JPH07217211A - Preventive structure against concrete crack - Google Patents

Abstract

PURPOSE:To prevent concrete from cracking, by providing a circulation coolant pipe in the inside of concrete structure installed adjacently to each other. CONSTITUTION:Coolant circulation pipes 3, 4 are installed in a prior element 1 and a posterior element 2 respectively. The circulation cooling pipes 3, 4 are constituted of upper and lower pipes 5, 6, lower pipes 7, 8 and upper pipes 9. The pipes 5, 6 are connected to each other through the pipes 9 and flexible connection pipes 10. A circulation pump 11 is connected between the pipes 10 and the pipes 3, 4 are unified to one path to circulate the same coolant. The hydration heat of the element 2 is transferred to the element 1 through the coolant in the pipe to reduce the temperature rise of the element 2. The temperature of the element 2 approaches gradually that of the element 1 and the temperature difference therebetween is reduced and cracks of the elements 1, 2 resulting from the difference of the thermal contraction rate are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete crack prevention structure applied to a mass concrete structure such as a continuous underground wall and a dam.

[0002]

2. Description of the Related Art For example, when constructing a continuous underground wall, the structural type is selected after considering the wall thickness, depth, soil condition, design load, etc. In the above, the underground continuous wall is divided into a plurality of elements, and the elements are sequentially constructed to construct a concrete structure. Then, in the case of such a construction method, a plurality of preceding elements are installed at a constant interval, then, between each of these preceding elements, since the trailing element is installed to connect the preceding element, After concrete casting of the trailing element, the trailing element is constrained by the leading element, and distortion occurs inside the trailing element.

Specifically, as shown in FIG. 3, due to the heat of hydration of concrete, the temperature rises within 96 hours (4th day) from the time of placing, and thereafter the temperature gradually rises. Falls. As a result, a large temperature difference occurs between the preceding element that was placed first and the trailing element that was placed later, because of the different placement times, and as a result,
Due to the difference in the amount of heat shrinkage between the elements adjacent to each other, a large strain is generated inside the element. And
At this time, since the rear element is in a state of being in close contact with the preceding element, that is, in the state of being restrained, cracks may occur in these elements, and there is a risk that groundwater may seep out from the ground on the back side.

[0004]

As means for preventing such cracking of concrete, there are, for example, the following:
(1) In terms of materials and composition, reduce temperature rise due to heat of hydration of cement, (2) reduce kneading temperature of concrete by cooling with aggregate, etc. (3) Surround concrete around immediately after kneading Although there are measures such as cooling from above to reduce the kneading temperature, and (4) changing the amount of rebar and taking measures from the design side, the above-mentioned technologies (1), (3) and (4) have limited crack prevention effects. Therefore, the phenomenon such as water leakage was observed, and the technique (2) had a problem that although the predetermined effect was obtained, the material was expensive and the overall construction cost was high.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a concrete crack prevention structure capable of reliably preventing cracks by a simple construction method.

[0006]

In order to achieve the above object, the first invention is characterized in that a concrete structure provided adjacent to each other is provided with a pipe through which a refrigerant is circulated. .

According to the second aspect of the present invention, the preceding concrete structure that is placed first, the trailing concrete structure that is placed after the preceding concrete structure and adjacent to the preceding concrete structure, and these concretes are used. A pipe provided inside each of the structures for circulating a refrigerant, wherein the pipe in the preceding concrete structure and the pipe in the following concrete structure are connected to each other and the same refrigerant is circulated. Is characterized by.

According to a third invention, in any one of the first and second inventions, the pipe is arranged so as to meander in a concrete structure.

[0009]

According to the first aspect of the present invention, the refrigerant is circulated through the pipes provided inside the concrete structure to reduce the temperature rise of the concrete structure. A large temperature difference with respect to the structure is prevented.

According to the second aspect of the present invention, pipes for circulating a refrigerant are provided inside each of the preceding concrete structure and the following concrete structure that is placed adjacent to the preceding concrete structure. Since the piping in the preceding concrete structure and the piping in the following concrete structure are connected to each other to circulate the same refrigerant, the heat of hydration of the following concrete structure is circulated through the refrigerant in the piping. Is moved to the preceding concrete structure to reduce the temperature rise of the following concrete structure, the temperature of the following concrete structure gradually approaches the temperature of the preceding concrete structure, and finally the same. Thus, these concrete structures can be cooled at the same time. That is, in the second invention, it is possible to prevent a temperature difference from occurring between the preceding concrete structure and the following concrete structure, which are adjacent to each other, and as a result, a difference in heat shrinkage amount between these concrete structures occurs and the concrete structure It prevents the body from cracking.

In the third invention, since the pipe is arranged so as to meander in the concrete structure, the heat of the concrete structure is applied to the refrigerant in the pipe or the heat of the refrigerant is applied to the concrete structure. It can be transmitted efficiently.

[0012]

EXAMPLE A concrete crack prevention structure according to the present invention will be described with reference to FIGS. First, reference numerals 1 and 2 in FIG. 1 are elements of a concrete structure applied to a building such as an underground continuous wall and a dam. The reference element 2 is a trailing element that is placed adjacent to the preceding element 1 after the preceding element 1.

Inside the leading element 1 and the trailing element 2, cooling pipes 3 and 4 in which a refrigerant is circulated are provided, respectively. These cooling pipes 3 and 4 include upper and lower pipes 5 and 6 arranged along the vertical direction, lower pipes 7 and 8 connecting the lower parts of the upper and lower pipes 5 and 6 to each other, and upper and lower pipes 5 and 6, respectively. Upper piping 9 for connecting the upper part
And is arranged so as to meander as a whole, thereby increasing the contact area with the cast concrete and increasing the heat transfer efficiency to each element 1 and 2. Has become.

The upper and lower pipes 5 in the cooling pipes 3 and 4
6, the lower pipes 7 and 8 are made of, for example, iron pipes, and are fixed to the reinforcing rods when the reinforcing rods are assembled before placing concrete. Further, a flexible pipe such as a rubber pipe or an iron pipe is used as the upper pipe 9 so that it can be easily removed after the concrete is hardened.

Also, the upper and lower pipes 5 of the preceding element 1,
The upper and lower pipes 6 of the succeeding element 2 are connected to each other by a flexible connecting pipe 10 together with the upper pipe 9, and a transportation means such as a circulation pump 11 is provided in the middle of the connecting pipe 10, whereby each element is provided. The 1.2 cooling pipes 3 and 4 form a single flow path so that the same refrigerant is circulated. The upper pipe 9 and the connecting pipe 10
This is not limited to the use of a flexible pipe such as a rubber pipe, but an iron pipe may be used as long as it can be easily removed after hardening of concrete. Also, the cooling pipes 3 and 4
Water, chlorofluorocarbon, or the like may be used as the refrigerant circulated inside. Further, in the present embodiment, only one set of the upper and lower pipes 5 and the lower pipe 7 is provided for the preceding element 1,
The present invention is not limited to this, and multiple sets of upper and lower pipes 5 and lower pipes 7 may be provided.

In the concrete crack prevention structure constructed as described above, the leading element 1 and the trailing element 2 placed adjacent to the leading element 1 are placed.
The cooling pipes 3 and 4 in which the refrigerant is circulated are provided in the interior of each of the
Since the same refrigerant is circulated by connecting them to the cooling pipes 4 inside, the heat of hydration of the trailing element 2 is transferred to the preceding element 1 via the refrigerant inside these cooling pipes 3 and 4. As a result, the temperature rise of the succeeding element 2 is reduced.

This will be explained with reference to FIG. 2. In FIG. 2, the reference numeral (a) indicates a temperature curve after placing concrete (that is, a conventional temperature curve) when cooling is not performed by the cooling pipes 3 and 4. ), And symbols (b) and (c) show the temperature curves of the preceding element 1 and the following element 2, respectively, when the concrete crack prevention structure according to the present invention is adopted. After the preceding concrete 1 has been cooled, the following concrete 2 is placed, and when the refrigerant is circulated in the cooling pipes 3 and 4 at this time, the refrigerant in the cooling pipes 3 and 4 is used. , The heat of hydration of the trailing element 2 is transferred to the leading element 1, and as shown by the reference numeral (c), the trailing element 2
Temperature rise is reduced (the temperature rise reduction amount is indicated by m),
The trailing element 2 is prevented from having a large temperature difference (the temperature difference is indicated by n) with respect to the leading element 1.

At this time, as indicated by the symbol (b),
The preceding element 1 also rises slightly due to the heat of hydration of the following element 2, but the temperature rise of the preceding element 1 causes the temperature of the preceding concrete 1 to approach the temperature of the following element 2 conversely. Also in this point, it is prevented that the succeeding element 2 has a temperature difference (the temperature difference is indicated by n) with respect to the preceding element 1. In this way, the temperature rise of the trailing element 2 is suppressed, and after the temperature rise peak (4 days: 96 hours) elapses, the temperature of the trailing concrete 2 (c) and the temperature of the leading element 1 are increased. (B) approaches both of them while descending together, that is, the temperature difference between the temperature (c) of the following concrete 2 and the temperature (b) of the preceding element 1 converges toward 0. Become. Therefore, in the above concrete crack prevention structure, it is possible to prevent a large temperature difference between the preceding element 1 and the following element 2 that are adjacent to each other from occurring, and as a result, the thermal contraction amount of these elements 1 and 2 is prevented. It is possible to prevent cracks from occurring in the elements 1 and 2 due to the difference.

In the above embodiment, the two adjacent
By circulating a common refrigerant for the two elements 1 and 2,
Although the elements 1 and 2 are cooled, the present invention is not limited to this, and the refrigerant may be individually supplied to each of the elements 1 and 2 after the concrete is placed. Then, in this case, the heat recovered by the refrigerant in the elements 1 and 2 is radiated in the air outside the elements 1 and 2 (at this time, a cooling device may be separately provided), thereby cooling. It is advisable to circulate the generated refrigerant again in each of the elements 1 and 2. In the above embodiment, the two elements 1 and 2 have been described as an example. However, after the trailing element 2 is placed, the trailing element 2 is further rearward (shown by reference numeral 20). ), And a cooling pipe (not shown) in the trailing element 20 and a trailing element 2 (in this case, the trailing element 2 becomes a “leading element”).
It is advisable to connect the internal cooling pipe 4 with a connecting pipe to perform the same cooling as above.

In the above embodiment, the preceding element 1
In the above, the refrigerant is circulated only in the set of the upper and lower pipes 5 and the lower pipe 7 in the cooling pipe 4, but how many sets of the upper and lower pipes 5 and the lower pipe 7 are circulated in the refrigerant, Various selections are possible depending on the connection form of the upper pipe 9 and the connection pipe 10, and are within the range of design items. In addition, in the above elements 1 and 2, when the construction work is completed,
The upper pipe 9 and the connecting pipe 10 are removed, and grout is injected into the upper and lower pipes 5 and 6 and the lower pipes 7 and 8 of the cooling pipes 3 and 4,
Fill.

[0021]

As is apparent from the above description, according to the first aspect of the present invention, the temperature rise of the concrete structure is reduced by circulating the refrigerant through the pipe provided inside the concrete structure. As a result, it is possible to prevent a large temperature difference between the concrete structures adjacent to each other as in the conventional case. As a result, it is possible to prevent the concrete structures from cracking due to the difference in heat shrinkage between the adjacent concrete structures.

According to the second aspect of the present invention, the inside of the preceding concrete structure and the following concrete structure that is placed adjacent to the preceding concrete structure are provided with pipes through which the refrigerant is circulated. Since the piping in the preceding concrete structure and the piping in the following concrete structure are connected to each other to circulate the same refrigerant, the heat of hydration of the following concrete structure is circulated through the refrigerant in the piping. Is moved to the preceding concrete structure to reduce the temperature rise of the following concrete structure, the temperature of the following concrete structure gradually approaches the temperature of the preceding concrete structure, and finally the same. As a result, these concrete structures can be cooled. That is, the second
In the invention of 1, the temperature difference between the preceding concrete structure and the following concrete structure which are adjacent to each other is prevented from occurring, and as a result, a difference occurs in the heat shrinkage amount of these concrete structures and the concrete structure is cracked. It is prevented from occurring.

In the third invention, since the pipe is arranged so as to meander in the concrete structure, the heat of the concrete structure is applied to the refrigerant in the pipe or the heat of the refrigerant is applied to the concrete structure. It can be transmitted efficiently.

[Brief description of drawings]

FIG. 1 is a front view showing a concrete crack prevention structure according to an embodiment of the present invention.

FIG. 2 is a graph showing a temperature rise curve after placing concrete, based on the concrete crack prevention structure of FIG.

FIG. 3 is a graph showing a conventional temperature rise curve after placing concrete.

[Explanation of symbols]

 1 Leading element (leading concrete structure) 2 Trailing element (backing concrete structure) 3 Cooling pipe (piping) 4 Cooling pipe (piping)

Claims (3)

[Claims] 1. A concrete crack prevention structure, characterized in that a pipe through which a refrigerant is circulated is provided inside concrete structures provided adjacent to each other. 2. A preceding concrete structure that has been previously cast, a following concrete structure that has been cast after the preceding concrete structure and adjacent to the preceding concrete structure, and each of these concrete structures. A pipe in which the refrigerant is circulated provided inside, and a pipe in the preceding concrete structure and a pipe in the following concrete structure are connected to each other, and the same refrigerant is circulated. Concrete crack prevention structure. 3. The concrete crack prevention structure according to claim 1, wherein the pipe is arranged so as to meander in the concrete structure.