JP2940367B2 - Concrete casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of placing concrete, and more particularly to a method of placing mass concrete in nuclear facilities.

[0002]

2. Description of the Related Art With the enlargement of concrete structures, there are increasing problems related to temperature cracks caused by heat of hydration of concrete.

That is, in a concrete structure having a large member cross section, the heat of hydration of the cement is accumulated, the internal temperature rises, and the subsequent cooling generates a large tensile stress.
Temperature cracks easily occur.

[0004] The concrete of such a structure is treated as so-called mass concrete, and special consideration is required in design and construction.

[0005] Mass concrete is said to correspond to, for example, a wall having a temperature rise of 15 ° C or more due to heat of hydration and a wall thickness of about 60 cm or more.

[0006] Further, even in a member having a small member cross section, in the case of a large temperature change or in the case of concrete with a rich mixture, similar temperature cracks may occur due to external restraint conditions, and it is necessary to consider mass concrete.

[0007] As a method of controlling the temperature cracking of the mass concrete from the construction side, there are pre-cooling for cooling water and aggregate with ice or liquid nitrogen at the time of kneading the concrete, or a pipe provided before casting. Pipe cooling for removing heat of hydration of concrete by passing cooling water is well known.

[0008]

Here, when mass concrete is divided into several sections and poured, the temperature difference between the new and old concretes increases, and the constraint of the newly poured concrete by the old concrete increases.
As a result, temperature cracks may easily occur.

Particularly, in a wall member rising from a large-section base floor, the wall member made of new concrete is greatly restrained by the base floor made of old concrete, and cracks are easily generated.

Further, in radioactive waste pits and the like, since it is necessary to construct walls and the like with a material that does not deteriorate for a long period of time, it is not possible to use waterproof paint or the like on a portion where cracks are likely to occur. There has been a problem that a liquid having a capacity may flow into groundwater through cracks.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a concrete casting method capable of preventing a temperature crack at a joint portion of mass concrete.

[0012]

In order to achieve the above object, a concrete casting method according to the present invention is characterized in that a first pipe is piped in a first concrete casting area to concrete. A first step of casting and curing the same, and a second step adjacent to the first concrete casting area.
And placing the concrete in a concrete placing area of the concrete and curing the same.
And cooling the concrete in the first concrete casting area by passing hot water through the first pipe while cooling the concrete in the concrete placing area.

[0013] The concrete casting method of the present invention comprises:
2. The method according to claim 1, wherein the second step is performed before placing concrete.
And the cooling step includes passing cold water through the second pipe.

Further, the concrete casting method of the present invention comprises:
The second step of claim 2 includes a step of passing the cold water through the second pipe to convert it into hot water, and passing the hot water through the first pipe.

[0015] The concrete casting method of the present invention comprises:
The second step of claim 2, wherein the temperature of at least one of hot water passing through the first pipe and cold water passing through the second pipe is set in the first concrete casting area and the second concrete casting. The method includes a step of controlling using at least one of the temperatures in the region.

Further, the concrete casting method of the present invention comprises:
The second step of claim 1 includes a step of placing precooled concrete in the second concrete placing area.

[0017]

In the concrete casting method of the present invention, first, as a first step, a first pipe is piped in a first concrete casting area, for example, a foundation floor area, and concrete is cast and cured.

Next, as a second step, concrete is poured into a second concrete placing area adjacent to the first concrete placing area, for example, a wall area, and the concrete is cured.

Here, in the second step, while the concrete in the second concrete casting area is cooled by a predetermined method, hot water is passed through the first pipe to make the first concrete.
Warm the concrete in the concrete casting area.

To cool the concrete in the second concrete casting area, so-called pipe cooling in which cold water is passed through a pipe (second pipe) previously piped to the second concrete casting area, or The pre-cooled concrete is cast into a second concrete casting area.

The temperature of the hot or cold water can be controlled using, for example, the temperature in the first concrete casting area and the temperature in the second concrete casting area.

When the water that has passed through the second pipe is passed through the first pipe, the first hydration heat generated from the concrete in the second concrete placing area, that is, the new concrete, is effectively used. The concrete in the concrete casting area, that is, the old concrete, will be warmed,
It will save energy.

When the new concrete is cooled by the above-described procedure and the old concrete is warmed by passing warm water through the first pipe, the temperature difference between the internal temperature and the surface temperature of the new concrete is reduced, and the temperature gradient is reduced.

Therefore, the external constraint of the new concrete by the old concrete is reduced, and the temperature crack of the mass concrete is less likely to occur.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the concrete placing method of the present invention is applied to a foundation floor and a wall member such as a radioactive waste pit will be described below with reference to the accompanying drawings.

FIG. 1 is a flowchart showing the procedure of the concrete placing method of the present embodiment, and FIG. 2 shows the concrete placing according to the flowchart of FIG.

In the concrete casting method of the present embodiment, first, as shown in FIG. 2A, as a first step, a first concrete casting area, for example, a foundation floor area 11 on the ground 13 is moved to a first floor. 1 is piped (FIG. 1, step 1).

Next, as shown in FIG. 2 (b), concrete 14 is poured into the foundation floor area 11 (FIG. 1, step 2), and predetermined curing is performed.

Next, as a second step, a second pipe 16 is laid in a wall region 15 rising from the base floor region 11 (step 3 in FIG. 1). Then, as shown in FIG. Pour concrete 17 into the area 15 (FIG. 1,
Step 4).

The pipe 16 is a metal pipe having a high thermal conductivity such as a steel pipe having a diameter of about 1 inch, and is preferably piped at a pitch of, for example, 50 cm.

For the concrete 17, it is preferable to use fly ash cement, medium heat Portland cement, blast furnace cement or the like having a small heat of hydration to minimize the temperature rise due to the heat of hydration.

After the concrete 17 is cast, the first pipe 12 and the second pipe 12 are kept until the internal temperature reaches the maximum temperature.
Hot water and cold water are passed through the pipes 16 of FIG. 1 (FIG. 1, step 5) to absorb the heat of hydration of the new concrete 17 by the cold water to suppress the temperature rise and to warm the old concrete 14.

Then, the temperature difference between the internal temperature and the surface temperature of the new concrete is reduced and the temperature gradient is reduced, and the restraint of the new concrete from the old concrete after cooling is reduced, so that the temperature crack of the mass concrete is less likely to occur. .

Here, the warmed water passing through the second pipe 16 is passed through the first pipe 12 and used as hot water,
Further, if the water cooled through the first pipe 12 is returned to the second pipe 16 and circulated as cold water, the heat of hydration generated from the concrete 17 is reduced to the concrete 14.
Can be used effectively for global warming.

FIG. 3 schematically shows the temperature distribution in the concrete 17 and the concrete 14. As can be seen in the figure, concrete 17, concrete 1
The temperature gradient 21 when cooling and heating the concrete 4 is the largest, the temperature gradient 22 when the concrete 17 is cooled is the largest, and the temperature gradient 23 when the concrete 17 is cooled and the concrete 14 is heated is the smallest. .

After the concrete 17 has reached the maximum temperature,
The flow of the cold and hot water is stopped, and the concretes 14 and 17 in the base floor area 11 and the wall area 15 are gradually cooled (step 6).

When the wall area 18 is further constructed as shown in FIG. 2C, concrete can be cast in the same manner.

That is, after the pipe 19 is laid in the wall area 18, concrete is poured into the wall area 18, and after the concrete is poured, cold water is passed through the pipe 19 while warming the concrete 17 through the pipe 16. The concrete can be cooled, the rise in the internal temperature of the new concrete can be suppressed, and the temperature gradient can be reduced.

As described above, in the concrete placing method of the present embodiment, the old concrete is warmed while the new concrete is cooled. Therefore, the rise in the internal temperature of the new concrete is suppressed, and the internal constraint stress is reduced. At the same time, the temperature difference between the new concrete and the old concrete, that is, the temperature gradient becomes smaller, and the external restraint stress received from the old concrete also becomes smaller.

Therefore, the temperature crack at the joint between the new concrete and the old concrete is greatly reduced as compared with the conventional one, and the problem such as water leakage through the crack in the radioactive waste pit or the like can be avoided. .

In the present embodiment, so-called pipe cooling, in which cold water is passed through a pipe 16 previously buried in the concrete 17 to cool the concrete 17 in the wall area 15, is performed. May be poured into the wall region 15.

In this case, the aggregate, water, etc. may be cooled in advance with ice or liquid nitrogen, and the temperature of kneading may be adjusted.

In this embodiment, the foundation floor is treated as ordinary concrete. However, if it is better to treat the foundation floor as mass concrete from the viewpoint of the thickness of the members, concrete 14 is cast. It is preferable to reduce the temperature rise due to the heat of hydration of the concrete 14 by passing cold water through the first pipe 12 until the internal temperature reaches the maximum temperature, thereby preventing temperature cracking. Further, the concrete 14 may be cooled by pre-cooling instead of such pipe cooling.

In this embodiment, in order to effectively use the heat of hydration, the water heated by absorbing the heat of hydration is passed through the pipe buried in the old concrete. It may be passed through a pipe.

Although not specifically mentioned in the present embodiment, the temperature of the cold water or the hot water may be controlled using the concrete temperature value measured in the foundation floor area or the wall area.

In such a case, the temperature crack control of the mass concrete can be performed more precisely.

In this embodiment, after the concrete is poured into the wall area, the hot water is passed through the pipe buried in the old concrete. However, the hot water may be passed before the casting.

In this case, the temperature of the old concrete can be increased without delaying the temperature of the new concrete.

[0049]

As described above, the concrete casting method of the present invention comprises the first step of laying concrete by laying a first pipe in the first concrete casting area and curing the concrete. A second step of placing concrete in a second concrete placement area adjacent to the first concrete placement area and curing the concrete, wherein the second step comprises a step of: While cooling the concrete in a predetermined manner while warming the concrete in the first concrete casting area by passing hot water through the first pipe, the temperature cracks at the joint of mass concrete can be reduced. It can be avoided beforehand.

[0050]

[Brief description of the drawings]

FIG. 1 is a flowchart of a concrete casting method according to the present embodiment.

FIG. 2 is a view showing a situation where concrete is poured according to the flowchart of FIG. 1;

FIG. 3 is a diagram showing temperature gradients of new concrete and old concrete.

[Explanation of symbols]

 1, 2 First step 3, 4, 5, 6 Second step 11 Foundation floor area (first concrete casting area) 15 Wall area (second concrete casting area) 14, 17 Concrete 12 First pipe 16 Second pipe

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Noritori Takeda 2-3-3 Kandaji-cho, Chiyoda-ku, Tokyo Obayashi Corporation Tokyo Head Office (56) References 62-164964 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E04G 21/02 103 E04G 21/02 104 C04B 40/02

Claims (5)

(57) [Claims] 1. A first step of laying and curing concrete by piping a first pipe in a first concrete casting area, and a second concrete area adjacent to the first concrete casting area A second step of casting concrete in the casting area and curing the concrete, wherein the second step cools the concrete in the second concrete casting area by a predetermined method, while cooling the first concrete. A method for placing concrete, comprising the step of warming concrete in the first concrete placing area by passing hot water through a pipe. 2. The method according to claim 1, wherein the second step includes a step of previously piping a second pipe in the second concrete placing area before placing the concrete, and the cooling step includes supplying cold water to the second pipe. The method for placing concrete according to claim 1, further comprising a step of passing. 3. The concrete casting method according to claim 2, wherein the second step includes a step of passing the cold water through the second pipe into hot water and passing the hot water through the first pipe. 4. The method according to claim 1, wherein at least one of a temperature of hot water passing through the first pipe and a temperature of cold water passing through the second pipe is set in the first concrete casting area and the second concrete. 3. The concrete casting method according to claim 2, further comprising the step of controlling using at least one of the temperatures in the casting area. 5. The concrete casting method according to claim 1, wherein the second step includes a step of placing precooled concrete in the second concrete placing area.