JP6929215B2 - Specimen curing method for evaluation of concrete structure strength - Google Patents

Description

The present invention relates to a concrete structure strength evaluation method and a concrete structure strength evaluation device.

Conventionally, in order to evaluate the structural strength of concrete, a core vertically extracted from a simulated column member (1 m × 1 m × 1 m) shown in JASS5 T-605 “Method for estimating structural concrete strength by core specimen” is used. The strength test was performed after cutting and shaping to a predetermined size. Such a method required a great deal of effort to prepare for the strength test. As a method for evaluating the strength of a concrete structure for solving such a problem, the one described in Patent Document 1 is known. The method for evaluating the strength of a concrete structure in Patent Document 1 is such that the evaluation can be easily performed by using a simple heat insulating curing container.

Japanese Unexamined Patent Publication No. 2-300646

Here, in the above-mentioned concrete structure strength evaluation method, a period of 3 months is required per season in order to evaluate the concrete structure strength correction value. Therefore, a long period of time was required to evaluate the structure strength correction values for three seasons. Therefore, it has been required to shorten the period required for evaluation.

Therefore, an object of the present invention is to provide a concrete structure strength evaluation method and a concrete structure strength evaluation device capable of shortening the evaluation period.

The concrete structure strength evaluation method according to one embodiment of the present invention is a concrete structure strength evaluation method for evaluating the strength of a concrete structure, and is a specimen preparation step of preparing a concrete specimen at a target temperature. A step of accommodating the specimen in a vacuum adiabatic curing container and a temperature holding step of maintaining the temperature of the specimen at a target temperature for a predetermined period are provided.

The concrete structure strength evaluation method includes a specimen preparation step of preparing a concrete specimen, a containment step of accommodating the specimen in a vacuum insulation curing container, and a temperature holding step of maintaining the temperature of the specimen for a predetermined time. , Equipped with. As a result, the strength of the concrete structure can be evaluated by performing a strength test on the specimen that has been cured for a predetermined time in the temperature holding step. Here, in the specimen preparation process, a concrete specimen is prepared at the target temperature. Further, in the temperature holding step, the temperature of the specimen is held at the target temperature. Therefore, the evaluation can be performed at a target temperature different from the environmental temperature at the time of the evaluation. For example, when evaluating each season of winter, standard season, and summer, it is conventionally necessary to evaluate based on the environmental temperature corresponding to the season at the time of evaluation. That is, in order to perform the evaluation corresponding to the winter season, it is necessary to wait for the actual winter season, and to perform the evaluation corresponding to the summer season, it is necessary to wait for the actual summer season. Therefore, in order to evaluate for three seasons, it is necessary to actually evaluate according to the timing of winter, standard season, and summer, and the time required for evaluation becomes long. On the other hand, in the concrete structure strength evaluation method according to the present invention, the evaluation can be performed at a target temperature different from the environmental temperature. Therefore, by evaluating a season different from the actual season, it is possible to evaluate three seasons at the same time. As a result, the period required for evaluation can be shortened.

In the method for evaluating the strength of a concrete structure, in the temperature holding step, the temperature of the specimen may be held by arranging the vacuum adiabatic curing container in the heat medium and cooling or heating the heat medium. By cooling or heating the heat medium in this way, the temperature of the specimen can be easily maintained.

In the method for evaluating the strength of a concrete structure, in the specimen preparation step, a specimen having a target temperature may be prepared by kneading the concrete and then adjusting the concrete to a target temperature. Even if the temperature of the concrete material in the preparatory stage and the temperature when kneading the concrete are not adjusted to the target temperature, by adjusting the specimen to the target temperature after kneading the concrete, the evaluation is sufficiently reproducible. It can be performed. As a result, it is possible to save the trouble of adjusting the temperature of the concrete material in the preparatory stage and adjusting the temperature when kneading the concrete.

The concrete structure strength evaluation device is a concrete structure strength evaluation device that evaluates the strength of a concrete structure, and houses a vacuum adiabatic curing container for accommodating a concrete specimen and a vacuum adiabatic curing container, and also. A tank for storing the heat medium and a temperature adjusting unit for adjusting the temperature of the heat medium in the tank are provided.

According to this concrete structure strength evaluation device, the same action and effect as the above-mentioned concrete structure strength evaluation method can be obtained.

According to one embodiment of the present invention, it is possible to provide a concrete structure strength evaluation method capable of shortening the evaluation period and a concrete structure strength evaluation device.

It is a figure which shows the evaluation apparatus of the concrete structure strength which concerns on embodiment of this invention. It is a figure which shows the cross section in the vertical direction of a specimen in detail. It is a flow chart which shows the evaluation method of the concrete structure strength. It is a table which shows the experimental outline of Experimental Example 1. It is a table which shows the planned composition of concrete used in an Example and a comparative example. It is a figure which shows the structure of the simple insulation curing container used in the comparative example. It is a graph which shows the temperature history of Examples 1, 3 and 5 and Comparative Examples 1, 3 and 5. It is a table which shows the experimental result of Experimental Example 1. It is a graph which plotted the structure strength correction value of the corresponding temperature variable curing and simple adiabatic curing. It is a table which shows the experimental outline of Experimental Example 2. It is a table which shows the experimental outline of Experimental Example 2. It is a table which shows the experimental result of Experimental Example 2. It is a table which shows the experimental outline of Experimental Example 3. It is a table which shows the planned composition of concrete used in an Example and a comparative example. It is a figure which shows the structure of the column simulation member used in the comparative example. It is a table which shows the experimental result of Experimental Example 3.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a diagram showing an evaluation device for the strength of a concrete structure according to an embodiment of the present invention. FIG. 1A is a side view of the evaluation device. FIG. 1B is a cross-sectional view of the evaluation device along the line Ib-Ib of FIG. The evaluation device 1 includes a tank 2, a vacuum adiabatic curing container 3, a heater 4, and a refrigerator 6.

The tank 2 houses the vacuum adiabatic curing container 3 and stores the heat medium 19. In this embodiment, the tank 2 has a hexahedral box shape. Further, the upper wall of the tank 2 is configured to be openable and closable as a lid. A space for accommodating the vacuum insulation curing container 3 is secured in the tank 2. In FIG. 1, a space for accommodating two vacuum insulation curing containers 3 is secured in the tank 2, but a space for one vacuum insulation curing container 3 may be secured. Space for three or more may be secured. Further, in the space in the tank 2, the heat medium 19 is stored in a place other than the place where the vacuum heat insulating curing container 3 is arranged. The heat medium 19 is not particularly limited as long as it can adjust and maintain the temperature of the specimen 10 via the vacuum adiabatic curing container 3, but water may be adopted, for example.

The vacuum adiabatic curing container 3 accommodates the concrete specimen 10. As shown in FIG. 1, the vacuum adiabatic curing container 3 is composed of a box-shaped main body portion 15 having an opening at the top and a lid portion 16. A heat insulating material is used for each surface of the main body 15 and the lid 13. As the heat insulating material, for example, styrofoam, urethane foam, vacuum heat insulating material, or the like having high heat insulating performance is used.

Here, the specimen 10 is a columnar member in which concrete is formed into a predetermined size (for example, a length of 200 mm and a diameter of 100 mm). As shown in FIG. 1, a plurality of specimens 10 are arranged in the internal space of the main body 15. In the example of the figure, a total of 9 pieces are arranged in 2 rows vertically and 3 rows horizontally. However, the number and arrangement of the specimens 10 arranged in the vacuum adiabatic curing container 3 are not particularly limited.

FIG. 2 is a diagram showing in detail a vertical cross section of the specimen. As shown in FIG. 2A, the specimen 10 is packed with the hardened cement 11 after kneading placed inside the lightweight mold 12. The lightweight formwork 12 is a cylindrical formwork having an open top, such as a tin plate or a plastic one.

The cement hardened body 11 is concrete, mortar, cement paste or the like, and the temperature rises due to heat of hydration using Portland cement or an admixture such as blast furnace slag or fly ash added to the binder. Refers to all things that can be expected.

In at least one of the test pieces 10, the thermometer 13 is embedded inside the cement hardened body 11 as shown in FIG. 2B. As the thermometer 13, for example, a thermocouple is used. For example, in the specimen 10 in the center of the container, the thermometer 13 is embedded inside the cement hardened body 11. In this embodiment, the thermometer 13 is provided on at least one of the specimens 10 in the center of the horizontal row.

As shown in FIG. 1, the heater 4 and the refrigerator 6 are provided on a part of the outer surface of the tank 2. The heater 4 heats the heat medium 19 in the tank 2 while circulating the heat medium 19 in the tank 2 with a pump. The refrigerator 6 cools the heat medium 19 while circulating the heat medium 19 in the tank 2 with a pump. The heater 4 and the refrigerator 6 function as a temperature adjusting unit for adjusting the temperature of the heat medium 19 in the tank 2. The heater 4 and the refrigerator 6 adjust the heat medium 19 in the tank 2 so as to be constant at the target temperature. That is, when the heat medium 19 in the tank 2 is higher than the target temperature, the refrigerator 6 cools the heat medium 19. When the heat medium 19 in the tank 2 is lower than the target temperature, the heater 4 heats the heat medium 19. A temperature detection unit (not shown) may be provided in the tank 2, and the heater 4 and the refrigerator 6 may heat or cool based on the difference between the temperature detection unit and the target temperature.

Next, a method for evaluating the strength of the concrete structure according to the present embodiment will be described with reference to FIG. FIG. 3 is a flow chart showing a method for evaluating the strength of a concrete structure. In this method, the evaluation device 1 described above is used.

Here, the evaluation target in the evaluation method of the present embodiment will be described. "Structural strength" is the strength of temperature-variable curing of various concretes at a age of 91 days. Further, here, the "structure strength correction value" is evaluated. _{The structure strength correction value 28} S ₉₁ is evaluated as the “structure strength correction value”. This value indicates the difference in structure strength at 91 days of material age from the standard curing strength of 29 days of material age.

The target temperature for evaluation is determined before the evaluation method is performed. Here, the target temperature is a temperature for reproducing the season to be evaluated in the year. When evaluating the strength of a concrete structure in winter, for example, the target temperature may be set to 10 ° C. When evaluating the strength of a concrete structure in the standard period (spring / autumn), for example, the target temperature may be set to 20 ° C. When evaluating the strength of a concrete structure in summer, for example, the target temperature may be set to 30 ° C. The target temperature may be different from or the same as the environmental temperature at the time of evaluation. The environmental temperature is the ambient temperature when the evaluation method is carried out, and is the indoor temperature at which the evaluation is performed.

Specifically, when the strength of the concrete structure in the summer is evaluated in advance in the standard period, the target temperature (30 ° C.) is higher than the environmental temperature (20 ° C.). When the strength of the concrete structure in winter is evaluated in advance in the standard period, the target temperature (10 ° C.) is lower than the environmental temperature (20 ° C.). When the strength of the concrete structure in the standard period is evaluated in advance in the summer, the target temperature (20 ° C.) is lower than the environmental temperature (30 ° C.). When the strength of the concrete structure in the standard period is evaluated in advance in winter, the target temperature (20 ° C.) is higher than the environmental temperature (10 ° C.).

As shown in FIG. 3, a specimen preparation step (step S10) for preparing a concrete specimen 10 at a target temperature is executed. In the specimen preparation step S10, after the concrete is kneaded, the concrete is adjusted to the target temperature to prepare the specimen 10 having the target temperature. In the specimen preparation step S10, the concrete prepared by the predetermined planned formulation is kneaded. The material temperature of concrete is equal to the environmental temperature, and the kneading temperature of concrete is also equal to the environmental temperature. After the concrete is kneaded, the concrete temperature is adjusted to the target temperature. Even if the target temperature is different from the environmental temperature, the material temperature and the kneading temperature may remain the environmental temperature.

When the target temperature is higher than the environmental temperature, the concrete temperature is raised to the target temperature by heating the concrete after kneading. For example, concrete is kneaded in a special pad under environmental temperature. On the other hand, prepare hot water in a boat, which is a container larger than the dedicated pad. After the concrete is kneaded, soak it in the boat together with the special pad. As a result, the concrete temperature can be heated to the target temperature. The method of heating the concrete after kneading is not particularly limited, and heating may be performed by a heating means other than hot water.

If the target temperature is lower than the environmental temperature, the concrete temperature is lowered to the target temperature by cooling the concrete after kneading. For example, concrete is kneaded in a special pad under environmental temperature. On the other hand, prepare ice and water in a boat, which is a container larger than the dedicated pad. After the concrete is kneaded, soak it in the boat together with the special pad. As a result, the concrete temperature can be cooled to the target temperature. The method of cooling the concrete after kneading is not particularly limited, and cooling may be performed by a cooling member other than ice. In addition, salt water or the like may be used so that the water in the boat can be easily cooled.

After the concrete temperature reaches the target temperature by temperature adjustment, a slump test, an air volume test, and a concrete temperature test are carried out on the concrete. Further, the specimen 10 is created by driving the concrete into the lightweight formwork 12. When the target temperature is equal to the environmental temperature, various tests are performed on the concrete in which the concrete temperature remains the environmental temperature without adjusting the temperature, and the concrete is driven into the lightweight formwork 12.

Next, the accommodating step (step S20) of accommodating the specimen 10 created in S10 in the evaluation device 1 is executed. In the accommodating step S20, a plurality of specimens 10 are arranged in the vacuum adiabatic curing container 3 and accommodated in a vacuum state. The vacuum adiabatic curing container 3 containing the specimen 10 is immersed in the heat medium 19 in the tank 2.

Next, a temperature holding step (step S30) of holding the temperature of the specimen 10 at the target temperature for a predetermined period is executed. In the temperature holding step S30, the vacuum adiabatic curing container 3 is arranged in the heat medium 19, and the temperature of the specimen 10 is maintained through the vacuum adiabatic curing container 3 by cooling or heating the heat medium 19. There is. When the target temperature is higher than the temperature of the heat medium, the heater 4 heats the heat medium to keep the heat medium at the target temperature. When the target temperature is lower than the temperature of the heat medium, the refrigerator 6 cools the heat medium to keep the heat medium at the target temperature. When the temperature of the heat medium is equal to the target temperature, the heating by the heater 4 and the cooling by the refrigerator 6 are stopped. In the temperature holding step S30, the heat medium 19 may be kept at the target temperature, and the specimen 10 may be stored in the vacuum adiabatic curing container 3 for 2 weeks. The storage period is not particularly limited to two weeks. That is, the temperature of the poured concrete self-heats due to hydration, reaches the maximum temperature, then gradually decreases due to natural cooling, and returns to the same temperature as the outside air (see, for example, FIG. 7). The storage period may be appropriately changed from 2 weeks as long as the temperature of the specimen 10 is set to a period necessary for returning to the outside air in this way. Further, in the temperature holding step S30, the specimen 10 is held at the target temperature, but the temperature of the specimen 10 itself is not always constant in the step, and as described above, the temperature is temporarily increased due to self-heating. Will be higher. That is, regardless of the temperature of the specimen 10, maintaining the temperature corresponding to the environmental temperature in which the specimen 10 is arranged at the target temperature corresponds to the temperature holding in the temperature holding step S30.

In the temperature holding step S30, for example, a thermometer 13 shown in FIG. 2 may be used to perform measurement for keeping the temperature of the specimen 10 at the target temperature. For the measurement, another method may be adopted as long as the temperature of the specimen 10 is directly measured, and further, the temperature of the specimen 10 is indirectly measured as long as the temperature of the specimen 10 can be grasped. The measuring method may be adopted. For example, if there is a gap between the inner wall of the hole for accommodating the specimen of the heat insulating material in the vacuum insulation curing container 3 and the specimen 10, a thermocouple may be inserted into the gap. The temperature of the specimen 10 may be grasped based on the temperature of the thermocouple.

After the temperature holding step S30 is completed, the specimen 10 is taken out from the vacuum insulation curing container 3 and the post-curing step of performing post-curing is executed (step S40). In post-curing, the specimen 10 is stored in a thermostatic state set at a target temperature in a sealed state. Post-curing is carried out up to 91 days of age.

After the post-curing step S40 described above is completed, the compressive strength test of the specimen 10 is performed. On the other hand, a part of the specimen 10 prepared in the specimen preparation step S10 is used as a standard curing specimen. The standard curing specimen is underwater cured at 20 ° C. until the age of 28 days. After that, the compressive strength test of the standard curing specimen is performed. _{The structure strength correction value 28} S ₉₁ is obtained from the difference between the compressive strength of the specimen 10 having a material age of 91 days and the compressive strength of the standard curing specimen.

The steps shown in FIG. 3 may be executed simultaneously for the three target temperatures. That is, a specimen 10 having a target temperature of 10 ° C., a specimen 10 having a target temperature of 20 ° C., and a specimen having a target temperature of 30 ° C. are simultaneously prepared, and variable temperature curing and post-curing are performed simultaneously at each target temperature. It's okay.

Next, the method for evaluating the strength of the concrete structure and the action / effect of the evaluation device 1 for the strength of the concrete structure according to the present embodiment will be described.

The concrete structure strength evaluation method includes a specimen preparation step S10 for preparing a concrete specimen 10, a storage step S20 for accommodating the specimen 10 in a vacuum insulation curing container 3, and holding the temperature of the specimen 10 for a predetermined time. The temperature holding step S30 is provided. Thereby, the strength of the concrete structure can be evaluated by performing the strength test on the specimen 10 cured for a predetermined time in the temperature holding step S30. Here, in the specimen preparation step S10, the concrete specimen 10 is prepared at the target temperature. Further, in the temperature holding step S30, the temperature of the specimen 10 is held at the target temperature. Therefore, the evaluation can be performed at a target temperature different from the environmental temperature at the time of the evaluation. For example, when evaluating each season of winter, standard season, and summer, it is conventionally necessary to evaluate based on the environmental temperature corresponding to the season at the time of evaluation. That is, in order to perform the evaluation corresponding to the winter season, it is necessary to wait for the actual winter season, and to perform the evaluation corresponding to the summer season, it is necessary to wait for the actual summer season. Therefore, in order to evaluate for three seasons, it is necessary to actually evaluate according to the timing of winter, standard season, and summer, and the time required for evaluation becomes long. On the other hand, in the concrete structure strength evaluation method according to the present embodiment, the evaluation can be performed at a target temperature different from the environmental temperature. Therefore, by evaluating a season different from the actual season, it is possible to evaluate three seasons at the same time. As a result, the period required for evaluation can be shortened.

In the method for evaluating the strength of a concrete structure, in the temperature holding step S30, the vacuum adiabatic curing container 3 is arranged in the heat medium 19, and the heat medium 19 is cooled or heated to maintain the temperature of the specimen 10. It's okay. By cooling or heating the heat medium 19 in this way, the temperature of the specimen 10 can be easily maintained.

In the method for evaluating the strength of a concrete structure, in the specimen preparation step S10, the specimen 10 having the target temperature may be created by adjusting the concrete to the target temperature after kneading the concrete. Even if the temperature of the concrete material in the preparatory stage and the temperature when kneading the concrete are not adjusted to the target temperature, it is sufficiently reproducible by adjusting the specimen 10 to the target temperature after the concrete is kneaded. Evaluation can be performed. As a result, it is possible to save the trouble of adjusting the temperature of the concrete material in the preparatory stage and adjusting the temperature when kneading the concrete.

The concrete structure strength evaluation device 1 is a concrete structure strength evaluation device for evaluating the strength of a concrete structure, and includes a vacuum insulation curing container 3 for accommodating a concrete specimen 10 and a vacuum insulation curing container 3. A tank 2 for accommodating and storing the heat medium 19 and a heater (temperature adjusting unit) 4 and a refrigerator (temperature adjusting unit) 6 for adjusting the temperature of the heat medium 19 in the tank 2 are provided.

According to the concrete structure strength evaluation device 1, the same action and effect as the above-mentioned concrete structure strength evaluation method can be obtained.

The present invention is not limited to the above-described embodiment. For example, as an evaluation device, the one shown in FIG. 1 is illustrated, but any configuration or shape may be adopted as long as the curing temperature of the specimen can be maintained at the target temperature, and the gist of the present invention. It can be changed as appropriate within the range that does not deviate from.

Further, the procedure of the evaluation method is not limited to the above-mentioned method, and steps may be added or changed as appropriate without departing from the gist of the present invention.

[Experimental Example 1]
In Experimental Example 1, the evaluation result when the strength of the concrete structure was evaluated using the variable temperature curing according to the present invention was compared with the evaluation result when the conventional simple heat insulating curing was used. In the variable temperature curing of Experimental Example 1, the case where the target temperature was equal to the environmental temperature was evaluated. In the variable temperature curing of Experimental Example 1, as shown in FIG. 1, a vacuum insulation curing container, a water temperature control type water circulation pump (1000 × 600 × 900 mm) and a water tank (970 × 730 × 920 mm) equipped with a refrigerator and a heater are provided. ) Was used. The vacuum insulation curing container (430 × 335 × 420 mm) can accommodate six specimens having a diameter of 10 × 20 cm. This evaluation device is also used in Experimental Examples 2 and 3 described later.

A specimen subjected to temperature variable curing under the conditions that the environmental temperature is 10 ° C. and the target temperature is 10 ° C. will be described. First, when making concrete, the work was carried out in a constant temperature room having an environmental temperature of 10 ° C. The materials used were stored in a constant temperature room at 10 ° C from the previous day in advance. Concrete was kneaded using a biaxial mixer having a capacity of 100 L in the planned formulation shown in FIG. Then, for the samples confirmed to satisfy the target values in the fresh concrete test, standard curing specimens and variable temperature curing specimens were collected.

The standard curing specimen was demolded the next day, cured in water at 20 ° C. until the age of 28 days, and then subjected to a compressive strength test. On the other hand, the specimen for variable temperature curing was set in the vacuum adiabatic curing container shown in FIG. 1 by a predetermined method, and then stored in a water tank having a curing water temperature of 10 ° C. for 2 weeks. Then, these specimens were taken out and stored as a post-curing treatment in a constant temperature room at 10 ° C. until the age of 91 days. The test specimens for variable temperature curing thus obtained were designated as Examples 1 and 2. In FIG. 5, the specimen using "N50" concrete was designated as Example 1, and the specimen using "FC50" concrete was designated as Example 2. Then, the compressive strength test of the temperature-variable curing specimen according to Examples 1 and 2 was performed. Examples 3 and 4 are specimens cured under the same conditions as in Examples 1 and 2 except that the target temperature and the environmental temperature are 20 ° C., and the compressive strength of the specimens according to Examples 3 and 4 is also defined. The test was conducted. Examples 5 and 6 are specimens cured under the same conditions as in Examples 1 and 2 except that the target temperature and the environmental temperature are 30 ° C., and the compressive strength of the specimens according to Examples 5 and 6 is also defined. The test was conducted.

Specimens subjected to simple heat insulation curing and post-curing after being prepared under the same conditions as in Examples 1 and 2 were designated as Comparative Examples 1 and 2. The Styrofoam mold shown in FIG. 6 was used as the container for simple heat insulation curing. The simple heat insulating curing container 20 shown in FIG. 6 includes a cylindrical main body 23 and a lid 24 on a disk. The main body 23 and the lid 24 are made of a styrofoam heat insulating material. A heat-generating concrete 22 is arranged in the center of the internal space of the main body 23, and a plurality of specimens 21 are arranged around the heat-generating concrete 22. Further, one of the specimens 21 is provided with a thermocouple 26. The specimens according to Comparative Examples 1 and 2 were housed in this simple heat insulating curing container and stored in a constant temperature room at 10 ° C. for 2 weeks. Subsequent post-curing of Comparative Examples 1 and 2 was the same as in Examples 1 and 2. Similarly, the specimens corresponding to Examples 3 and 4 were designated as Comparative Examples 3 and 4, and the specimens corresponding to Examples 5 and 6 were designated as Comparative Examples 5 and 6. The conditions of Examples 1 to 6 and Comparative Examples 1 to 6 are shown in FIG.

(Temperature history result)
FIG. 7 shows an example of the temperature history of variable temperature curing (Examples 1, 3 and 5) and simple heat insulating curing (Comparative Examples 1, 3 and 5) for ordinary concrete (N50) having a W / C of 50%. This temperature history is data acquired by a thermocouple attached to the specimen. As can be understood from FIG. 7, the maximum temperature of the temperature variable curing specimen according to each example tends to be slightly lower than that of the simple adiabatic curing specimen according to each comparative example, but the temperatures of both are shown. It was understood that the history tended to be similar.

(Result of compressive strength and structure strength correction value ₂₈ S ₉₁₎
A list of strength results of various concretes is shown in FIG. Here, if the structure strength correction value of the temperature variable curing of the same concrete at the same kneading temperature and the structure strength correction value of the simple heat insulation curing are close to each other, it can be evaluated that the accuracy of both evaluation methods is good. .. _{That is, by comparing the structure strength correction value (28} S ₉₁ ) of Example 1 and Comparative Example 1 and the structure strength correction value of Example 2 and Comparative Example 2, the structure strength of both is compared. The closeness of the reinforcement value can be evaluated. Therefore, based on the result of FIG. 8, the structure strength correction values of the corresponding temperature variable curing and the simple adiabatic curing are plotted in FIG. As shown in FIG. 9, sufficient approximation was confirmed between the structural strength correction values of the variable temperature curing and the simple adiabatic curing.

[Experimental Example 2]
In Experimental Example 1, it was understood that the structure strength correction value by the evaluation method using the temperature variable curing of the present invention and the structure strength correction value by the evaluation method using the conventional simple adiabatic curing are comparable. .. Therefore, in Experimental Example 2, the speed of evaluation of the structure strength correction value by variable temperature curing was examined. For example, using a concrete sample in the standard period, it was verified whether the structural strength correction value in the summer and winter can be evaluated in advance.

The outline of the experiment of Experimental Example 2 is shown in FIGS. 10 and 11. Here, for convenience, the concrete kneading temperature equivalent to the standard period is defined as 20 ± 2 ° C, the concrete kneading temperature equivalent to winter is 10 ± 2 ° C, and the concrete kneading temperature equivalent to summer is 30 ± 2 ° C. .. In FIG. 10, when the structure strength correction value in winter is preempted by using temperature variable curing in the standard period (Examples 7 and 8), and the structure strength correction value in summer is used in the standard period by using a temperature variable curing device. The implementation conditions in the case of preemption (Examples 9 and 10) are shown. In FIG. 11, the implementation of the case where the structure strength correction value in the standard period is preempted in the summer (Examples 11 and 12) and the case where the structure strength correction value in the standard period is preempted in the winter (Examples 13 and 14). Shows the conditions. For comparison with each of the examples, the implementation conditions of the structure strength correction value by the conventional simple heat insulation curing are also shown as Comparative Examples 7-14. In Examples 7, 9, 11, 13 and Comparative Examples 7, 9, 11, 13, "N50" was used as the concrete, and Examples 8, 10, 12, 14 and Comparative Examples 8, 10, 12, 14 were used. Then, "FC50" was used as concrete.

Here, the procedure in the case of preemptively evaluating the structure strength correction value in winter in the standard period using variable temperature curing (that is, Example 7) will be described. Since the standard period, when concrete is kneaded at an environmental temperature of 20 ° C. and a material temperature of 20 ° C., concrete having a kneading temperature of 20 ° C. is produced (this is called a sample having a temperature of 20 ° C.). The sample having a temperature of 20 ° C. is changed to a sample having a temperature of 10 ° C., which is the target temperature, by cooling the sample in order to anticipate the structure strength correction value in winter.

In this way, the procedure for changing the temperature of the concrete to the target temperature after kneading will be described. First, ice was put into the boat, and then water was added to make ice water at about 0 ° C. The kneaded sample at a temperature of 20 ° C. was put into a special vat (made of stainless steel). The special bat that was thrown in was gently soaked on the boat. At this time, the work was carried out with the utmost care so that ice water would not enter the special bat. The sample temperature in the special vat was measured with a thermometer, and it was confirmed whether the temperature was within the target temperature of 10 ± 3 ° C. If the target temperature was not reached, ice was added to the boat, or the concrete was kneaded again with a rubber spatula so that the concrete temperature would be uniform. The sample temperature was measured in the same manner as described above, and it was confirmed that the temperature was within the target temperature of 10 ± 3 ° C. A slump test, an air volume test, and a concrete temperature test were carried out using a sample having a temperature of 10 ° C. Using a sample having a temperature of 10 ° C., it was driven into a summit mold can having a diameter of 10 × 20 cm to prepare 12 sealed specimens. Of the 12 specimens, 6 were set in a temperature variable curing container (vacuum heat insulating curing container), and then the temperature variable curing container (vacuum heat insulating curing container) was housed in a water tank, and the water temperature of the water tank was set to 10 ° C. Was set to, and curing was performed for 2 weeks. Then, the specimen was taken out from the water tank and sealed and cured in a room at 10 ° C. until the age of 91 days. A compressive strength test was conducted on a specimen that was 91 days old. Three of the remaining six specimens were cured in standard water until the age of 28 days, and the remaining three were reserved. A compressive strength test was conducted on a specimen that was 28 days old. A structure strength correction value was obtained from the difference between the standard curing strength of 28 days of age and the sealing strength of 91 days of age. As a result, the structure strength correction value obtained by using the sample in which the sample temperature is changed from 20 ° C. to 10 ° C., and the structure strength correction value in winter in the standard period are pre-empted by using temperature variable curing. It is a value.

In addition, in FIG. 10, a case where the structure strength correction value in the summer season is pre-empted by using the temperature variable curing in the standard season (Example 9) will be described with an example. Since the standard period, when concrete is kneaded at an environmental temperature of 20 ° C and a material temperature of 20 ° C, concrete with a kneading temperature of 20 ° C is produced (this is called a sample with a temperature of 20 ° C). This temperature is 20 ° C. In order to anticipate the structure strength correction value in summer, the sample was changed to a sample having a target temperature of 30 ° C. by heating. In this case, hot water of about 60 ° C. was poured into the boat, and a sample having a temperature of 20 ° C. kneaded into a special vat (made of stainless steel) was put into the boat. As a result, the sample temperature in the dedicated vat was measured with a thermometer and adjusted to be within the target temperature of 30 ± 3 ° C. Other procedures were the same as the procedure of Example 7 described above.

(Result of compressive strength and structure strength correction value ₂₈ S ₉₁₎
The experimental results of Experimental Example 2 are shown in FIG. FIG. 12 shows the results of the structure strength correction values of the temperature variable curing obtained by the pre-emptive evaluation method of Examples 7 to 14. In addition, the structure strength correction value (results of Comparative Examples 7 to 14) of the simple heat insulating curing for comparison is also shown. Further, in the leftmost column of FIG. 12, the difference in the structure strength correction value between each example and each comparative example is shown. From this, it was understood that the average value of the difference between the two structure strength correction values was 2 N / mm ² and the standard deviation was 1.19 N / mm ² , and the difference between the two structure strength correction values was small. Therefore, it is possible to anticipate the structure strength correction value in winter or summer by using the sample in the standard period, or to anticipate the structure strength correction value in the standard period by using the sample in summer or winter. It was understood that it was possible by the method.

[Experimental Example 3]
In an actual ready-mixed concrete plant, a verification experiment was conducted to verify whether it is possible to anticipate the structural strength correction value in the summer using the actual concrete sample in the standard period. The outline of the experiment is shown in FIG. In mid-October, which is a standard phase were each prepared by 4m ³ fly ash Class B concrete and fly ash Class C concrete using actual kneading mixer with mixed concrete plant. For example, in the case of fly ash type B concrete, after manufacturing, the concrete was loaded on an agitator truck, and about 30 L of the concrete was discharged to a cat, and this was used as a sample. The samples were transported to a 20 ° C laboratory in a ready-mixed concrete plant. After confirming the temperature of this sample, the sample was transferred to a special vat. The boat was filled with hot water in advance, and a special bat containing the sample was soaked in it. While paying close attention not to let the hot water enter the sample, while checking the temperature of the sample with a thermometer, the sample was kneaded again using a rubber spatula or the like so that the temperature of the sample became uniform. When it was confirmed that the temperature of the sample reached the target temperature of 30 ° C., a fresh test was carried out, and 12 sealed specimens were prepared using a summit mold can of φ10 × 20 cm. After that, a simple heat insulating curing container (vacuum heat insulating container) in which six specimens were set was installed in the water tank relocated to the ready-mixed concrete test room. The temperature of the water in the aquarium was set to the target temperature of 30 ° C, and after curing for 2 weeks, the specimen in the simple heat insulating curing container was taken out and sealed and cured indoors at 30 ° C until the age of 91 days. A compressive strength test was conducted on the specimens that became. Such a specimen was designated as Example 15. Three of the remaining six specimens were used as specimens for underwater curing at a age of 28 days, and the remaining three specimens were used as spares. A compressive strength test was conducted on a specimen that was 28 days old. The fly ash class C concrete was also carried out in the same manner as the class B concrete, and was set as Example 16.

As a comparative example, an evaluation method using the simple heat insulating curing container 20 shown in FIG. 6 and an evaluation method using a 1 × 1 × 1 m pillar simulated member (so-called structure) 30 as shown in FIG. 15 are adopted. bottom. For the simple heat insulation curing of the comparative example and the production of concrete for the column simulation member, 4 m ^{3 of} fly ash B type concrete and fly ash C type concrete were produced at the ready-mixed concrete plant at the end of July, which is the summer, using an actual machine kneading mixer. .. For example, in the case of fly ash type B concrete, after manufacturing, the concrete was loaded on an agitator truck, then discharged to a cat and subjected to a fresh test to confirm a concrete kneading temperature of 32 ° C. Further, as shown in FIG. 6, a specimen for simple heat insulation curing was prepared, the specimen was sealed and cured until the lumber age was 91 days, and a compressive strength test was conducted on the specimen at the lumber age of 91 days. These specimens were designated as Comparative Examples 15 and 16. On the other hand, in the case of the column simulation member, as shown in FIG. 15, concrete 32 was cast in the formwork. The upper and lower two surfaces were covered with a heat insulating material 37, and the four sides were cured, and after 5 days of age, the mold was removed and exposed until 91 days of age. Two days before the material age of 91 days, a core boring of φ10 cm was performed vertically from the simulated member, and a 1 m core was pulled out. Then, after cutting and shaping to a predetermined size (20 cm) to prepare a specimen 31, a compressive strength test was conducted on the specimen of 91 days old. These specimens were designated as Comparative Examples 17 and 18. In addition, a compressive strength test was conducted on a 28-day-old underwater curing specimen. The composition of the concrete used is shown in FIG.

(Result of compressive strength and structure strength correction value ₂₈ S ₉₁₎
The result of Experimental Example 3 is shown in FIG. The structural strength correction values obtained for Examples 15 and 16 in which the sample of the actual machine-kneaded concrete in the standard period was changed to the sample of 30 ° C. equivalent to the summer as the target temperature were -7.7 N / mm ² , -10. It was .4 N / mm ^2. On the other hand, the structural strength correction values obtained for Comparative Examples 15 and 16 by simple heat insulation curing were -7.6 N / mm ² and -9.3 N / mm ² . Than this, the difference in the structure intensity correction value of both curing in the fly ash Class B concrete was 0.1 N / mm ^2, the fly ash Class C concrete was 1.1 N / mm ^2, showed a good value rice field. The structural strength correction values obtained for Comparative Examples 17 and 18 using the column simulation members were -9.6 N / mm ² and -12.0 N / mm ² . Than this, the difference in the structure intensity correction value of the specimen due to variable temperature curing and the bar simulating member is fly ash Class B concrete was 1.9 N / mm ^2, the fly ash Class C concrete 1.6 N / mm ² Yes, it showed a good value. From the above, regarding the sample of actual machine-kneaded concrete in the standard period, the sample was warmed with hot water and changed to the target temperature of 30 ° C to make concrete equivalent to summer, and the structural strength correction value was taken in advance. As a result, as a comparative example, the difference between the structure strength correction value by simple heat insulation curing prepared using a sample of actual machine-kneaded concrete in summer and the structure strength correction value by the core of the pillar simulation test piece is 2N / mm ² It was understood that the evaluation method according to the present invention was not inferior to the conventional evaluation method. That is, by changing the actual machine-kneaded concrete sample in the standard period to the concrete sample temperature equivalent to the summer and performing temperature variable curing, it is possible to anticipate the structure strength correction value in the summer in the standard period, and the structure strength correction value. Was demonstrated to be obtained in a short period of 3 months.

1 ... Evaluation device, 2 ... Tank, 3 ... Vacuum insulation curing container, 4 ... Heater (temperature control unit), 6 ... Refrigerator (temperature control unit), 10 ... Specimen, 20 ... Heat medium.

Claims (3)

Evaluating the strength of a concrete structure This is a specimen curing method for evaluating the strength of a concrete structure.
Specimen preparation process to create a concrete specimen at the target temperature,
And accommodation step for accommodating the specimen to adiabatic aging vessel,
A specimen curing method for evaluating the strength of a concrete structure, comprising a temperature holding step of holding the temperature of the specimen at the target temperature for a predetermined period of time. The temperature holding step, the pre-Kidan heat aging vessel was placed in the heat medium, by cooling or heating the heat transfer medium, and maintaining the temperature of the specimen, the concrete according to claim 1 Specimen curing method for evaluation of structural strength. The concrete structure strength according to claim 1 or 2, wherein in the test piece preparation step, the concrete is kneaded and then the concrete is adjusted to the target temperature to prepare the test piece at the target temperature. Specimen curing method for evaluation.

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