JPS6375259A - Method for casting mass concrete - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to concrete for submerged boxes for submarine tunnels, bottom plates of water treatment plants, sewage treatment plants, side wall concrete, LNG tank side wall concrete, nuclear reactor structures, etc. Concerning the method of placing mass concrete.

[Problem that the invention seeks to solve]

The pipe cleaning method is known as a means of artificially controlling the temperature of concrete after pouring in order to suppress cracks that occur as the concrete hardens. It was designed for cooling, and was not capable of cooling the concrete temperature for a long period of time, about one month after pouring, which is necessary to prevent cracks. In addition, heat insulating sheets, heat insulating mats, etc. are used to keep concrete warm after pouring, but these methods only cover the concrete surface after pouring to prevent it from rapidly cooling down, so it is necessary to actively It was not designed to specifically control the concrete temperature. In the past, there was no means to control the temperature of concrete over a long period of time, so it was difficult to prevent cracks during mass concrete pouring.

In particular, in a mass concrete structure 3 consisting of a bottom slab 1 and a wall 2 as shown in Fig. 5, the wall 2 is subject to significant restraint by the bottom slab 1, so it is practically difficult to prevent the occurrence of cracks. Ta.

In such cases, conventionally, it usually took about two weeks to one month for the construction process to take place after the bottom slab 1 was poured and the wall 2 was poured, and the wall 2 was poured after the bottom slab 1 had cooled down. Because of this, cracks were likely to occur. Furthermore, even if the wall 2 is kept warm and cured using a heat insulating sheet, etc., sufficient heat retention is not achieved, and the wall cools down rapidly after reaching its peak temperature, making it impossible to prevent cracks from occurring due to cooling. There wasn't.

This invention was made in view of the above circumstances. The purpose is to propose a method for placing mass concrete that is less prone to cracking.

[Means for solving problems]

This method of placing mass concrete, when constructing a structure made of mass concrete, divides the mass concrete into multiple concrete units, buries water pipes for temperature control, and pours the existing concrete. The temperature difference between the temperature of the unit and the temperature raised due to the hydration reaction of the poured concrete unit placed in contact with the unit is reduced by passing water through the water pipe to raise the temperature of the existing concrete unit, and The temperature of the joint concrete unit is controlled by passing water through the water pipe, and the temperature decrease rate after the peak of the hydration reaction is controlled to be slow.

This pouring method will be explained below with reference to the embodiment shown in FIGS. 1 and 2 (aL (b)).

When constructing a mass concrete structure 3 consisting of a bottom plate 1 and walls 2, etc., first, a concrete unit 4-1 is placed in the bottom plate 1, water pipes 5 for temperature control are buried in parallel inside the concrete unit 4-1, and the bottom plate is constructed by burying water pipes 5 for temperature control in parallel. form 1.

Prior to pouring concrete on wall 2, water pipe 5
The temperature of the bottom plate 1 is raised by passing hot water 6-a at a'c (30 to 50 degrees Celsius) through the tank, and at the same time, storing the hot water 6 on the top surface of the bottom plate 1, and attaching a heat insulating material 7 to the side of the bottom plate 1 to keep it warm. We aim to (1st
．． (See Figure 2 (a)) Once the bottom plate 1 has reached the desired temperature, concrete units 4-2 are poured into the wall 2, and at the same time water pipes 5 are buried and the wall 2 is poured in contact with the bottom plate 1. Form a seam. At this time, the temperature of concrete unit 4-2 C rises due to the hydration reaction, so continue to flow hot water 6-a' to water pipe 5 of bottom plate 1 to keep the temperature difference between concrete unit 4-2 and concrete unit 4-2 at a small value. . After the concrete unit 4-2 reaches its peak temperature, a heat insulating material 7 is placed on its side to protect it, and at the same time hot water 6-b of b ''c is passed through the water pipe 5 to bring the temperature of the concrete unit 4-2. In addition, the temperature of the concrete unit 4-2 is controlled by passing warm water 6-b of b'c through the water pipe 5 in the bottom plate 1 section to slow down the temperature drop rate. In addition, water continues to flow through the water pipe 5 to the bottom plate 1 part, and the temperature difference with the concrete unit 4-2 is maintained at a small value, and the concrete unit 4-2 is hardened while gradually cooling the whole. Then, the wall body 2 is formed.

Figure 3 shows the concrete unit 4-1 (
It is a correlation graph between the material age (number of days) and concrete temperature of concrete unit 4-2 (bottom slab portion) and concrete unit 4-2 (wall portion).

The broken line part shows the case where temperature is controlled by this pouring method, and the temperature difference T between the bottom slab part and the wall part at the peak time and after is made small compared to the solid line part where temperature control is not performed. There is no need to slow the temperature down rate.

FIG. 4 shows an example of a suitable concrete IJ-cont temperature control device used in this pouring method.

Hot water header pipes 8.8 are attached to both ends of each of the groups of water pipes 5 buried in the bottom plate 1 and the wall body 2, and a feed pipe 9 and a return pipe 10 are connected to the header pipes to circulate hot water. In the figure, 11 is a boiler, 12 is a hot water pump, and 13 is 1
Next hot water drum, 14 is a control valve, 15 is a numerical controller,
16 is a heat exchanger, 17 is a circulation hot water drum, and 18 is a variable displacement hot water circulation pump.

[For production]

This method of placing mass concrete consists of the above configuration. In this pouring method, mass concrete is divided into multiple concrete units and placed, and the temperature difference between the existing concrete unit and the pouring concrete unit placed in contact with it is small during heating and curing. The strain stress generated between the two due to the difference becomes small, and cracks can be suppressed.

In addition, since the concrete is slowly cooled after the peak temperature, the elongation capacity of the concrete increases, and the occurrence of cracks due to cooling can be suppressed.

〔Effect of the invention〕

The present invention is as described above, and according to this pouring method, a mass concrete structure can be constructed while suppressing cracks.

[Brief explanation of the drawing]

Fig. 1.2 (a), (bl is a vertical cross-sectional view and a perspective view showing the method of placing mass concrete in the example in the order of steps, respectively, Fig. 3 is a correlation graph between material age and concrete temperature in the example, Fig. 4 is a schematic diagram of a concrete temperature control device suitable for use in this pouring method, and Fig. 5 is a partial sectional view of a conventional mass concrete structure. 1...Bottom slab, 2... ...Wall body, 3...
・・Mass concrete structure, 4-1.4-2・・・・
... Concrete unit, 5 ... Water pipe, 6 ...
...Hot water, 7...Heat insulation material, 8...Hot water header pipe, 9...Feed pipe, 10...
Return pipe, 11... Boiler, 12...
Hot water pump, 13... Primary hot water drum, 14.
... Control valve, 15 ... Numerical controller,
16... Heat exchanger, 17... Circulating hot water drum, 18... Hot water circulating pump.

Claims (1)

[Claims] (1) When constructing a structure made of mass concrete, the mass concrete is divided into multiple concrete units, and temperature control water pipes are buried and poured, and the temperature of the previously poured existing concrete unit and this are Water is passed through the water pipe to raise the temperature of the existing concrete unit, and the temperature difference between the temperature and the temperature that has increased due to the hydration reaction of the poured concrete units placed in contact with each other is made small, and A method for placing mass concrete, characterized in that the temperature is controlled by passing water through the water pipes, and the rate of temperature drop after the peak of the hydration reaction is slow.