conventional method for reducing temperature cracks has the following technical problems.

[0005]

That is, the above-mentioned conventional method for reducing temperature cracks requires new equipment and special management techniques, which considerably increases the cost. It becomes difficult to apply to general construction work except for large cases.

Therefore, for example, concrete materials,
Although it is being studied from the viewpoint of compounding technology, cement concrete is basically a composite material that is vulnerable to tension and bending, has relatively low crack resistance, and has found a method to effectively reduce temperature cracking. There is no present.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to effectively reduce temperature cracks without requiring new equipment or special management techniques. It is to provide a construction method that can perform

[0008]

Means for Solving the Problems In order to achieve the above object, the present invention relates to a method for constructing a mass concrete structure having a large member cross section, wherein the concrete for forming the mass concrete structure is included in the concrete. Synthetic resin powder that dissolves by the heat of hydration reaction was mixed. According to the method for reducing the temperature cracking of the concrete thus configured, the synthetic resin powder mixed into the concrete dissolves by the heat of hydration reaction of the concrete, so that the temperature rise is reduced by the heat of dissolution accompanying the dissolution. . The synthetic resin cured after dissolution can be dispersed in the structure to improve the toughness of the cement matrix, especially the tensile strength, and to increase the crack resistance. As the synthetic resin powder, a polyvinyl alcohol-based powder having a melting point of 50 to 80 ° C can be used.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. In the method for reducing temperature cracks according to the present invention, the difference between the maximum internal temperature of concrete and the external temperature due to heat of hydration reaction is 25 mm for a wall-shaped member having a minimum cross section of 80 cm or more, or 50 cm or more on a floor slab.
It is applied when constructing mass concrete structures that are expected to be at or above ° C.

When such a mass concrete structure is formed, as shown in FIG. 1, cement A, coarse aggregate B, fine aggregate C, various admixtures D, and water E, which are constituent materials of the concrete, are shown in FIG. Is put into the kneading apparatus 10, and these are mixed and stirred to produce concrete of a predetermined composition.

At this time, in the present invention, a synthetic resin powder F that is dissolved by the heat of hydration reaction of the concrete is mixed with the above-mentioned concrete constituent materials A to E. This synthetic resin powder is put into the kneading apparatus 10, and the process of kneading with the constituent materials A to E of concrete and the casting of concrete start a hydration reaction of the cement A, and the inside rises to a predetermined temperature. The period is maintained in a powder state.

As such a synthetic resin powder F, for example, a polyvinyl alcohol-based powder having a melting point of 50 to 80 ° C. can be used. The amount of the synthetic resin powder F added is determined by the calorific value of the hydration reaction based on the compounding amount of the cement A,
What is necessary is just to set suitably considering the difference between the heat of dissolution of the synthetic resin powder F, the restrained state of the concrete structure, and the outside air temperature.

When concrete mixed with the synthetic resin powder F is kneaded and produced, concrete is poured to construct a mass concrete structure. When the hydration reaction of the poured concrete starts and the internal temperature rises to a predetermined temperature, the dissolution of the synthetic resin powder F contained in the concrete starts.

When the melting of the synthetic resin powder F starts, a part of the heat of hydration reaction of the concrete is consumed as the heat of melting of the powder F, whereby the rise in the internal temperature of the concrete is reduced.

The dissolved synthetic resin powder F diffuses into the fine voids in the concrete in the course of hardening and then hardens, thereby increasing the toughness of the hardened concrete and improving the tensile strength.

From the above, it is possible to reduce the temperature stress generated when constructing a mass concrete structure and to improve the crack resistance. These synergistic effects allow the temperature crack of the mass concrete structure to be reduced. Can be reduced.

Further, such an effect can be obtained only by mixing the synthetic resin powder F when kneading the concrete, and no special equipment or management technique is required.

[0018]

As described above in detail in the embodiments,
ADVANTAGE OF THE INVENTION According to the concrete temperature crack reduction method of this invention, generation | occurrence | production of the crack of a mass concrete structure can be reduced effectively with a simple structure.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a kneaded state of concrete used in a concrete temperature cracking reduction method according to the present invention.

[Explanation of symbols]

 A Cement B Coarse aggregate C Fine aggregate D Admixture E Water F Synthetic resin powder

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Sakuhiro Nagao 4-640 Shimoseito, Kiyose-shi, Tokyo Inside Obayashi Corporation Technical Research Institute

Claims (2)

[Claims] When constructing a mass concrete structure having a large member cross section, a synthetic resin powder that is dissolved by the heat of hydration reaction of the concrete is mixed into the concrete for forming the mass concrete structure. Method to reduce temperature cracks in concrete. 2. The method according to claim 1, wherein said synthetic resin powder is of a polyvinyl alcohol type.