JP2014009530A - Pipe cooling system and pipe cooling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique, in cooling concrete by pipe cooling, to find out appropriate completion of cooling in consideration of a material age of concrete and to provide a pipe cooling system and a pipe cooling method to realize the technique.SOLUTION: A pipe cooling system comprises concrete temperature acquisition means and determination means. The determination means determines whether or not concrete cooling needs to be continued by comparing a temperature difference Tg(d) with an allowable temperature difference Ta(d) which is calculated on the basis of tensile stress intensity σi(d) of concrete at a material age d, an elastic coefficient Ee(d) of the concrete and a heat expansion coefficient αc of the concrete.

Description

  The present invention mainly relates to concrete pipe cooling, and more specifically to a pipe cooling system and a pipe cooling method capable of determining an appropriate cooling end.

  Concrete is the most important construction material together with steel, and is used in various structures including civil engineering structures such as dams, tunnels, and bridges, and architectural structures such as housing complexes and office buildings. This concrete structure may be manufactured in advance at a factory, etc., and transported to a specified location. However, in the case of a civil engineering structure or a building structure, it is constructed by placing concrete directly in a specified location. There are many. In any case, concrete (fresh concrete) in which cement, water, aggregates, etc. are mixed is placed in the formwork, and the concrete structure is constructed by removing the formwork after the concrete has hardened. It is common.

  As described above, concrete is a material that hardens over time. Specifically, as shown in FIG. 7, as the internal temperature of the concrete rises with time (FIG. 7 (a)), its strength also increases. It is a material that rises (FIG. 7 (b)) and improves its elastic modulus (FIG. 7 (c)). By the way, cracking of concrete may occur in the process of changing from fresh concrete to “cured concrete” or while being used as a structure after curing. Some concrete cracks are harmless without affecting the use of the structure, but there are also harmful cracks that have a significant impact on the use of the structure. For this reason, the cause and mechanism of the occurrence of cracks have been sufficiently elucidated so far, and various methods have been adopted as countermeasures.

  The types of cracks are classified according to the cause of the cracks, and are further roughly divided into causes before and after hardening the concrete. Causes before hardening include “initial cracks” caused by mold movement and abnormal setting of cement, “plastic shrinkage cracks” caused by rapid drying of the surface during curing, and the like. On the other hand, the causes after hardening are “dry shrinkage cracks” caused by shrinkage of cement gel due to water loss, “temperature cracks” caused by heat of hydration of cement, corrosion of reinforcing bars and alkali aggregate reaction. Examples include “physical / chemical cracks” that occur, and “structural cracks” that occur due to the action of excessive loads and the settlement of structures.

  It has been clarified by past studies and achievements that these cracks can be generally suppressed by appropriate design (mixing), construction, and curing. For example, in the case of a temperature crack, since it occurs due to a temperature difference between the inside and outside of the housing as described later, the following measures are adopted at the time of design and construction respectively. In other words, as a countermeasure at the time of designing, in order to suppress the rise in heat of hydration, the formulation design is devised, such as the use of low exothermic cement, the reduction of cement amount, the use of an admixture that reduces heat of hydration. . Alternatively, the installation of a crack-inducing joint may be planned for the purpose of inducing a crack in a place where there is no influence even if a crack is relatively generated. Typical measures at the time of construction include pre-cooling, post-cooling, and long-term insulation curing. Pre-cooling is to cool the fresh concrete temperature at the time of pouring, using flaky ice for mixing water, spraying liquid nitrogen during mixing in mixers and track agitators, various cooling methods Is adopted.

  Post-cooling has a method of promoting natural cooling by providing a temperature diffusion surface inside the housing, such as a cooling slot, but pipe cooling, which cools concrete by passing cooling water through the pipe laid in the housing, is the mainstream. It is. In this pipe cooling, a cooling pipe such as a thin-walled steel pipe (hereinafter referred to as “cooling pipe”) is laid in the housing in advance, and after placing concrete, water or air at a low temperature (for example, concrete temperature −20 ° C. or less) ( Hereinafter, it is a rational and economical method that can be realized with relatively simple equipment and work by simply taking the “refrigerant” into the cooling pipe. Moreover, if there are rivers, ponds, etc. near the concrete placement site, it is easy to procure refrigerants, and cracking countermeasures can be implemented at a lower cost.

  Also, when it is necessary to develop concrete strength early, such as when it is necessary to complete a structure in a dry season in a river, etc. It may be difficult to cope with concrete blending such as use of cement and reduction of cement amount. If an early strong cement is used, as shown in FIG. 7 (a), the concrete temperature rises quickly, that is, tensile stress is generated in a state where the tensile strength is low, and this causes the occurrence of temperature cracking. . On the other hand, the pre-cooling measures are relatively expensive and require considerable equipment, and may not be adopted due to cost and yard problems. Pipe cooling can be used without any particular problem in such a case, so it can be said that this is an effective countermeasure against temperature cracks.

  However, pipe cooling has not been used so often until now. This is due to the fact that “horizontal pipe cooling” in which the cooling pipes are arranged horizontally is the mainstream. Usually, countermeasures against temperature cracks are often performed on mass concrete, which is large massive concrete. In the concrete standard method, when the plate thickness is 80-100 cm or more with a wide slab and the wall thickness is 50 cm or more with a wall having a constraint at the lower end, measures against temperature cracking are taken as mass concrete. If the mass concrete has a large spread in a plane, the arrangement of the cooling pipes is easy, and horizontal pipe cooling is also easy to adopt. However, mass concrete that needs countermeasures against temperature cracking includes columnar objects such as bridge piers and wall-shaped objects such as large-scale retaining walls. These columnar and wall-shaped mass concretes generally have a relatively small horizontal cross section and are long in the vertical direction. In such a case, horizontal pipe cooling is difficult to employ. This is because the installation of horizontal cooling pipes in a narrow area is extremely complicated due to the presence of reinforcing bars, and it is divided into a large number of lifts (vertical placement blocks), so this complicated piping work is repeated. Because it must be done.

  By the way, in addition to horizontal pipe cooling, there is a technique called “vertical pipe cooling” in which cooling pipes are arranged in the vertical direction. The vertical pipe cooling is basically the same as the horizontal pipe cooling, but since there is various know-how in the details, it is actually being implemented by some people with many achievements. If the cooling pipe is laid in the vertical direction in advance, this vertical pipe cooling can be suitably used for the above-mentioned column-shaped and wall-shaped mass concrete without the need for piping the cooling pipe for each driving lift. In addition, since the water (refrigerant) that has flowed through the cooling pipe can be used as it is for surface submersion curing, it is an extremely rational countermeasure technique. That is, if this vertical pipe cooling and horizontal pipe cooling are appropriately adopted according to the situation, it is considered that pipe cooling is a more general countermeasure against temperature cracking.

  On the other hand, when pipe cooling is employed, cooling (cooling) must be continued for a while after the concrete is placed, and there is a case where it is not possible to immediately move to the next process.

  As will be described later, since temperature cracks are caused by the temperature difference between the inside and outside of the concrete (outside air), the maximum temperature of the concrete after placing is the outside air temperature as shown in FIG. It is desirable to cool until they are equivalent. However, there are many cases where it is not possible to devote sufficient time to cooling, such as when the construction is performed in a short drought period as described above, or when construction is required for a limited period in an urban area. In addition, the case of monitoring the concrete temperature after placing is rather rare, and there are many cases in which it cannot be grasped that the concrete temperature is equal to the outside air temperature. Therefore, it is common to finish the cooling in 7 days after placing, regardless of the concrete temperature state.

  The concrete temperature change after placing varies depending on the pipe cooling method, the shape and size of the concrete, the curing method, the outside temperature, etc., that is, it should be different for each construction site. Nevertheless, when the cooling period is set to 7 days uniformly, as shown in FIG. 8B, the cooling may end while the concrete is significantly higher than the outside temperature. In this case, there is a possibility that temperature cracking may occur despite pipe cooling. Or as shown in FIG.8 (c), although concrete is already cooled sufficiently, it may be wasted cooling. In this case, unnecessary costs and labor are required, and the timing for shifting to the next process is also delayed.

  Furthermore, the end time of cooling should not be determined until the concrete temperature becomes equal to the outside air temperature, but should be determined after taking into consideration the age of the concrete. This is because the strength of concrete is an important factor in the occurrence of temperature cracks, and this concrete strength changes with the passage of time (that is, the age of the concrete) as described above. By setting the cooling period in consideration of the age of the concrete, it is possible to provide high-quality concrete without cracks and eliminate unnecessary cooling.

  As described above, it is extremely important for pipe cooling to measure the end timing, but no technology related to the end of pipe cooling has been proposed so far. Although Patent Document 1 is focused on the maximum temperature of concrete after placing, it is intended to adjust the concrete temperature by design and construction and is not related to the end of pipe cooling. Moreover, although there exists patent document 2 as what estimates the stress degree of concrete paying attention to age and temperature, this is not related with completion | finish of pipe cooling.

JP 2002-227414 A JP 2006-010420 A

  As already mentioned, it is extremely important to determine the appropriate end time for pipe cooling, but no technology has been proposed to improve it. An object of the present invention is to provide a technique for determining an appropriate cooling end in consideration of the age of concrete in concrete pipe cooling, and to provide a pipe cooling system and a pipe cooling method for realizing this. .

  The invention of the present application focuses on the concrete temperature after placement and the outside air temperature, and further the age of the concrete in determining the end of pipe cooling. is there.

  The pipe cooling system of the present invention suppresses a temperature rise in the concrete by allowing a coolant to flow through a cooling pipe laid in the concrete, and includes a concrete temperature grasping means and a judging means. The concrete temperature grasping means obtains the maximum internal temperature Tc (d) of the concrete at a predetermined age d. On the other hand, the determination means determines whether or not to continue the concrete cooling, and has a temperature difference calculation function, an allowable temperature difference calculation function, and a determination function. Here, the temperature difference calculation function calculates the temperature difference Tg (d) between the outside air temperature Te (d) and the concrete internal maximum temperature Tc (d) at the age d, and the allowable temperature difference calculation function at the age d. Based on the tensile stress degree σi (d) of concrete, the elastic modulus Ee (d) of concrete, and the thermal expansion coefficient αc of concrete, an allowable temperature difference Ta (d) at the age d is calculated. The determination function compares the temperature difference Tg (d) with the allowable temperature difference Ta (d), and determines whether the concrete cooling is continued based on this comparison.

In the pipe cooling system of the present invention, the allowable temperature difference Ta (d) can be obtained by the following equation. However, C is a predetermined constant.
Ta (d) = σi (d) / [C × αc × Ee (d)]

  The pipe cooling system of the present invention may further include a refrigerant temperature measuring means. The refrigerant temperature measuring means measures a temperature change of the refrigerant while flowing. In this case, the concrete internal maximum temperature Tc (d) can be estimated based on the temperature change of the refrigerant measured by the refrigerant temperature measuring means.

  The pipe cooling system of the present invention may further include one or more concrete temperature measuring means. The concrete temperature measuring means measures the temperature inside the concrete. In this case, the maximum concrete internal temperature Tc (d) can be estimated based on the temperature of the concrete measured by the concrete temperature measuring means.

  The pipe cooling method of the present invention is a method of suppressing the temperature rise inside the concrete by allowing the coolant to flow through the cooling pipe laid in the concrete, the temperature grasping step, the outside air temperature setting step, the temperature difference calculating step, And a determination step. In the temperature grasping step, the maximum concrete internal temperature Tc (d) at a predetermined age d is obtained, and in the outside air temperature setting step, the outside air temperature Te (d) at the material age d is set. In the temperature difference calculating step, a temperature difference Tg (d) between the concrete maximum internal temperature Tc (d) and the outside air temperature Te (d) is calculated. In the determining step, the allowable temperature difference Ta (d) at the material age d is calculated. Based on the comparison with the temperature difference Tg (d), whether to continue the concrete cooling is determined. The allowable temperature difference Ta (d) is calculated based on the concrete tensile stress σi (d), the elastic coefficient Ee (d), and the thermal expansion coefficient αc of the concrete at the age d.

  The pipe cooling method of the present invention can be a method further comprising a refrigerant temperature measuring step. In the refrigerant temperature measurement step, the temperature change of the refrigerant while flowing is measured. In this case, the concrete maximum internal temperature Tc (d) is obtained based on the temperature change of the refrigerant.

  The pipe cooling method of the present invention can be a method further comprising a concrete temperature measuring step. In the concrete temperature measuring step, the temperature inside the concrete is measured using one or two or more concrete temperature measuring means installed in the concrete in advance. In this case, the maximum concrete internal temperature Tc (d) is obtained based on the concrete temperature measured by the concrete temperature measuring means.

The pipe cooling system and the pipe cooling method of the present invention have the following effects.
(1) Since it is possible to accurately determine the cooling end time, it is possible to save unnecessary costs and labor due to unnecessary cooling, and it is possible to promptly move to the next process, thereby contributing to shortening the work period.
(2) Since the end of cooling is determined according to the age of the concrete material, it is possible to make an extremely accurate end determination.
(3) By estimating the concrete temperature based on the temperature change of the refrigerant that has passed through, it is possible to determine the end of cooling without installing a thermometer in the housing. Alternatively, it is possible to easily cope with an unexpected situation such as failure of a thermometer installed in concrete.

1 is an overall perspective view showing a pipe cooling system and a pipe cooling method. The schematic diagram which shows the condition which installed the thermometer in the housing and the cooling pipe. The perspective view which shows the condition where the cooling pipe was inserted in the casing pipe embed | buried in concrete. (A) is a detailed view showing a parallel type branch pipe, (b) is a detailed view showing a series type branch pipe. The temperature change figure which shows continuing cooling until the temperature difference of concrete maximum temperature and external temperature turns into an allowable temperature difference. The model figure which approximated the temperature distribution inside concrete with a quadratic curve. (A) is a relationship figure which shows the time-dependent change of the internal temperature of concrete, (b) is a relation figure which shows the time-dependent change of the tensile strength of concrete, (c) is a relation figure which shows the time-dependent change of the static elastic modulus of concrete. (A) is a temperature change diagram when cooling is continued until the concrete temperature becomes equal to the outside temperature. (B) is the result of continuing cooling for 7 days. The temperature change figure which shows that, (c) is a temperature change figure which shows that cooling is continued even after concrete temperature becomes equivalent to external temperature as a result of continuing cooling for seven days.

  An example of an embodiment of a pipe cooling system and a pipe cooling method of the present invention will be described with reference to the drawings.

[Overview]
1. Temperature cracks Since the present invention is a technology related to pipe cooling that suppresses temperature cracks, first, temperature cracks will be briefly described. It is known that cracks occur when a significant temperature difference occurs between the inside and near the surface of the concrete during the curing period. This is a so-called “temperature crack” phenomenon. This temperature crack is roughly divided into those caused by internal restraint and those caused by external restraint.

  As concrete hardens, the reaction between water and cement occurs. At that time, heat of hydration is generated, so the internal temperature of the concrete rises with time. However, if the outside air temperature is low, the portion close to the concrete surface (outer peripheral portion) does not increase so much by heat transfer. In addition, when a new concrete is handed over the existing concrete, the temperature of the concrete outer peripheral portion does not increase so much by conducting heat to the low temperature existing concrete. As a result, a remarkable temperature difference occurs between the inside and the outer periphery of the concrete, and a temperature crack occurs due to the tensile force acting on the outer periphery due to the difference in volume expansion. This is a temperature crack due to internal restraint.

  When the concrete reaches a predetermined temperature, it starts to drop in temperature. As the temperature drops, concrete tends to shrink as a whole, but it cannot be shrunk freely because it is in a restrained state where it is in contact with existing concrete. As a result, a difference in volume change occurs in the concrete, and a temperature crack occurs due to the tensile force acting inside. This is a temperature crack due to external constraints. Note that temperature cracks due to external constraints often result in cracks penetrating the housing.

  In order to suppress the temperature cracks generated by such a mechanism, it is necessary to suppress the temperature rise inside the concrete. Here, the suppression of the temperature rise has the meaning of lowering the maximum temperature of the concrete and the meaning of lowering the concrete temperature at an early stage. As described above, the temperature crack is caused by the tensile stress due to the volume change of the concrete. The stress is determined by the product of strain and elastic modulus. Naturally, the smaller the elastic modulus, the smaller the stress applied. As shown in FIG. 7C, the elastic modulus of the concrete is small while the age is young. In other words, if the concrete is young, even if the internal temperature rises, so much tensile stress does not occur. On the other hand, concrete that has been aged has a large elastic modulus, and it reacts sensitively to temperature rise and generates considerable tensile stress. Moreover, the actual concrete peak time tends to be generally delayed from that obtained by temperature analysis, and this is one factor that causes temperature cracking. Thus, how early the concrete temperature is lowered (during young age) is an important factor in cooling.

2. Pipe Cooling Next, an outline of pipe cooling will be described. The invention of the present application has a technical feature in that the end of cooling by pipe cooling is determined, and various pipe cooling types can be adopted in performing cooling. Of course, horizontal pipe cooling or vertical pipe cooling can be performed, but here, for convenience, the case of vertical pipe cooling will be described. FIG. 1 is an overall perspective view showing a pipe cooling system and a pipe cooling method. The frame 1 in this figure is a pier constructed in a river, and is constructed in a state where it is dried by a closing sheet pile 2. A plurality (ten in the figure) of casing pipes 31 are installed in the housing 1 in advance, and cooling pipes 32 are inserted into the casing pipe 31. In this figure, a flexible hose is used as the cooling pipe 32.

  In this case, the refrigerant flowing through the cooling pipe 32 is river water and is pumped up by a water intake pump. Cooling water (refrigerant) pumped up by the water intake pump is stored in the water tank by the water intake hose, further pumped up by the water supply pump 33, and sent to the first branch pipe 35 through the first water supply hose 34. The second water supply hose 36 branched from the first branch pipe 35 is connected to the second branch pipe 37 and further branches into a plurality of cooling pipes 32 from here. Thus, one end of the cooling pipe 32 is connected to the second branch pipe 37 and the other end extends to the vicinity of the bottom of the casing pipe 31, whereby the cooling water can flow from the top of the housing 1 to the bottom. it can. The cooling water that has flowed to the bottom of the frame 1 may be returned to the upper surface of the concrete and stored on the upper surface of the frame 1 for water curing, or drained into a river or the like through a drain pipe 38 as shown in FIG. .

3. Cooling Completion Determination An outline of the cooling end determination, which is a technical feature of the present invention, will be described. FIG. 5 is a temperature change diagram showing that cooling is continued until the temperature difference between the maximum concrete temperature and the outside air temperature reaches a predetermined threshold (allowable temperature difference). As shown in this figure, in the present invention, the end of cooling is determined based on the temperature difference between the maximum concrete internal temperature and the outside air temperature. For example, when this temperature difference falls below a predetermined threshold (allowable temperature difference) (below the allowable temperature difference or less than the allowable temperature difference), it is determined that the cooling is finished. The “allowable temperature difference” used here is calculated according to the age of concrete at the time of determination. That is, the allowable temperature difference in the age is calculated based on the tensile stress degree of the concrete at the age, the elastic coefficient of the concrete at the age, and the thermal expansion coefficient of the concrete.

  Concrete cracks occur when the maximum principal tensile stress level generated in concrete exceeds the tensile stress level of concrete. Furthermore, the degree of tensile stress of concrete changes with age, and the elastic modulus of concrete used when obtaining stress from strain also changes with age. Therefore, in order to accurately determine the end of cooling, it is necessary to consider the age of the concrete.

  In addition, although the temperature inside concrete can also be estimated by the concrete temperature measurement means previously installed in the concrete, it can also be estimated from the temperature change of the cooling water flowing through the cooling pipe 32. Since the cooling water lowers the concrete temperature by exchanging heat with the concrete, the temperature of the cooling water after sufficiently flowing through the housing 1 is higher than that immediately after entering the housing 1. Should be. For example, when cooling water is allowed to flow from the upper part to the lower part using the cooling pipe 32 and is discharged as it is from the lower end, the upper refrigerant thermometer 5U shown in FIG. 2 has the lowest temperature. The temperature should be higher in the order of 5C and the lower refrigerant thermometer 5L. Or it is a case where the cooling pipe 32 is inserted in the casing pipe | tube 31, Comprising: A cooling water is made to flow through from the upper part to a lower end in the cooling pipe 32, and between the casing pipe | tube 31 and the cooling pipe | tube 32 flows upwards. When the temperature is lowered with cooling water, the lower refrigerant thermometer 5L shown in FIG. 2 has the lowest temperature, and hereinafter, the central refrigerant thermometer 5C and the upper refrigerant thermometer 5U should show higher temperatures in this order. If these things are utilized, concrete internal maximum temperature can be estimated based on the measurement result of refrigerant thermometer 5U, 5C, 5L.

  Hereinafter, the present invention is divided into a “pipe cooling system” and a “pipe cooling method”, and will be described in detail for each constituent element. The contents common to the pipe cooling system and the pipe cooling method will be described in the example of the pipe cooling system, and the contents specific to the pipe cooling method will be described.

[Pipe cooling system]
1. Refrigerant The refrigerant is a low-temperature medium that flows through the refrigerant pipe 32, and water is a typical example. In addition to water, air or the like can be used, or a liquid other than water or a gas other than air can be used. The refrigerant needs to be at a low temperature, and the temperature can be designed as appropriate. In general, the refrigerant is set to a temperature 20 ° C. or more lower than the concrete temperature to be placed. Here, the case where the refrigerant is “water” will be described, and this water is referred to as “cooling water”.

2. Cooling tube The cooling tube 32 is a hollow tube because it allows cooling water to flow through it. In FIG. 1, a flexible hose is used, but other various types of tubes such as a thin-walled steel tube and a vinyl chloride tube can be used. Can be used. The cooling pipe 32 is installed in the range in which the concrete temperature is to be lowered in the casing 1. For example, when the entire casing 1 is to be cooled, the cooling pipe 32 is densely planar as shown in FIG. 1 and from the top to the bottom. 32 is arranged.

  In order to cool the concrete of the casing 1, the cooling pipe 32 is embedded in the casing 1, but the concrete may be cast with the cooling pipe 32 installed at a predetermined position in the formwork. However, as shown in FIG. 3, the casing pipe 31 can be embedded in the concrete, and the cooling pipe 32 can be inserted therein. The casing pipe 31 (or the cooling pipe 32) needs to be self-supporting in the mold, and can be attached to a reinforcing bar in the mold, a frame made of shape steel (for example, angle steel), or the like. In the case of vertical pipe cooling, concrete can be cast for each lift with the casing pipe 31 (or cooling pipe 32) installed, but in the case of horizontal pipe cooling, the concrete surface is placed each time the lift is cast. The cooling pipe 32 (or the casing pipe 31) is installed in this.

3. Refrigerant pressure feeding means The refrigerant pressure feeding means supplies cooling water into the cooling pipe 32, and the water supply pump 33 shown in FIG. 1 is preferably used. As shown in FIG. 1, cooling water can be stored in a water tank as a water source, pumped from here by a water supply pump 33, and sent to water, or depending on the situation at the site, the water supply pump 33 can be directly installed in a water source such as a river. It can also be pumped up.

  Usually, since a large number of cooling pipes 32 are installed in the housing 1, a branching unit is placed between the water supply pump 33 and the cooling pipe 32. This branching means is not limited to one place, and may be installed at a plurality of places. In FIG. 1, there are one parent branch pipe (first branch pipe 35) and two child branch pipes (second branch pipe 37). Placed in place. FIG. 4 is a detailed view showing a branch pipe, where (a) shows a parallel-type branch pipe and (b) shows a series-type branch pipe. This branch pipe is provided with a main pipe 35a and a plurality of (six locations in the figure) branch openings 35b. Cooling water supplied from the water supply pump 33 enters the main pipe 35a and is connected to the cooling pipe 32 connected to the branch opening 35. Sent. Of course, the branch pipe is preferably made of a material or a structure that takes water pressure into consideration.

4). Concrete temperature grasping means The concrete temperature grasping means obtains the concrete maximum internal temperature Tc at a predetermined time after placing. At this time, the concrete maximum internal temperature Tc is recorded together with the concrete age d. That is, the concrete internal maximum temperature Tc is recorded by specifying when it was acquired. Here, for the sake of convenience, the concrete internal maximum temperature is expressed as Tc (d) in order to clarify that it is a function of the age d (hereinafter referred to as the concrete internal maximum temperature Tc (d)). The age d here is a concept that means an elapsed time from a predetermined reference time, and the reference time can be the time when the fresh concrete is kneaded or when the concrete has been placed. .

  Acquisition of the concrete internal maximum temperature Tc (d) is roughly classified into a method using a concrete temperature measuring means and a method estimating from a temperature change of cooling water. First, a method using a concrete temperature measuring means will be described. The concrete thermometer 4 (concrete temperature measuring means) measures the concrete temperature in a state of being embedded in the housing 1 as shown in FIG. 2, and can be exemplified by a thermocouple, for example. In addition, in order to embed in concrete, the concrete thermometer 4 is attached using a reinforcing bar before placing.

  By performing the temperature analysis, the position indicating the maximum temperature in the housing 1 can be grasped in advance. Therefore, if the concrete thermometer 4 is installed at that position, the concrete temperature measured by the concrete thermometer 4 can be obtained as the concrete internal maximum temperature Tc (d) at the age d (during measurement). In addition, the temperature analysis performed here can employ | adopt various analysis methods, such as a finite element method, a finite difference method, a Schmidt method, and a Carlson method. The result (predicted temperature) obtained by the temperature analysis can be recorded on a storage medium (computer hard disk, CD-ROM, etc.) in a format that can be processed by a computer, for example.

  On the other hand, it is not always possible to install the concrete thermometer 4 at a position showing the maximum temperature. In this case, the concrete internal maximum temperature Tc (d) is estimated based on the measurement value of the concrete thermometer 4. For this estimation, for example, various estimation equations such as a quadratic curve as shown in FIG. 6, a cubic curve, other higher-order curves, an exponential function, temperature analysis, and the like can be used. When estimating by a quadratic curve, the temperature distribution inside the concrete is approximated by a quadratic curve, and the maximum concrete internal temperature Tc (d) is estimated based on the measured value of the concrete thermometer 4. Alternatively, a temperature distribution obtained by temperature analysis can be used. That is, the concrete temperature actually measured by the concrete thermometer 4 is compared with the temperature distribution at the age d (measurement time), and the maximum temperature in the analysis is obtained from the temperature difference between the measured temperature and the predicted temperature (analysis temperature). Is adjusted to the maximum concrete internal temperature Tc (d). Therefore, it is necessary to clarify the installation position of the concrete thermometer 4 (where it is installed in the housing 1), and it is desirable to install two or more concrete thermometers 4 at different positions.

  Next, a method for estimating from the temperature change of the cooling water will be described. When the concrete temperature is indirectly estimated from the temperature change of the cooling water, the temperature change of the cooling water is grasped. As described above, the temperature drop of the concrete is performed by heat exchange with the cooling water. By grasping the temperature difference of the cooling water before entering the housing 1 and when leaving the housing 1, the temperature of the concrete is reduced. The amount of descent can be estimated. Therefore, it is necessary to measure the temperature of the cooling water at two or more locations. Desirably, the cooling water temperature immediately before entering the housing 1 or immediately after entering the housing 1 is measured, the cooling water temperature immediately after exiting the housing 1 or immediately before exiting, and the temperature difference is grasped. As shown in FIG. 2, the coolant temperature near the center may be measured. When measuring the temperature of the cooling water, a refrigerant thermometer (refrigerant temperature measuring means) such as a thermocouple is attached to the surface (outside) of the refrigerant pipe 32, or a refrigerant thermometer is attached inside the refrigerant pipe 32 and measured. Similarly to the concrete thermometer 4, the refrigerant thermometer can use a thermocouple or the like.

  By analyzing based on the temperature change of the cooling water, the temperature distribution of the concrete at the material age d can be estimated. For example, if the calorific value is calculated using various conditions such as concrete volume, shape, placement temperature, arrangement and number of cooling pipes 32, flow rate (flow velocity) of cooling water, etc., the temperature distribution of the concrete can be obtained. it can. Further, at this time, the temperature distribution at the material age d based on the temperature analysis can be used. This calculation can be executed by temperature estimation means using a computer, and can be processed by a computer as a program, for example.

  The concrete internal maximum temperature Tc (d) obtained by the concrete temperature measuring means using the technique using the concrete temperature measuring means or the technique estimated from the temperature change of the cooling water is stored in a storage medium (for example, in a computer processable format). It can be recorded on a computer hard disk or CD-ROM.

5. Determination means The determination means determines whether to continue the concrete cooling (cooling). As described above, if the temperature difference between the concrete maximum internal temperature Tc (d) and the outside air temperature Te (d) is equal to or less than (less than) the allowable temperature difference, it is determined that the cooling can be terminated (FIG. 5). Therefore, the determination means has a function (temperature difference calculation function) for calculating the temperature difference Tg (d) between the concrete maximum internal temperature Tc (d) and the outside air temperature Te (d). Further, the allowable temperature difference Ta (d) varies depending on the material age d, that is, it is obtained using the material age d as a variable, and the determination means also has a function of calculating this (allowable temperature difference calculating function). . In addition, in order to clarify that the outside air temperature Te (d), the temperature difference Tg (d), and the allowable temperature difference Ta (d) are functions of the material age d, as with the concrete internal maximum temperature Tc (d), Each is expressed using the age d.

(Temperature difference calculation function)
In order to calculate the temperature difference Tg (d), it is necessary to set the outside air temperature Te (d) in addition to the maximum concrete internal temperature Tc (d) acquired by the concrete temperature grasping means. The outside air temperature Te (d) can be obtained by directly measuring the temperature of the outside air at the material age d. Alternatively, the outside air temperature Te (d) at the date and time corresponding to the material age d can be estimated based on the past performance (temperature data). If the outside air temperature Te (d) can be set, the temperature difference Tg (d) is obtained by obtaining the difference from the concrete internal maximum temperature Tc (d) by the following equation.
Temperature difference Tg (d) = Tc (d) −Te (d) (Equation 1)

(Allowable temperature difference calculation function)
In general, prediction of a temperature crack is performed by obtaining a “temperature crack index” by temperature analysis. The temperature crack index is a value obtained by dividing the tensile stress σi (d) of concrete at a predetermined age by the maximum principal tensile stress of the concrete. When the temperature crack index falls below 1.0, a temperature crack occurs. is expected. That is, it can be said that the fact that the maximum principal tensile stress level of concrete is lower than the tensile stress level σi (d) is a measure for terminating the cooling. In addition, it is known that the tensile stress degree σi (d) of concrete changes with the age d as shown in FIG. 7 (b), and in order to clarify that it is also a function of the age d. The tensile stress is expressed using the material age d.

  The maximum principal tensile stress degree of concrete is determined by the product of strain εc (d) and concrete elastic modulus Ee (d). Since the strain εc (d) and the elastic modulus Ee (d) of the concrete also show different values depending on the material age d, here, in order to clarify that it is a function of the material age d, it is expressed using the material age d. Yes. It is known that the elastic modulus Ee (d) of concrete changes with time as shown in FIG. 6C, for example, and the elastic modulus Ee (d) of the concrete at a predetermined age d using this linearity. ).

On the other hand, the strain εc (d) can be calculated using the thermal expansion coefficient αc of concrete. The thermal expansion coefficient αc is an index representing the degree of expansion and contraction with temperature, and the unit is the reciprocal of ° C. That is, the strain can be obtained by multiplying the thermal expansion coefficient αc by the temperature, and if this temperature is the temperature difference Tg (d), the maximum strain of the concrete at that age can be obtained. For example, to obtain the maximum strain εc (d), the following equation can be exemplified.
εc (d) = C × αc × Tg (d) (Formula 2)

C shown in Formula 2 is a predetermined constant, and is a value determined according to the estimation formula used when estimating the temperature distribution inside the concrete. For example, when a quadratic curve is selected as the estimation formula, C can be obtained by the following formula.
C = m / (1-ν) (Formula 3)
Here, ν is the Poisson's ratio of the concrete, and m is a coefficient determined by the position showing the maximum temperature in the concrete. For example, as shown in FIG. 6, when the maximum temperature is shown at a position away from the central axis (X axis) of the concrete casing 1 and this He is 1/6 of the total thickness H of the casing 1, the coefficient m is 3 / 8 is given. When the maximum temperature is indicated on the central axis (X axis) of the concrete frame 1 (that is, when He = 0), 2/3 is given as the coefficient m. In addition, although the strain calculated | required by Formula 2 is based on what is called internal restraint, and demonstrates below when this strain is made into the maximum strain, what added the strain by external restraint is similarly considered as the maximum strain. You can also.

When the maximum strain εc (d) and the concrete elastic modulus Ee (d) are obtained, the maximum principal tensile stress degree σmax (d) of the concrete can be calculated by the following equation.
σmax (d) = εc (d) × Ee (d) = C × αc × Tg (d) × Ee (d) (Formula 4)
If the maximum principal tensile stress level σmax (d) of the concrete is equal to or lower than the tensile stress level σi (d) of the concrete, it can be expressed by the following equation.
σi (d) ≧ σmax (d) = C × αc × Tg (d) × Ee (d) (Formula 5)
∴Tg (d) ≦ σi (d) / [C × αc × Ee (d)] (Formula 6)

  That is, Expression 6 is one cooling termination condition, and the right side of Expression 6 is the allowable temperature difference Ta (d) at that time. The cooling end condition is not limited to the case where the maximum main tensile stress level σmax (d) is equal to or lower than the tensile stress level σi (d), or the tensile stress level σi (d Various conditions such as 90% or less can be set. In any case, the end of cooling can be determined based on the temperature difference Tg (d) and the allowable temperature difference Ta (d) (determination function). When it is determined that the cooling is to be continued (not terminated), the above-described series of processing can be repeatedly performed until it is determined that the cooling is completed.

(Process by program)
The determination means may be processed by a computer as a program. This program reads the concrete maximum internal temperature Tc (d), the outside air temperature Te (d), the age d, and the coefficient of thermal expansion αc, and the function of calculating the temperature difference Tg (d) using these (temperature) Difference calculation function), and further, a function (allowable temperature difference calculation function) for calculating the elastic modulus Ee (d), tensile stress σi (d), and allowable temperature difference Ta (d) of the concrete. In addition, a function (determination function) for comparing the temperature difference Tg (d) and the allowable temperature difference Ta (d) to determine the continuation / end of cooling and a function for outputting the determination result to a display or a printing press are provided. You can also.

[Pipe cooling method]
1. Temperature grasping step The temperature grasping step is a step for obtaining the concrete internal maximum temperature Tc (d) at a predetermined age d, and the content thereof is the same as the description of the “concrete temperature grasping means” of the pipe cooling system. As described above, the concrete internal maximum temperature Tc (d) can be selected from either the method using the concrete temperature measuring means or the method estimating from the temperature change of the cooling water.

2. Outside air temperature setting step The outside air temperature setting step is a step of setting the outside air temperature Te (d) at a predetermined material age d, and the content thereof is the same as described in the “temperature difference calculation function” of the pipe cooling system. is there.

3. Temperature difference calculating step The temperature difference calculating step is a step of calculating a temperature difference Tg (d) between the concrete maximum internal temperature Tc (d) and the outside air temperature Te (d), and the content is “temperature difference of pipe cooling system”. This is the same as described in “Calculation function”.

4). Determination step The determination step is a step of determining whether or not the concrete cooling should be continued based on a comparison between the allowable temperature difference Ta (d) and the temperature difference Tg (d) at a predetermined age d, and the content thereof is pipe cooling. This is the same as the description of the “determination means” of the system. The allowable temperature difference Ta (d) is calculated based on the tensile stress σi (d) of concrete at a predetermined age d, the elastic modulus Ee (d) of concrete at the age d, and the thermal expansion coefficient αc of concrete. The contents are the same as the description of the “allowable temperature difference calculation function” of the pipe cooling system. In addition, when it is determined that the cooling is continued (not finished), the temperature grasping process to the determination process can be repeatedly performed until it is determined that the cooling is finished.

  The pipe cooling system and the pipe cooling method of the present invention can be used for civil engineering structures such as bridge substructures and dams, building structures such as office buildings, and other various concrete structures. Considering that the present invention provides a high-quality concrete structure with few temperature cracks, it can be said that the invention can be used not only industrially but can also make a great social contribution.

DESCRIPTION OF SYMBOLS 1 Housing 2 Cut sheet pile 31 Casing pipe 32 Cooling pipe 33 Water supply pump 34 First water supply hose 35 First branch pipe 35a Main pipe 35b (Branch pipe) branch port 36 Second water supply hose 37 Second branch pipe 38 Drain pipe 33 Water supply pump 4 Concrete thermometer 5U Upper refrigerant thermometer 5C Central refrigerant thermometer 5L Lower refrigerant thermometer

Claims (7)

In the pipe cooling system that suppresses the temperature rise inside the concrete by flowing the coolant through the cooling pipe laid in the concrete,
Concrete temperature grasping means for obtaining the concrete internal maximum temperature Tc (d) at a predetermined age d;
Judgment means for judging whether to continue concrete cooling,
The determination means includes
A temperature difference calculating function for calculating a temperature difference Tg (d) between the outside air temperature Te (d) at the material age d and the maximum concrete internal temperature Tc (d);
The allowable temperature difference Ta (d) at the age d is defined as the tensile stress σi (d) of the concrete at the age d, the elastic modulus Ee (d) of the concrete at the age d, and the thermal expansion coefficient αc of the concrete. Based on the allowable temperature difference calculation function to calculate,
A pipe cooling system comprising: a judgment function for comparing the temperature difference Tg (d) and the allowable temperature difference Ta (d) and judging whether to continue the concrete cooling based on the comparison. 2. The pipe cooling system according to claim 1, wherein the allowable temperature difference Ta (d) is obtained by the following equation using a predetermined constant C.
Ta (d) = σi (d) / [C × αc × Ee (d)] Furthermore, a refrigerant temperature measuring means for measuring a temperature change of the refrigerant while flowing is provided,
The pipe cooling system according to claim 1 or 2, wherein the concrete internal maximum temperature Tc (d) is estimated based on a temperature change of the refrigerant measured by the refrigerant temperature measuring means. Furthermore, it comprises one or more concrete temperature measuring means for measuring the temperature inside the concrete,
3. The pipe cooling system according to claim 1, wherein the concrete internal maximum temperature Tc (d) is estimated based on the temperature of the concrete measured by the concrete temperature measuring means. In the pipe cooling method that suppresses the temperature rise inside the concrete by allowing the coolant to flow through the cooling pipe laid in the concrete,
A concrete temperature grasping step for obtaining the concrete internal maximum temperature Tc (d) at a predetermined age d;
An outside air temperature setting step for setting the outside air temperature Te (d) at the material age d;
A temperature difference calculating step of calculating a temperature difference Tg (d) between the concrete internal maximum temperature Tc (d) and the outside air temperature Te (d);
A determination step of determining whether to continue the concrete cooling based on a comparison between the allowable temperature difference Ta (d) and the temperature difference Tg (d) in the material age d,
The allowable temperature difference Ta (d) is calculated based on the tensile stress σi (d) of the concrete at the age d, the elastic modulus Ee (d) of the concrete at the age d, and the thermal expansion coefficient αc of the concrete. Pipe cooling method characterized by being made. Furthermore, a refrigerant temperature measurement step of measuring a temperature change of the refrigerant while flowing,
The pipe cooling method according to claim 5, wherein the concrete internal maximum temperature Tc (d) is obtained based on a temperature change of the refrigerant. Furthermore, using one or more concrete temperature measuring means installed inside the concrete, comprising a concrete temperature measuring step of measuring the temperature inside the concrete,
6. The pipe cooling method according to claim 5, wherein the concrete internal maximum temperature Tc (d) is obtained based on a temperature measured by the concrete temperature measuring means.