JP2018178377A - Method of partial cooling of concrete and circulation cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for setting the end time period of cooling, which can precisely restrain a temperature crack in partial cooling of concrete, a method of partial cooling of concrete that realizes the technology, and a circulation cooling system.SOLUTION: A method of partial cooling of a concrete of the present invention is a method of cooling for only a "cooling range", and is a method comprising a prior analysis step and a cooling step. In the prior analysis step, an "end time period of cooling" to stop cooling of concrete is set and in the cooling step, concrete at the cooling range is cooled until the end time period of cooling. Further in the prior analysis step, the minimum value of the cracking index of a placed concrete body finds as the "minimum cracking index" of concrete, and the end time period of cooling is set so that the minimum cracking index exceeds a "threshold used for the end time period of cooling".SELECTED DRAWING: Figure 5

Description

  The present invention mainly relates to post cooling of concrete, and more specifically, a concrete part cooling method capable of partially cooling concrete after setting an appropriate end time in advance, and a circulating cooling system It is about

  Concrete is one of the most important construction materials as well as steel materials, and is used in various structures including civil engineering structures such as dams, tunnels and bridges, and building structures such as apartment buildings and office buildings. Although this concrete structure may be manufactured beforehand in a factory etc. and transported to a predetermined place, in the case of a civil engineering structure or a building structure, it is often constructed directly at a predetermined place (site). In any case, concrete (fresh concrete) in which cement, water, aggregate and the like are mixed is poured into the formwork, and after the concrete hardens, the formwork is removed to construct a concrete structure.

  As described above, concrete is a material that hardens with the passage of time, and as the internal temperature rises due to the hydration reaction of the concrete according to the passage of time, the material also increases its strength and the elastic modulus also It is. By the way, a crack may occur in the process from becoming fresh concrete to "hardened concrete" or while being used as a structure after hardening. Some concrete cracks are harmless, which does not affect the application of the structure, but there are also harmful cracks that have a significant impact on the application. Therefore, there are many areas where the cause and mechanism of the occurrence of cracking have been clarified, and various measures have been adopted as a countermeasure.

  The types of cracks are classified according to their causes, and are further classified into causes before hardening of concrete and causes after hardening. The causes before hardening include "initial cracking" caused by movement of the mold and abnormal cement setting, and "plastic shrinkage cracking" caused by rapid drying of the surface during curing. On the other hand, as a cause after hardening, "dry shrinkage cracking" caused by shrinkage of cement gel accompanied by water loss, "physical / chemical cracking" caused by corrosion of rebar or alkaline aggregate reaction, excessive load Examples include “structural cracks” and the like that are caused by the action and settlement of the structure.

  In addition, in the case of a concrete structure having a relatively large thickness (so-called mass concrete), temperature cracking may be a problem. The thermal cracks are roughly classified into those caused by internal restraint and those caused by external restraint, and the process (mechanism) until the crack occurs is different.

  During the hardening of concrete, a reaction between water and cement takes place, but the temperature of the concrete rises with time because heat of hydration is generated. However, if the outside air temperature is low, the surface temperature of the concrete does not increase so much in the portion (peripheral portion) near the concrete surface due to heat release (heat transfer) to the outside air. As a result, a significant temperature difference occurs between the inner and outer peripheral portions of the concrete, and thermal expansion occurs inside, while the outer peripheral portion does not thermally expand so much, so tensile force acts on the outer peripheral portion. It is the temperature crack by internal restraint that is generated by this tensile force.

  On the other hand, when the concrete reaches a predetermined temperature, it turns to temperature drop, and the heat tends to shrink as a whole due to the temperature drop. However, where it is in contact with existing concrete or the like, it can not be contracted freely because it is in a restrained state. As a result, a tensile force acts on a part of the concrete which is particularly restrained to the outside. It is a temperature crack by an external restraint that is generated by this tensile force. In addition, the temperature crack by external restraint often becomes a crack which penetrates a housing.

  As described above, although the generation mechanism is different between the thermal crack due to the internal restraint and the thermal crack due to the external restraint, they are common in that the temperature rise of the concrete caused by the heat of hydration of cement is the cause. Therefore, the method of suppressing the temperature rise of concrete is the mainstream as a countermeasure against the temperature crack. For example, as a countermeasure at the time of design, for the purpose of suppressing an increase in heat of hydration, a combination design is made such as use of low heat generation cement, reduction of cement amount, use of admixture to reduce heat of hydration. . Alternatively, the installation of a crack-inducing joint may be planned for the purpose of inducing a crack at a location where there is no impact even if a crack occurs relatively.

  Typical measures against temperature cracking during construction include pre-cooling, post-cooling, and long-term heat insulation curing. Precooling is to cool fresh concrete at the time of casting, and it uses flaked ice as mixing water, injects liquid nitrogen during mixing in a mixer or track agitator, and various cooling methods are adopted. It is done.

  Post-cooling includes a method of promoting natural cooling by providing a temperature diffusion surface inside a casing such as a cooling slot, and pipe cooling which cools concrete by passing cooling water through a pipe. In this pipe cooling, a cooling pipe such as thin-walled steel pipe (hereinafter referred to as "cooling pipe") is laid in advance in a housing, and low temperature water, air, etc. (hereinafter referred to as "refrigerant") after pouring concrete It is a rational and economical method that can be realized by means of relatively simple equipment and work.

  Conventionally, the main purpose of post cooling is to lower the maximum temperature of the concrete (hereinafter referred to as "peak temperature"), and the peak temperature of the entire member to a predetermined temperature (ambient temperature or expected final temperature) at an early stage It was supposed to go down. Therefore, generally, post-cooling is performed on the entire cast concrete, and it is general to end when a predetermined period (about several hours to half a day) has elapsed from when it is determined that the peak temperature has been reached. there were. However, the inventors have found that it is more effective to partially cool the cast concrete with regard to temperature cracking due to external restraint, as a result of research. For convenience of explanation, cooling performed on the entire concrete is referred to as "total cooling", and cooling performed partially is referred to as "partial cooling".

  When partial cooling is performed on an externally restrained portion (hereinafter referred to as "restrained portion"), the maximum temperature of the restrained portion is reduced, so that the tensile stress of the entire member becomes uniform, as a result, local It is possible to avoid that the cracking index becomes smaller. In addition, by providing a range to be cooled (hereinafter referred to as “cooling range”) and a range not to be cooled (hereinafter referred to as “non-cooling range”), “tagging effect” can be received, and further effectively It is possible to suppress temperature cracking due to external restraint. Hereinafter, the “tag tightening effect” will be described.

  As a matter of course, the temperature condition differs between the cooling range and the non-cooling range, and therefore, the time of conversion from thermal expansion to contraction and the mode of shape change accompanying contraction are also different. In other words, as shown in FIG. 1, apparently different behavior is exhibited in the cooling range and the non-cooling range. FIG. 1 is a model diagram showing the shape change of the expansion period and the contraction period in concrete subjected to external restraint, (a) shows a case without post cooling, (b) shows a case with partial cooling There is. As shown in FIG. 1 (b), focusing on the non-cooling range at the time of contraction, the non-cooling range shrinks by itself and tries to shrink the cooling range as well, that is, non-cooling so as to introduce compressive force into the cooling range. It can be seen that the range is deformed. As a result, even if a tensile force due to external restraint is generated in the cooling range (that is, a constrained portion), the tensile force is reduced (relaxed) by the effect of introducing the compressive force from the non-cooling range, and the temperature crack due to the external restraint Occurrence is suppressed. The tensile force reduction effect by the compressive force from this non-cooling range is the above-mentioned "tagging effect".

  For the reason described above, the inventors have concluded that "partial cooling", in which only the restricted portion is cooled, is effective as a measure against temperature cracking due to external restraint. So far, although the technique of merely partially cooling is disclosed in Patent Document 1, partial cooling based on the above reasons has not been proposed.

JP, 2016-11582, A

  By the way, as described above, the thermal cracking due to the external restraint is generated when the thermal contraction accompanied by the temperature drop is restrained, and the larger the degree of the temperature drop, the easier it is generated. Therefore, post cooling is performed to lower the peak temperature of the concrete, but the heat shrinkage is increased by cooling, and since the rise of the concrete temperature is stagnated, the development of its strength is delayed, and rather cracking occurs. There is also an aspect that it becomes easier. Therefore, cooling is ended at an early stage, that is, when a predetermined period has elapsed from when it is determined that the peak temperature has been reached. Note that the reason for continuing only for a predetermined period after reaching the peak temperature is to prevent another temperature rise (rebound).

  Even if partial cooling is performed as a measure against thermal cracking due to external restraint, it is important to stop the cooling at an early stage to prevent an increase in thermal contraction and a delay in strength development. However, as described above, until now, it is only considered to "wait for a predetermined period after reaching the peak temperature and end", and the timing when cooling is ended appropriately (so-called logically) (hereinafter referred to as " There is not much proposed about the technology of setting the end of cooling. Furthermore, when partial cooling is performed, the technology for setting the end of cooling has not been proposed until now. An object of the present invention is to provide a technology for setting a cooling end period capable of appropriately suppressing temperature cracking in partial cooling of concrete, and provides a concrete partial cooling method and a circulating cooling system that realize this. It is to be.

  The present invention focuses on finding the minimum cracking index of concrete when performing partial cooling of concrete, and setting the cooling end based on the minimum cracking index and the threshold for the final period, It was done based on the idea that was not.

  The concrete part cooling method according to the present invention is a method of cooling only the “cooling range” of the target concrete, and is a method including a pre-analysis step and a cooling step. In the pre-analysis process, "the end of cooling" to stop the cooling of the concrete is set, and in the cooling process, the concrete in the cooling range is cooled until the end of cooling. In the pre-analysis process, the minimum value of the crack index of the concrete after being cast is determined as the "minimum crack index", and the cooling end period is set such that the minimum crack index exceeds the "final threshold" (preset).

  The concrete part cooling method of the present invention can also be a method further including a temperature measurement step of measuring the temperature of concrete after being cast. In this case, in the pre-analysis step, the time at which the concrete temperature after pouring is maximum is calculated as the “temperature peak time”, and the cooling period after the temperature peak time is determined as the “post peak cooling period”. In the cooling step, the cooling end is corrected based on the concrete temperature obtained at the pre-analysis step, the concrete temperature obtained at the temperature measurement step, and the post-peak cooling period, and the corrected cooling end is reached. Stop.

  The concrete part cooling method of the present invention can also be a method of setting the cooling range of concrete in the pre-analysis step. In this case, the minimum cracking index is obtained while changing the “analysis cooling range”, and the “analysis cooling range” is set as the actual cooling range when the minimum cracking index exceeds the “range threshold” set in advance. Do. Note that the cooling range on analysis can be determined by setting the range in the vertical direction, and based on this, the “cooling range that defines the height” can be set, or the analysis can be done by setting the horizontal range. The upper cooling range can be defined, and based on this, the "cooling range with defined width" can be set.

  The concrete part cooling method of the present invention can also be a method further including a heat retention and curing step of holding and curing a "non-cooling range" of the target concrete which is not subjected to partial cooling.

  The concrete part cooling method of the present invention can also be a method of cooling concrete in a cooling range by "pipe cooling". In this case, in the cooling step, the refrigerant is pumped and flowed by the pressure-feeding means into the cooling pipe embedded in a substantially horizontal (horizontally included) posture inside the concrete in the cooling range.

  The concrete part cooling method of the present invention can also be a method of performing pipe cooling on tunnel lining concrete. In this case, in the cooling step, the refrigerant is pumped using a circulating cooling system into a cooling pipe embedded in a substantially horizontal (horizontally included) posture inside the tunnel lining concrete in the cooling range. This circulation cooling system includes pumping means and refrigerant cooling means installed in a movable formwork carriage (hereinafter referred to as "centle") for tunnel lining concrete, and the refrigerant is pumped by this pumping means, Circulating cooling is performed by cooling the warmed refrigerant discharged from the cooling pipe by the refrigerant cooling means.

  The circulating cooling system according to the present invention is to allow the refrigerant to flow through the cooling pipe embedded in a substantially horizontal (horizontally included) posture only in the cooling range of the tunnel lining concrete, and the analysis means, the pumping means, and the refrigerant cooling It is equipped with means. The analysis means is a means for determining the minimum crack index of the concrete after being cast, and determining the end of cooling so that the minimum crack index exceeds the end threshold. Further, the refrigerant cooling means installed in the center is a means for cooling the refrigerant discharged from the cooling pipe, and the pumping means similarly installed in the center is until the refrigerant cooled by the refrigerant cooling means reaches the end of cooling It is a means for pumping into the cooling pipe.

The concrete portion cooling method and circulating cooling system of the present invention have the following effects.
(1) By reducing the maximum temperature of the constrained portion, it is possible to make the tensile stress of the entire member uniform, and as a result, it is possible to avoid that the crack index becomes small locally.
(2) The “tagging effect” can be received, that is, the tensile force generated in the restrained portion is reduced, so that the crack can be more effectively suppressed.
(3) Since it is possible to set an appropriate cooling end, it is possible to more effectively suppress temperature cracking.
(4) Since the partial cooling is performed, the cost for equipment such as a cooling pipe and the cost for operation such as cooling can be significantly reduced as compared with the conventional overall cooling.
(5) By setting an appropriate end of cooling period, wasteful cost and labor due to unnecessary cooling can be saved, and it is possible to quickly shift to the next step, thereby contributing to shortening of the work period.
(6) If partial cooling of tunnel lining concrete is performed using a circulation cooling system, it can be carried out along with the movement of the center, so partial cooling can be performed extremely efficiently.

(A) is a model diagram showing the shape change of concrete in the expansion period and the contraction period in the case where post cooling is not performed, and (b) is a model diagram showing the shape change of concrete in the expansion period and the contraction period in the case where partial cooling is performed . The model figure which shows the cooling range and non-cooling range of object concrete typically. The graph which compared the relationship between the elapsed time after concrete pouring, and concrete stress in the case without cooling, the case of whole cooling, and the case of partial cooling. (A) shows the relationship between elapsed time after concrete pouring and concrete temperature, the case without cooling, the case partially cooling only for 1 day after pouring, the case partially cooling for 2 days after pouring, and the case partially cooling for 5 days after pouring Graphs for comparison, (b) shows the relationship between elapsed time after concrete pouring and concrete stress, the case without cooling, the case partially cooled for only 1 day after casting, the case partially cooled for 2 days after casting, 5 days after casting The graph figure which compared by the case which carried out partial cooling. The flow figure showing the flow of the main processes of the concrete part cooling method of the present invention. The flow figure which shows an example of the procedure which sets a cooling range by performing temperature stress analysis, changing the cooling range on analysis. (A) is a model figure which performs temperature stress analysis, changing the cooling range on analysis, (b) is a graph which shows the result of performing temperature stress analysis, changing the cooling range on analysis. The flowchart which shows an example of the procedure which sets the end of cooling by temperature stress analysis. (A) is a graph showing the change in cracking index when the cooling period in analysis is 2 days, (b) is a graph showing the change in cracking index when the cooling period in analysis is 5.5 days Figure. The graph which shows the relationship between the cooling period on analysis, and the minimum crack index. (A) is a model figure which shows the circulation cooling system installed in the tunnel pit, (b) is a block diagram which shows the main structures of a circulation cooling system. The fragmentary sectional view which shows the structure which makes removable the part near a concrete wall surface among cooling pipes. The fragmentary sectional view which shows the end of the cooling pipe with which the grout hose smaller diameter than the cooling pipe was connected.

  The concrete part cooling method of this invention and the example of embodiment of a circulation cooling system are demonstrated based on figures. The circulating cooling system of the present invention is used when carrying out the concrete portion cooling method of the present invention for tunnel lining concrete. Therefore, first, the method of partially cooling concrete according to the present invention will be described, and then the circulating cooling system according to the present invention will be described.

1. Concrete part cooling method (overall summary)
The concrete part cooling method of the present invention is a method of cooling only a cooling range in concrete (hereinafter referred to as "target concrete") to be cooled. FIG. 2 is a model diagram schematically showing the cooling range 110 and the non-cooling range 120 of the target concrete 100. As shown in this figure, the target concrete 100 is constructed in contact with a restraining body 200 such as existing concrete or foundation rock, that is, it is constructed in an environment in which a temperature crack is likely to occur due to external restraint. And let the predetermined range set from the position which touches the restraint object 200 among object concrete 100 be "cooling range 110", and let the range except cooling range 110 be "non-cooling range 120."

  The objective concrete 100 is not totally cooled but partially cooled, as described above, to reduce the maximum temperature of the constrained portion to equalize the tensile stress and thereby suppress the decrease in the cracking index. It is for suppressing a crack effectively by receiving a tightening effect.

  FIG. 3 is a diagram showing the relationship between elapsed time after concrete placement and concrete stress, and is a graph comparing the case without cooling (no countermeasure), the case with overall cooling, and the case with partial cooling. In addition, in FIG. 3, while showing concrete stress with a continuous line, the tensile strength of the concrete which expresses is shown with a broken line. As can be seen from this figure, although both the overall cooling and the partial cooling both stop stretching of the concrete stress once after cooling down, when you look at the subsequent elongation, the partial cooling is clearly more effective than the overall cooling. The rise is getting smaller. Also from this result, it is recognized that partial cooling is more effective than whole cooling for temperature cracking due to external restraint.

  Moreover, in the concrete part cooling method of this invention, the time (cooling end period) which stops cooling of the object concrete 100 is beforehand set before cooling in a field (field) actually. As described above, even if partial cooling is performed as a measure against thermal cracking due to external restraint, it is important to stop the cooling at an early stage to prevent an increase in heat shrinkage and a delay in strength development, that is, appropriate cooling By setting the final period, it is possible to realize an effective crack countermeasure.

  FIG. 4 is a graph comparing the case without cooling (no countermeasure) with the case partially cooled for only 1 day after incorporation, the case partially cooled for 2 days after implantation, and the case partially cooled for 5 days after implantation (a Figure is a diagram showing the relationship between elapsed time after concrete pouring and concrete temperature, and (b) is a diagram showing relationship between elapsed time after concrete pouring and concrete stress. In addition, while FIG.4 (b) shows concrete stress with a continuous line, the tensile strength of the concrete which expresses is shown with a broken line.

  As can be seen from FIG. 4 (a), naturally, the earlier the cooling is stopped, the smaller the temperature drop will be, but if it is stopped too early, the temperature will rise again after stopping (rebound as in the case of one day cooling) ) Will occur. As a result, the peak temperature is higher than in the other cases (2 days cooling and 5 days cooling), and as shown in Fig. 4 (b), the concrete stress is lower in the 1 day cooling case than in the 2 day cooling case. growing. In the case of cooling for 5 days, the concrete temperature drops most quickly as shown in FIG. 4 (a), but the tensile strength and stress of the concrete are closest to each other as shown in FIG. 4 (b). Therefore, the “cracking index” obtained by dividing the tensile strength of concrete by the stress of the concrete shows the smallest value, that is, the case of 5-day cooling is the case most likely to cause the temperature crack.

  Even if partial cooling is performed as described above, the effect of suppressing thermal cracking greatly differs depending on the timing of stopping the cooling. Therefore, in the present invention, it is decided to rationally set an appropriate end of cooling. Hereinafter, with reference to FIG. 5, the main elements constituting the method of partially cooling a concrete according to the present invention will be described in detail.

(Pre-analysis process)
FIG. 5 is a flow diagram showing the flow of the main steps of the method for cooling a concrete part of the present invention. As shown to this figure, the concrete part cooling method of this invention performs a pre-analysis process first (Step 100). Then, in the pre-analysis step, the cooling range 110 is mainly set (Step 110), and the end of cooling is set (Step 120).

  The cooling range 110 can be set based on thermal stress analysis using a three-dimensional finite element method (FEM). For example, the temperature stress history of the target concrete 100 is calculated under the condition that cooling is not performed, and a crack index is further obtained for each node, and a range where the crack index falls below a predetermined threshold is set as a cooling range. Alternatively, a plurality of patterns of cooling range (hereinafter referred to as “analysis cooling range”) serving as analysis conditions may be determined, and a pattern of which “minimum crack index” is maximum may be set as the cooling range. This “minimum crack index” determines the history of the crack index for each node by thermal stress analysis, extracts the minimum value for each node, and further indicates the crack index indicating the minimum value among the minimum values of all the nodes. It is obtained by extracting.

  FIG. 6 is a flow chart showing an example of a procedure of setting a cooling range by performing a temperature stress analysis while changing a cooling range on analysis. FIG. 7 (a) is a model diagram for performing the temperature stress analysis while changing the cooling range H on the analysis, and FIG. 7 (b) is a graph showing the result. FIG. 7A is a so-called 1⁄4 model in which the reverse T retaining wall is divided into four parts (two parts in each of the extension direction and the front and back direction). At the stage of setting the cooling range, since the cooling period (that is, the final period of cooling) has not been determined yet, first, a temporary cooling period (for example, two days after pouring concrete) is set (Step 111).

  When the temporary cooling period is set, an analytical cooling range is determined as an initial value (Step 112). For example, in the case of FIG. 7A, since the target concrete 100 is a wall portion of the inverted T-shaped retaining wall and the restraint 200 is a footing portion, a region extending upward from the upper end of the footing is analyzed The cooling range is H. When the cooling range H on analysis is determined, temperature stress analysis is performed (Step 113). Furthermore, while changing the cooling range H on the analysis (for example, while expanding each 50 cm), repeated thermal stress analysis is performed to create a “cooling range-cracking index graph” shown in FIG. 7B (Step 114). In FIG. 7 (b), the horizontal axis is the analytical cooling range H (the width from the upper end of the footing), and the vertical axis is the crack index, showing changes in the crack index at each node.

  When the “cooling range-cracking index graph” can be created, the cooling range 110 to be actually cooled is determined (Step 115). Specifically, an analytical cooling range H is determined as the cooling range 110 when the minimum cracking index exceeds a preset threshold (hereinafter, referred to as “range threshold” in the sense of a threshold for range setting). . For example, the threshold for range is shown in the “cooling range-cracking index graph” shown in FIG. 7B, and the horizontal axis value (analysis where the minimum cracking index (the lowest point of plural line graphs) exceeds this range threshold line The upper cooling range H), that is, the appropriate analytical cooling range H among the appropriate ranges shown in the figure, is selected, and this is determined as the cooling range 110.

  As the cooling range, only the vertical range (that is, the range that defines the height) may be set as described above, and additionally (or instead), the horizontal range (that is, the width) ) May be set. When the range in the horizontal direction is set as the cooling range, as shown in FIG. 7A, the range expanded by a predetermined width from the center of the member is defined as “analysis cooling range B”, and the above procedure (vertical range The cooling range 110 is set by performing the same procedure as in the setting procedure of FIG. When the target concrete 100 is to be divided into a plurality of lifts, the cooling range 110 may be set for each lift.

  By the way, one of the reasons is that partial cooling is subject to the tag tightening effect, but by setting the non-cooling range 120 to a considerable area (height, width or area), this tag tightening effect is obtained. The inventors have confirmed that it becomes larger. For example, when the ratio (Rc / Ru) of the region Rc of the cooling range 110 to the region Ru of the uncooling range 120 is taken as the uncooling ratio, all crack indices show 1 or more when the uncooling ratio exceeds a predetermined threshold. . Therefore, the cooling range may be set such that the non-cooling ratio exceeds a predetermined threshold. It is desirable that the uncooled range 120 be in a state where its temperature is not deprived (thermal expansion) when subjected to the tag tightening effect, and that the cooled range 110 is in a cooled state, that is, a compressive force is introduced. It is desirable that it is easy to be

  As shown in FIG. 5, when the cooling range 110 can be set, the end of cooling is set (Step 120). Also in this case, similarly to the setting of the cooling range 110, the setting can be made based on the temperature stress analysis using a three-dimensional FEM. FIG. 8 is a flow chart showing an example of a procedure for setting the cooling end period by temperature stress analysis. In the example of this flow chart, first, the cooling range 110 already determined is set as an input value (Step 121), and a temporary cooling end (hereinafter referred to as "analytical cooling end") is set as an input value (Step 122). ). When the cooling range 110 and the cooling end on the analysis can be set as the input value, the temperature stress analysis is performed (Step 123). Furthermore, while changing the cooling end on the analysis (for example, while extending each day), the thermal stress analysis is repeated to create the “cooling end-cracking index graph” (Step 124).

  FIG. 9 is a graph showing the change in the cracking index after concrete pouring, where (a) shows the case where the cooling period in analysis is 2 days, and (b) shows the cooling period in analysis 5.5 days And the case is shown. The crack index shown in this figure is obtained by selecting and plotting the crack index having the smallest value among all the nodes at that time (horizontal axis value). Then, further extract the crack index (that is, the minimum crack index) of the smallest value among FIG. 9A and FIG. 9B, and make the horizontal axis the end of cooling on analysis and the vertical axis the crack index What is plotted in FIG. 10 is the “end of cooling-cracking index graph” shown in FIG.

  When the "last cooling stage-crack index graph" can be created, the final cooling stage is decided in order to set the cooling period to be actually cooled (Step 125). Specifically, an analytical cooling end when the minimum crack index exceeds a preset threshold (hereinafter, referred to as “final threshold” in the sense of a threshold for setting the end) is determined as the cooling end. For example, the “end of cooling-cracking index graph” shown in FIG. 10 indicates the end threshold, and the minimum crack index exceeds the end threshold line (horizontal end on analysis), ie, the appropriate range shown in the figure. Among them, an appropriate analytical end of cooling is selected, and this is determined as the end of cooling. Note that the range threshold and the end period threshold can be separately set as different values, or can be set as the same value as a common threshold (that is, without separating the range threshold and the end period threshold).

(Cooling process)
As shown in FIG. 5, when the pre-analysis step (setting of the cooling range and setting of the cooling end period) is finished, partial cooling is actually performed on the cooling range 110 in the target concrete 100 (Step 200). As this partial cooling method, various methods conventionally used as post cooling can be adopted, including pipe cooling in which a refrigerant is allowed to flow through a pipe in a housing. For example, when the tunnel lining concrete constructed on the invert concrete which is the restraint body 200 is the target concrete 100, the cooling pipe is buried in a substantially horizontal (horizontally included) posture in the cooling range 110 set in advance, Partially horizontal pipe cooling can be performed by pumping the refrigerant into the cooling pipe using pumping means such as a pump after pouring concrete. In this case, it is more preferable to use the circulation cooling system of the present invention described later.

  As described above, in order to receive a larger tag tightening effect, the non-cooling range 120 is in a thermally expanded state (the concrete temperature is rising), and the cooling range 110 introduces a compressive force. It should be easy to do. Therefore, it is desirable to set the end of cooling period while the concrete temperature of the uncooled range 120 is rising. Further, even if the concrete temperature in the non-cooling range 120 is rising (or even falling), the non-cooling range 120 can be kept warm and cured so as to introduce a larger compressive force into the cooling range 110 (Step 300). By heat retention and curing, the non-cooling range 120 is thermally expanded to a larger extent, and accordingly, a greater compressive force can be introduced into the cooling range 110 at the time of contraction.

  As a method of heat retention curing, it is possible to adopt heat insulation curing in which a heat insulating mat is placed on the surface of concrete, or heat curing curing in which heating is actively performed, or various methods conventionally used can be adopted. In addition, since the purpose of heat retention curing in the non-cooling range 120 is to introduce a compressive force to the cooling range 110 after stopping the cooling, the heat retention curing may be started immediately after the cooling stop in the cooling range 110. In order to improve the efficiency of heat retention, heat retention may be started simultaneously with the start of partial cooling.

  Partial cooling is continuously performed, and partial cooling is stopped at the end of cooling set in the pre-analysis process (Step 600). Alternatively, it is possible to measure the actual concrete temperature of the cooling range 110 during partial cooling (temperature measurement step: Step 400), correct the end of cooling according to the measurement result (Step 500), and then stop partial cooling. In this case, in the pre-analysis step, the maximum concrete temperature after pouring (that is, the peak temperature) and the time to reach the peak temperature (hereinafter referred to as "analysis temperature peak time") are calculated. The cooling period after the end of cooling to the analysis temperature peak time (hereinafter referred to as “peak post-cooling period”) is determined. Then, the peak temperature obtained in the analysis is compared with the time (hereinafter referred to as “measured temperature peak time”) measured at the site (site) and the analysis temperature peak time, and if they match, the end of cooling Wait for and, if different, correct the end of cooling. When the end of cooling is to be corrected, it is preferable to set a new end of cooling by adding the post-peak cooling period obtained in the analysis to the measured temperature peak timing.

2. Circulating Cooling System Next, a circulating cooling system 300 of the present invention will be described with reference to FIG. FIG. 11 (a) is a model diagram showing the circulation cooling system 300 installed in the tunnel shaft, and FIG. 11 (b) is a block diagram showing the main configuration of the circulation cooling system 300. As shown in FIG. The circulation cooling system 300 of the present invention is used for the concrete part cooling method described so far, and therefore the description overlapping with the contents described in the concrete part cooling method is avoided, and the contents specific to the circulation cooling system 300 I will explain only. That is, the contents not described here are the same as those described in the concrete part cooling method.

  As shown in FIG. 11 (a), the circulating cooling system 300 is used more effectively when partially cooling tunnel-lined concrete (target concrete 100) constructed on invert concrete (restraint 200). Can. As shown in FIG. 11 (b), the circulation cooling system 300 includes an analysis means 301, a pumping means 302, and a refrigerant cooling means 303. In addition, a return tank 304, a water pipe 305, a drainage pipe 306, a cooling pipe It can also be configured to include 307.

  The analysis unit 301 performs the processing performed in the “pre-analysis step” described above, that is, the setting of the cooling range and the setting of the cooling end period, and further calculates the peak temperature and the analysis temperature peak timing, and cooling after the peak Processing such as setting of a period and correction of the end of cooling can also be performed. The analysis means 301 can be manufactured as a dedicated one, or a general purpose computer device can be used.

  The pumping means 302, the refrigerant cooling means 303, and the return tank 304 are installed on a movable formwork carriage (centle) for tunnel lining concrete, and the cooling pipe 307 is embedded in advance in the tunnel lining concrete. Of course, the cooling pipe 307 is embedded only in the cooling range 110 set by the analysis means 301 in the tunnel lining concrete, and its posture is substantially horizontal (including horizontal) along the tunnel axial direction.

  The pumping means 302 and the cooling pipe 307 (inflow port) are connected by the water pipe 305, the cooling pipe 307 (outlet) and the return tank 304 are connected by the drainage pipe 306, and the return tank 304 and the refrigerant cooling means 303, refrigerant cooling The means 303 and the pumping means 302 are connected by a predetermined pipe, and the refrigerant (water, air, etc.) pumped by the pumping means 302 is circulated to return to the pumping means 302 again via each means.

  The refrigerant pumped by the pumping means 302 passes through the water pipe 305 and flows into the cooling pipe 307 (inflow port), and further flows through the cooling pipe 307 while cooling the cooling range 110. It is discharged to the drain pipe 306 from the discharge port). At this time, since heat exchange is performed with the concrete in the cooling range 110, the temperature of the refrigerant is raised (for example, in the form of hot water) and discharged. The refrigerant that has passed through the drain pipe 306 is stored in the return tank 304, and the stored refrigerant is sequentially sent to the refrigerant cooling means 303 and cooled again. Then, the cooled refrigerant is again pumped by the pumping unit 302. As described above, the pressure-feeding means 302 continues to pressure-feed the refrigerant, and stops the pressure-feeding of the refrigerant at the end of the cooling period set by the analyzing means 301.

  As shown in FIG. 12, it is good to make it the structure which can be removed after a cooling stop as shown in FIG. Specifically, sockets are provided at both ends (that is, the inlet and outlet) of the main pipe of the cooling pipe 307, and the nipple N is screwed into the socket S using the inner screw of the socket S and the outer screw of the nipple N. Put it on. The nipple N is disposed such that a portion of the nipple N is embedded in the concrete and another portion is out of the concrete. Since the nipple N is screwed into the socket S, it can be removed relatively easily even after the cooling is stopped by grasping and turning the part that has come out of the concrete. It is preferable to apply a release agent such as grease in advance to the screw portion of the socket S and the nipple N in order to facilitate the removal of the nipple N.

  In addition, since the cooling pipe 307 is filled with a filler such as mortar after the cooling is stopped, it is preferable to install a check valve G at the end of the main pipe of the cooling pipe 307. Further, it is preferable to connect a grout hose G having a diameter smaller than that of the cooling pipe 307 to the end of the cooling pipe 307 as shown in FIG. 13 at a point where it is not necessary to cool and the filler flows out from the top to the bottom. Thereby, the free fall of the filler in the cooling pipe 307 can be prevented, and as a result, the unfilled portion of the cooling pipe 307 can be eliminated. The inlet and outlet of the cooling pipe 307 may be provided in the invert concrete portion.

  The concrete part cooling method and circulating cooling system according to the present invention include tunnel lining concrete, civil engineering structures such as superstructures and substructures of bridges, retaining walls, culverts and dams, or building structures such as collective housing and office buildings, It can be used for various other concrete structures. If the present invention provides a so-called high-quality concrete structure with few thermal cracks, it can be said that it can be expected not only to be industrially usable but also to be expected to contribute significantly to society.

DESCRIPTION OF SYMBOLS 100 Target concrete 110 Cooling range 120 (of target concrete) Non-cooling range 200 (of target concrete) 200 Restraint body 300 Circulating cooling system 301 of this invention Analysis means 302 (of circulating cooling system) 302 (of circulating cooling system) Pumping means 303 Refrigerant cooling means 304 (Circulation cooling system) 304 Return tank 305 (Circulation cooling system) Water pipe 306 (Circulation cooling system) Water pipe 306 (Circulation cooling system) Drain pipe 307 (Circulation cooling system) Cooling pipe H Analysis Upper cooling range S socket N nipple V check valve G grout hose

Claims (9)

A method of suppressing cracking of concrete by dividing concrete into a cooling range and a non-cooling range and cooling only to the cooling range,
The pre-analysis process which sets the cooling end period which stops cooling of concrete,
Cooling the concrete in the cooling range to the end of the cooling period;
In the pre-analysis step, the minimum value of the crack index of the concrete after being cast is determined as the minimum crack index, and the cooling end period is set so that the minimum crack index exceeds a predetermined threshold for end period.
Concrete part cooling method characterized by It further comprises a temperature measurement process to measure the concrete temperature after casting,
In the pre-analysis step, the time at which the concrete temperature after casting becomes maximum is calculated as the temperature peak time, and the cooling period after the temperature peak time is determined as the post-peak cooling period,
In the cooling step, the pre-analysis step is performed based on the concrete temperature of the temperature peak time obtained in the pre-analysis step, the concrete temperature obtained in the temperature measurement step, and the post-peak cooling period Correct the set cooling end and stop the cooling at the corrected cooling end,
The concrete part cooling method according to claim 1, characterized in that: In the pre-analysis step, the minimum cracking index is determined while changing the cooling range on analysis, and the cooling range on analysis above the threshold for the range set in advance is set as the cooling range.
In the cooling step, the concrete in the cooling range set in the preliminary analysis step is cooled.
The concrete part cooling method according to claim 1 or 2 characterized by things. In the pre-analysis step, a cooling range on analysis is set by setting a range in the vertical direction, and the cooling range having a defined height is set.
The concrete part cooling method according to claim 3 characterized by things. In the pre-analysis step, a cooling range on analysis is determined by setting a range in the horizontal direction, and the cooling range having a defined width is set.
The concrete part cooling method according to claim 3 or 4 characterized by things. A heat retention curing process for heat retaining and curing concrete in the uncooled range,
The concrete part cooling method according to any one of claims 1 to 5, further comprising: In the cooling step, the refrigerant is pumped and flowed by a pumping means into a cooling pipe embedded horizontally or in a substantially horizontal posture inside the concrete in the cooling range, thereby cooling the concrete in the cooling range.
The concrete part cooling method according to any one of claims 1 to 6, characterized in that: The target to be cooled is tunnel lining concrete,
In the cooling step, a tunnel cooling concrete in the cooling range is cooled using a circulating cooling system,
The circulating cooling system has the pumping means and refrigerant cooling means installed on a mobile formwork carriage for tunnel lining concrete, and the pumping means pumps the refrigerant and discharges the refrigerant discharged from the cooling pipe. The refrigerant is cooled by the refrigerant cooling means, and the refrigerant cooled by the pumping means is pumped.
The concrete part cooling method according to claim 7, characterized in that: A circulating cooling system in which a refrigerant is allowed to flow through a cooling pipe embedded horizontally or substantially horizontally only in a cooling range of tunnel lining concrete,
Analysis means for determining the end of cooling to stop cooling of the concrete;
Pumping means installed on a mobile formwork carriage for tunnel lining concrete,
Refrigerant cooling means installed on the movable formwork carriage for the tunnel lining concrete;
The analysis means determines the minimum value of the cracking index of the concrete after being cast as a minimum cracking index, and determines the cooling end period so that the minimum cracking index exceeds a predetermined ending threshold value.
The refrigerant cooling means cools the refrigerant discharged from the cooling pipe,
The pumping means pressure-feeds the refrigerant cooled by the refrigerant cooling means into the cooling pipe until the cooling end phase determined by the analysis means is reached.
Circulating cooling system characterized by

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