JPS61254756A - How to place 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 Field of Industrial Application This invention relates to a method for placing concrete, and more particularly to a method for placing concrete that suppresses an increase in concrete temperature due to water utilization during concrete placement.

Problems to be Solved by the Invention When placing mass concrete, a large cross-sectional area is filled with concrete, so the temperature rises due to heat generation due to the water use reaction of the cement in the concrete. This temperature rise may cause temperature stress during the subsequent temperature drop, leading to the risk of cracks in the concrete.

Various measures have been taken to minimize this heat generation and temperature rise! there was. In other words, the following measures are taken: ■Reducing the amount of cement.■Using low-heat-generating cement.■Lowering the pouring temperature of concrete.■Devising ways to cure the concrete after pouring. Moreover, sufficient effects were not always obtained.

This invention was made in view of the above circumstances. The purpose is to propose a concrete pouring method that suppresses the temperature rise of poured concrete, prevents the occurrence of cracks, and casts high-quality concrete with high construction efficiency.

Means for Solving the Problems The method for placing concrete according to the present invention involves, prior to placing concrete, placing precast concrete blocks in the space where concrete is to be placed, leaving a gap into which ready-mixed concrete is poured. The method is characterized in that a precast concrete block is placed in the ready-mixed concrete that has been set aside or poured, and the ready-mixed concrete is placed integrally with the precast concrete block.

Function: The precast concrete block used in the concrete placing method of the present invention does not generate heat, but absorbs the heat of the adjacent heating element.

Therefore, if precast concrete blocks are placed side by side in a formwork in which mass concrete is to be cast, or are placed in poured ready-mixed concrete, and ready-mixed concrete is placed in the spaces between the blocks, water utilization of the ready-mixed concrete is possible. is absorbed by the block, suppressing the temperature rise to a low level,
It is integrated with a precast concrete block and can be used to place fresh concrete.

Example: When pouring a concrete slab with a thickness of 2 m, a concrete slab with a diameter of 80 cm and a height of 2 m is placed in the formwork 1, as shown in Fig. 1.
As shown in Fig. 2, cylindrical precast concrete blocks 1 are arranged side by side with a mutual spacing (D) of 1rIL, and ready-mixed concrete 3 having the following composition is poured into the gap, and the blocks 2 and ready-mixed concrete 3 are integrated. A concrete slab was poured. Block 2 occupied 58% of the bulk volume, and fresh concrete accounted for 42%.

In addition, the surface of block 2 was made uneven in order to improve the shear conduction of the joint surface.

Fresh concrete composition Cement: Ordinary cement 252Kf/♂, Fireash 58KVWLs Unit water volume 137KvrrL
3 Amm water reducer Hozolith 8,725 to 9/♂ slump 1
2cIIL The relationship between the elapsed time and temperature of the poured concrete slab is shown in the graph in Figure 5.

In this drawing, ■ is the temperature at a height of 1 m in the part where a precast concrete block could not be placed, ■ is the temperature at a height of 1 rIL in the middle part of the six precast concrete blocks (point B in Figure 2), and ■ is the temperature at a height of 1 m above the This is the temperature at a position 5 cIL below the upper surface of point B. In case (2), the temperature increased from 28°C at the time of implantation to 38°C, reaching a maximum of 66°C. ■ is 2
The temperature increased by 2°C and remained at a maximum of 50°C. As a result, there were no cracks in the area where the blocks were placed, and a high-quality concrete slab could be poured.

In addition, if the ready-mixed concrete has the fluidity to flow around between the reinforcing bars, it can be poured and placed densely between the blocks.

Effects This invention is as described above. This pouring method provides the following effects. ■The temperature rise is small, eliminating the risk of cracking. ■Working conditions can be improved by reducing the long hours of work, often late at night, associated with the large volume of mass concrete pouring. ■Precast concrete blocks can be manufactured in factories and are of high quality using hardened concrete. ■The placed precast concrete blocks can be used as scaffolding, for example, as a reinforcing bar frame for the top end reinforcement of a concrete slab.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the state in which the concrete slab of the example is placed, Figure 2 is a plan view showing the arrangement of precast concrete blocks, and Figure 3 is the relationship between the temperature of the poured concrete slab and the number of days elapsed. It is a correlation graph. 1. Formwork, 2.-Precast concrete block, 3. Ready-mixed concrete.

Claims (1)

[Claims] (1) Prior to pouring concrete, place precast concrete blocks in the space to be poured leaving a gap for pouring fresh concrete, or place precast concrete blocks in the poured fresh concrete. A concrete placing method characterized by placing ready-mixed concrete integrally with a precast concrete block.