JP2012237152A - Method for cooling concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cooling concrete, which achieves high cooling efficiency and prevents the concrete from being dried during cooling, with simplified equipment for the method.SOLUTION: A method for cooling concrete after casting comprises the steps of: forming a cooling hole formed of a bottomed vertical hole 5 in the top face 1a of a cast concrete body 1, with the inside surface 5a composed of exposed surface of the concrete body 1; and supplying air into water in a pool part 7 for reserving water at the bottom of the vertical hole 5 formed in the step of forming the cooling hole, through a blast pipe 9 inserted into the water in the pool part 7.

Description

  The present invention relates to a concrete cooling method for cooling concrete after placing.

  In general, since the placed concrete body generates temperature stress due to hydration heat generation after placing, it needs to be cooled to prevent cracking due to the temperature stress. Conventionally, the technique of the following patent document 1 is known as a cooling method after placing concrete. In this cooling method, a concrete body is cooled by placing a vertical spiral pipe and placing concrete, and then inserting a water supply pipe into the spiral pipe to supply water.

JP 2007-303159 A

  However, in the cooling method of Patent Document 1, used cooling water overflows from the spiral tube. Since the used cooling water after cooling the concrete body is strongly alkaline, a predetermined process is required when the used cooling water is discarded, and a large-scale processing facility is required. Further, even if the cooling water is circulated, a large and high-cost device such as a chiller is similarly required. Here, in order to omit the water treatment and the water circulation as described above, a method of sending cooling air into the spiral pipe is also conceivable. However, when air is used as the refrigerant, the cooling efficiency is inferior compared to when water is used as the refrigerant. On the other hand, in order to improve the cooling efficiency, it is conceivable to send cooling air into the vertical hole after the spiral tube is removed. However, in this case, since the cooling air directly contacts the inner side surface of the vertical hole, the concrete body is easily dried from the inner side surface, and the quality of the concrete body may be deteriorated.

  In view of the circumstances as described above, it is an object of the present invention to provide a concrete cooling method capable of simplifying necessary equipment, obtaining cooling efficiency, and suppressing drying of the concrete being cooled.

  The cooling method of the present invention is a concrete cooling method for cooling after placing concrete, and has a bottomed cooling hole in a state in which the surface of the concrete body is exposed to the inner surface on the top surface of the placed concrete body. A cooling hole forming step for forming the water, and an air supply step for storing water at the bottom of the cooling hole formed in the cooling hole forming step and feeding cooling air into the water through a blower pipe inserted into the water. It is characterized by having.

  According to the cooling method of the present invention, the concrete body is cooled by the cooling air flowing in the cooling holes of the concrete body. Thus, since air is used as the refrigerant, it is not necessary to process the used refrigerant, and the equipment can be simplified. Further, the surface of the concrete body itself is exposed on the inner surface of the cooling hole, and the cooling air contacts the surface of the concrete body. Therefore, the cooling air can take heat directly from the concrete body, and the cooling efficiency can be improved. Moreover, the humidity of cooling air rises because the cooling air passes through the water stored in the bottom of the cooling hole. Therefore, the cooling air with high humidity flows in the cooling hole as a refrigerant. Therefore, even if the cooling method of the present invention is a system in which cooling air is in direct contact with the surface of the concrete body itself, drying of the concrete body can be suppressed.

  In the air supply process, the cooling air may contain mist. According to this configuration, the humidity of the air flowing through the cooling holes is further increased, so that the effect of suppressing the drying of the concrete body is further enhanced.

  Moreover, it is preferable that the front-end | tip part of the ventilation pipe inserted in water by an air_supply process is provided with two or more exhaust ports of cooling air. According to this configuration, since the bubbles discharged from the front end portion of the blower pipe become finer, the effect of increasing the humidity of the cooling air is increased, and as a result, the effect of suppressing the drying of the concrete body is increased.

  Moreover, the front-end | tip part of a ventilation pipe | tube is formed by bundling a plurality of pipes through which cooling air passes, and the opening at the end of each pipe may constitute the above-mentioned exhaust port. According to this configuration, a blower pipe having a plurality of exhaust ports provided at the distal end portion is realized with a simple structure.

  In the air supply process, a water supply pipe may be further inserted into the cooling hole, and water from the outside may be replenished to the bottom of the cooling hole through the water supply pipe. According to this structure, the water which decreases by transpiration from the bottom part of a cooling hole can be replenished from the outside.

  According to the concrete cooling method of the present invention, necessary equipment can be simplified, cooling efficiency can be obtained, and drying of the concrete during cooling can be suppressed.

It is sectional drawing which shows the placement process of the concrete which concerns on the cooling method of this invention. It is sectional drawing which shows the cooling hole formation process in the cooling method of this invention. It is sectional drawing which shows the air supply process in the cooling method of this invention. It is a front view which shows an example of an air duct. It is a bottom view which shows the front-end | tip part of the ventilation pipe | tube of FIG. It is a front view which shows the other example of a ventilation pipe | tube. It is a graph which shows the test result which the present inventors conducted. It is a graph which shows the other test result which the present inventors conducted. It is a graph which shows the further another test result which the present inventors conducted. It is a graph which shows the further another test result which the present inventors conducted.

  Hereinafter, a preferred embodiment of a concrete cooling method according to the present invention will be described in detail with reference to the drawings.

  1 to 3 show a concrete body 1 targeted by the cooling method of the present embodiment. The concrete body 1 is, for example, a part of a reinforced concrete structure and is a reinforced concrete body having a large cross section called “mass concrete”. Since the concrete body 1 has a large cross section, there is a tendency that the temperature difference between the inside and outside at the time of hardening after placement tends to be large, and cooling is particularly required after placement.

  As shown in FIG. 1, the concrete body 1 is placed in a state where a plurality of cylindrical spiral tubes 3 are vertically embedded. At this time, the plurality of spiral tubes 3 are regularly arranged on the concrete body 1 in, for example, a lattice-like arrangement as viewed from above. When the concrete body 1 is hardened to some extent when a predetermined time has passed since the placement (for example, the day after placement), the spiral tube 3 is removed as shown in FIG. A bottomed vertical hole (cooling hole) 5 extending vertically downward from the upper surface 1a of the concrete body 1 is formed as a trace after removing the spiral tube 3 (cooling hole forming step). On the inner surface 5a of the vertical hole 5, the background of the concrete body 1 is exposed, and the surface of the concrete body 1 itself is directly exposed. In FIG. 2 and subsequent figures, only one of the plurality of vertical holes 5 formed is shown.

  Subsequently, as shown in FIG. 3, water is accumulated at the bottom of the vertical hole 5 to form the water reservoir 7, and the blower tube 9 is inserted into the vertical hole 5. The tip nozzle 9 a of the blower tube 9 is inserted into the water of the water reservoir 7. From this state, cooling air is sent into the water of the reservoir 7 through the blower tube 9 (air supply process). Then, the cooling air is discharged into the water from the tip nozzle 9a of the blower tube 9, and ascends the water reservoir 7 as bubbles. Further, the cooling air flows upward in the vertical hole 5 above the water surface of the water reservoir 7 and is finally discharged to the outside from the upper end opening of the vertical hole 5. At this time, the cooling air takes heat away from the concrete body 1 while being in contact with the inner side surface 5a in the portion above the water surface of the water reservoir 7, so that the cooling of the concrete body 1 is realized.

  Since the water in the reservoir 7 is gradually lost due to transpiration, it is necessary to replenish appropriately. Therefore, a water supply pipe 23 for appropriately feeding water from the water supply unit 21 to the water storage unit 7 is inserted into the vertical hole 5. The upstream end of the water supply pipe 23 is connected to the water supply part 21, and the downstream end of the water supply pipe 23 is inserted into the water of the reservoir part 7. What is necessary is just to set the water supply speed | rate by the water supply pipe | tube 23 to 100-500 mL per hour, for example so that the water supply amount by the water supply pipe | tube 23 and the transpiration | evaporation amount of the water of the reservoir 7 may balance. For example, when the hole diameter of the vertical hole 5 is 3 cm, the water supply speed is 100 mL / hour, and when the hole diameter of the vertical hole 5 is 10 cm, the water supply speed is 500 mL / hour. Water supply by the water supply pipe 23 may be performed constantly, or may be performed once at regular intervals. Moreover, the pipe diameter of the water supply pipe 23 is 0.5-3 cm, for example, As the water supply pipe 23, the vinyl hose made from a vinyl chloride etc. can be used, for example.

  The dimensions of the water supply pipe 23 can be appropriately changed as long as water can flow and can be inserted into the vertical hole 5 together with the blower pipe 9. Moreover, since it is sufficient if water can be replenished to the water reservoir 7, it is not essential to insert the downstream end of the water supply pipe 23 into the water of the water reservoir 7, and the downstream end of the water supply pipe 23 is the water surface of the water reservoir 7. It may be above.

  Due to the presence of the water supply unit 21 and the water supply pipe 23 as described above, water lost by transpiration from the water storage unit 7 can be supplemented from the outside. Moreover, when the water in the reservoir 7 is appropriately replaced, the temperature rise of the water can be suppressed, and the cooling efficiency reduction in the cooling of the concrete body 1 can be suppressed.

  The concrete body 1 is cured while being cooled by the cooling method described above, and then the vertical holes 5 are filled with a repairing mortar using a general mortar pouring method, or vertically with concrete using a general concrete filling method. The hole 5 is filled (backfilling step). In addition, when the hole diameter of the vertical hole 5 is less than 70 mm, it is preferable to use a mortar filling method, and when the hole diameter of the vertical hole 5 is 70 mm or more, it is preferable to use a concrete filling method.

  Next, the configuration of the blower that sends out the cooling air will be specifically described. The blower unit includes the above-described blower tube 9 and a mist fan 13 that blows cooling air into the upstream end of the blower tube 9. The mist fan 13 is a commercially available fan used for humidifying and curing concrete, and is a fan that sends out mist-containing wind. The mist fan 13 is connected to the rear end of the blower tube 9 via the minute blower 15 and the blower hose 17. The diameter of the air duct 9 is, for example, 2 to 8 cm. In addition, since the several ventilation hose 17 can be connected to the minute ventilation part 15, the wind from one mist fan 13 can be divided and sent to the several vertical hole 5. FIG.

  As shown in FIG. 4, an air collecting portion 9 b that collects cooling air from the mist fan 13 is provided at the rear end portion of the air duct 9. The tip of the blower hose 17 is connected to the air collecting part 9b. As shown in FIGS. 4 and 5, a ventilation portion 9d formed by bundling a plurality of tubes 9c is provided on the downstream side of the air collection portion 9b. And the front-end | tip of the ventilation part 9d functions as the above-mentioned front-end | tip nozzle 9a. That is, the tip nozzle 9a is formed by bundling a plurality (four in this case) of tube bodies 9c, and the opening at the tip of the tube body 9c discharges the cooling air into the water of the water reservoir 7. It functions as an exhaust port 9f. Note that the number of the tube bodies 9c is not limited to four, and the ventilation portion 9d may be a bundle of a large number of tube bodies 9c.

  Instead of the blower tube 9, a blower tube 109 shown in FIG. 6 may be used. The blower pipe 109 has a ventilation part 109d formed of a single tube instead of the ventilation part 9d. And the nozzle component 109a provided with many exhaust ports is attached to the downstream end of the ventilation part 109d. As the nozzle component 109a, a commercially available metal nozzle of a type having a large number of exhaust ports may be used as appropriate, and thus detailed description and illustration of the nozzle component 109a are omitted.

  According to the tip nozzles 9a and 109a provided with such a plurality of exhaust ports 9f, the bubbles discharged into the water of the reservoir 7 can be made fine.

  In addition, in the example of FIG. 3, although the mist fan 13 and the water supply part 21 are installed in the upper surface 1a of the concrete body 1, the mist fan 13 and the water supply part 21 may be installed in places other than the upper surface 1a of the concrete body 1. . If the mist fan 13 and the water supply unit 21 are installed on other than the upper surface 1a of the concrete body 1, it is possible to avoid the upper surface 1a from being damaged by the installation of the mist fan 13 and the water supply unit 21. On the other hand, if the mist fan 13 and the water supply unit 21 are installed on the upper surface 1a of the concrete body 1, labor for piping and the like is reduced, and work efficiency is improved. For example, if this cooling operation is performed on the next day after placing, since the upper surface 1a has already been hardened to some extent, the mist fan 13 and the water supply unit 21 can be installed on the upper surface 1a. In this case, it is preferable to cure the upper surface 1a with a curing sheet or the like.

  Next, the effect by the cooling method mentioned above is demonstrated.

  According to the cooling method described above, the concrete body 1 is cooled by the cooling air flowing in the vertical holes 5 provided in the concrete body 1. Thus, since air is used as the refrigerant, it is not necessary to process the used refrigerant, and the equipment can be simplified. Further, the surface of the concrete body 1 itself is exposed on the inner surface 5 a of the vertical hole 5, and the cooling air contacts the surface of the concrete body 1. Therefore, cooling air takes heat directly from the concrete body 1, and as a result, cooling efficiency can be improved. Moreover, the humidity of cooling air rises because cooling air passes through the water of the reservoir part 7. Therefore, the cooling air having high humidity flows in the vertical holes 5 as a refrigerant. Therefore, even if the above-described cooling method is a method in which cooling air is in direct contact with the surface of the concrete body 1 itself, drying of the concrete body 1 can be suppressed.

  As described above, according to the above-described cooling method, necessary equipment can be simplified, cooling efficiency can be obtained, and drying of the concrete body 1 during cooling can be suppressed.

  Further, in the air supply process, mist is included in the cooling air by using the mist fan 13. With this configuration, the humidity of the air flowing in the vertical holes 5 is further increased, and the drying suppression effect of the concrete body 1 is further enhanced.

  In addition, since there are a plurality of exhaust ports 9f in the tip nozzle 9a of the blower tube 9, and there are also a number of exhaust ports in the nozzle part 109a of the blower tube 109, the cooling air discharged into the water is also present. Bubbles become finer. Therefore, the contact area between the cooling air and water increases when passing through the water reservoir 7, and the effect of increasing the humidity of the cooling air is increased. As a result, the effect of suppressing the drying of the concrete body can be further enhanced. it can. Further, when a plurality of tubes are bundled like the blower tube 9 to form the tip nozzle 9a, a plurality of exhaust ports 9f can be provided at the tip of the blower tube with a simple structure.

  The depth of the vertical hole 5 is preferably 50 to 90% of the thickness (vertical width) of the concrete body 1. When the depth of the vertical hole 5 is shallower than the above lower limit, sufficient cooling efficiency cannot be obtained. When the depth of the vertical hole 5 is deeper than the above upper limit, the labor of the backfilling process is large. From this viewpoint, the depth of the vertical hole 5 is more preferably 70 to 80% of the thickness of the concrete body 1.

  Further, the hole diameter of the vertical hole 5 is set according to the bar arrangement condition of the concrete body 1. Specifically, the hole diameter of the vertical hole 5 is preferably 1/5 to 4/5 of the maximum perforation of the reinforcing bar contained in the concrete body 1. When the hole diameter of the vertical hole 5 is smaller than the above lower limit, sufficient cooling efficiency cannot be obtained, and when the hole diameter is larger than the upper limit, it is difficult to form the vertical hole 5 avoiding the reinforcing bars. . From this point of view, the hole diameter of the vertical hole 5 is more preferably 1/2 to 3/4 of the maximum perforation of the reinforcing bar contained in the concrete body 1.

The arrangement density of the vertical holes 5 is set according to the hole diameter in view of cooling efficiency. Specifically, it is preferable to set so as to satisfy the relationship of the following formula (1).
α = 901 × lnφ + 830 (1)
However, α is the reciprocal [cm ² / piece] of the arrangement density of the vertical holes 5 when the concrete body 1 is viewed from above. That is, the value of α means the area (area viewed from above) of the concrete body 1 that should bear the cooling per vertical hole 5. Φ is the hole diameter [cm] of the vertical hole 5.

Hereinafter, the test that is the basis of the above equation (1) will be described. The inventors conducted a test for cooling the concrete body 1 using the above-described cooling method. Specifically, pore diameter φ of the vertical holes 5 of ways 3 (30 mm, 50 mm, 100 mm) and, the value of α of two types (500 cm ² / present, 2800 cm ² / present) and the total six in combination of Concrete bodies 1 were prepared, and each specimen was cooled by the above-described cooling method. Then, the sensor is set at the center position of each specimen, and the maximum value of the temperature at the center of each specimen during cooling (hereinafter referred to as “maximum center temperature”) is measured. The correlation between parameters was obtained by plotting. That is, as shown in FIG. 7, the relationship between the value and the maximum center temperature of α is represented graphically L ₃₀ when a pore size of phi = 30 mm, it represented graphically L ₅₀ when a pore size of phi = 50 mm, pore size It is represented by the graph _{L 100} was found at phi = 100 mm.

Here, assuming that the maximum center temperature of the specimen is 60 ° C., the relationship between the hole diameter φ and the value of α is as shown in FIG. 8 from the graphs L ₃₀ , L ₅₀ , L ₁₀₀ of FIG. Desired. That is, each intersection point of each graph L ₃₀ , L ₅₀ , L ₁₀₀ in FIG. 7 and a straight line indicating the maximum center temperature of the test body = 60 ° C. is obtained, and the values of φ and α at each intersection point are plotted. Is the graph of FIG. Note that “60 ° C.” in the above condition is an upper limit value of the maximum center temperature for suppressing the probability of occurrence of temperature cracks in the specimen. The correlation indicated by the three points plotted in FIG. 8 is approximated by the above equation (1). That is, the maximum center temperature of the concrete body 1 during cooling can be suppressed to 60 ° C. by setting the values of the hole diameter φ and α so as to satisfy the relationship of the formula (1). As a result, the concrete body The probability of occurrence of temperature cracks 1 can be kept low.

Regarding the arrangement density of the vertical holes 5, according to the above formula (1), when the hole diameter of the vertical holes 5 is 30 mm, 5.7 vertical holes 5 are provided per 1 m ² , and the hole diameter of the vertical holes 5 is 50 mm. In some cases, 4.2 vertical holes 5 are provided per 1 m ² , and when the diameter of the vertical holes 5 is 100 mm, 3.5 vertical holes 5 are provided per 1 m ² .

  Moreover, it is preferable that the depth of the water storage part 7 is 80 mm or more. If the depth of the water reservoir 7 is less than 80 mm, the effect of wetting the cooling air cannot be obtained sufficiently. Furthermore, the depth of the water reservoir 7 is preferably 1/3 or less of the depth of the vertical hole 5. Further, when the depth of the water reservoir 7 is deeper than 1/3 of the depth of the vertical hole 5, the area of the inner side surface 5a corresponding to the cooling air is reduced, and sufficient cooling efficiency is obtained. Absent.

  Hereinafter, the test which became the basis which makes the preferable depth of the water storage part 7 80 mm or more is demonstrated. First, the inventors cast concrete and provided the vertical holes 5 in the concrete body 1. Thereafter, the water content of the concrete body 1 after cooling is completed by cooling the concrete body 1 by flowing air of various humidity into the vertical hole 5 without emptying the water and so on. Was measured. FIG. 9 shows a correlation between the humidity (%) of the inflowed air (that is, the air that contacts the inner surface 5a of the vertical hole 5; hereinafter referred to as “contact air humidity”) and the moisture content of the concrete body 1. It was.

  In general, the moisture content of a well-cured concrete needs to be 10-15%. Therefore, it was found from the correlation in FIG. 9 that the contact air humidity needs to be 80 to 100%.

  On the other hand, in the cooling method described above, the inventors have changed the depth of the reservoir portion 7 and the humidity of the cooling air fed from the air collecting portion 9b (inflow air humidity) while changing the inside of the vertical hole 5. The test which measures the humidity (contact air humidity) of the cooling air which contacts the side surface 5a was done. As a result of the test, the correlation between the depth of the reservoir 7 and the contact air humidity was as shown in FIG. According to FIG. 10, when the depth of the water reservoir 7 is 80 mm or more, it has been found that the contact air humidity is 80 to 100% regardless of the inflow air humidity. Therefore, by setting the depth of the water reservoir 7 to 80 mm or more, the contact air humidity becomes 80 to 100%, and as a result, the moisture content of the concrete becomes a good value of 10 to 15%.

  In addition, it is more preferable when the depth of the water reservoir 7 is 100 mm or more. That is, as shown in FIG. 10, if the depth of the water reservoir 7 is 100 mm or more, the contact air humidity can be close to 100% regardless of the inflow air humidity. Therefore, by setting the depth of the water reservoir 7 to 100 mm or more, the above-described good concrete moisture content can be realized with a margin.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this embodiment. For example, instead of the mist fan 13 used in the cooling method of the embodiment, a normal blower may be used.

  DESCRIPTION OF SYMBOLS 1 ... Concrete body, 1a ... Upper surface, 5 ... Vertical hole (cooling hole), 5a ... Inner side surface, 7 ... Reservoir part, 9,109 ... Air blower, 9a ... Tip nozzle (tip part of air blower), 9c ... Tube body, 9f ... exhaust port, 23 ... water supply pipe, 109a ... nozzle component (tip of air blower pipe)

Claims (5)

A concrete cooling method for cooling after placing concrete,
A cooling hole forming step of forming a bottomed cooling hole in a state in which the surface of the concrete body is exposed to the inner surface on the upper surface of the placed concrete body;
An air supply step of storing water at the bottom of the cooling hole formed in the cooling hole forming step, and sending cooling air into the water through a blower pipe inserted into the water;
A method for cooling concrete, comprising: In the air supply process,
The concrete cooling method according to claim 1, wherein fog is included in the cooling air.   The method for cooling concrete according to claim 1 or 2, wherein a plurality of exhaust ports for the cooling air are provided at a distal end portion of the blower pipe inserted into the water in the air supply step. . The tip of the blast tube is formed by bundling a plurality of tubes through which the cooling air passes,
The concrete cooling method according to claim 3, wherein an opening at an end portion of each tubular body constitutes the exhaust port. In the air supply process,
The method for cooling concrete according to any one of claims 1 to 4, wherein a water supply pipe is further inserted into the cooling hole, and water from the outside is replenished to the bottom of the cooling hole through the water supply pipe. .

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