JP2004360333A - Pipe cooling method for mass concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pipe cooling method for mass concrete, which effectively suppresses thermal cracking of the mass concrete. <P>SOLUTION: Two cooling pipes 24, 26 are arranged in a form 100 beforehand, and by feeding cooling water into the cooling pipes 24, 26, the mass concrete 22 placed in the form 100 is cooled. At this time the cooling pipes 24, 26 are arranged so that the cooling water is fed from a central portion 22A of the mass concrete 22 to a peripheral portion 22B of the same. Although the central portion 22A of the mass concrete 22 assumes high temperatures, it is fed with the cooling water immediately after feeding, and therefore the central portion 22A is effectively cooled by heat exchange with the cooling water. Further the cooling water warmed by the heat exchange with the central portion 22A is fed to the peripheral portion 22B as warm water, and therefore the peripheral portion 22B which assumes relatively low temperatures is warmed by the warm water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of the present application is a method of cooling a mass concrete pipe, that is, a cooling pipe is arranged in a mold in advance, and cooling water is supplied to the cooling pipe to cool the mass concrete cast in the mold. How to do it.
[0002]
[Prior art]
In a structure having a large cross-sectional size, such as a foundation of a dam or a large bridge, the cast concrete becomes a large block of so-called mass concrete. In this mass concrete, a large internal stress is generated by the heat of hydration of the cement when hardening, so that a temperature crack is easily generated.
[0003]
For this reason, various techniques for cooling the hardened mass concrete have been conventionally developed, and a pipe cooling method is known as one of them.
[0004]
In this pipe cooling method, for example, as described in “Patent Document 1”, a cooling pipe is placed in a mold in advance, and cooling water is supplied to the cooling pipe, so that the cooling pipe is driven into the mold. The installed mass concrete is cooled so that the difference between the maximum inside temperature and the outside temperature does not become too large.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2003-65983 [Problems to be Solved by the Invention]
However, in the above conventional pipe cooling method, no special consideration is given to the piping path of the cooling pipe, and the mass concrete poured into the formwork is cooled uniformly at both the center and the periphery. However, there are the following problems.
[0006]
In other words, mass concrete poured into the formwork has a high temperature at its center, while its peripheral portion has a relatively low temperature due to the heat radiation from the formwork. There is a problem that the temperature gradient inside the concrete cannot be moderated, and thus the effect of suppressing mass cracking of the mass concrete is not sufficient.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pipe cooling method for mass concrete that can effectively suppress the occurrence of temperature cracks.
[0008]
[Means for Solving the Problems]
The present invention is intended to achieve the above object by devising a piping path of a cooling pipe.
[0009]
That is, the pipe cooling method for mass concrete according to the present invention is as follows.
In the cooling method of the mass concrete pipe, a cooling pipe is arranged in advance in the mold, and cooling water is supplied to the cooling pipe to cool the mass concrete cast in the mold.
A pipe route of the cooling pipe is set so that the cooling water is supplied from a center portion of the mass concrete to a peripheral portion thereof.
[0010]
The above-mentioned "cooling pipe" is a concrete piping route or a material of the cooling pipe, provided that the piping route is set so that cooling water is sent from the center of the mass concrete to the peripheral portion. There is no particular limitation on the configuration such as the shape and the cross-sectional shape.
[0011]
The "center portion" and "peripheral portion" need only be the central portion and the peripheral portion of the mass concrete in at least one cross section including the center position of the mass concrete.
[0012]
Effects of the Invention
As shown in the above configuration, the pipe cooling method for mass concrete according to the present invention includes a method in which a cooling pipe is arranged in a mold in advance, and cooling water is supplied to the cooling pipe, so that the pipe is poured into the mold. It is designed to cool the mass concrete, but at this time, the cooling pipe piping route is set so that cooling water is sent from the center of the mass concrete to the peripheral edge, so the following Such an operation and effect can be obtained.
[0013]
That is, the mass concrete poured into the formwork has a high temperature at the center, but the cooling water immediately after being supplied is sent to the center, so the center is cooled by heat exchange with the cooling water. The part will be cooled efficiently. Then, since the cooling water warmed by the heat exchange with the central portion becomes hot water and is sent toward the peripheral portion, the relatively low temperature peripheral portion is warmed by the hot water.
[0014]
As described above, according to the present invention, not only can the mass concrete cast in the formwork be cooled, but also the heat of hardening at the center can be distributed to the peripheral portion, so that the inside of the mass concrete can be distributed. The temperature gradient can be moderated, whereby the occurrence of temperature cracks can be effectively suppressed.
[0015]
In the above configuration, if a plurality of cooling pipes are arranged, a piping route for supplying cooling water from the center of the mass concrete to the peripheral edge can be set to a relatively simple shape. .
[0016]
By the way, when casting is performed using high-strength concrete (that is, concrete having a compressive strength of more than 36 N per 1 mm 2), the unit cement amount increases, so that the heat of hydration also increases and the mass The temperature gradient inside the concrete tends to be steep. Therefore, in such a case, it is particularly effective to adopt the configuration of the present invention.
[0017]
Structures such as the column caps of prestressed concrete bridges and the sprinkling parts of reinforced concrete arch bridges, which use high-strength concrete, have a smaller cross-section of mass concrete than dams and underground structures. The length of the cooling pipe required for sending the cooling water from the center to the peripheral edge of the cooling pipe can be made relatively short.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is an arch axis orthogonal cross-sectional view showing a sprinkling portion 20 of a reinforced concrete arch bridge constructed by applying a mass concrete pipe cooling method according to an embodiment of the present invention.
[0020]
The sprinkling section 20 has a configuration in which two cooling pipes 24 and 26 are embedded in a mass concrete 22 having a horizontally long and substantially rectangular cross section orthogonal to the arch axis.
[0021]
The mass concrete 22 is made of high-strength concrete. Each of the cooling pipes 24 and 26 is a synthetic resin pipe (for example, a polyethylene resin pipe having an inner diameter of about 20 mm). Each of the cooling pipes 24 and 26 is arranged so that a cross section orthogonal to the arch axis is divided into two right and left sides with respect to the arch axis Ax, and the interior thereof is filled with cement 28.
[0022]
The piping paths of the cooling pipes 24 and 26 are set so as to extend in the arch axis direction at substantially equal intervals in the vertical and horizontal directions (e.g., at 400 mm intervals), and to be folded at portions near both ends in the arch axis direction of the mass concrete 22. Have been. At this time, of the sixteen straight portions 24S and 26S extending in the arch axis direction in each of the cooling pipes 24 and 26, six are located at the center portion 22A of the mass concrete 22 (generally inside the ellipse indicated by the two-dot chain line in FIG. ), And the remaining ten are located at the peripheral edge 22 </ b> B of the mass concrete 22.
Next, a pipe cooling method for mass concrete according to the present embodiment will be described.
[0023]
FIG. 2 is a cross-sectional view orthogonal to the arch axis showing the sprinkling part 20 during construction, and FIG. 3 is a perspective view thereof. In FIG. 3, for convenience of explanation, the sprinkling section 20 is shown in a transparent manner with the left and right divided into two equal parts.
[0024]
As shown in these drawings, in the present embodiment, when the sprinkling section 20 is installed, two cooling pipes 24 and 26 are arranged in the mold 100 in advance, and these cooling pipes 24 and By sending cooling water (for example, tap water) to 26, the mass concrete 22 cast in the formwork 100 is cooled.
[0025]
At this time, the piping paths of the cooling pipes 24 and 26 are set so that the cooling water is sent from the central portion 22A of the mass concrete 22 to the peripheral edge portion 22B.
[0026]
Specifically, the space in the mold 100 is bisected to the left and right in the cross section orthogonal to the arch axis, and each is equally divided into 16 rectangular areas 1 to 16 in four stages vertically and four rows horizontally. The piping route is set so that the straight portions 24S and 26S of the cooling pipes 24 and 26 pass through the center positions of the rectangular areas 1 to 16, respectively. After supplying the cooling water to the six rectangular areas 1 to 6 located at the center 22A of the mass concrete 22, the cooling water is supplied to the remaining ten rectangular areas 7 to 16 located at the peripheral edge 22B of the mass concrete 22. Water.
[0027]
In order to realize this, each cooling pipe 24, 26 has its water supply end 24a, 26a separated from the linear part 24S, 26S of the rectangular area 1 located near the second-stage arch axis Ax from the top of the mold 100. It is arranged so as to extend to the outside, and its drain ends 24b, 26b extend from the linear portions 24S, 26S of the uppermost rectangular area 16 adjacent to the rectangular area 1 to the outside of the formwork 100. To be placed. The 16 linear sections are arranged such that the cooling water supplied from the water supply ends 24a, 26a to the cooling pipes 24, 26 is supplied to the 16 rectangular areas 1 to 16 in this order. The ends of 24S and 26S are connected to each other.
[0028]
In FIG. 2, “•” marks in the cross sections of the cooling pipes 24 and 26 indicate that the cooling water is sent to the near side of the paper, and “x” marks indicate that the cooling water is Indicates that the water will be sent to the other side.
The state of water supply in each of the cooling pipes 24 and 26 will be specifically described as follows.
[0029]
That is, first, water is supplied to the rectangular area 1, then water is sequentially supplied to the rectangular areas 2 and 3 adjacent to the outside in the second stage, and then water is supplied to the third rectangular area 4 adjacent to and below the rectangular area 3. In the third stage, water is sequentially supplied to the rectangular areas 5 and 6 adjacent inside the third stage. Then, after water is supplied to the lowermost rectangular area 7 adjacent below the rectangular area 6, water is sequentially supplied to the outer rectangular areas 8, 9, and 10 at the lowermost level, and then to the rectangular area 10. Water is sequentially supplied to the adjacent third-stage rectangular area 11, the second-stage rectangular area 12, and the uppermost rectangular area 13, and further to the innermost adjacent rectangular areas 14, 15, 16 at the uppermost stage.
[0030]
By performing the water supply in this manner, when the pipe cooling for the mass concrete 22 is completed, the inside of each of the cooling pipes 24 and 26 is filled with cement 28 to improve the strength of the sprinkling section 20.
[0031]
As described in detail above, the mass concrete pipe cooling method according to the present embodiment arranges two cooling pipes 24 and 26 in the mold 100 in advance, and supplies cooling water to each of the cooling pipes 24 and 26. Is supplied to cool the mass concrete 22 cast in the formwork 100. At this time, the piping paths of the cooling pipes 24 and 26 extend from the center 22A of the mass concrete 22. Since the cooling water is set to be supplied to the peripheral portion 22B, the following operation and effect can be obtained.
[0032]
That is, the mass concrete 22 cast in the formwork 100 has a high temperature at the center portion 22A, but the cooling water immediately after the supply is supplied to the center portion 22A. The central portion 22A is efficiently cooled by the heat exchange. Since the cooling water warmed by the heat exchange with the central portion 22A becomes hot water and is sent to the peripheral portion 22B, the relatively low temperature peripheral portion 22B is heated by the hot water. It becomes.
[0033]
FIG. 4 is a graph showing the temperature distribution of the mass concrete 22 cast in the formwork 100. FIG. 4 (a) shows the temperature distribution in a horizontal section including the arch axis Ax, and FIG. The temperature distribution in the vertical section including the arch axis Ax is shown.
[0034]
A graph A indicated by a thick solid line in the drawing is a temperature distribution in a case where pipe cooling is performed by devising a piping path of a cooling pipe as in the present embodiment. On the other hand, a graph D shown by a broken line in the same figure is a temperature distribution when pipe cooling is not performed, and a graph B shown by a two-dot chain line and a graph C shown by a thin solid line in the same figure are pipes of a cooling pipe. It is a temperature distribution when pipe cooling is performed without devising a route.
[0035]
At this time, a graph B indicated by a two-dot chain line is a temperature distribution when pipe cooling is performed in a state where the cooling pipe is arranged only in the central portion 22A of the mass concrete 22 with the arrangement of the straight portions similar to FIG. . Graph C shown by a thin solid line shows the arrangement of the straight line portion as in FIG. 2, and after the water is supplied from the rectangular area 13 at the upper left end to each of the uppermost rectangular areas, the second and third stages are horizontally oriented. This is a temperature distribution in a case where pipe cooling is performed in a state where a pipe route is set such that water is supplied to the rectangular area 10 at the lowermost left end portion so as to be turned back.
[0036]
As shown by the graph D, when the pipe cooling was not performed, the temperature of the central portion 22A of the mass concrete 22 was increased (specifically, the temperature became close to 100 ° C.), and the central portion 22A and the peripheral portion were not cooled. Since the temperature difference from 22B is considerably large, temperature cracks are likely to occur.
[0037]
On the other hand, as shown by the graphs A, B, and C, when the pipe cooling is performed, the temperature of the central portion 22A of the mass concrete 22 becomes lower than when the pipe cooling is not performed. Temperature cracks are less likely to occur.
[0038]
However, as shown by the graph B, when pipe cooling is performed in a state where the cooling pipe is arranged only in the central portion 22A, the temperature of the central portion 22A and the temperature of the peripheral portion 22B are reduced although the temperature of the central portion 22A is lowered. Since the difference is reduced only by the temperature drop of the central portion 22A, it is insufficient to suppress the occurrence of temperature cracks. In addition, as shown in the graph C, when pipe cooling is performed in a pipe route that horizontally turns each stage from the uppermost stage to the lowermost stage, the temperature of the central portion 22A and the peripheral edge portion 22B in the horizontal cross section is reduced. Although the difference can be slightly reduced, in the vertical cross section, the temperature of the cooling water greatly differs between the uppermost stage located on the upstream side and the lowermost stage located on the downstream side even at the same peripheral portion 22B. Therefore, the temperature difference between the central portion 22A and the peripheral portion 22B cannot be reduced. Therefore, even in this case, it is insufficient to suppress the occurrence of temperature cracks.
[0039]
On the other hand, as shown by the graph A, when pipe cooling is performed by sending cooling water from the central portion 22A of the mass concrete 22 to the peripheral portion 22B, the temperature of the central portion 22A is significantly lower. On the other hand, since the temperature of the peripheral portion 22B rises to some extent, the temperature difference between the central portion 22A and the peripheral portion 22B can be sufficiently reduced.
[0040]
As described above, according to the present embodiment, not only can the mass concrete 22 cast in the formwork 100 be cooled, but also the heat of hardening of the central portion 22A can be distributed to the peripheral portion 22B. In addition, the temperature gradient inside the mass concrete 22 can be moderated, so that the occurrence of temperature cracks can be effectively suppressed.
[0041]
In particular, in the present embodiment, since the two cooling pipes 24 and 26 are arranged, the piping path for sending the cooling water from the central portion 22A of the mass concrete 22 to the peripheral portion 22B is relatively simple. The shape can be set. In addition, since the two cooling pipes 24 and 26 are arranged symmetrically to the left and right, it is possible to distribute the heat of curing of the central portion 22A to the peripheral portion 22B in a well-balanced manner.
[0042]
In the present embodiment, casting is performed using high-strength concrete. However, in such a case, since the unit cement amount is large, the heat of hydration increases, and the casting is performed in the mold 100. Since the temperature gradient inside the provided mass concrete 22 tends to be steep, it is particularly effective to employ the pipe cooling method of the present embodiment.
[0043]
At this time, the sprinkling part 20 of the reinforced concrete arch bridge to which the pipe cooling method according to the present embodiment is applied has a smaller cross-sectional size of the mass concrete 22 than dams, underground structures, and the like. Even when the cooling water is supplied from the central portion 22A to the peripheral portion 22B of the mass concrete 22, the lengths of the cooling pipes 24 and 26 can be made relatively short. .
[0044]
In the above-described embodiment, the space in the mold 100 is divided into two equal parts on the left and right sides in the cross section orthogonal to the arch axis, and each is equally divided into 16 rectangular areas 1 to 16, and these 16 rectangular areas The cooling water is supplied to the mass concrete 1 in the order of the numbers. However, the cooling water is set so that the cooling water is supplied from the central portion 22A of the mass concrete 22 to the peripheral portion 22B. Needless to say, other piping paths may be employed.
FIG. It is a figure like FIG. 2 which shows the modification of the said embodiment.
[0045]
As shown in the figure, in this modification, pipe cooling is performed using four cooling pipes 32, 34, 36, 38.
[0046]
That is, in the present modification, the space in the mold 100 is divided into four equal parts vertically, horizontally, and horizontally about the arch axis Ax in a cross section orthogonal to the arch axis, and each of the four parts is divided into 18 sections in three steps vertically and six rows horizontally. The pipes are equally divided into rectangular areas 1 to 18, and the piping positions are set so that the center positions of the rectangular areas 1 to 18 pass through the straight portions 32S, 34S, 36S, 38S of the cooling pipes 32, 34, 36, 38. Keep it. Then, after supplying cooling water to the ten rectangular areas 1 to 10 located in the center part 22A of the mass concrete 22 in this order, the remaining eight rectangular areas located in the peripheral part 22B of the mass concrete 22 The cooling water is sent to the cooling water 11 to 18 in this order.
[0047]
Even in the case where the pipe cooling method as in the present modification is adopted, the cooling water is supplied from the central portion 22A of the mass concrete 22 to the peripheral edge portion 22B of the cooling concrete pipes 32, 34, 36, 38. Since it is set so that the mass concrete 22 cast in the formwork 100 can be cooled and the temperature gradient inside the mass concrete 22 can be moderated, similarly to the above embodiment. Thereby, the occurrence of temperature cracks can be effectively suppressed.
[0048]
In the present modified example, since the four cooling pipes 32, 34, 36, and 38 are arranged point-symmetrically about the arch axis Ax, the cooling pipe 32 extends to the peripheral edge portion 22B of the hardening heat of the central portion 22A of the mass concrete 22. Temperature distribution can be performed in a well-balanced manner. In addition, since these four cooling pipes 32, 34, 36, 38 have a large number of linear portions 32S, 34S, 36S, 38S, the temperature gradient inside the mass concrete 22 can be further moderated. Thus, the occurrence of temperature cracks can be more effectively suppressed.
[0049]
In addition, instead of using a plurality of cooling pipes as in the above-described embodiment and modified examples, one cooling pipe is used, and the cooling water is directed from the central portion 22A of the mass concrete 22 to the peripheral edge portion 22B of the mass concrete 22. Of course, it is also possible to set so that water is supplied.
[Brief description of the drawings]
FIG. 1 is a cross-section orthogonal to an arch axis showing a sprinkling portion of a reinforced concrete arch bridge constructed by applying a mass concrete pipe cooling method according to an embodiment of the present invention. FIG. FIG. 3 is a perspective view showing the above-mentioned sprinkling part during construction. FIG. 4 is a graph showing the temperature distribution of mass concrete poured into a formwork. ) Shows the temperature distribution in the horizontal section including the arch axis, and FIG. 5B shows the temperature distribution in the vertical section including the arch axis. FIG. 5 shows a modification of the above embodiment, similar to FIG. Figure [Explanation of symbols]
20 Sprinkling part 22 Mass concrete 22A Central part 22B Peripheral part 24,26,32,34,36,38 Cooling pipe 24S, 26S, 32S, 34S, 36S, 38S Linear part 24a, 26a Water supply end 24b, 26b Drainage end Part 28 Cement 100 Formwork Ax Arch axis

Claims (3)

In the cooling method of the mass concrete pipe, a cooling pipe is arranged in the mold in advance, and cooling water is supplied to the cooling pipe to cool the mass concrete cast in the mold.
A mass concrete pipe cooling method, characterized in that a pipe route of the cooling pipe is set so that the cooling water is supplied from a central portion of the mass concrete to a peripheral portion thereof. 2. The mass concrete pipe cooling method according to claim 1, wherein a plurality of said cooling pipes are arranged. The method according to claim 1 or 2, wherein the casting is performed using high-strength concrete.

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