JPS6313507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a method for curing mass concrete.

<Prior art and its problems> During the hardening process of concrete, heat of hydration is generated by the reaction between cement and water.

In particular, in large mass concrete structures such as dams and tanks, the heat of hydration inside the structure is poorly radiated, so they are subject to external restraints due to internal temperature rise.
Furthermore, since the surface of the structure in contact with the outside air radiates a large amount of heat, it is subject to internal constraints due to an increase in the temperature difference between the inside and outside.
As a result, temperature stress occurs in the mass concrete, causing cracks.

Conventionally, as a method of suppressing the generation of temperature stress in mass concrete, there has been a method using buried pipe cooling, such as the method disclosed in Japanese Patent Publication No. 56-2180, to suppress the temperature rise inside a mass concrete structure. However, the disadvantage is that the construction costs are high due to pipe costs, cooling costs, injection costs, etc.

In addition, as shown in Japanese Patent Publication No. 45-16418, for example, an elastic hose is buried in an expanded state, and after the concrete hardens, it is contracted and pulled out, and cooling water is injected into the concrete structure. A method of forming a hole has also been proposed, but it has the disadvantage that it becomes difficult to pull out the hose when forming a deep injection hole.

Furthermore, one way to reduce the temperature difference between the inside and outside of a mass concrete structure is to use heat retention (heat supply) curing to raise the temperature of the surface of the structure, but this method is disadvantageous in reducing the temperature, which is the ultimate purpose of mass concrete. act.

The present invention was made in view of the above-mentioned problems, and its purpose is to radiate the hydration heat peculiar to mass concrete structures, reduce the internal temperature and the temperature difference between the outside and outside, and suppress the generation of temperature stress. The purpose is to provide a concrete curing method.

<<Means for Solving the Problems>> In order to achieve the above object, the present invention provides a structure in which a mass concrete structure is slightly sloped from the horizontal so that one outer surface of the structure leads to the opposite outer surface. A convection groove is provided, the water is flooded with a water surface in contact with the outer surface of the structure, and natural convection of the flooded water and water surface heat radiation are used to create a natural flow between the flooded water and the convection groove. It is characterized in that it is circulated and cured in the flooded water while dissipating the heat of hydration within the mass concrete structure.

<<Example>> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Here, we will take concrete bottom slabs found in underground LNG storage tanks as an example, and Figures 1 and 2 show the following:
A cross-sectional view and a plan view are shown, respectively, in the case where a convection groove with a slight slope from the horizontal is provided so as to communicate from the side surface of the bottom slab concrete to the opposite side surface.

In the figure, numeral 1 indicates a bottom plate-shaped concrete which is a mass concrete structure. Reference numeral 2 designates a convection groove which is slightly sloped from the horizontal so as to communicate from the side surface 7, which is one outer surface, of the concrete bottom slab 1 to the opposite side surface 7'. The convection groove 2 is formed by using a member (not shown) that can be removed or buried to form a predetermined groove during concrete pouring.

In addition, the convection grooves 2 are designed by taking into account the thickness, area, and expected amount of heat of hydration of the mass concrete.
Size, slope, depth position, number of groove holes,
Intervals etc. are determined.

Further, at both ends of the convection groove 2, communication pipes 8, 8' extending toward the upper surface side of the bottom plate-shaped concrete 1 are provided.
are provided for each.

In this case, the upper surface 3 of the bottom plate-shaped concrete 1
is the convection groove 2 with a slight slope from horizontal.
It is desirable to have the same slope according to

Then, on the upper surface 3 of the bottom plate-shaped concrete 1, flooding 6 is performed having a water surface 5 in contact with the outside air 4.

In the above configuration, the flooded water 6 in the convection groove 2
is heated to a high temperature by heat exchange with the heat of hydration in the central part of the bottom slab-shaped concrete 1, and becomes an upward flow 9, which moves toward the water surface 5 of the flooded water 6 through the communication pipe 8.

The high temperature water 6 that has reached the water surface 5 is exposed to the atmosphere 4.
The temperature decreases due to heat dissipation to.

Further, the stored water 6, whose temperature has been reduced by atmospheric heat radiation, increases in specific gravity and moves downward as a downward flow 10 into the convection slot 2 through the communication pipe 8'.

In addition, if the circulation amount of natural convection is not large,
If necessary, a pump or the like can be used to supplement forced circulation of convection.

In addition, if the outside temperature is high and it is difficult to dissipate heat from the water surface of the reservoir 6 to the atmosphere, a heat insulating material or the like that can be controlled at a predetermined temperature may be brought into contact with the water surface of the reservoir 6 to promote convection. Can be done.

In this way, the natural convection due to the temperature difference in the flooded water 6 and the heat radiation from the water surface 5 to the atmosphere of the flooded water 6 are used to cause natural circulation, and the heat of hydration in the bottom slab-shaped concrete 1 is radiated, and the bottom slab To suppress the generation of temperature stress by reducing the internal temperature and temperature difference between the inside and outside of shaped concrete 1.

In this case, the reduction in temperature difference between inside and outside is due to the following action.

The water that has exchanged heat with the heat of hydration of the bottom slab concrete 1 in the convection groove 2 mixes with the flooded water 6 by convection, thereby increasing the temperature of the flooded water 6 in contact with the outer surface of the bottom slab concrete 1.

Therefore, the outer surface of the bottom plate-shaped concrete 1 is also flooded 6.
The temperature will rise compared to when no
The temperature inside the bottom slab concrete 1 decreases by exchanging heat with the water in the convection grooves 2, so the temperature inside and outside of the bottom slab concrete 1 becomes closer, so the temperature difference can be reduced, and the temperature stress due to twisting can be reduced. Can be done.

When the concrete 1 has been cured in the manner described above, the flooded water 6 is removed from the convection grooves 2 of the bottom slab-shaped concrete 1, and post-cast concrete is poured.

<<Effects of the Invention>> As detailed above, according to the present invention, a convection groove that penetrates from one outer surface of the structure to the opposite outer surface and has a slight slope from the horizontal is provided in a mass concrete structure. Since the structure is constructed with a water surface that is in contact with the outside air, natural convection due to the temperature difference between the inside and outside of the mass concrete structure and water surface heat dissipation into the atmosphere are utilized. Since the heat of hydration within the mass concrete structure is dissipated through natural circulation, the generation of temperature stress due to the decrease in the internal temperature and the temperature difference between the inside and outside of the mass concrete structure is suppressed, resulting in a high-quality mass concrete structure without cracks. I can make things.

Furthermore, according to the present invention, since the water stored on the mass concrete structure has a large heat capacity, it is possible to utilize the initial cooling energy against the initially low water temperature, and also to alleviate the temperature shock to the mass concrete caused by a sudden drop in outside temperature. In addition, since post-cast concrete is placed in the convection groove, it becomes a shear key, eliminating the need for shear reinforcing bars, and also eliminating the need for large-scale equipment required for concrete curing. , low maintenance costs, and secondary effects such as not being a major support for the process.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a sectional view and a plan view showing an embodiment of the concrete growing method according to the present invention. 1...Bottom plate-shaped concrete, 2...Convection groove,
6...Flooding, 8,8'...Communication pipe, 9...Upflow,
10...downward flow.

Claims (1)

[Claims] 1. A convection groove with a slight slope from the horizontal is provided in a mass concrete structure so as to communicate from one outer surface of the structure to the other outer surface, and a convection groove with a water surface in contact with the outer surface of the structure is installed. By using the natural convection of the flooded water and water surface heat radiation, natural circulation is caused between the flooded water and the convection groove, and the heat of hydration in the mass concrete structure is radiated while the water is heated. A mass concrete curing method characterized by curing in water.