JPH07224535A - Concrete crack prevention method - Google Patents

Abstract

PURPOSE:To inhibit the generation of cracks on concrete without using cooling water. CONSTITUTION:A plurality of sheaths 3, which are so designed that steel wire 27 may be inserted later to introduce prestress into the concrete, are installed into a form 23 used to place a skeleton, such as beams 22 of a bridge pier substantially in parallel. After the placement of concrete 20, one end of each hole marked with an arrow A or an arrow B formed by a hollow part 3s of each sheath 3 is connected to either one of two cooling units 5a, 5a as a mouth 2p. An open air 40 is incorporated into each hole 2s by driving the cooling units 5a so that air currents FL-A and FL-B flowing in opposite directions to each other may be formed in each hole 2s respectively, thereby loading the heat of cement hydration reaction generated by the concrete around the holes 2s on the air current FL-A and FL-B and carrying and discharging the outside the holes 2s and preventing a rise in the temperature in the beams 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete crack preventing method suitable for use in preventing temperature cracking of mass concrete.

[0002]

2. Description of the Related Art Conventionally, when mass concrete is constructed,
It is known that the reaction hydration heat of cement generated during hardening of concrete causes a tensile force inside the concrete skeleton, and as a result, so-called thermal cracking occurs in the concrete skeleton. Therefore, in order to prevent such temperature cracks, a sheath is embedded inside the concrete skeleton, and after pouring the concrete, cooling water is circulated in the sheath to cool the inside of the concrete skeleton, whereby the concrete There is a method to prevent cracks by a water-cooled concrete cooling method that suppresses the temperature rise inside the body.

[0003]

However, in order to carry out the method of cooling concrete with water in this way, it is necessary to install equipment for circulating cooling water at the concrete pouring site. Requires a large-capacity water tank, cooling device, pump, etc.,
It will be very large. Also, the cost is enormous. Therefore, if the facilities that can be installed on the site are limited, or if construction restrictions are imposed from the economical aspect,
This is an unsuitable method. Moreover, after cooling, water must be recovered from the inside of the concrete skeleton and treated, which is very complicated. Furthermore, if the water is not completely recovered, the unrecovered water will exude to the outer wall of the body and stain the wall surface, or the water remaining inside the body will be filled into the reinforcing bars or sheath for filling. There is also the risk of adversely affecting the curing of the material. Therefore, in view of the above circumstances, the present invention provides a concrete crack preventing construction method capable of appropriately suppressing a temperature rise inside the concrete skeleton due to cement hydration heat without using cooling water. is there.

[0004]

[Means for Solving the Problems] That is, according to the present invention, the skeletons (22), (31), (3) made of concrete (20) are used.
5) and (36) are placed, the hollow part (3
s), (33s) formed space forming member (3),
(33) is placed in a mold (23), and concrete (20) is placed in the mold (23) to remove the skeletons (22), (31), (35), (36). , The hollow portions (3s), (33) of the space forming members (3), (33) inside the skeletons (22), (31), (35), (36).
The holes (2s) and (30) are formed by arranging the holes (2s) and (30), and one end side (2p), (3)
0p) is connected to the intake means (5a), and the hole (2s),
The other end sides (2q) and (30q) of (30) are communicated with the air intake means (5a) through the holes (2s) and (30),
By driving the suction means (5a), the other end side (2q),
From the (30q) into the holes (2s) and (30), the outside air (4
0) and the outside air (40) causes the holes (2
s), (30) forming the air flow (FL-A), (FL-B) from the other end side (2q), (30q) to the one end side (2p), (30p). The air flow (FL
-A), the holes (2s), (30) along (FL-B)
The outside air (40) moving inside causes the holes (2s), (3
The heat generated by the concrete (20) around (0) is transferred to the holes (2s), (3) from the suction means (5a).
0) The heat is released to the outside, and the skeletons (22), (31),
It is constructed so as to prevent cracks due to the temperature rise of (35) and (36). Further, in the present invention, a plurality of the holes (2s) and (30) are formed substantially parallel to each other inside the skeletons (22), (31), (35) and (36), and the plurality of holes (2s) are formed. , (30) when forming the air flows (FL-A) and (FL-B) respectively, the air flows (FL) inside the skeletons (22), (31), (35) and (36). -A), (FL-B) direction (arrow A direction),
It is configured so that the directions (arrow B directions) are opposite to each other. Further, in the present invention, a plurality of the holes (2s) are formed inside the body (22), and the plurality of holes (2s) are formed.
s), the hole (2s) located in the central portion (SP1) of the skeleton (22) has a larger capacity (Q) than the hole (2s) located in the peripheral portion (SP2) (FL-). A), (F
LB) is formed. In addition, in the present invention, the hole (2s) is a hole for installing a tension member (2s) for introducing prestress to the body (22).
x). Further, in the present invention, the hole (30) is configured to form a cavity inside the body (31). Further, in the present invention, the skeletons (22), (3
1) and (35) are characterized by being horizontal members. Furthermore, the present invention is configured such that, when the frame is a horizontal member, the horizontal member is a bridge pier (22). In the present invention, the air precooling means (11) is provided on the other end side (2q) of the hole (2s).
Is connected to the outside air (40) in a freely cooling manner,
The air precooling means (11) is configured to precool the outside air (40) drawn into the hole (2s). The numbers in parentheses () indicate the corresponding elements in the drawings for convenience, and therefore the present description is not limited to the description in the drawings. The same applies to the following action columns.

[0005]

With the above-mentioned structure, the present invention is adapted to the outside air (40).
Heats the concrete (20) with an air flow (FL-A),
As a result of being conveyed and discharged out of the holes (2s) and (30) along (FL-B), the skeletons (22), (31), and (3) are discharged.
5) and (36) act to prevent the temperature rise. Further, in the present invention, the outside air (40) acts so as to convey the heat of the concrete (20) along each of a plurality of air flows (FL-A) and (FL-B) heading in opposite directions. Further, in the present invention, in the hole (2s) located in the central portion (SP1) of the skeleton (22), the peripheral portion (S
The air flow (FL-A), (FL-B) having a larger capacity (Q) than the hole (2s) at the position P2) acts so that the heat transfer of the concrete (20) is carried out by the large heat transfer capacity. To do. Further, in the present invention, one hole (2
s) heat transfer of concrete (20) and tension material (27)
It serves as a dual purpose of installation. Further, in the present invention, the hole (30) in which the heat transfer of the concrete (20) is carried out acts as a cavity and is placed inside the skeleton (31). Further, in the present invention, the holes (2s) and (30) are horizontally formed with the space forming members (3) and (33) oriented horizontally, and the horizontal holes (2s) and (30) are formed. ) Inside air flow (FL-
A) and (FL-B) are used to build the frame (2
The heat of the concrete (20) of (2), (31) and (35) acts to convey and discharge the heat to the outside of the horizontal holes (2s) and (30). Further, in the present invention, the intake means (5a) is installed on the scaffold for constructing the bridge pier, and the work is performed so as to prevent cracks due to the temperature rise of the skeleton (22). Further, in the present invention, the outside air (40) precooled through the precooling means (11) acts so as to move inside the hole (2s) along the airflows (FL-A) and (FL-B). To do.

[0006]

EXAMPLE FIG. 1 is a front view showing an example of a bridge pier during construction of a beam portion using the crack prevention construction method according to the present invention.
1 is a side view of the bridge pier shown in FIG. 1, FIG. 3 is a view showing an example of the concrete cooling device used in the bridge pier construction shown in FIG. 1, FIG. 4 is a view taken along the line IV in FIG. 3, and FIG. Fig. 6 is a diagram showing the relationship between the concrete temperature and the cross section of the concrete cooled by the crack prevention construction method of the present invention, and Figs. 7 to 9 are a series of construction procedures of the crack prevention construction method of the present invention. FIG. 10, FIG. 10 is a view showing a temperature change state of concrete constructed according to the present invention, FIG. 11 is a conceptual diagram showing another method of the crack prevention construction method according to the present invention, and FIG. 12 is a crack prevention construction method according to the present invention. The figure which shows another example of the concrete structure applied, FIG. 13 is the figure which shows another example of the concrete structure to which the crack prevention construction method by this invention is applied, and FIG. 14 is the crack prevention by this invention. Is a diagram illustrating still another example of the concrete structure engineering method is applied.

As shown in FIG. 1 or 2, the bridge pier 1 under construction has a structural frame 2 made of reinforced concrete, and the structural frame 2 is a leg 2 which is erected and supported on the ground 39.
1 and a frame that is a horizontal member mounted on the leg portion 21, that is, a beam 22 that is a bridge pier.
The leg portion 21 has a rectangular cross section and has already passed a predetermined number of days after the concrete has been cast. The beam 22 has the concrete welded to the upper side of the leg portion 21 so as to be connected thereto. In shape, it is within 3 days after placing concrete. On the bottom surface and the side surface of the beam 22 other than the portion connected to the leg portion 21, a mold 23 is provided by the mold 23.
In a molded form, the mold 23 is not removed yet and remains, and the mold 23 is supported by a plurality of temporary support columns 25. In addition, a plurality of steps of scaffolding plates 26 are erected on the plurality of columns 25 so as to horizontally connect the adjacent columns 25 to each other. The plate 26 is provided with cooling device installation portions 26a and 26a, which are located on the right side and the left side in FIG.

As shown in FIG. 1 or 2, the beam 22 is made of a steel pipe, a resin pipe, or the like, and has a hollow portion 3 inside.
a plurality of sheaths 3 which are space forming members in which s is formed,
The beams 22 are embedded in such a manner that they penetrate in the left-right direction of FIG. 1 (the direction intersecting the plane of FIG. 2), which is the longitudinal direction thereof,
Each sheath 3 has a hole 2 s formed inside the frame of the beam 22 by the hollow portion 3 s. That is, the beam 22 of the pier 1 has a predetermined number of days elapsed since the concrete was placed so that the vehicle load applied to the beam 22 can be accurately supported when the roadbed is erected on the beam 22 later. After that, pre-stress will be introduced along the left-right direction of FIG.
The hole 2s formed by the sheath 3 will later become a hole 2sx (shown in FIG. 9) which is a tension material installation hole through which a steel wire for tension is inserted.

In addition, as shown in FIG.
As shown in FIG. 5, a concrete cooling device 5 for performing a sheath cooling for preventing concrete cracks of the beam 22 which is a skeleton is provided.
Are cooling units 5 each of which constitutes an intake means.
In the embodiment, there are two a. As shown in FIG. 1, the two cooling units 5a and 5a are temporarily installed in the cooling device installation portions 26a and 26a, respectively, and each cooling unit 5a includes a propeller fan 6 as shown in FIG. have. The propeller fan 6 can be blown and driven with the blowing direction of the propeller fan 6 in the normal rotation direction being the arrow J direction in FIG.
As shown in FIG. 5, an exhaust port 6a is formed on the back surface of the so that the inside and outside of the propeller fan 6 communicate with each other.
Further, on the intake side shown on the left side of the propeller fan 6 in FIG. 3,
As shown in FIG. 3, the damper 7 is provided in such a manner that the amount of air blown by the propeller fan 6 is variable depending on the angle of the blade portion 7a, and on the intake side shown on the left side of FIG. 3 of the damper 7,
A distribution box 9 formed in the shape of an inner container is detachably arranged so as to be connected to the damper 7 so as to communicate therewith.

Inside the distribution box 9, an air circulation space 9s,
It is formed in a substantially columnar shape, and on the intake side shown on the left side of FIG. 3 of the distribution box 9, as shown in FIG. 3 or 4, a predetermined number of intake parts 91 are respectively on the intake side. It is provided in a projected form on the left side of FIG. A mouth 91a is formed in each intake portion 91 so that the inside and outside of the air circulation space 9s communicate with each other, and the mouth 91a of each intake portion 91 is formed.
A holding portion 91b is provided in the vicinity in the form of a bamboo-shaped step. A flexible hose 10 made of a flexible pipe material is connected to each of the intake portions 91 via the holding portion 91b in a manner that prevents the flexible hose 10 from falling off from the intake portion 91. As shown in FIG. 1, the other suction side on the left side (not shown) is connected to the mouth 2p which is one side of the hole 2s formed inside the beam 22 by the sheath 3.

By the way, in the plurality of holes 2s of the beam 22, as shown in FIG. 1 or FIG.
When using, the hole 2sa whose air ventilation direction is oriented in the direction of arrow A in FIG. 1 and the hole 2sb oriented in the direction of arrow B of FIG. The holes 2sa and 2 are temporarily set so that they are alternately arranged.
As shown in FIG. 1, sb is connected to different cooling units 5a so that the directions of the air flows FL-A and FL-B formed here are opposite to each other. That is, the hole 2sa has the sheath end on the right side in FIG. 1, that is, the arrow A direction side as the mouth 2p, and is connected to the intake hose 91 of the cooling unit 5a shown on the right side in FIG. 1 by the flexible hose 10 connected to the mouth 2p. Connected, while hole 2sb
The flexible hose 10 connected to the mouth 2p of the sheath end on the left side of FIG.
1 is connected to each intake portion 91 of the cooling unit 5a shown on the left side of FIG. As shown in FIG. 1, the other end of the mouth 2p of each hole 2s is opened as an open end 2q with the sheath 3 forming the hole 2s opening so that the hole 2s communicates with the outside. Therefore, each hole 2s has an exhaust port 6a of the cooling unit 5a connected to the mouth 2p on one end side through the flexible hose 10 and an opening end 2q on the other end side of the hole 2s. They are in communication with each other.

Further, the plurality of holes 2s and each cooling unit 5
As shown in FIG. 2, each of the intake portions 51 of a has a plurality of holes 2
As shown in FIG. 4, the holes 2s located in the central portion SP1 of the beam 22 of s are connected to the intake portions 91 located in the middle POS1 of the distribution box 9, respectively.
The middle POS 1 is a position where the air flow rate Q by the propeller fan 6 becomes large as compared with other areas.
Therefore, at the time of sheath cooling, which will be described later, the holes 2s located in the central portion SP can form air flows FL-A and FL-B having a larger volume than the holes 2s located in the peripheral portion SP2. In the embodiment, for convenience of drawing, the total number of the air intake portions 91 provided in the two cooling units 5a and the total number of the holes 2s do not match. The distribution box 9 provided with a predetermined number of intake portions 91 such that the total amount of 2 s and the total amount of the intake portions 91 match is attached to the damper 7 and used.

Since the bridge pier 1 has the above-mentioned structure, when the bridge pier 1 is constructed, when the leg portion 21 which is the lower part of the structural frame 2 is formed by driving, the structural frame 2 is constructed.
The concrete 20 of the beam 22, which is the frame formed by the horizontal member on the upper part of, is placed. That is, when the concrete of the leg portion 21 is hardened, the formwork 23 is assembled and installed via the pillar 25 and the scaffolding plate 26 in a form corresponding to the cast shape of the beam 22, as shown in FIG. 7. At this time, in the formwork 23, a predetermined number of sheaths 3 required for introducing prestress to the beam 22 later are formed such that the hollow portion 3s penetrates in the longitudinal direction of the beam 22 shown in the left-right direction in FIG. Install each so that Then, as shown in FIG.
Concrete 20 is placed in the form 23. Then, the beam 22 which is a part of the structural body 2 is formed into a predetermined shape by the hardening of the concrete 20. Then, inside the beam 22, the holes 2 are formed by the hollow portions 3s of the plurality of sheaths 3.
s extend along the longitudinal direction of the beam 22 and are formed and arranged so as to penetrate the beam 22.

By the way, the concrete 20 of the beam 22 is
If no cooling curing is performed after the casting, the center portion SP1 of the beam 22 is higher than the dangerous temperature T1 by about 3 days after the casting due to the heat of hydration generated by the hardening of the cement, as shown by the dashed line in FIG. As such, there is a danger of a sudden temperature rise. That is, the concrete 20 generates heat due to the cement hydration reaction when hardening the concrete, and the temperature thereof rises. As the temperature rises, the tensile force acts inside the member in such a manner that the member in the middle of hardening expands. Then,
The beam 22 is a leg portion 2 which has already been cast and hardened through the bottom portion thereof.
Since it is in the form of being bonded to No. 1, the tensile force generated at the time of curing is constrained by the cured legs 21, and the beam 22 is exposed to the risk of thermal cracking. This dangerous temperature that is a standard for the occurrence of temperature cracks is the temperature T1 shown in FIG. Therefore, in order to release the heat of hydration of the concrete 20 generated inside the beam 22 to the outside, that is, outside the hole 2s, by the concrete cooling device 5, when the concrete pouring work is performed as described above as shown in FIG. Perform the sheath cooling work.

Therefore, first, as shown in FIG. 1, each cooling unit 5a of the concrete cooling device 5 is connected to each of the plurality of holes 2s formed in the beam 22. At this time, the cooling unit 5a shown on the right side of FIG.
1 and the cooling unit 5a shown on the left side of FIG.
One end of the flexible hose 10 is connected to the end portion of the sheath 3 forming each mouth 2p so as to connect to b.
The other end of the flexible hose 10 is inserted into each intake portion 91 and connected to each other. Further, as shown in FIG. 2, the hole 2s located in the central portion SP1 of the beam 22 is connected to the intake portion 91 located in the center POS1 of each distribution box 9, and the hole 2s located in the peripheral portion SP2 of the beam 22 is , P of distribution box 9
It is connected to the intake section 91 located in OS2. When each hole 2s is thus connected to each cooling unit 5a, the opening end 2q and the exhaust port 6a of each cooling unit 5a communicate with each other through the hole 2s.

In this state, the two cooling units 5a, 5
a, respectively, so that each of the holes 2s has its opening end 2
The outside air 40 is drawn in from q. For this purpose, first, each propeller fan 6 is driven while adjusting each damper 7. Then, the cooling unit 5a is driven by the propeller fan 6 so that the air corresponding to the blowing amount Q of the propeller fan 6 is sent in the direction of arrow J in FIG.
The inside air is sucked toward the cooling units 5a, 5a (that is, the arrow A direction side or the B direction side). As a result, each hole 2
s, as shown in FIG.
8 is drawn into the hole 2sa connected to the cooling unit 5a on the arrow A direction side shown in the right side of FIG. 8, and the air flow FL-A in the direction of the arrow A direction, and the arrow B direction shown on the left side of FIG. In the hole 2sb connected to the side cooling unit 5a, an air flow FL-B having a shape directed in the direction of the arrow B is formed in opposite directions as an air flow having a shape corresponding to the blown air amount Q. That is, in each hole 2s, the outside air 40 corresponding to the blown air volume Q is supplied with the respective air flows FL-A and FL-B.
Flow in the direction of arrow A or B along the direction of.

As described above, when the outside air 40 is drawn into the hole 2s and the outside air 40 flows in the direction of arrow A or B along the direction of the air flow FL-A, FL-B, the hole 2s passes through the hole 2s. The moving outside air 40 absorbs the heat of hydration of the concrete of the beam 22 in which the cement 20 is generated by the hydration reaction of cement as described above around the hole 2s, and the air flow FL.
It is placed on -A and FL-B and conveyed in the direction of arrow A or B. That is, as shown in FIG. 6LINE1, a concrete horizontal frame-like body having a beam shape like the beam 22 and having a certain thickness has a high temperature in the middle portion when it is hardened. In the hole 2s formed in
When the outside air 40 is passed through the air flows such as the air flows FL-A and FL-B, the temperature of the skeleton is measured as shown in FIG.
As shown in FIG. 6, a distribution state is formed in which the opening end 2q is the lowest and rises toward the mouth 2p, but is always below LINE1 in FIG. That is, the outside air 40 having a temperature lower than the body internal temperature of the beam 22 and the like takes away the heat generated by the concrete 20 of the beam 22 and conveys the heat along the air flows FL-A and FL-B. .

Therefore, in the beam 22 of the pier 1, as shown in FIG.
As shown in FIG. 2, in the hole 2sa among the plurality of holes 2s, the airflow FL-A directed in the direction of the arrow A, and the hole 2sa.
In the holes 2sb arranged alternately with the air flow FL in the direction of arrow B
-B causes the outside air 40 to flow through the holes 2s in opposite directions, and the outside air 40 flows through the holes 2s during the flow process of the holes 2s.
The heat is transferred in such a manner that the heat of the concrete 20 of the surrounding beam 22 is taken away. Then, the beam 22 is provided with a plurality of holes 2s so as to have a uniform temperature distribution state without cooling only on one side of both longitudinal end portions thereof.
The heat generated by the beam 22 is transferred and released. And
The outside air 40 flowing through the respective holes 2s in the direction of the arrow A or the direction of the arrow B and having a temperature rise is cooled by the cooling unit 5a.
It is discharged from the exhaust port 6a of the propeller fan 6 to the outside of the hole 2s, that is, the outside of the beam 22. Further, in the beam 22, the portion arranged near the peripheral portion SP2 is the outside air 4
While it can release the heat of hydration of concrete to a certain degree,
A portion located near the central portion SP1 is likely to experience a temperature rise. However, when performing the above-mentioned sheath cooling,
The hole 2s located in the central portion SP1 is provided with a PO in the center of the distribution box 9.
By connecting the intake portions 91 located at S1 respectively, extremely accurate heat release can be performed.

That is, in each cooling unit 5a, as shown in FIG. 3, since the inner diameter of the distribution box 9 is larger than the outer diameter of the rotating blades of the propeller fan 6, the vicinity of the position close to the axial center of the propeller fan 6 is obtained. The blast condition is stable. That is, in the air circulation space 9s in the center POS1 portion, the air flow is stable and the loss is reduced. Therefore, the beam 2
In the hole 2s of the central portion SP1 which is connected to the air intake portion 91 located at the center POS1 among the plurality of holes 2s of 2, the air flow rates Q of the air flows FL-A and FL-B are different from those at other positions, that is, the periphery. Air flows FL-A, FL-B formed in the holes 2s of the portion 2q
The air flow rate is larger than the air flow rate Q of, and as a result, a larger heat transfer capacity is held as the air flow rate Q is larger. Therefore, in the beam 22, it is possible to reliably radiate the heat of the portion of the concrete 20 where the temperature is likely to rise to the outside of the hole 2s. As a result, the beam 22 has its central portion S
Since the hardening of the concrete proceeds in such a manner that the temperature difference between P1 and the peripheral portion SP2 does not occur as much as possible, it is possible to exhibit a homogeneous and robust structural state.

In this way, the concrete 2 of the beam 22 is
For about 3 days after placing 0, the hole 2
When sheath cooling is performed while the cooling unit 5a is connected to the sheath 3 forming s via the flexible hose 10, the temperature T of the beam 22 reaches the dangerous temperature T1 as shown by the solid line in FIG. Instead, the temperature begins to drop.
That is, the initial stage of the cement hydration reaction is completed. Therefore, the heat of cement hydration generated when the concrete 20 of the beam 22 is hardened does not raise the temperature of the beam 22 until it reaches the dangerous temperature T1 where temperature cracking may occur, and the heat is accurately applied to the holes 2s. As a result, the temperature cracks of the beam 22 are prevented.

As described above, in the concrete cooling device 5, the cooling units 5a and 5a having a simple structure using the propeller fan 6 are installed on the uppermost scaffolding plate 26, and the outside air 40 is sucked and drawn into each hole 2s. The temperature cracking of the beam 22 can be prevented only by doing so. Therefore, large scale facilities for cooling water and circulating the cooled water are not required, as is the case when cracking is prevented by a water-cooled concrete cooling method. For this reason, the cooling equipment that should be installed on the scaffold is also lightweight. As a result, the pillar 2
The sheath cooling can be smoothly performed even on the scaffolding plate 26 supported by 5. Further, since the cooling water is not passed through the hole 2s, there is no risk that the weight of the beam 22 applied to the support column 25 increases due to the sheath cooling. Furthermore, since the work of collecting water from each hole 2s is not required after the cooling work is completed, the labor for the water collecting work is unnecessary. In addition, even if the sheath 3 is damaged, the hole 2s
Since water is not passed through, there is no risk that water will flow from the damaged portion of the sheath 3 to the reinforcing bar of the beam 22 and rust it. In this way, the cooling unit 5a is immediately stopped when the temperature drop of the beam 22 starts as shown by the solid line in FIG.
Stop the sea cooling. This is for avoiding the occurrence of cracks due to the rapid temperature drop of the beam 22 and the failure to express the final strength.

By the way, since the bridge pier 1 is for roads, the prestressing work is performed on the beam 22 about one week after the concrete is placed, as described above. That is, since the sheath 3 that has previously formed the hole 2s used for the sheath cooling was originally installed for prestress introduction, the hole 2s formed by the sheath 3 will now be as shown in FIG. In addition, it is used as a hole 2sx for introducing prestress. Then, the hole 2sx is first inserted into the hole 2sx.
Is used as the holes 2sa and 2sb for sheath cooling, and when the air flows FL-A and FL-B are formed therein, the outside air 40 is simply flowed through the holes 2sa and 2sb. As soon as the operation of the cooling unit 5a is stopped and the air flows FL-A and FL-B are stopped, a state where only the outside air 40 is statically arranged is formed in the holes 2sa and 2sb. . That is, at the time of trying to perform the prestress introduction work, the water content of the cooling water is not placed in the hole 2sx. Therefore, the prestressing work can be started immediately without the need to clean the hole 2sx.

Therefore, as shown in FIG. 9, tensioning steel wires 27 are inserted through the respective holes 2sx. Then, a tensioning force is appropriately introduced to each of the steel wires 27, and the tensioned steel wires 27 are attached to the appropriate fasteners 271 and 27.
The beam 22 is unbonded or fastened to the beam 22 through the hole 2, or the hole 2sx is filled with an appropriate filling material 29 which is hardened with time. Then, as described above, there is no moisture in the hole 2sx, so there is no risk of the steel wire 27 into which the tension has been introduced contacting the moisture and rusting, and the tension is in a suitable state. Then, the beam 22 is introduced and loaded. Further, the curing of the filler is sure. Thus, when constructing the beam 22,
By installing the sheath 3 in the mold 23, the formed hole 2s is used as a sheath cooling hole 2 for preventing cracking of the beam 22 until about 3 days after concrete placement.
It is very efficient because it can be used twice as sa and 2sb and after completion of the cooling operation as the holes 2sx for introducing prestress for different purposes with different dates and times of use.

In the above-mentioned example, the outside air 40 is drawn into the hole 2s directly from the opening end 2q by the cooling unit 5a connected to the mouth 2p through the flexible hose 10, and the outside air 40 is supplied to the air flow FL-A. , FL-B was used to flow. However, as shown in FIG. 11, an appropriate air cooling device 11 may be connected to the opening end 2q of the hole 2s as an air precooling unit. The air cooling device 11 allows the outside air 40 that is drawn into each hole 2s by the air flows FL-A and FL-B to pass therethrough, and at the time of the passage, the outside air 40 can be cooled to a temperature lower than the original outside air temperature. Therefore, the air cooling device 11 can send the outside air 40 into the hole 2s as the cooling outside air 40 '. Then, when the outside air temperature is high, the cooling outside air 40 'pre-cooled through the air cooling device 11 is drawn into the hole 2s, and the cooling outside air 40' is placed on the air flows FL-A and FL-B and passes through the hole 2s. By doing so, the heat generated by the beam 22 around the hole 2s can be more effectively taken, and the heat can always be reliably discharged to the outside of the hole 2s of the beam 22. Therefore, even when the hot outside air 40 in summer is used, the temperature rise of the beam 22 can be accurately prevented and the crack can be surely prevented.

In the above-described embodiment, since the cooling unit 5a having the inner diameter of the distribution box 9 larger than the outer diameter of the rotating blade of the propeller fan 6 is used, the central portion of the plurality of holes 2s of the beam 22 is used. The example in which the hole 2s located at SP1 is connected to the air intake portion 91 located at the center POS1 has been described. However, this is the air flow F of the hole 2s in the central portion SP1.
This is because the air flow rate Q of LA and FL-B is made larger than the air flow rate Q of the air flows FL-A and FL-B of the holes 2s located in the peripheral portion SP2, and such measures are unnecessary. If so, you can omit it. Alternatively, the cooling unit 5
In the case where a mechanism is provided in the air circulation space 9s of the distribution box 9 of the air intake means such as a for varying the air flow rate Q for each air intake portion 91, a large air flow rate is correspondingly increased. Q
2s located in the central portion SP1 in the intake portion 91 that can be seen by
It is only necessary to connect the air intake portion 9 to obtain the large air flow rate Q.
1 is not always the center P of the intake means such as the cooling unit 5a.
It is not always located in OS1.

Further, in the embodiment, the example in which the frame for which cracking is to be prevented is the beam 22 of the pier 1, but the application of the present invention is not limited to such pier beams. For example, the structure that should prevent cracking is shown in FIG.
As shown in FIG. 3, it may be a hollow slab 31 in which a cavity 30 is formed. That is, the cavity 30 is a hole that remains as a cavity inside the hollow slab 31, and is used as a hole for sheath cooling. It should be noted that the cavity 30 has an inner form 33 in which a hollow portion 33s is formed.
Is installed in the formwork at the time of construction of the hollow slab 31 as a space forming member.
Is placed inside the hollow slab 31 by pouring. Then, at the time of sheath cooling, one end of the cavity 30 on the front side (or the back side) of the plane of FIG.
The cooling unit 5a is connected to the cooling unit 5a at 0p, and the opening 30q on the other end side located on the back side (or the front side) of the paper of FIG. Then, the opening end 3 is provided via the cooling unit 5a.
The outside air 40 is drawn into the cavity 30 from 0q, and the outside air 40 causes the air flows FL-A and FL- in a direction intersecting the plane of FIG.
If B is formed, the concrete 20 of the hollow slab 31
The heat generated by the cement hydration reaction that occurs when the
The air is conveyed outside the cavity 30 in the form of being conveyed by the outside air 40 moving inside the cavity 30 along the air flows FL-A and FL-B. Therefore, similar to the case of the beam 22 of the pier 1 described above, cracking due to the temperature rise of the hollow slab 31, which is the skeleton, is prevented. Then, since the slab provided in such a building dislikes water, the cooling water is usually passed through the inside of the skeleton to cool the concrete, and a method for preventing temperature cracks has been shunned. If it is used, even if such cooling water is not used, it is possible to easily prevent an increase in the body temperature, prevent temperature cracks, and construct a robust structure. Further, the holes 2s and the cavities 30 for forming the air flows FL-A and FL-B to convey the heat of hydration, the holes 2sx for installing the tension member for introducing prestress to the beam 22 and the hollow slab. Three
1 does not need to be a hole for residual formation of the cavity 30 and may be used for other purposes or from the beginning for air flow FL-1, F
It may be a hole provided for forming L2. The holes 2s and the holes such as the cavities 30 may be filled with the filling material 29 or the like or may be left as voids.

Further, as shown in FIG. 13, the skeleton for which cracking should be prevented may be the basic concrete 35 of the underground tank for storage of liquefied natural gas (LNG). When the concrete is cast after the side wall portion 34 is constructed, the basic concrete 35 is restrained by the side wall portion 34 and cracks easily occur. In order to prevent the cracks, the internal temperature of the frame and the external temperature of It must be installed under strict control so that the difference is below a specified temperature. However, at this time, the foundation concrete 35
Is underground, and the space 350 above the basic concrete 35 is hard to work, so it was very difficult to cool the concrete using a large-scale cooling facility here. At this time, according to the present invention, as described above, since it is possible to prevent the concrete from cracking with light equipment and without using cooling water by the force of the air using the outside air 40, It is possible to suitably prevent even fine cracks in the basic concrete 35 and build a robust underground tank without lowering the construction efficiency.

Further, in any of the above-described embodiments, the frame made of concrete for which cracking is to be prevented is the beam 22, the hollow slab 31, and the basic concrete 35.
Although an example of a horizontal member such as the above has been described, the skeleton to be prevented from cracking may be a shielding wall 36 as shown in FIG. That is, as shown in FIG. 14, after the foundation 37 is cast in a flat plate shape and constructed, the shielding wall 36 constructed in the shape of a wall is constrained by the constructed foundation 37, so that the cause of cracking is greatly increased. It is in the form of holding. Therefore, the shielding wall 36
When the concrete 20 is poured, a sheath 3 similar to that used for the beam 22 of the pier 1 is previously installed in the formwork, and the air flow FL is provided in the hole 2s formed by the hollow portion 3s of the sheath 3. The heat generated by the concrete may be radiated to the outside of the hole 2s in the form of -A and FL-B. That is, the present invention uses the outside air 40 to circulate the heat of the concrete to the outside of the skeleton by using the outside air 40 without having to circulate the cooling water, even if the skeleton is made of concrete other than the horizontal member, such as the shielding wall 36. It is always possible to accurately prevent cracks. Further, in the examples, all of the holes 2
Although the example in which the holes such as s and the cavity 30 are formed in a substantially horizontal direction has been described, such holes may be formed and arranged so as to extend in the vertical direction inside the skeleton made of concrete. Further, in the embodiment, the sheath 3 and the inner mold 33 used for forming the holes inside the body are left buried inside the body. The space forming member may be one in which a release agent is applied to the outer periphery of the space forming member and the space forming member is removed after the holes are formed.

Further, in the embodiment, an example is described in which a plurality of holes 2s or cavities 30 are formed in parallel inside the body made of concrete. However, such holes 2s, 30 are It is not always necessary that all of them are arranged in parallel, and the open ends 2q and 30 of each of the holes are
As long as the other end of q or the like can communicate with the intake unit such as the cooling unit 5a through the hole, the arrangement directions of the plurality of holes may intersect. Therefore, the air flows FL-A and FL- formed in the plurality of holes.
The direction of B and the combination thereof are not limited to the forward and reverse directions as described in the embodiment, and the mouth 2 which is one end side from the opening ends 2q and 30q which are the other end sides of each hole.
As long as the shape is directed toward p, 30p, etc., it may be formed to be directed in any other direction.

Furthermore, in the embodiment, the holes 2s,
Although the intake unit for forming the air flows FL-A and FL-B in the holes of the cavity 30 and the like is the cooling unit 5a in which the damper 7, the distribution box 9 and the like are connected to the propeller fan 6, the intake is described. The configuration of the means is not limited to this.
That is, the intake means is connected to the mouths 2p, 30p, etc., which are one end side of the hole 2s, the cavity 30 and the like, so that the outside air 4 is introduced into the hole from the opening ends 2q, 30q which are the other end side of the hole.
Other configurations may be used as long as they are of a suction type so that 0 can be called. Further, the number of intake means provided is not limited to two, but is arbitrary. For example, the air flow directed in a plurality of directions may be formed by using only one intake means.

[0031]

As described above, according to the present invention, when the frame 20, such as the beam 22, the hollow slab 31, the basic concrete 35, the shield wall 36, etc. is cast by the concrete 20, the hollow portions 3s, 33s, etc. The space forming member, such as the sheath 3 and the inner mold 33, in which the hollow portion is formed is formed into the mold 23.
It is installed inside and the concrete 20 is placed in the form 23 to form the skeleton in the form of arranging holes 2s, cavities 30, etc. by the hollow portion of the space forming member inside the skeleton. Then, an intake means such as a cooling unit 5a is connected to one end side of the mouths 2p and 30p of the hole, and the other end side of the opening ends 2q and 30q of the hole is connected to the intake means through the hole. , An air flow FL that drives the intake means to draw the outside air 40 into the hole from the other end side and moves from the other end side of the hole to the one end side by the outside air 40.
-A, FL-B are formed, and the air flows FL-A, FL-B
The outside air 40 moving along the inside of the hole conveys the heat generated by the concrete 20 around the hole to release the heat from the intake means to the outside of the hole, and cracks due to the temperature rise of the skeleton. Since the outside air 40 conveys the heat of the concrete 20 to the outside of the holes along the air flows FL-A and FL-B, the temperature rise of the skeleton is prevented. Therefore, in the present invention, the heat due to the cement hydration reaction generated when the concrete 20 around the hole is hardened is transferred to the outside of the hole by the air flows FL-A and FL-B, and the heat of the concrete inside the frame is discharged. It is possible to prevent heat from accumulating, thereby appropriately suppressing the temperature rise of the skeleton, and as a result, it is possible to preferably prevent cracking due to the temperature rise of the skeleton in the initial stage of driving. And the air flow FL-A,
The FL-B can be formed by driving the intake means to draw the outside air 40 into the hole from the other end side and flowing the outside air 40 from the other end side toward the one end side. There is no need to cool the body with cooling water inside. That is,
Since other heat is used to release the heat of the concrete, no other refrigerant is required. For this reason, the intake means only needs to be able to draw the outside air 40 into the hole, so that the device configuration is simple and a large-capacity water tank or cooling device, such as when cooling the body with water, There is no need for a pump to circulate the cooling water. Therefore, the cost is low. Further, since the present invention can be easily carried out as long as the space forming member is installed in the mold, the construction conditions are not restricted and the invention can be applied to a small site. Further, since the outside air 40 carrying the heat of the concrete is discharged to the outside of the hole through the intake means, it is not necessary to collect it like cooling water, and the labor is not required. Furthermore, since no cooling water is used, the cooling water in the holes leaks out to the outer wall of the body and stains the wall surface, or the cooling water remaining inside the body is used to reinforce the reinforcing steel or to fill the sheath. There is no risk of adversely affecting the cure.

Further, in the present invention, a plurality of holes such as the holes 2s and the cavities 30 are formed substantially parallel to each other inside the body of the beam 22, the hollow slab 31, the side wall portion 35, the shielding wall 36 and the like, and the plurality of holes are formed. The air flows FL-A, F are respectively provided in the holes.
When forming L-B, the air flow FL- inside the body
When the A and FL-B directions (arrow A direction) and (arrow B direction) are configured to be opposite to each other, the outside air 40 has a plurality of opposite directions (arrow A direction) and (arrow B direction). The heat of the concrete 20 can be carried along each of the air streams FL-A and FL-B. Then, as described above, the air flows FL-A, FL are driven by the driving of the intake means.
-When the outside air 40 is loaded on B and drawn into the hole for circulation, the temperature of the body is the other end side of the hole (that is, the suction side).
Is the lowest, and a temperature distribution state in which the temperature rises toward the one end side connected to the intake means is formed. Therefore,
Air flow FL-A, F of a plurality of substantially parallel holes formed in the body
If the directions of L-B are opposite to each other, the outside air 40 flows through the plurality of holes in opposite directions (direction of arrow A) and (direction of arrow B), respectively. The outside air 40 flowing in each direction conveys heat in such a manner that the heat of the concrete 20 around each hole is taken away. As a result, the heat generated by the concrete is intensively conveyed from one place to one place, and is not emitted intensively, and the heat generated at each place of the body is in the opposite direction (direction of arrow A). ), (Arrow B direction). As a result, the skeleton can exhibit a uniform temperature distribution state. In this way, if the temperature unevenness is not formed in the skeleton, it is more surely prevented from cracking in the entire area, and as a result of concrete curing under the average temperature condition in the entire area of the skeleton, the structural state of the skeleton is also It is homogenized and becomes good quality.

Further, in the present invention, a plurality of holes such as the holes 2s are formed inside the skeleton of the beam 22 and the like, and among the plurality of holes, the hole located at the central portion SP1 of the skeleton is: When the air flows FL-A and FL-B having a larger capacity Q are formed than the holes 2s at the peripheral portion SP2, the holes at the central portion SP1 of the skeleton have a larger capacity than the holes at the peripheral portion SP2. The heat transfer of the concrete 20 can be performed by the large heat transfer capacity of the Q air flows FL-A and FL-B. Then, normally, the peripheral part SP of the body
In the case of No. 2, since there is a contact surface with the outside air 40, heat is easily released into the outside air 40. Therefore, the peripheral portion SP2
Although the temperature does not rise so much at the time of hardening, the heat due to the cement hydration reaction does not easily escape to the outside and is easily accumulated in the central portion SP1. Therefore, if no treatment is applied to the body,
The temperature rise in the central portion SP1 is more severe than in the peripheral portion SP2. Therefore, in the hole located in the central portion SP1 where the temperature rises sharply as described above, the heat transfer is performed by the air flows FL-A and FL-B having a larger capacity Q than the holes located in the peripheral portion SP2 as described above. Then, the heat generated by the concrete 20 in the central portion SP1 is sequentially released to the outside of each hole, that is, the outside of the skeleton, and as a result, a sharp temperature rise in the central portion SP1 is prevented. As a result, the temperature distribution of the skeleton becomes more uniform, so that even in mass concrete where the temperature difference between the peripheral portion SP2 and the central portion SP1 becomes extremely large in the initial stage after placing, the occurrence of temperature cracks can be prevented more accurately. It is possible to

Further, in the present invention, if the holes such as the hole 2s are holes for tensioning material such as the hole 2sx for introducing prestress to the frame such as the beam 22, it is possible to set the hole 1s.
The holes can be used for two purposes of heat transfer of the concrete 20 and installation of a tension material such as the steel wire 27. That is, when prestressing is planned to be introduced after the skeleton is placed, the space forming member such as the sheath 3 is installed in the mold serving as the skeleton, and the tension member is provided by the hollow portion 3s of the space forming member. It is necessary to form an installation hole in the body.
In such a case, a new space forming member is installed to prevent cracking of the concrete of the frame, and the air flow F
Even without forming a dedicated hole for LA and FL-B,
Using the tension material installation holes, an intake means is connected to one end side thereof, and the outside air 40 is drawn into the tension material installation holes from the other end side thereof, and the air flows FL-A, FL- are introduced therein. B can be easily formed. Therefore, the time and effort required for the work are reduced. At this time, the temperature of the concrete 20 of the skeleton rises the most due to the cement hydration reaction, which causes the factor of the initial crack generation to become the highest from the point where it is a predetermined time (usually about 3 days) immediately after the concrete is placed. If the pre-stress is introduced into the frame after a certain number of days have passed after the concrete is placed (usually about 7 days later), the time to prevent cracking and the time to install the tension material Can be shifted. In this way, there is no problem even if the above-mentioned one hole is used for the two purposes of heat transfer of the concrete 20 and installation of the tension material. Since one hole is also used for two purposes, it is not necessary to temporarily form many holes inside the body and fill the holes later, or to increase the number of cross-section defects unnecessarily. Absent. Further, the tension material such as the steel wire 27 for introducing the prestress is in a state of being easily affected by rust by applying a large tensile force. Therefore, since such a tension material dislikes even a slight amount of water, it is preferable that the tension material installation hole 2sx is always in a dry state. At this time, in the present invention, the tension material installation hole 2sx is used as a hole for forming the air flows FL-A and FL-B for the crack prevention treatment of the concrete of the skeleton. By circulating only the holes, it is possible to use the holes in the extremely dry state as the tension member installation holes 2sx after the crack prevention treatment without collecting the cooling water from the holes or cleaning the cooling water.

Further, in the present invention, when the holes such as the cavities 30 are configured so as to form residual cavities inside the skeleton such as the hollow slab 31, the holes through which the heat of the concrete 20 is transferred are formed. , Can be placed inside the body as a cavity. That is, Hollow Slab 3
In the skeleton such as the first skeleton, for the purpose of reducing the weight of the skeleton, a structure may be adopted in which a cavity is arranged inside the skeleton. In such a case, the inner mold 33 is used and the inner mold 33 is
A hole such as the cavity 30 due to the hollow portion 33s is formed inside the body. Therefore, if one end side of the hole for the cavity is used as the mouth 30p and the intake means is connected, and the other end side of the hole is used as the opening end 30q, the outside air 40 is drawn into the hole from the other end side. A hole for a cavity is provided with the air flow FL-A,
It can be used as a hole for forming FL-B. Then, it is not necessary to form the holes dedicated to the airflows FL-A and FL-B for preventing the cracking of the concrete of the skeleton, so that the labor is saved accordingly. In addition, it is not preferable that moisture remains in the hole for forming a cavity inside the skeleton as described above, but in the present invention, the water is circulated in the hole to prevent cracking of the concrete of the skeleton. Since only the outside air 40 is allowed to pass through and no cooling water is passed through the hole, there is a risk that water will remain in the hole that is the cavity and water will exude from the end of the cavity and adversely affect the body. Is avoided.

Further, in the present invention, when the frames such as the beam 22, the hollow slab 31, and the foundation concrete 35 are constructed as horizontal members, the sheath 3 and the inner mold 33 are formed.
The holes such as the hole 2s and the cavity 30 are horizontally formed by horizontally directing the space forming members such as the horizontal direction, and the air members FL-A and FL-B in the horizontal holes form the frame formed by the horizontal member. The heat of the concrete 20 can be transferred and discharged to the outside of the horizontal hole. Then, in such a horizontal member, the holes for heat release are sometimes formed horizontally (that is, it is possible to arrange the holes horizontally in the horizontal member because the number of the holes is smaller). Such a hole has a drawback that it becomes difficult to collect the cooling water when the cooling water is circulated through the hole. However, in the present invention, by connecting the intake means to one end side of such a horizontal hole, the air flows FL-A, FL-in a form in which the outside air 40 drawn into the hole from the other end side of the hole is circulated. B by concrete 2
Since the heat of 0 is transferred and released, the outside air 40
Is smoothly distributed. Therefore, the heat generated by the concrete 20 of the frame is smoothly transferred. Further, since it is not necessary to recover the outside air 40 after the crack prevention treatment due to the temperature rise of the concrete 20 is performed, the work is easy.

Further, in the case where the skeleton of the present invention is a horizontal member, if the horizontal member is configured as a bridge pier such as a beam 22, the cooling unit 5a or the like is mounted on a scaffold on which the pier is constructed. It is possible to prevent cracking due to the temperature rise of the body by installing the air intake means and performing work. Then, when constructing such a structure of the bridge pier, in addition to the horizontal member of the bridge pier as described above, it is necessary to work at a high place by forming a scaffold by the pillars 25 and the scaffolding board 26. In addition, the work space on the scaffold, the weight of equipment that can be installed here, and the types of work that can be performed are subject to various restrictions. Therefore, it is difficult to install cooling water circulation equipment for concrete cooling in the structure of the bridge pier that requires work at a high place on such scaffolding. It was difficult to do the process. However, in the present invention, the device to be lifted on the scaffold may be a simple intake means capable of drawing the outside air 40 into the hole formed inside the body, so that the intake means is light in weight and Easy to handle. Further, as described above, it is necessary to let the outside air 40 flow through the holes formed inside the body.
Therefore, there is no concern that the weight of the cooling water will be applied to the pillars 25 or the like that support the form 23 when the concrete is poured into the frame. Therefore, even with such a bridge pier, it is possible to easily take measures to prevent cracking due to temperature rise of concrete.

Further, in the present invention, an air pre-cooling means such as an air cooling device 11 is connected to the other end side of the opening end 2q of the hole such as the hole 2s so that the outside air 40 can be cooled.
When the air precooling means 11 is configured to precool the outside air 40 drawn into the hole 2s, the outside air 40 'precooled via the precooling means is the airflow FL-A, F.
It is possible to move in the hole 2s along LB. Then, in the summer when the temperature of the outside air 40 is high, if the air flows FL-A and FL-B are formed in such a manner that the outside air 40 'pre-cooled through the pre-cooling means is drawn into the holes to pass therethrough. The cold outside air 40 'can more efficiently take away the heat generated by the concrete 20 around it during its hardening, and the heat can be accurately conveyed and discharged to the outside of the hole. Therefore, even when the hot outside air 40 in summer is used, it is possible to reliably prevent the temperature of the body from rising and prevent cracking. In addition,
Even when such a pre-cooling means is used for the application of the present invention, the medium for pre-cooling generation through the pre-cooling means is the outside air 40, so that a tank for storage is required as in the case of generating and circulating cooling water. do not do. Therefore, all the devices required for the present invention are small.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a bridge pier during construction of a beam portion using the crack prevention construction method according to the present invention.

FIG. 2 is a side view of the pier shown in FIG.

FIG. 3 is a diagram showing an example of a concrete cooling device used in the bridge pier construction shown in FIG.

FIG. 4 is a view on arrow IV in FIG.

5 is a view on arrow V in FIG. 3. FIG.

FIG. 6 is a diagram showing the relationship between the cross section of concrete being cooled by the crack prevention construction method according to the present invention and the concrete temperature.

FIG. 7 is one of a series of diagrams showing a construction procedure of a crack prevention construction method according to the present invention.

FIG. 8 is one of a series of diagrams showing a construction procedure of the crack prevention construction method according to the present invention.

FIG. 9 is one of a series of diagrams showing a construction procedure of a crack prevention construction method according to the present invention.

FIG. 10 is a diagram showing a temperature change state of concrete constructed according to the present invention.

FIG. 11 is a conceptual view showing another method of the crack prevention construction method according to the present invention.

FIG. 12 is a diagram showing another example of a concrete structure to which the crack prevention construction method according to the present invention is applied.

FIG. 13 is a view showing still another example of a concrete structure to which the crack preventing construction method according to the present invention is applied.

FIG. 14 is a diagram showing still another example of a concrete structure to which the crack preventing construction method according to the present invention is applied.

[Explanation of symbols]

 20 …… Concrete 22 …… Body (beam) 31 …… Body (hollow slab) 35 …… Body (basic concrete) 36 …… Body (shielding wall) 3 …… Space forming member (sheath) 33 …… Space forming member ( Inner form) 3s, 33s ... Hollow part 2s ... Hole 2sx ... Tension material fastening hole (hole) 30 ... Hole (cavity) 2p, 30p ... One end side (mouth) 2q, 30q. Side (opening end) 5a ... intake means (cooling unit) 11 ... pre-cooling means (air cooling device) 40 ... outside air FL-A, FL-B ... air flow SP1 ... central part of the body SP2 ... of the body Peripheral area

Claims (8)

[Claims] 1. When placing and constructing a skeleton made of concrete, a space forming member having a hollow portion is installed in a mold, and concrete is cast in the mold to form the skeleton. The space forming member is formed in such a manner that a hole is formed by the hollow portion of the space forming member, an intake means is connected to one end side of the hole, and the other end side of the hole and the intake means are communicated via the hole, The intake means is driven to draw the outside air into the hole from the other end side, and the outside air forms an air flow from the other end side of the hole toward the one end side. The heat generated by the concrete around the hole is carried by the outside air moving in the hole, and the heat is released from the intake means to the outside of the hole to prevent cracking due to the temperature rise of the skeleton. Cracked concrete Preventive construction method. 2. A plurality of the holes are formed substantially parallel to each other inside the body, and when the air flow is formed in each of the plurality of holes,
The method for preventing cracking of concrete according to claim 1, wherein the directions of the air flows inside the body are opposite to each other. 3. A plurality of the holes are formed inside the body, and the hole located in the center of the body out of the plurality of holes is provided with a larger volume of air flow than the holes located in the peripheral portions. The method for preventing cracking of concrete according to claim 1, which is configured to be formed. 4. The method for preventing cracking of concrete according to claim 1, wherein the hole is a tension member installation hole for introducing prestress to the skeleton. 5. The method for preventing cracking of concrete according to claim 1, wherein the hole is for forming a cavity inside the body. 6. The method for preventing cracking of concrete according to claim 1, wherein the skeleton is a horizontal member. 7. The method for preventing cracking of concrete according to claim 6, wherein the horizontal member is a bridge pier. 8. An air precooling means is connected to the other end of the hole so as to allow the outside air to cool therethrough, and the air precooling means precools the outside air drawn into the hole. The construction method for preventing cracking of concrete according to claim 1, which is configured.