JPS6157769A - Prevention of cracking of 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] This invention relates to a method for preventing cracks in concrete.
In particular, it relates to a method for preventing initial temperature cracks that occur after pouring.

As is well known, after concrete is poured, the temperature of the concrete increases due to the heat of hydration of the cement, and as this temperature reaches a peak and then decreases, if deformation is restrained, cracks (initial temperature cracks) will occur. arise.

These cracks become more noticeable as the cross-sectional size of the concrete 1 increases, as the cement content in the concrete increases, and as the degree of restraint it receives increases.

By the way, in the past, almost no measures have been taken to prevent this cracking, and only the cracks that have occurred have been repaired by methods such as cutting and coating.

However, initial temperature cracks often penetrate through the cross section, which not only reduces the strength and durability of the component, but also impairs its aesthetic appearance and requires significant repair costs.

The present invention was made in view of the above-mentioned conventional circumstances, and its purpose is to provide a concrete crack prevention method that can suppress initial temperature cracking of concrete with a relatively simple structure. It is about providing.

In order to achieve this objective, this invention uses a metal member with good thermal conductivity for the formwork when constructing a concrete structure using a formwork, and a water sprinkler is attached to the outer surface of the formwork. Then, water is intermittently sprinkled on the outer surface of the formwork by the water spraying device from just before the concrete is poured until the concrete temperature Iff after pouring reaches its highest, absorbing the reaction heat during setting and hardening of the concrete. It is characterized by

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the method for preventing cracks in concrete according to the present invention, and this figure shows an example of application in the case of constructing a wall portion of a retaining wall made of concrete.

The wall part of the retaining wall is constructed using flat metal formwork 10.10.
The formwork 10 is connected horizontally and erected so as to face each other.
It is formed by pouring concrete 12 into a space separated by .

Here, the crack prevention method of the present invention is based on concrete 1
2, J along the outer surface of the formwork 1o:
The water sprinkler 14 is installed in this manner.

The watering device 14 includes a wire rod 18 that is secured to the formwork 10 at appropriate points and connected at both ends with turnbuckles 16, a watering tube 22 suspended from the wire rod 18 by a hanging tool 20, and a watering duplex 22. The system consists of a water supply pump (not shown) that supplies cooling water to the system.

The wire rods 18 and the watering tubes 22 are arranged in multiple stages so as to vertically divide the formwork 10 at predetermined intervals. A large number of opposing pores 24 are bored.

The water sprinkling device 14 configured in this manner is used immediately before pouring the concrete 12 for constructing the retaining wall, and water is sprayed onto the outer surface of the formwork 10 from the pores 24 of the water sprinkling tube 22.
When the entire surface of the formwork 10 becomes wet, the process is stopped once, and when it starts to dry, watering is performed intermittently.

Further, intermittent watering is performed until the temperature of the concrete 12 reaches its peak.

This is because if water is sprinkled until the temperature of the concrete 12 drops past its peak, the cooling rate increases, which tends to induce cracking.

In addition, although the method of watering is illustrated using the watering chicove 22 in the above embodiment, the implementation of the present invention is not limited to this, and other means may be used as long as it is possible to do so without wetting the formwork 10. Good too.

As described above in detail in the Examples, in the concrete crack prevention method according to the present invention, concrete is intermittently poured on the surface of a metal formwork from immediately before pouring until the temperature reaches its peak. By sprinkling water, the heat of hydration of the cement in the concrete is absorbed by the latent heat of vaporization of water, and excellent effects such as effectively suppressing cracks caused by temperature rise can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention.

Claims (1)

[Claims] When constructing concrete structures using formwork, the formwork is made of metal members with good thermal conductivity, and a water sprinkler is attached to the outside surface of the formwork, so that the formwork starts immediately before pouring the concrete. A concrete product characterized in that water is intermittently sprinkled on the outer surface of the formwork by the water spraying device until the temperature of the concrete after pouring reaches its highest, absorbing reaction heat during setting and hardening of the concrete. How to prevent cracks.