Air pipe cooling construction method using cooling air

Abstract

To provide an operation method for an air pipe cooling construction method using cooling air, which can achieve both the restraint of enlargement and cost of equipment necessary to supply a coolant and the supply of the coolant having cooling efficiency enough to restrain temperature rise of concrete.SOLUTION: An air pipe cooling construction method using cooling air includes measuring a temperature of concrete C after placing the same, starting supply of cool air or increasing a supply amount of the cool air when the measured temperature reaches a direction issued value of a predefined temperature control upper limit, and stopping supply of the cool air or decreasing a supply amount of the cool air when the measured temperature reaches a direction issued value of a predefined temperature control lower limit.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an air pipe cooling method that uses cooled air to suppress the temperature rise of concrete after it has been poured. [Background technology]

[0002] It is known that concrete generates heat as it hardens due to the hydration reaction of cement. This heat is called hydration heat, and the temperature rise inside the concrete due to hydration heat after pouring can exceed 30-40°C for thick components. The concrete expands due to the temperature rise caused by hydration heat, and then shrinks as the temperature drops after hardening. If this shrinkage is restrained by the ground, bedrock, existing concrete, etc., tensile stress is generated, which can cause cracks in the concrete structure. These cracks are generally called thermal cracks, and if they become excessive, they can have a negative impact on the durability of the concrete structure.

[0003] The pipe cooling method has been known as a conventional method for suppressing the temperature rise of concrete after pouring. This method involves laying pipes in advance that connect the inside and outside of the poured concrete frame via reinforcing bars or the like arranged within the concrete pouring area, and introducing a refrigerant such as water or air from one end of the pipe to the other during or after pouring the concrete, thereby suppressing the temperature rise of the poured concrete (see, for example, Patent Documents 1 and 2). It has also been proposed to control the temperature of the refrigerant introduced into the pipe (see, for example, Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-92633 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-159905 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-89357 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-36546 Summary of the Invention [Problem to be solved by the invention]

[0005] Among the methods for suppressing the temperature rise of concrete after pouring, using water as a refrigerant has excellent cooling efficiency, but requires large-scale equipment for pumping, recovering, and circulating the water. Furthermore, in order to prevent water leakage within the concrete, it is necessary to increase the strength of the piping, which poses the problem of unavoidable increases in costs along with the construction of the equipment.

[0006] On the other hand, when air is used as a refrigerant, the problems associated with using water as a refrigerant are not present, but because air has a lower specific heat than water, its function as a refrigerant can be significantly reduced depending on the conditions at the concrete pouring site. For example, when the temperature at the concrete pouring site is high, the cooling efficiency of air is poor, and the cooling process takes a long time.

[0007] In view of the problems inherent in the method of suppressing the temperature rise of concrete after pouring, the applicant previously proposed an air pipe cooling method using cooled air (see Patent Application No. 2023-31527), which is capable of simultaneously reducing the scale and costs of the equipment required to supply the refrigerant and supplying a refrigerant with sufficient cooling efficiency to suppress the temperature rise of the concrete.The present invention aims to provide a specific method of operating this air pipe cooling method using cooled air. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the air pipe cooling method using cooled air of the present invention is an air pipe cooling method using cooled air, in which compressed air is supplied from a compressed air supply source to a cold air generator, and the cold air generated by the cold air generator is supplied to a pipe member placed in the concrete, thereby cooling the concrete after it has been poured.The method is characterized in that it measures the temperature of the concrete after it has been poured, and when the measured temperature reaches a preset upper temperature control command value, it starts the supply of cold air or increases the amount of cold air supplied, and when the measured temperature reaches a preset upper temperature control command value, it stops the supply of cold air or decreases the amount of cold air supplied. Here, the term "cold air generator" refers to one that uses the vortex tube principle.

[0009] In this case, the temperature of the concrete after pouring can be measured at the position of a pipe member disposed in the concrete through which cold air is supplied.

[0010] The preset temperature control upper limit instruction value and the preset temperature control lower limit instruction value may be constant values.

[0011] Furthermore, the temperature of the concrete after pouring can be measured at a position away from the pipe member disposed in the concrete through which the cold air is supplied.

[0012] In addition, the predetermined temperature control upper limit instruction issuance value and the temperature control lower limit instruction issuance value can be variable values ​​calculated based on the predicted temperature history of the concrete when cooling is performed based on the results of a preliminary analysis.

[0013] The amount of cold air supplied can be increased or decreased by controlling the pressure of compressed air supplied from the compressed air supply source to the cold air generator. [Effects of the Invention]

[0014] According to the air pipe cooling method using cooled air of the present invention, compressed air is supplied from a compressed air supply source to a cold air generator, and the cold air generated by the cold air generator is introduced into a pipe member, and the introduced cold air cools the concrete.By using air as a refrigerant, the problems that arise when using water as a refrigerant are solved, and it is possible to achieve both a reduction in the scale and cost of the equipment required to supply the refrigerant and a supply of a refrigerant with sufficient cooling efficiency to suppress the temperature rise of the concrete. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram showing an embodiment of an air pipe cooling method using cooling air according to the present invention. [Figure 2] FIG. 2 is a detailed explanatory diagram of the air pipe cooling method using the same cooling air. [Figure 3] 10 is an explanatory diagram of the measurement position of the temperature of concrete after pouring in the air pipe cooling method using the same cooling air. [Figure 4] FIG. 10 is an explanatory diagram showing an example of an operation method of the air pipe cooling method using the same cooling air. [Figure 5] FIG. 10 is an explanatory diagram showing an example of an operation method of the air pipe cooling method using the same cooling air.

[0016] Hereinafter, an embodiment of the air pipe cooling method using cooling air of the present invention will be described with reference to the drawings.

[0017] 1 and 2 show an embodiment of the air pipe cooling method using cooling air according to the present invention. This air pipe cooling method using cooled air is an air pipe cooling method that supplies cooled air to a pipe member 1 that is to be placed inside the concrete structure S to be constructed, and uses cooled air to cool the concrete C after it has been poured.Compressed air is supplied from a compressed air supply source 2 to a cold air generator 3, and the cold air A1 generated by the cold air generator 3 is introduced into the pipe member 1, and the introduced cold air A1 cools the concrete C.

[0018] In this embodiment, compressed air is supplied from a compressed air supply source 2 to a cold air generator 3 arranged at the opening 11 of the pipe member 1, and the cold air A1 generated by the cold air generator 3 is introduced into the inner part of the pipe member 1 via an air pipe 43, the introduced cold air A1 cools the concrete C, and after cooling the concrete C, the cold air A1 is released from the opening 11 of the pipe member 1. The warm air A2 generated by the cold air generator 3 is released directly into the atmosphere from the cold air generator 3, but if necessary, the warm air A2 can be directed at the exposed surface or formwork surface of the concrete C to prevent temperature differences from occurring in the concrete C.

[0019] Here, it is preferable to use a steel pipe with a diameter of about 25 to 200 mm, which has good thermal conductivity, for the pipe member 1. In this embodiment, the pipe member 1 consists of a plurality of independent pipes arranged vertically within the concrete structure S to be constructed over the entire height direction (height H of the concrete structure S: 5000 mm), and each pipe member 1 is arranged in parallel in the width direction (width W of the concrete structure S: 10000 mm) at intervals of 300 to 1000 mm, preferably 400 to 800 mm (500 mm in this embodiment). Furthermore, if the thickness of the concrete structure S to be constructed is, for example, greater than 1000 mm, the pipe members 1 are arranged in parallel (in a matrix or staggered pattern) in the thickness direction of the concrete structure S to be constructed. In addition to steel pipes, various pipe materials such as aluminum pipes, synthetic resin pipes, and paper pipes (void pipes) can be used for the pipe member 1. However, in consideration of the cooling effect, it is preferable to use steel pipes. Furthermore, various pipe shapes such as straight pipes and corrugated pipes can be used. In addition, for example, metal fins can be formed on the inner and / or outer surfaces of the deep part of the tubular member 1 (the part to be cooled: approximately 0 to 2000 mm from the lower end of the tubular member 1) to enable efficient heat exchange with the cold air A1 of the tubular member 1.

[0020] Compressed air supply source 2 uses compressor 21 and receiver tank 22, and compressor 21 and receiver tank 22 are connected to cold air generator 3 via air pipes 41, 42 and branch 42a, each approximately 9 to 100 mm in diameter. Air hoses approximately 9 to 100 mm in diameter can be used for air pipes 41, 42. Branch 42a is configured by appropriately combining pipe components such as elbows, tee pipes, sockets, bushings, and nipples, and is equipped with a flow control valve, solenoid valve (ON-OFF valve) (not shown), and pressure control valve (not shown), allowing for adjustment of the flow rate of compressed air supplied to each cold air generator 3, ON / OFF control of the compressed air supply, and adjustment of the compressed air pressure. The compressor 21 can be a general-purpose compressor capable of supplying compressed air of 0.5 MPa or more, preferably 0.7 MPa or more, but taking pressure loss into consideration, a high-pressure compressor capable of supplying compressed air of 1.0 MPa or more may also be used to ensure sufficient source pressure. Furthermore, the compressor 21 can be used in combination with a refrigerated air dryer, if necessary. The receiver tank 22 is provided to prevent pulsation of the compressed air supplied to the cold air generator 3, to protect the compressor 21, and to act as a buffer. By using the receiver tank 22, compressed air at a constant pressure can be stably supplied to the cold air generator 3.

[0021] The cold air generator 3 uses a device that generates cold air A1 based on the vortex tube principle. The vortex tube principle utilizes the property of air that compressed air supplied by a component called a bushing generator rotates at high speed, causing it to flow into a nozzle at a speed close to the speed of sound, expanding and losing some of its pressure, thereby separating the cold air that has had its heat removed from the warm air that has absorbed the heat.This cold air is utilized in the present invention. The cold air generator 3 must be a device that generates cold air A1 in accordance with the heat generation amount of the concrete C. In this embodiment, an ultra-low temperature air generator "Tohama Air Cooler AC-70 Type" (product name) manufactured by Tohama Kogyo Co., Ltd. is used, and the cold air generator 3 is arranged at the opening 11 of each pipe member 1 consisting of multiple independent pipes. The operating conditions of the cold air generator 3 are, for example, the intake air volume of compressed air of 0.1 to 3.0 m 3 / min, the discharge volume of cold air A1 is 0.1 to 2.0 m 3 The flow rate is set to / min, the pressure is 0.2 to 1.0 MPa, and the temperature is set to about -30 to 20°C, preferably about -20 to 10°C, and more preferably about -10 to 5°C.

[0022] In this embodiment, as a specific method of operating this air pipe cooling method using cooled air, the temperature of the concrete C after pouring is measured, and when the measured temperature reaches a preset upper temperature control limit command value, the supply of cold air is started or the amount of cold air supplied is increased, and when the measured temperature reaches a temperature control lower limit command value, the supply of cold air is stopped or the amount of cold air supplied is reduced.

[0023] The temperature of the concrete C after pouring is measured at the position of the pipe member 1 arranged in the concrete C to which cold air is supplied, as shown in FIG. Specifically, a temperature measuring sensor 51 (for example, a general-purpose sensor such as a thermistor (for example, Ondotori (registered trademark) manufactured by T&D Corporation), a thermocouple, etc.) is placed on the outer surface of the pipe member 1, and information is transmitted to the control unit, thereby making it possible to measure the temperature of the concrete C in real time. One or more sensors 51 (in this embodiment, three sensors spaced apart in the vertical direction) are arranged near the position where cold air is supplied to the pipe member 1, which is likely to become cold when cooled. If multiple sensors 51 are installed, the average value, median value, maximum value (relative to the temperature control upper limit instruction value), or minimum value (relative to the temperature control lower limit instruction value) can be selected and used.

[0024] In this case, the preset temperature control upper limit instruction value and temperature control lower limit instruction value can be set to constant values.

[0025] Figure 4 shows a demonstration example in which the temperature of concrete C after pouring is measured, and when the measured temperature reaches the preset upper temperature control limit command value, the supply of cold air is started, and when the measured temperature reaches the lower temperature control limit command value, the supply of cold air is stopped. In this example, the temperature control range is set to 5°C (lower limit of temperature control) to 10°C (upper limit of temperature control), the upper limit of temperature control is set to 9.0°C, and the lower limit of temperature control is set to 6.5°C, and operation is performed for 48 hours from the start of cooling.

[0026] According to the operation method of this air pipe cooling method using cooled air, the preset upper temperature control limit and lower temperature control limit are constant values, and when the preset upper temperature control limit is reached, the supply of cold air is started, and when the preset lower temperature control limit is reached, the supply of cold air is stopped. Therefore, with simple control, after pouring, The temperature rise of concrete C can be suppressed.

[0027] In addition, the preset upper temperature control limit instruction issuance value and the lower temperature control limit instruction issuance value can be variable values ​​calculated based on the predicted temperature history of the concrete when cooling is performed based on the results of a preliminary analysis. Here, the preliminary analysis can be performed using a conventional concrete temperature stress analysis method.

[0028] The temperature of the concrete C after pouring is measured at a position away from the pipe member 1 placed in the concrete C to which cold air is supplied, as shown in FIG. Specifically, a temperature measuring device sensor 52 (for example, a general-purpose sensor such as a thermistor (for example, Ondotori (registered trademark) manufactured by T&D Corporation), a thermocouple, etc.) is placed at a position away from the pipe member 1, and information is transmitted to the control unit, thereby making it possible to measure the temperature of the concrete C in real time. The sensor 52 is arranged so that one sensor (in this embodiment, at the mid-height between the adjacent pipe members 1) (or two sensors including a spare) is placed at a position where the temperature rise inside the concrete C due to hydration heat after pouring is at its maximum.

[0029] Figure 5 shows a demonstration example in which the temperature of concrete C after pouring is measured, and when the measured temperature reaches the preset upper temperature control limit, the amount of cold air supplied is increased, and when the measured temperature reaches the lower temperature control limit, the amount of cold air supplied is decreased. In this example, the temperature control range from the fluctuation value calculated based on the predicted temperature history of the concrete when cooling is performed based on the results of the preliminary analysis is set to -5°C (lower limit of temperature control) to +5°C (upper limit of temperature control), and operation is performed for 48 hours from the start of cooling.

[0030] The amount of cold air supplied can be increased or decreased by controlling the pressure of the compressed air supplied from the compressed air supply source 2 to the cold air generator 3. Table 1 shows the relationship between the pressure (and volume) of compressed air supplied from the compressed air supply source 2 to the cold air generator 3 and the volume (and temperature) of the cold air generated by the cold air generator 3.

[0031] [Table 1]

[0032] According to the operating method of this air pipe cooling method using cooled air, the preset upper temperature control limit instruction issuance value and the lower temperature control limit instruction issuance value are set as variable values ​​calculated based on the predicted temperature history of the concrete when cooling is performed based on the results of a preliminary analysis, and cooling is performed based on the temperature at the position where the temperature rise inside the concrete C due to heat generated by hydration after pouring is at its maximum, so that the temperature rise of the concrete C after pouring can be accurately suppressed.

[0033] The air pipe cooling method using cooling air of the present invention has been described above based on its embodiment, but the present invention is not limited to the configuration described in the above embodiment, and the configuration can be changed as appropriate within the scope of the spirit of the present invention, such as adopting the embodiment described in the air pipe cooling method using cooling air previously proposed by the present applicant. [Industrial Applicability]

[0034] The air pipe cooling method using cooled air of the present invention can achieve both the reduction of the scale and cost of the equipment required for supplying the refrigerant and the supply of a refrigerant with sufficient cooling efficiency to suppress the temperature rise of concrete, and therefore can be widely used for suppressing the temperature rise of concrete after pouring. [Explanation of symbols]

[0035] 1 Pipe member 11 Opening 2. Compressed air supply source 21 Compressor 22 Receiver tank 3. Cold air generator 41 Air pipe 42 Air pipe 42a Branch 43 Air pipe A1 Cold air A2 Warm air C. Concrete S Concrete Structure

Claims

1. An air pipe cooling method using cooled air, in which compressed air is supplied from a compressed air supply source to a cold air generator, and the cold air generated by the cold air generator is supplied to pipe members arranged in concrete to cool the concrete after it has been poured, characterized in that the temperature of the concrete after it has been poured is measured, and when the measured temperature reaches a preset upper temperature control command value, the supply of cold air is started or the amount of cold air supplied is increased, and when the measured temperature reaches a preset lower temperature control command value, the supply of cold air is stopped or the amount of cold air supplied is reduced.

2. 2. The air pipe cooling method using cooled air according to claim 1, wherein the temperature of the concrete after pouring is measured at the position of a pipe member placed in the concrete through which the cold air is supplied.

3. 2. The air pipe cooling method using cooling air according to claim 1, wherein the preset upper temperature control limit instruction value and the preset lower temperature control limit instruction value are constant values.

4. The air pipe cooling method using cooled air as described in claim 1, characterized in that the temperature of the concrete after pouring is measured at a position away from the pipe member placed in the concrete through which the cold air is supplied.

5. 5. The air pipe cooling method using cooling air according to claim 4, wherein the preset upper temperature control limit instruction issuance value and the lower temperature control limit instruction issuance value are fluctuation values ​​calculated based on the predicted temperature history of the concrete when cooling is performed based on the results of a preliminary analysis.

6. The air pipe cooling method using cooling air according to any one of claims 1 to 5, characterized in that the amount of cold air supplied is increased or decreased by controlling the pressure of compressed air supplied from a compressed air supply source to the cold air generator.

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