Apparatus for evaluating characteristics of concrete and method for evaluating characteristics of concrete

Abstract

To provide an evaluation apparatus capable of acquiring various physical property values required for evaluating the risk of thermal cracking while using the same concrete material as that used on-site.SOLUTION: An evaluation apparatus includes: a strength test section including a plurality of first cylindrical bodies; an unconstrained test section including a first rectangular frame body with a bottom; a constrained test section including a second rectangular frame body with a bottom, both ends of which in a longitudinal direction are constrained by a constraining steel material having a thermal expansion coefficient of less than 1×10-6 / °C; a heat-insulating housing container for covering the strength test section, the unconstrained test section, and the constrained test section; and a thermometer capable of measuring a temperature change in the housing container. The unconstrained test section has a first strain sensor installed inside the first rectangular frame, and the constrained test section has a second strain sensor installed on the constraining steel material.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an evaluation apparatus for evaluating the characteristics of concrete, and a method for evaluating the characteristics of concrete using this apparatus.

Background Art

[0002] Generally, concrete (mass concrete) used for large-scale (large-sized, large cross-section) structures is likely to generate thermal strain due to temperature changes in the part. Thermal strain can cause thermal cracking of mass concrete. Therefore, it is important to evaluate the risk of thermal cracking of mass concrete.

[0003] As an apparatus used for experimentally evaluating the properties of thermal cracking of concrete, an apparatus called TSTM (Thermal Stress Testing Machine) is known. This apparatus is a uniaxial restraint type test apparatus capable of arbitrarily controlling the temperature condition and restraint condition of concrete in an adiabatic state. According to the TSTM apparatus, it is possible to perform a restraint test for evaluating the properties of concrete by changing the temperature condition under restraint, and an unrestrained test for evaluating the properties of concrete by changing the temperature condition in an unrestrained state.

[0004] However, due to circumstances such as the need for water flow control for temperature management, more specifically, control of water temperature and water volume, the scale of the TSTM apparatus becomes large. In addition, in order to maintain the accuracy of test results at a high level, maintenance of the control mechanism and the like is necessary. Due to such circumstances, the TSTM apparatus is usually installed in a test room having a large space, and it is difficult to evaluate the concrete actually used on site.

[0005] Patent Document 1 discloses a test apparatus that is excellent in handleability and can perform a test on the mechanical properties of concrete in a state where an adiabatic state is reproduced.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When evaluating the risk of temperature cracking in mass concrete, generally, after obtaining various concrete physical properties, a method of calculating temperature stress by numerical analysis using these data as input values is adopted. In this numerical analysis, various physical property values of concrete are required. Typical examples include physical property values such as compressive strength, tensile strength, Young's modulus, temperature rise amount, autogenous shrinkage strain, and coefficient of thermal expansion.

[0008] By using the test apparatus disclosed in Patent Document 1, although adiabatic temperature characteristics and mechanical characteristics such as compressive strength can be obtained, the data necessary for evaluating the risk of temperature cracking are insufficient.

[0009] In view of the above problems, an object of the present invention is to provide an evaluation apparatus capable of obtaining various physical property values necessary for evaluating the risk of temperature cracking while using concrete of the same material as the concrete used on site. Another object of the present invention is to provide a method for evaluating the characteristics of concrete using this evaluation apparatus.

Means for Solving the Problems

[0010] The evaluation apparatus according to the present invention is an evaluation apparatus for evaluating the characteristics of concrete to be measured, and a strength test section including a plurality of first cylindrical bodies into which the concrete can be placed, an unrestrained test section including a bottomed first rectangular frame body into which the concrete can be placed, including a bottomed second rectangular frame body into which the concrete can be placed, and both ends in the longitudinal direction of the second rectangular frame body having a coefficient of thermal expansion of 1×10 -6A restraint test section restrained by a restraint steel material below / °C, a heat-insulating containment vessel covering the strength test section, the unrestrained test section, and the unrestrained test section, and a thermometer capable of measuring temperature changes inside the containment vessel. The unrestrained test section has a first strain sensor installed inside the first rectangular frame body. The restraint test section is characterized by having a second strain sensor installed on the restraint steel material.

[0011] The above evaluation device is used with a plurality of test specimens formed by placing concrete to be evaluated in each of the first cylindrical body, the first rectangular frame body, and the second rectangular frame body, in a state where they are arranged inside a heat-insulating containment vessel. Here, as the concrete to be evaluated, it is possible to use the concrete placed at the site, or it is also possible to use the concrete of the same material as the concrete scheduled to be placed at the site and supplied from a concrete plant.

[0012] A plurality of test specimens (strength test specimens) obtained by placing concrete in the first cylindrical body are installed inside the containment vessel.

[0013] For example, every time a predetermined age timing arrives, the target age strength test specimens belonging to the plurality of strength test specimens are taken out from the containment vessel, and by performing a Young's modulus measurement test on the target age strength test specimens, the temporal change pattern of the Young's modulus of the concrete can be calculated. The Young's modulus measurement test is performed, for example, by a method conforming to JIS A 1149:2017 "Test Method for Static Elastic Modulus of Concrete".

[0014] As a more specific example, every time the material age reaches 1 day, 3 days, 7 days, 14 days, and 28 days, the strength test specimens are taken out from the storage container and the above tests are executed. At this time, a heat-insulating filler may be installed in the storage container so as to fill the gap (the occupied area of the original strength test specimen) generated by taking out the strength test specimen. As the heat-insulating filler, typically, expanded beads, polystyrene foam, rock wool, glass wool, urethane foam, etc. can be used.

[0015] Also, by performing a compressive strength test on the target age strength test specimen, the change mode of the compressive strength of concrete over time can be calculated. The compressive strength test is performed, for example, by a method compliant with JIS A 1108:2018 "Method for Testing Compressive Strength of Concrete". The compressive strength test may be performed in parallel with the above Young's modulus measurement test. In addition, the correlation between the two may be derived using the compressive strength of concrete and the Young's modulus of concrete for each material age obtained in this way.

[0016] Also, by performing a splitting tensile strength test on the target age strength test specimen, the change mode of the splitting tensile strength of concrete over time can be calculated. The splitting tensile strength test is performed, for example, by a method compliant with JIS A 1113:2018 "Method for Testing Splitting Tensile Strength of Concrete".

[0017] When performing a compressive strength test and a splitting tensile strength test on strength test specimens of the same material age, it is preferable to prepare at least twice the number of strength test specimens as the number of types of material age. For example, every time the material age reaches 1 day, 3 days, 7 days, 14 days, and 28 days, two or more strength test specimens are taken out from the storage container and the compressive strength test and the splitting tensile strength test are performed. The compressive strength test and the Young's modulus measurement test may be performed in parallel on the same strength test specimen.

[0018] In addition, the same test may be performed on a plurality of strength test specimens of the same age, and the value obtained by calculation based on the measured values obtained (for example, the average value) may be used as the measured value obtained from the test results.

[0019] As described above, each time the age timing arrives, the strength test specimen is taken out from the storage container. On the other hand, the unconstrained test specimen and the constrained test specimen are placed in the storage container for a long period (for example, a number of days of 25 days or more). From this perspective, in order to easily take out the strength test specimen, the storage container is made of a heat insulating material and has a removable lid portion, and it is preferable to install the strength test specimen above (closer to the lid portion) the unconstrained test specimen and the constrained test specimen in the storage container.

[0020] As a more detailed example, The storage container has a bottom portion installed at a position facing the lid portion and side portions covering the bottom portion from four sides. The unconstrained test portion and the constrained test portion are arranged in a direction along the bottom portion. The plurality of first cylindrical bodies included in the strength test portion may be arranged in a direction along the bottom portion in a state of being placed directly above the first rectangular frame body included in the unconstrained test portion and the second rectangular frame body included in the constrained test portion.

[0021] A test specimen (unconstrained test specimen) obtained by placing concrete in the first rectangular frame body is realized in a state where a first strain sensor is embedded inside. As the first strain sensor, for example, an embedded strain gauge can be used. By acquiring the change over time of the measured value of the first strain sensor, the change over time of the unconstrained strain of the concrete to be measured can be obtained.

[0022] A test specimen (constrained test specimen) obtained by placing concrete in the second rectangular frame body is configured in a state of being constrained by an extremely low constraint steel material with a coefficient of thermal expansion of less than 1×10 -6 / °C. As the constraint steel material, for example, invar steel material (coefficient of thermal expansion is 0.5×10-6 It is possible to utilize (to the extent of / ℃). A second strain sensor is installed in the restraint steel material. As a detailed example, after machining a part of the threaded portion of the restraint steel material, the second strain sensor is fixedly installed. For example, a strain gauge can be used as the second strain sensor. By obtaining the change over time in the measured value of the second strain sensor, the change over time in the strain of the concrete under measurement under restraint can be obtained.

[0023] The unrestrained test specimen and the restrained test specimen are housed in a heat-insulating container together with a plurality of strength test specimens. Since these test specimens generate heat as the age progresses and the hydration reaction proceeds, the temperature inside the container rises due to this heat generation. Then, when the progress of the hydration reaction reaches a saturated state, the rate of temperature rise inside the container relaxes, and after further passage of time, it eventually drops to a temperature equivalent to the outside air temperature. That is, the unrestrained test specimen and the restrained test specimen are placed under the same temperature history inside the heat-insulating container.

[0024] The measured value of the first strain sensor corresponds to the value of the free strain, which reflects the strain associated with the temperature history and the autogenous shrinkage strain. On the other hand, the measured value of the second strain sensor installed in the restraint steel material is the steel material strain, which corresponds to the value of the strain in the restrained state, reflecting the strain associated with the temperature history and the autogenous shrinkage strain. Therefore, based on the measured value of the first strain sensor and the measured value of the second strain sensor, more specifically, based on the difference value between the measured value of the first strain sensor and the measured value of the second strain sensor, the value of the restrained strain can be obtained. That is, the change over time in the restrained strain of the concrete under measurement can be obtained.

[0025] From the relationship between the force balance between the restrained steel and the concrete and the strain compatibility condition, the restraint stress generated in the concrete can be calculated by an operation based on the ratio of the restrained steel in the restraint test body (steel ratio), the Young's modulus of the restrained steel, and the value of the strain in the restrained state. As described above, as the value of the strain in the restrained state, the measured value of the second strain sensor can be used. As the Young's modulus of the restrained steel, the physical property value of the steel used as the restrained steel can be used. As the steel ratio, the value of the ratio between the area of the end portion in the longitudinal direction of the second rectangular frame body constituting the restraint test section and the cross-sectional area of the restrained steel can be used.

[0026] In this way, when the time-dependent change pattern of the restrained strain of the concrete to be measured and the time-dependent change pattern of the restraint stress are obtained, based on the correlation between the two, the apparent Young's modulus at the time of temperature rise and temperature drop can be calculated. The restraint stress and the restrained strain show a nearly linear correlation at the time of temperature rise and temperature drop, respectively. Therefore, by linearly approximating each correlation relationship based on, for example, the least squares method and deriving its slope, the apparent Young's modulus of the concrete to be measured at the time of temperature rise and temperature drop can be obtained. This apparent Young's modulus can be regarded as the Young's modulus considering both the elastic strain and the creep strain under the restraint stress that changes moment by moment.

[0027] On the other hand, as described above, by performing Young's modulus measurement tests on a plurality of strength test bodies with different ages, the time-dependent change of the actual Young's modulus of the concrete to be measured can be obtained. According to the "Guidelines for Crack Control of Mass Concrete 2016" of the Japan Concrete Institute (hereinafter simply abbreviated as "Guidelines"), the influence of creep is considered as a reduction in rigidity due to the effective Young's modulus obtained by multiplying the Young's modulus by a reduction coefficient. From this, the reduction coefficient of the Young's modulus of the concrete to be measured (at the time of temperature rise and temperature drop, respectively) can be calculated from the ratio between the actual Young's modulus obtained by the Young's modulus measurement test and the apparent Young's modulus (at the time of temperature rise and temperature drop, respectively).

[0028] According to the above control guidelines, regardless of the type and composition of the cement used in the concrete, the value of the reduction coefficient of Young's modulus uniformly determined during the heating and cooling periods is used. On the other hand, if the evaluation apparatus according to the present invention is used, a reduction coefficient of Young's modulus specific to the concrete to be measured can be obtained. Therefore, by using this value in numerical analysis, it becomes possible to more accurately evaluate the risk of thermal cracking of mass concrete.

[0029] In addition, the above evaluation apparatus is provided with a thermometer capable of measuring the temperature change in the storage container. Therefore, by acquiring the change history of the measured value of the thermometer, the effective age can be calculated. That is, the relationship between the age when the strength test specimen is taken out from the storage container and the effective age can be obtained.

[0030] Using the information regarding the correlation between the age when the strength test specimen is taken out from the storage container and the effective age thus obtained, various correlation information can be obtained. For example, the correlation between the time-dependent change pattern of the compressive strength of the concrete and the effective age of the concrete, which is obtained by performing a compressive strength test on the strength test specimens taken out for each age, can be obtained. Also, for example, the correlation between the time-dependent change pattern of the splitting tensile strength of the concrete and the effective age of the concrete, which is obtained by performing a splitting tensile strength test on the strength test specimens taken out for each age, can be obtained.

[0031] It is also possible to take out the unconstrained test specimen from the storage container after 25 days or more have passed since it was installed in the storage container, and read the measured value of the first strain sensor while applying a temperature change (for example, from the outside air temperature to about 60°C) in a heat-insulated environment, so as to obtain the relationship between the temperature and the measured value of the first strain sensor.

[0032] After 25 days or more have passed, it is considered that no additional autogenous shrinkage strain due to the hydration reaction occurs even when a temperature change is applied thereafter. That is, by causing a temperature change to an unrestrained specimen after 25 days or more have passed and obtaining the correlation between the temperature and the measured value of the first strain sensor, information regarding the thermal strain of the concrete can be obtained. Specifically, the coefficient of thermal expansion of the concrete can be obtained from the relationship between the temperature and the measured value of the first strain sensor. Typically, since the temperature and the measured value of the first strain sensor exhibit a nearly linear correlation, for example, the coefficient of thermal expansion of the concrete can be obtained by linearly approximating the correlation between the temperature and the measured value of the first strain sensor based on the least squares method and deriving its slope.

[0033] On the other hand, the measured value of the first strain sensor provided to the unrestrained specimen installed in the containment vessel is a value that reflects the thermal strain and the autogenous shrinkage strain based on the temperature history in the containment vessel. By multiplying the value of the temperature change in the state where the unrestrained specimen is installed in the containment vessel by the coefficient of thermal expansion of the concrete calculated by the above method, the value of the thermal strain that occurred in the unrestrained specimen installed in the containment vessel can be derived. Therefore, by subtracting the value of the thermal strain from the measured value of the first strain sensor provided to the unrestrained specimen installed in the containment vessel, the time-dependent change pattern of the autogenous shrinkage strain of the unrestrained specimen can be obtained. This autogenous shrinkage strain is the autogenous shrinkage strain of the concrete to be measured.

[0034] Therefore, based on the information regarding the correlation between the age of the material and the effective age obtained by the method described above, the correlation between the effective age of the concrete to be measured and the autogenous shrinkage strain can be obtained. The information regarding the correlation between the effective age of the concrete and the autogenous shrinkage strain can be used when evaluating the risk of thermal cracking by 3D-FEM analysis in the case of constructing an actual structure using the concrete.

[0035] In the above evaluation device, the thermometer can be installed at any position as long as the temperature inside the storage container is measured. However, from the perspective of accurately measuring the temperature of concrete, it is preferably attached to at least one of the strength test section, the unrestrained test section, and the restrained test section. However, as described above, since the strength test specimens are taken out for each age, when installing a thermometer in the strength test section, it is preferable to install it on the strength test specimen with the latest timing of being taken out from the storage container.

[0036] Note that the restrained test specimen includes concrete and a restraining steel material, and the restraining steel material has different specific heat, thermal conductivity, and heat capacity compared to concrete. On the other hand, the unrestrained test specimen does not include a restraining steel material. Therefore, from the perspective of accurately measuring the temperature of concrete, it is more preferable to install a thermometer on the unrestrained test specimen than on the restrained test specimen.

[0037] Furthermore, as described above, when obtaining the autogenous shrinkage strain of the unrestrained test specimen, it is calculated from the value of the thermal strain generated in the unrestrained test specimen. Therefore, from the perspective of improving this accuracy, it is more preferable that a thermometer is installed on the unrestrained test specimen. Furthermore, as described above, from the perspective of measuring the adiabatic test for the unrestrained test specimen taken out from the storage container in order to measure the coefficient of thermal expansion, it is more preferable that at least a thermometer is attached to the unrestrained test section.

[0038] The restrained test specimen and the unrestrained test specimen installed in the storage container are given a temperature history caused by the heat generation due to the hydration reaction of a plurality of strength test specimens installed in the same container. For example, when a thermometer is installed on the restrained test specimen or the unrestrained test specimen, the mode of temperature change for each age can be obtained. Therefore, by performing inverse analysis on the relationship between the age and the measured value of the thermometer attached to the restrained test specimen or the unrestrained test specimen, the adiabatic temperature rise characteristic of the concrete to be measured can be obtained. Information regarding the adiabatic temperature rise characteristic of the concrete can be used when evaluating the temperature cracking risk in a 3D-FEM analysis when constructing an actual structure using the concrete.

Advantages of the Invention

[0039] According to the evaluation device of the present invention, while using concrete of the same material as the concrete used on site, physical property values of various concretes can be obtained by a simple method.

Brief Description of the Drawings

[0040]

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MODE FOR CARRYING OUT THE INVENTION

[0041] The evaluation device according to the present invention is a device for evaluating the characteristics of concrete to be measured. Specifically, it is used in a state where a plurality of test specimens in which concrete to be measured is driven into a predetermined region are housed inside.

[0042] Hereinafter, embodiments of the evaluation apparatus and its usage method according to the present invention will be described with reference to the drawings as appropriate. However, the following drawings are schematically shown, and the dimensional ratios on the drawings do not match the actual dimensional ratios. Also, the dimensional ratios do not necessarily match among the respective drawings.

[0043] [Configuration of the Evaluation Apparatus] FIG. 1 is a perspective view schematically showing the appearance of the evaluation apparatus. The evaluation apparatus 1 includes a lid portion 2 and a storage container 3. Both the lid portion 2 and the storage container 3 are made of a heat insulating material, for example, formed of expanded polystyrene. The lid portion 2 is detachable from the storage container 3.

[0044] In the following description, the X - Y - Z coordinate system shown in FIG. 1 is referred to. Also, in the following description, when distinguishing positive and negative directions when expressing a direction, it is described with positive and negative signs, such as “+Z direction” and “-Z direction”. When expressing a direction without distinguishing positive and negative directions, it is simply described as “Z direction”. That is, in this specification, when simply described as “Z direction”, both “+Z direction” and “-Z direction” are included. Typically, the +Z direction is the vertically upward direction.

[0045] FIG. 2 is a schematic cross - sectional view when the evaluation apparatus 1 shown in FIG. 1 is cut along the X - Z plane at a position of a predetermined Y coordinate. FIG. 3 is a schematic plan view when the lid portion 2 is removed from the evaluation apparatus 1 shown in FIG. 1 and the evaluation apparatus 1 is viewed from the +Z side in the -Z direction.

[0046] As shown in FIGS. 2 to 3, the storage container 3 has a bottom portion 3b installed at a position facing the lid portion 2 in the Z direction, and side portions 3a that cover the upper part of the bottom portion 3b from all four sides. Inside the region surrounded by the side portions 3a and the bottom portion 3b, each test body (10, 20, 30) is installed.

[0047] The evaluation device 1 is used with the strength test specimens 10, the unrestrained test specimens 20, and the restrained test specimens 30 installed in the storage container 3. As shown in FIGS. 2 to 3, in the evaluation device 1 of the present embodiment, a plurality of strength test specimens 10 are installed closer to the lid portion 2 than the unrestrained test specimens 20 and the restrained test specimens 30. FIG. 3 illustrates an example in which 30 strength test specimens 10 are installed in the evaluation device 1.

[0048] FIG. 4 is a schematic plan view when a plurality of strength test specimens 10 are removed from the state of FIG. 2 and the evaluation device 1 is viewed from the +Z side in the -Z direction. As shown in FIGS. 2 and 4, in the evaluation device 1 of the present embodiment, the unrestrained test specimens 20 and the restrained test specimens 30 are located on the bottom portion 3b side and are arranged along the surface (X-Y plane) of the bottom portion 3b. FIG. 4 illustrates an example in which two unrestrained test specimens 20 and two restrained test specimens 30 are installed in the evaluation device 1.

[0049] FIG. 5 is a perspective view schematically showing the configuration of the strength test specimen 10. The strength test specimen 10 has, for example, a cylindrical cylinder 11 made of tinplate or plastic, and is formed by driving the concrete to be measured into the internal space 12 of the cylinder 11. The dimensions of the cylinder 11 are arbitrary. As an example, the diameter is 10 cm and the height is 20 cm. FIG. 3 shows a state in which 30 strength test specimens 10 in which the same material of concrete to be measured is driven into the internal space 12 of the cylinders 11 of the same dimensions are installed in the storage container 3. The cylinder 11 corresponds to the "first cylinder".

[0050] As shown in FIGS. 2 to 3, between the plurality of strength test specimens 10, for the purpose of ensuring the heat insulation of the internal space 12 of the cylinder 11, a heat-insulating filler 6 made of expanded beads, expanded polystyrene molded into the shape of the internal space 12, spray-type urethane foam, rock wool, glass wool, etc. is filled.

[0051] FIG. 6 is a plan view schematically showing the configuration of the unrestrained specimen 20. The unrestrained specimen 20 has a bottomed rectangular frame 21 made of wood or plywood. In the internal space 23 of the frame 21, a first strain sensor 25 is installed. Then, the concrete to be measured is driven into the internal space 23 of the frame 21 so as to embed the first strain sensor 25, thereby forming the unrestrained specimen 20. As the first strain sensor 25, for example, an embedded strain gauge can be used. The frame 21 corresponds to the "first rectangular frame body".

[0052] The dimensions of the frame 21 are arbitrary. As an example, it has a rectangular parallelepiped shape of 10 cm × 10 cm × 80 cm.

[0053] From the viewpoint of suppressing the deformation of the concrete by the frame 21, a buffer board made of polystyrene or the like may be attached to the side surface in the longitudinal direction of the frame 21, and a buffer film made of polyester or the like may be attached to the side surface and the bottom surface in the short direction.

[0054] In the example of FIG. 6, a signal line 27 is attached to the first strain sensor 25, and the measured value of the first strain sensor 25 is configured to be continuously or intermittently readable. However, as long as the measured value of the first strain sensor 25 can be continuously or intermittently read, it is not limited to a wired connection and may be a wireless connection.

[0055] The first strain sensor 25 is preferably composed of an embedded strain gauge equipped with a temperature measurement function. If the first strain sensor 25 does not have a temperature measurement function, a thermocouple (not shown) may be mounted on the frame 21 so that the temperature of the unrestrained specimen 20 can be measured.

[0056] FIG. 7 is a plan view schematically showing the configuration of the restrained specimen 30. The restrained specimen 30 is formed into a bottomed rectangular frame by a pair of side plates 31 arranged opposite to each other in the short direction, a pair of end plates 32 arranged opposite to each other in the long direction, and a bottom plate (not shown). This frame corresponds to the "second rectangular frame body".

[0057] The pair of end plates 32 are fixedly connected by the restraint steel 34. The end plate 32 and the restraint steel 34 are fixed, for example, by welding. The side plate 31 and the bottom plate are made of, for example, wood or plywood. Further, the end plate 32 and the restraint steel 34 are made of a steel material with an extremely low coefficient of thermal expansion of less than 1×10 -6 / °C. As a specific example, the end plate 32 and the restraint steel 34 are made of invar steel, tungsten, etc., and preferably invar steel.

[0058] In the restraint test body 30, the steel ratio of the restraint steel 34 is preferably 0.5% to 6%. Here, the steel ratio of the restraint steel 34 can be the value of the ratio of the cross-sectional area of the restraint steel 34 to the area of the end plate 32.

[0059] A second strain sensor 35 is installed on the restraint steel 34. As the second strain sensor 35, for example, a strain gauge can be used. Also, in the example of FIG. 7, a thermometer 36 made of a thermocouple is attached to the restraint steel 34. However, whether the restraint test body 30 has the thermometer 36 is optional.

[0060] The outer dimensions of the bottomed frame body formed by the side plate 31, the end plate 32, and the bottom plate are arbitrary. For example, it has a rectangular parallelepiped shape of 10 cm × 10 cm × 80 cm. The restraint test body 30 is formed by pouring the concrete to be measured into the internal space 33 of this bottomed frame body so as to embed the restraint steel 34.

[0061] It is also possible that a buffer film made of polyester or the like is attached to the side plate 31 and the bottom plate. The end plate 32 is provided for the purpose of receiving the expansion force by the end plate 32 and accurately measuring the expansion stress when the concrete expands due to heat generation at the initial time after the concrete is poured.

[0062] In the example of FIG. 7, a signal line 37 is attached to the second strain sensor 35, and the measured value of the second strain sensor 35 is configured to be continuously or intermittently readable. However, as long as the measured value of the second strain sensor 35 can be continuously or intermittently read, it is not limited to a wired connection and may be a wireless connection. Note that the temperature information measured by the thermometer 36 may also be configured to be continuously or intermittently readable in the same manner as the measured value of the second strain sensor 35.

[0063] As described above, in the state before the concrete is placed, the evaluation device 1 has, inside the storage container 3 that forms a heat-insulating storage container, a plurality of cylindrical bodies 11, a frame body 21 in which the first strain sensor 25 is installed in the internal space 23, and a frame body (31, 32) in which a restraint steel material 34 to which the second strain sensor 35 is attached is fixed in the internal space 33.

[0064] The cylindrical body 11 constitutes a strength test section, and when the concrete to be evaluated is placed in the internal space 12 of the cylindrical body 11, a strength test specimen 10 is formed. The frame body 21 and the first strain sensor 25 constitute an unconstrained test section, and when the concrete to be evaluated is placed in the internal space 23 of the frame body 21, an unconstrained test specimen 20 is formed. The frame body (31, 32), the restraint steel material 34, and the second strain sensor 35 constitute a constrained test section, and when the concrete to be evaluated is placed in the internal space 33 of the frame body (31, 32), a constrained test specimen 30 is formed.

[0065] In FIG. 4, the unconstrained specimen 20 and the constrained specimen 30 are arranged in the X-Y plane direction, and are illustrated so as to substantially close the internal space surrounded by the side surface of the storage container 3. The outer dimensions of the storage container 3 may be appropriately set according to the outer dimensions of the frame body 21 constituting the unconstrained specimen 20 and the outer dimensions of the frame bodies (31, 32) constituting the constrained specimen 30. However, when the unconstrained specimen 20 and the constrained specimen 30 are arranged without a gap in the X-Y plane direction, if a gap is generated between the side portion 3a of the storage container 3 and each specimen (20, 30), the gap may be filled with a heat-insulating filler 6.

[0066] [Method of Using the Evaluation Apparatus] When using the evaluation apparatus 1, each specimen (strength test specimen 10, unconstrained test specimen 20, constrained test specimen 30) formed by driving the concrete to be evaluated into each test section is installed in the inner space of the storage container 3 of the evaluation apparatus 1. Then, the lid portion 2 is arranged so as to cover the upper part of the storage container 3.

[0067] More specifically, the unconstrained specimen 20 and the constrained specimen 30 are installed on the surface of the bottom portion 3b. Then, a plurality of strength test specimens 10 are arranged along the X-Y plane direction on the upper surfaces of these specimens (20, 30). The unconstrained specimen 20 and the constrained specimen 30 may have a buffer film made of, for example, polyester attached to the open surface on the +Z side.

[0068] After each specimen (10, 20, 30) is installed in the evaluation apparatus 1, every time a predetermined age timing arrives, the strength test specimen 10 is taken out. After the strength test specimen 10 is taken out, it is preferable to install a heat-insulating filler 6 in the storage container 3 so as to fill the gap generated by taking out the strength test specimen 10.

[0069] For example, every time the material ages of 1 day, 3 days, 7 days, 14 days, and 28 days have passed, the strength test specimen 10 is taken out from the storage container. By performing a Young's modulus measurement test using the taken-out strength test specimens 10 of each material age, the relationship between the Young's modulus and the material age of the concrete to be measured can be obtained (see, for example, FIG. 8). Note that the Young's modulus measurement test can be performed, for example, by a method conforming to JIS A 1149:2017 "Test Method for Static Elastic Modulus of Concrete".

[0070] As described above, at least one of the unconstrained test specimen 20 and the constrained test specimen 30 installed in the storage container 3 is equipped with a temperature measurement function (thermometer). Since the internal space of the storage container 3 is covered with a heat insulating member, for example, the temperature history read from the first strain sensor 25 composed of an embedded type strain gauge equipped with a temperature measurement function and mounted on the unconstrained test specimen 20 can be regarded as the temperature history inside the storage container 3. Also, for example, the temperature history read from the thermometer 36 mounted on the constrained test specimen 30 can be regarded as the temperature history inside the storage container 3. As another example, a separate thermometer may be installed in the storage container 3, and in this case, the temperature history read from the thermometer can be regarded as the temperature history inside the storage container 3.

[0071] That is, according to the evaluation device 1, information regarding the temperature history inside the storage container 3 can be obtained. Based on this information regarding the temperature history, the relationship between the installation period (actual material age) of the test specimen installed in the storage container 3 and the effective material age can be obtained. As an example, based on the Arrhenius law of the following formula (1) defined in the cracking control guideline of mass concrete, the effective material age t e is calculated.

[0072]

Equation

[0073] Note that in the formula (1), △t i refers to the period (days) during which the temperature of a predetermined concrete continues, and T(△t i ) is △ti Refers to the temperature (°C) of the concrete that continues over a period.

[0074] As an example, concrete containing the materials shown in Table 1 below in the proportions shown in Table 2 was placed in each test section as the concrete to be evaluated, and specimens (10, 20, 30) were produced and installed in the evaluation apparatus 1.

[0075]

Table 1

[0076]

Table 2

[0077] Using the concrete of Example 1, each specimen was installed in the evaluation apparatus 1, and based on the temperature history measured by the thermometer, the relationship between the age (installation period) and the effective age in the evaluation apparatus 1 was obtained. Then, for the strength specimen 10 taken out from the storage container 3 every time a predetermined age arrived, a Young's modulus measurement test was conducted to obtain the correlation between the measured Young's modulus and the effective age. Fig. 9 shows the correlation between the Young's modulus and the effective age.

[0078] The Young's modulus measurement test and the compressive strength test can be carried out in parallel. Therefore, by conducting the compressive strength test on the strength specimen 10 taken out for each age, the relationship between the compressive strength and the age of the concrete to be measured can be obtained. The compressive strength test is carried out, for example, in accordance with the method specified in JIS A 1108:2018 "Method of Test for Compressive Strength of Concrete". Furthermore, since the relationship between the age and the effective age can be obtained as described above, the relationship between the compressive strength and the effective age can be obtained. Fig. 10 is a graph showing the correlation between the compressive strength and the effective age measured using the concrete of Example 1. Also, based on the results shown in Figs. 9 and 10, the correlation between the Young's modulus and the compressive strength may be derived. Fig. 11 is a graph showing the correlation between the compressive strength and the Young's modulus measured using the concrete of Example 1.

[0079] It is also possible to take out the strength test specimens 10 from the storage container 3 at the same age as the age at which the compressive strength test is performed, and perform the splitting tensile strength test using the strength test specimens 10 of each age. In this case, from the viewpoint of performing the splitting tensile strength test and the Young's modulus measurement test (and the compressive strength test) on the strength test specimens 10 of the same age, it is preferable to install in the evaluation apparatus 1 a number of strength test specimens 10 that is at least twice the number of types of ages for which the tests are to be performed.

[0080] The splitting tensile strength test is performed, for example, by a method conforming to JIS A 1113:2018 "Method for Testing Splitting Tensile Strength of Concrete". As described above, since the relationship between the age and the effective age can be obtained, the relationship between the splitting tensile strength and the effective age can be obtained.

[0081] Therefore, by comparing the compressive strength and the splitting tensile strength at the same effective age, the relationship between the compressive strength and the splitting tensile strength can also be obtained. FIG. 12 shows the correlation between the compressive strength and the splitting tensile strength measured using the concrete of Example 1.

[0082] The storage container 3 is maintained in a heat-insulated state, and a plurality of test specimens (10, 20, 30) are arranged inside. Since these test specimens (10, 20, 30) generate heat as the age elapses and the hydration reaction progresses, the temperature inside the storage container 3 rises due to this heat generation. Then, when the progress of the hydration reaction reaches a saturated state, the rate of temperature rise inside the storage container 3 is alleviated, and after a further period elapses, it drops to a temperature equivalent to the outside air temperature. That is, the unrestrained test specimen 20 and the restrained test specimen 30 are placed under the same temperature history inside the heat-insulating storage container 3.

[0083] The change over time of the strain value read from the first strain sensor 25 mounted on the unrestrained specimen 20 corresponds to the change over time of the unrestrained strain of the concrete to be measured under the state placed in the above temperature history. The change over time of the strain value read from the second strain sensor 35 mounted on the restrained specimen 30 corresponds to the change over time of the strain under restraint of the concrete to be measured placed in the above temperature history. FIG. 13 is a graph schematically showing the change pattern of the measured value of the first strain sensor 25 and the change pattern of the measured value of the second strain sensor 35. Further, FIG. 14 is a graph showing the change pattern of the measured value S1 of the first strain sensor 25 mounted on the unrestrained specimen 20 using the concrete of Example 1 and the change pattern of the measured value S2 of the second strain sensor 35 mounted on the restrained specimen 30 using the concrete of Example 1.

[0084] The measured value S1 of the first strain sensor 25 corresponds to the value of the free strain in which the strain associated with the above temperature history and the autogenous shrinkage strain are reflected. On the other hand, the measured value S2 of the second strain sensor 35 corresponds to the value of the strain in the restrained state in which the strain associated with the temperature history and the autogenous shrinkage strain are reflected. Therefore, by calculating the difference value S3 between the measured value S1 of the first strain sensor 25 and the measured value S2 of the second strain sensor 35, the change over time of the restrained strain ε s of the concrete to be measured can be obtained.

[0085] In addition, the restraining stress can be obtained from the force balance relationship between the restraining steel 34 and the concrete placed in the restrained specimen 30. For example, the restraining stress F can be calculated by the following equation (2). In equation (2), E s corresponds to the Young's modulus of the restraining steel 34, p corresponds to the steel ratio of the restraining steel 34 in the restrained specimen 30, and s2 corresponds to the measured value of the second strain sensor 35 mounted on the restrained specimen 30. In equation (2), the tensile stress is expressed as a positive value and the compressive stress is expressed as a negative value. F = -E s ·p·s2…(2)

[0086] For example, by performing the operation of the above formula (2), it is possible to obtain the time-dependent change pattern of the restraint stress F in the concrete placed in the restraint test body 30. FIG. 15 is a graph schematically showing the change pattern of the restraint stress F.

[0087] A correlation is recognized between the change pattern of the restraint stress F obtained in this way and the change pattern of the restraint strain ε s FIG. 16 is a graph schematically showing the correlation between the restraint stress and the restraint strain.

[0088] As schematically shown in FIG. 16, the restraint stress and the restraint strain show a substantially linear correlation at the time of temperature rise (curve Eca1) and at the time of temperature drop (curve Eca2), respectively. Therefore, by linearly approximating each correlation relationship based on, for example, the least squares method and deriving its slope, the apparent Young's modulus of the concrete to be measured at the time of temperature rise and at the time of temperature drop can be obtained. This apparent Young's modulus can be regarded as a Young's modulus considering both the elastic strain and the creep strain due to the time-varying restraint stress.

[0089] FIG. 17 is a graph showing the correlation between the restraint stress and the restraint strain calculated based on the results shown in FIG. 14. In the case of the results in FIG. 17, the apparent Young's modulus of the concrete to be measured at the time of temperature rise is 4.8 kN / mm 2 and the apparent Young's modulus of the concrete to be measured at the time of temperature drop is 29.4 kN / mm 2 are obtained respectively.

[0090] On the other hand, as described above with reference to FIG. 9, by performing a Young's modulus measurement test on the strength test specimens 10 taken out from the evaluation device 1 for each age, the change over time in the Young's modulus of the concrete to be measured can be obtained. Based on the ratio of this measured Young's modulus to the apparent Young's modulus derived by calculation using the above method, the reduction coefficient of the Young's modulus of the concrete to be measured can be determined. FIG. 18 is a graph showing the relationship between the reduction coefficient of the Young's modulus calculated by the above calculation and the effective age. In practice, the average value of the reduction coefficient of the Young's modulus over the heating period can be used as the reduction coefficient of the Young's modulus of the concrete to be measured during heating. Similarly, the average value of the reduction coefficient of the Young's modulus over the cooling period can be used as the reduction coefficient of the Young's modulus of the concrete to be measured during cooling. In the example of FIG. 18, the reduction coefficient of the Young's modulus of the concrete to be measured during heating can be determined to be 0.28 and during cooling to be 1.00, respectively.

[0091] Also, after a period during which the hydration reaction is considered to have sufficiently progressed, the unconstrained specimen 20 may be taken out of the storage container 3 and a separate heat insulation test may be performed. The timing for taking out the unconstrained specimen 20 is set to the timing when the temperature of the storage container 3 has decreased until the indicated value of the thermometer installed in the storage container 3 and the temperature of the atmosphere in which the storage container 3 is installed are approximately the same. For example, it can be the timing when 25 days or more have elapsed.

[0092] The unconstrained specimen 20 is installed in a thermostatic bath programmed to generate a temperature history set within a range of, for example, 20°C to 60°C, and the correlation between the measured value of the first strain sensor 25 attached to the unconstrained specimen 20 and the temperature is obtained.

[0093] An example of the temperature history is as follows. 20 °C (held for 3 hours) → temperature increase at 5 °C / h → 30 °C (held for 3 hours) → temperature increase at 5 °C / h → 40 °C (held for 3 hours) → temperature increase at 4 °C / h → 50 °C (held for 3 hours) → temperature increase at 5 °C / h → 60 °C (held for 3 hours) → temperature decrease at 5 °C / h → 50 °C (held for 3 hours) → temperature decrease at 5 °C / h → 40 °C (held for 3 hours) → temperature decrease at 5 °C / h → 30 °C (held for 3 hours) → temperature decrease at 5 °C / h → 20 °C (held for 3 hours)

[0094] The above temperature increase and decrease are regarded as one cycle. For example, a temperature change of 2 cycles is applied to the unrestrained specimen 20. Then, under the above temperature history, at each time zone where the temperature is held (for example, 20 °C, 30 °C, 40 °C, 50 °C, 60 °C), the measured value of the first strain sensor 25 is read when the indicated value of the thermometer mounted on the unrestrained specimen 20 becomes stable.

[0095] Figure 19 is a graph showing the relationship between the measured value of the first strain sensor 25 and the temperature when the above-mentioned heat insulation test was carried out on the unrestrained specimen 20 using the concrete of Example 1.

[0096] As described above, this heat insulation test was carried out on the unrestrained specimen 20 after a period during which the hydration reaction was considered to have sufficiently progressed. Therefore, even if a temperature change is applied to the unrestrained specimen 20 in the heat insulation test, it is considered that no additional autogenous shrinkage strain due to the hydration reaction occurs in the concrete cast into the unrestrained specimen 20. Thus, it can be said that the correlation between the measured value of the first strain sensor 25 and the temperature shown in Figure 19 is information reflecting the temperature strain of the concrete cast into the unrestrained specimen 20. As shown in Figure 19, since the temperature and the measured value of the first strain sensor 25 show a nearly linear correlation, for example, by linearly approximating the two based on the least squares method and deriving its slope, the coefficient of thermal expansion of the concrete cast into the unrestrained specimen 20, that is, the concrete to be measured, can be obtained.

[0097] The measured value S1 of the first strain sensor 25 of the unrestrained test specimen 20, measured in the state of being installed in the containment vessel 3 (see FIGS. 13 to 14), is a value reflecting the thermal strain and the autogenous shrinkage strain based on the temperature history in the containment vessel 3. As described above at the location where the effective age is derived, according to the evaluation device 1, information regarding the temperature history in the containment vessel 3 can be obtained. Therefore, by multiplying the temperature change value due to the temperature history by the coefficient of thermal expansion of the concrete to be measured, the value of the thermal strain of the concrete to be measured based on the temperature history in the containment vessel 3 can be obtained. By subtracting this value of the thermal strain from the measured value S1 of the first strain sensor 25 of the unrestrained test specimen 20, measured in the state of being installed in the containment vessel 3, the time-dependent change pattern of the autogenous shrinkage strain of the unrestrained test specimen 20, that is, the time-dependent change pattern of the autogenous shrinkage strain of the concrete to be measured can be obtained.

[0098] And as described above, based on the temperature change in the containment vessel 3, the correlation between the age and the effective age of the material in the containment vessel 3 has been obtained. Therefore, the correlation between the autogenous shrinkage strain of the concrete to be measured and the effective age of the concrete can be obtained. FIG. 20 is a graph showing the correlation between the autogenous shrinkage strain and the effective age of the concrete of Example 1, derived based on the results shown in FIGS. 14 and 19. The information regarding the correlation between the effective age and the autogenous shrinkage strain of the concrete obtained by the above method can be used when evaluating the temperature cracking risk in the case of constructing an actual structure using the concrete by 3D-FEM analysis.

[0099] Furthermore, as described above, since the temperature change in the containment vessel 3 has been obtained, for example, as schematically shown in FIG. 21, the relationship Ta between the age of the concrete to be measured and the amount of temperature rise can be obtained. Therefore, by performing inverse analysis of this relationship Ta, the adiabatic temperature rise characteristic Tb of the concrete to be measured, as schematically shown in FIG. 22, can be obtained.

[0100] As described above, according to the evaluation device 1 of the present invention, various physical property values related to the concrete to be measured can be directly obtained, and by performing arithmetic processing using the obtained physical property values, more physical property values can be obtained. By performing numerical analysis using the many physical property values thus obtained, it is possible to accurately evaluate the risk of thermal cracking of the structure (mass concrete) using the concrete to be measured.

[0101] [Alternative Embodiment] Hereinafter, an alternative embodiment will be described.

[0102] 〈1〉 In the above embodiment, every time a predetermined age timing arrives, the lid portion 2 is opened and the strength test specimen 10 is taken out upward. However, the direction of taking out the strength test specimen 10 is not limited to upward. For example, the position of the lid portion 2 may be set to the side, and the strength test specimen 10 may be taken out from the side.

[0103] 〈2〉 In the storage container 3, a number of strength test specimens 10 that is larger than the number of specimens to be taken out for each age and subjected to the above tests may be installed. The extra strength test specimens 10 installed are used for the purpose of causing a hydration reaction in the storage container 3 and raising the temperature in the storage container 3.

[0104] 〈3〉 When a plurality of restraint test specimens 30 are installed in the storage container 3, the average value of the restraint stress for each restraint test specimen 30, derived based on the measured values of the second strain sensors 35 mounted on each restraint test specimen 30, may be used as the restraint stress F.

[0105] Furthermore, in the above, the steel ratios of the restraint steel materials 34 mounted on each restraint test specimen 30 may be made different from each other. In this case, when calculating the restraint stress F, it is derived based on the measured values of the second strain sensors 35 mounted on each restraint test specimen 30 and the steel ratio of the restraint steel material 34 mounted on the corresponding restraint test specimen 30. And the average value of the restraint stress for each restraint test specimen 30 derived in this way may be used as the restraint stress F.

[0106] 〈4〉The number of unrestrained test specimens 20 installed in the accommodation container 3 may be one. Similarly, the number of restrained test specimens 30 installed in the accommodation container 3 may be one.

[0107] 〈5〉The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described. The scope of the present invention is indicated by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

Explanation of Reference Numerals

[0108] 1: Evaluation device 2: Lid part 3: Accommodation container 3a: Side part of the accommodation container 3b: Bottom part of the accommodation container 6: Filling material 10: Strength test specimen 11: Cylindrical body 12: Internal space 20: Unrestrained test specimen 21: Frame body 23: Internal space 25: First strain sensor 27: Signal line 30: Restrained test specimen 31: Side plate 32: End plate 33: Internal space 34: Restraining steel material 35: Second strain sensor 36: Thermometer 37: Signal line

Claims

1. An evaluation device for evaluating the properties of concrete to be measured, comprising: A strength test section including a plurality of first cylindrical bodies into which the concrete can be placed; An unrestrained test section including a bottomed first rectangular frame body into which the concrete can be placed; A restrained test section including a bottomed second rectangular frame body into which the concrete can be placed, and both ends in the longitudinal direction of the second rectangular frame body being restrained by restraint steel materials having a coefficient of thermal expansion of less than 1×10 -6 / °C; A heat-insulating container that covers the strength test section, the unrestrained test section, and the unrestrained test section; And a thermometer capable of measuring temperature changes in the container, The unrestrained test section has a first strain sensor installed inside the first rectangular frame body, The restrained test section has a second strain sensor installed on the restraint steel material. The evaluation device is characterized by this.

2. The container is made of a heat-insulating material and has a removable lid, The strength test section is located closer to the lid than the unrestrained test section and the restrained test section. The evaluation device according to claim 1 is characterized by this.

3. The container has a bottom installed at a position facing the lid and side portions covering the bottom on four sides, The unrestrained test section and the restrained test section are arranged in a direction along the bottom, The plurality of first cylindrical bodies included in the strength test section are arranged in a direction along the bottom in a state of being placed directly above the first rectangular frame body included in the unrestrained test section and the second rectangular frame body included in the restrained test section. The evaluation device according to claim 2 is characterized by this.

4. The strength test section includes a number of the first cylindrical bodies that is two or more times the number of types of target material ages for the strength test of the concrete. The evaluation device according to claim 1 or 2 is characterized by this.

5. The evaluation apparatus according to claim 1 or 2, further comprising a heat insulating filler filled in a space between the plurality of first cylindrical bodies.

6. The evaluation apparatus according to claim 1 or 2, wherein the thermometer is attached to the unconstrained test section.

7. A method for evaluating the properties of concrete, using the evaluation apparatus according to claim 1, comprising: Step (a) of installing, in the storage container, an unconstrained test specimen obtained by placing the concrete in the first rectangular frame body, a constrained test specimen obtained by placing the concrete in the second rectangular frame body, and a plurality of strength test specimens obtained by placing the concrete in the plurality of first cylindrical bodies; Step (b) of, every time a predetermined age timing arrives, taking out a target age strength test specimen belonging to the plurality of strength test specimens from the storage container, performing a Young's modulus measurement test on the target age strength test specimen, and calculating a change pattern over time of the Young's modulus of the concrete; Step (c) of calculating a change pattern over time of the restrained strain value of the concrete based on a first strain value that is a measured value of the first strain sensor of the unconstrained test section in a state where the unconstrained test section is installed in the storage container and a second strain value that is a measured value of the second strain sensor of the constrained test section in a state where the constrained test section is installed in the storage container; Step (d) of calculating a change pattern over time of the restrained stress of the concrete based on a steel ratio that is a ratio of the restrained steel in the constrained test specimen, a Young's modulus of the restrained steel, and the second strain value; Step (e) of calculating an apparent Young's modulus at each of the time of temperature rise and the time of temperature drop based on a correlation between the restrained strain value and the restrained stress; A method for evaluating the properties of concrete, comprising step (f) of deriving a reduction coefficient of the Young's modulus at each of the time of temperature rise and the time of temperature drop based on a ratio between the Young's modulus obtained in step (b) and the apparent Young's modulus obtained in step (e).

8. Step (g) of calculating the effective age of the target age strength test specimen at the age timing based on the temperature history in the storage container by the thermometer; The method for evaluating the properties of concrete according to claim 7, further comprising step (h) of obtaining the correspondence between the age of the concrete corresponding to the age timing and the effective age obtained by step (g).

9. Step (i) of performing a compressive strength test on the target age strength test specimen to obtain the change pattern of the compressive strength of the concrete over time; The method for evaluating the properties of concrete according to claim 8, further comprising step (j) of obtaining the relationship between the effective age and the compressive strength of the concrete based on the results of step (h) and step (i).

10. The method for evaluating the properties of concrete according to claim 9, further comprising step (k) of obtaining the relationship between the compressive strength and the Young's modulus of the concrete based on the results of step (b) and step (i).

11. Step (l) of performing a splitting tensile strength test on the target age strength test specimen to obtain the change pattern of the splitting tensile strength of the concrete over time; The method for evaluating the properties of concrete according to claim 9, further comprising step (m) of obtaining the relationship between the compressive strength and the splitting tensile strength of the concrete based on the results of step (i) and step (l).

12. After 25 days or more have elapsed since step (a), taking out the unrestrained test specimen from the storage container, applying a temperature change in a heat-insulated environment, and obtaining the coefficient of thermal expansion of the concrete from the relationship between the temperature and the measured value of the first strain sensor; A step (o) of calculating a time-dependent change pattern of the autogenous shrinkage strain of the concrete based on a change pattern of temperature strain obtained by multiplying the time-dependent change pattern of the temperature measured by the thermometer by the coefficient of thermal expansion and a change pattern of the first strain value obtained in the step (c). The method for evaluating the properties of concrete according to claim 8, further comprising a step (p) of obtaining a relationship between the effective age of the concrete and the autogenous shrinkage strain based on the results of the step (g) and the step (o).

13. The thermometer is attached to at least one of the unrestrained test section and the restrained test section. The method for evaluating the properties of concrete according to claim 7, further comprising a step (q) of obtaining the adiabatic temperature rise characteristics of the concrete by inverse analysis of the relationship between the age of the concrete and the measured value of the thermometer.

14. The storage container is made of a heat insulating material and has a removable lid. The strength test section is located closer to the lid than the unrestrained test section and the restrained test section. The step (b) includes, every time the age timing arrives, opening the lid, taking out the target age strength test specimen from the storage container, and installing an amount of heat-insulating filling material corresponding to the occupied area of the taken-out target age strength test specimen into the storage container. The method for evaluating the properties of concrete according to claim 7 is characterized by this.

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