JPS5947789B2 - How to prevent cracks in prestressed concrete structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The prestressed concrete reactor containment vessel has a mass concrete 1 structure in which the concrete thickness of the wall reaches 1 to 1.5 m, and the concrete of the containment vessel is prestressed I. Due to the introduction of resin, it is a high-strength concrete with a compressive strength of over 400 kg/crrf at 4 weeks of age, so a large amount of cement is used, and therefore a large amount of heat is generated during the curing process.

As a result, there is an extremely high risk that the PRESS I-REST reactor containment vessel will crack during its construction process.

However, due to its functionality, the containment vessel must be prevented from cracking as much as possible.

The present invention has been proposed in view of the above circumstances, and involves pouring concrete into a formwork for constructing prestressed concrete structures, and at the same time injecting cooling fluid into a sheath for inserting prestressed steel materials, which is set in advance within the formwork. The purpose of this method is to prevent cracks in prestressed concrete structures, which are characterized by circulating a prestressed concrete structure. The object of the present invention is to provide a method that can prevent the occurrence of cracks during the concrete hardening process.

In the present invention, as described above, the sheath for inserting the prestressed concrete steel is used to cast concrete for the frame within the formwork, and the By circulating a cooling fluid such as water or cold air through the sheath, water utilization heat of the cement in the concrete placed in the formwork is removed, and excessive temperatures during the hardening process of the poured concrete are removed.'' - It prevents the occurrence of cracks in concrete by preventing the concrete from rising.

As described above, according to the present invention, by utilizing the sheath for inserting the PC steel material embedded in the prestressed concrete structure and circulating the cooling fluid through the sheath,
Since the heat of hydration of the cement in the concrete is removed and the occurrence of cracks during the concrete hardening process is prevented, there is no need to prepare large-scale equipment for cooling the concrete, making it easy and economical. It is possible to achieve the intended purpose.

The present invention will be described below with reference to Examples.

Place the required reinforcement in the formwork for press I/rest concrete structure construction, set the sheath for inserting the PC steel material at each predetermined position, and pour the first layer of concrete into the formwork. , the sheath buried in the poured concrete is connected to a cooling fluid supply source via appropriate piping, and cooling fluid, such as cooling water, is circulated through the sheath to hydrate the cement in the poured concrete. Removes heat to prevent excessive temperature rise and prevents concrete from cracking during the curing process.

The circulation of the cooling water is carried out for three to four days to one week after concrete placement.

Next, the second layer of concrete 1 was poured, and cooling water was circulated in the same manner as described above through the sheath for inserting the PC steel material buried in the poured concrete to prevent the occurrence of cracks during the hardening process of the poured concrete. do.

After repeating the above-mentioned process to complete the pouring of concrete for the frame, insert the PC steel material into each sheath, anchor the PC steel material under tension to the concrete frame 1, and place it in the concrete. A prestress is introduced, and grouting is further performed within the sheath as necessary.

Note that when cooling water is used as the cooling fluid for circulating the sheath as described above, the work efficiency is high; however,
In order to prevent rust from forming inside the sheath, it is necessary to remove moisture remaining inside the sheath.

Cold gas may be used instead of cooling water, in which case there is no need for post-treatment of the inside of the sheath after the work is completed.

Although the present invention has been described above with reference to embodiments, the present invention is of course not limited to such embodiments, and modifications of God's design may be made without departing from the spirit of the present invention. .

Claims (1)

[Claims] 1. A prestressed concrete structure, characterized in that concrete is poured into a formwork for constructing a prestressed concrete structure, and a cooling fluid is circulated through a sheath for inserting a prestressed steel material into the same formwork. How to prevent cracks.