JP7412325B2 - Test method for mechanical properties of cementitious hardened bodies - Google Patents

Description

The present invention relates to a method for testing the mechanical properties of hardened cementitious materials.

For the purpose of evaluating the safety of concrete structures used in areas exposed to high-temperature outside air, and for the purpose of evaluating the fire resistance performance of concrete structures, research is conducted on the mechanical properties of hardened cementitious materials in high-temperature environments. Tests may be conducted.
Patent Document 1 describes a concrete test specimen loading heating device for precisely evaluating the high-temperature properties of concrete, in which a concrete test specimen with embedded thermocouples is subjected to vertical application in order to obtain a sample for evaluating the high-temperature properties of concrete. In the concrete test specimen loading and heating device, which is held in a pressing jig and housed inside a heating furnace, and heated at high temperature inside the heating furnace to analyze the temperature distribution state of the concrete specimen, the upper and lower pressurizing jigs are A heating medium that surrounds each of the tools and indirectly heats the concrete test specimen from a pressurizing jig, and a heating medium that surrounds the central concrete test specimen and directly heats the concrete test specimen are installed inside the heating furnace. A concrete specimen loading and heating device is described.

JP2009-168528A

When conducting various tests to evaluate the mechanical properties of hardened cementitious materials, the temperature of the specimen (hardened cementitious material) to be tested is maintained at a constant temperature from the start to the end of the test. There is a need to. However, particularly in the case of testing in a high temperature environment, there is a problem in that it is difficult to control the temperature of the specimen because the thermal conductivity of hardened cementitious bodies such as concrete is low.

The purpose of the present invention is to maintain the temperature of the test specimen (hardened cementitious material) at a constant temperature from the start to the end of various tests for evaluating the mechanical properties of hardened cementitious material. An object of the present invention is to provide a method for testing the mechanical properties of a hardened cementitious body, which can accurately evaluate the mechanical properties of a hardened cementitious body under a specific temperature (particularly at a high temperature).

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention discovered that when heating a cementitious hardened body through a space for indirect heating in a non-contact manner, a step of determining a first set temperature, which is a set temperature of a step of determining a set temperature; a step of heating the hardened cementitious body at the first set temperature using a first heating means; and a step of testing the mechanical properties of the hardened cementitious body after heating. and a step of measuring the mechanical properties of the hardened cementitious body using a mechanical property measuring means, and moving the hardened cementitious body to a second place using a second heating means. The present invention has been completed based on the discovery that the above object can be achieved by a method of heating at two set temperatures and maintaining the temperature of the hardened cementitious body at or near the target temperature in the measurement step.
That is, the present invention provides the following [1] to [7].
[1] A method for testing the mechanical properties of a hardened cementitious body at a target temperature, wherein the hardened cementitious body is placed through a space for indirect heating without contact. a first set temperature determining step of determining a first set temperature which is a set temperature when heating the first heating means; a second set temperature determination step of determining a second set temperature that is a set temperature during heating of the second heating means; a heating step of heating, a moving step of moving the cementitious hardened body that has been heated in the heating step to a place for testing mechanical properties, and a mechanical property test at the place for testing mechanical properties. a measuring step of measuring the mechanical properties of the hardened cementitious body using a characteristic measuring means, and heating the hardened cementitious body at the second set temperature using the second heating means. A method for testing the mechanical properties of a hardened cementitious body, characterized in that the temperature of the hardened cementitious body is maintained at or near the target temperature in the measuring step.

[2] The method for testing the mechanical properties of a hardened cementitious body according to the above [1], wherein the first heating means is a heating furnace disposed to accommodate the hardened cementitious body.
[3] The method for testing the mechanical properties of a cured cementitious body according to [1] or [2] above, wherein the second heating means is a sheet heater attached to the surface of the cured cementitious body.
[4] The method for testing the mechanical properties of a hardened cementitious material according to any one of [1] to [3], wherein the target temperature or a temperature near the target temperature is within a range of ±3° C. above the target temperature.

[5] The test method for the mechanical properties is a compressive strength test, and in the first set temperature determination step and the second set temperature determination step, the first set temperature is lower than the second set temperature. The method for testing the mechanical properties of a hardened cementitious material according to any one of [1] to [4] above, which determines a high value.
[6] The test method for the mechanical properties is a splitting crack initiation strength test, and in the first set temperature determination step and the second set temperature determination step, the first set temperature is changed to the second set temperature. The method for testing the mechanical properties of a hardened cementitious material according to any one of [1] to [4] above, which is determined to a value lower than the temperature.
[7] The test method for the mechanical properties is a notch bending strength test, and in the first set temperature determination step and the second set temperature determination step, the first set temperature is changed to the second set temperature. The method for testing the mechanical properties of a hardened cementitious material according to any one of [1] to [4] above, wherein the mechanical properties are determined to be a value equal to or lower than the temperature.

According to the method for testing the mechanical properties of hardened cementitious bodies of the present invention, the test specimen (hardened cementitious The temperature of the hardened cementitious body can be maintained at a constant temperature, and the mechanical properties of the hardened cementitious body at a specific temperature (particularly at a high temperature) can be accurately evaluated.

Side view of the specimen (а-2, a-3) and the state where the specimen was cut in the direction perpendicular to the axis of the specimen at the position of the A-A line in a-2 in the compressive strength test FIG. 3 is a sectional view (a-1) showing the. In the splitting crack initiation strength test, side view (b-1) and front view of the specimen installed in the compression testing machine (view from the top side of the cylindrical specimen installed in the compression testing machine: b -2). They are a side view (c-1), a top view (c-2) of the specimen, and a perspective view (c-3) of the specimen installed in a three-point bending test device in the notch bending test.

The method for testing the mechanical properties of a hardened cementitious material of the present invention is a method for testing the mechanical properties of a hardened cementitious material at a target temperature. a first set temperature determining step, which is the set temperature for heating of the first heating means disposed through a space for performing heating; a second set temperature determining step of determining a second set temperature that is a set temperature during heating of a second heating means disposed in contact with the hardened cementitious body; a heating step in which the hardened cementitious material is heated at a first set temperature using a heating method, a moving step in which the hardened cementitious material that has been heated in the heating step is moved to a location for testing mechanical properties, and a step for testing mechanical properties. a measuring step of measuring the mechanical properties of the hardened cementitious body using a mechanical property measuring means, and heating the hardened cementitious body at a second setting using a second heating means. In this method, the temperature of the hardened cementitious material is maintained at or near the target temperature during the measurement process.

Here, "cementitious hardened material" means a material formed by hardening a composition containing cement and water, such as a hardened material made of concrete, a hardened material made of mortar, and a hardened material made of cement paste. etc.
Furthermore, in this specification, "under high temperature" means an environment at a temperature higher than room temperature without heating (for example, the temperature in a laboratory; for example, 10 to 30° C.).
In addition, in this specification, the "target temperature" is a temperature determined as a target when testing the mechanical properties of a hardened cementitious material (particularly a test under high temperature), and is a temperature that is determined as a target when testing the mechanical properties of a hardened cementitious material (particularly a test under high temperature). , is an arbitrarily determined temperature. For example, the target temperature is a temperature arbitrarily determined within a temperature range of 20°C or higher, preferably 30 to 100°C, more preferably 35 to 90°C, particularly preferably 40 to 80°C. Furthermore, "the target temperature or a temperature in the vicinity thereof" is preferably a temperature within the range of ±3°C of the target temperature, more preferably within the range of ±2°C, particularly preferably within the range of ±1°C.
Each step will be explained in detail below.

[First set temperature determination process]
This step is a step of determining a first set temperature, which is a set temperature when heating a first heating means disposed through a space for performing non-contact indirect heating on the cementitious hardened body. It is.
The above-mentioned hardened cementitious body is the object of the test (the mechanical properties are measured in the measurement step described below) in the method for testing the mechanical properties of the hardened cementitious body of the present invention.
The first heating means is arranged such that there is a space between the heat generating part of the first heating means and the hardened cementitious body, and the said part is in direct contact with the hardened cementitious body. Any device may be used as long as it can indirectly heat the hardened cementitious material through the space without heating.
Specifically, heating furnaces, drying ovens, etc., which are arranged so that the hardened cementitious material can be accommodated through a space for indirectly heating the hardened cementitious material in a non-contact manner. can be mentioned.

[Second temperature setting process]
This step is a step of determining a second set temperature, which is a set temperature during heating of the second heating means disposed in contact with the hardened cementitious body in order to perform direct heating by contact.
In the present invention, in the measurement step (preferably all steps of the heating step, the moving step, and the measuring step), the second heating means are used.
The second heating means is disposed in contact with the hardened cementitious body to perform direct heating through contact.
The second heating means is not particularly limited as long as it can heat the hardened cementitious body while in contact with the hardened cementitious body, and examples thereof include a seat heater and the like. Seat heaters are plate-shaped and flexible, so even if the specimen has a curved surface (for example, a cylindrical specimen), it can be applied to a specific area of the surface (curved surface) of the hardened cementitious material. Can be installed.

The size of the area where the second heating means is in contact with the hardened cementitious material varies depending on the shape of the hardened cementitious material, but it must be large enough to heat the inside of the hardened cementitious material. Bye. The above-mentioned size is preferably 15% or more, more preferably 20% or more of the 100% surface area of the cementitious hardened body, from the viewpoint of being able to sufficiently heat the cementitious hardened body.
Further, when the hardened cementitious body is cylindrical or prismatic, the second heating means is preferably attached to a region including approximately the center portion of the side surface of the hardened cementitious body. This makes it possible to effectively heat the portions that are subjected to stress during testing.

There is no particular limitation on the timing of disposing the second heating means on the hardened cementitious body, but the point of view is that the temperature of the hardened cementitious body is maintained without becoming excessively low compared to the target temperature in a series of steps. Therefore, it is preferable to provide a second heating means to the hardened cementitious body before the heating step, during the heating step, or between the heating step and the moving step.
Further, it is preferable that the second heating means is heated in advance to a temperature near the second set temperature before being disposed.

[Heating process]
This step is a step of heating the cementitious hardened body using the first heating means at the first set temperature determined in the first set temperature determination step.
Further, the rate of temperature increase during heating (temperature increase per unit time) is preferably 2 to 5°C/hour, more preferably 3 to 4°C/hour.
If the temperature increase rate is 5° C./hour or less, damage to the hardened cementitious material due to cracking or the like can be prevented. If the temperature increase rate is 2° C./hour or more, the time required for heating can be shortened.
Moreover, when heating the cementitious cured body using the first heating means, it is preferable that the cementitious cured body is placed in a synthetic resin bag and sealed. Thereby, drying of the cementitious hardened body can be suppressed.

[Moving process]
This step is a step in which the hardened cementitious body that has been heated in the heating step is moved to a location for testing mechanical properties.
From the viewpoint of more accurately measuring the mechanical measurement of the hardened cementitious body at high temperatures, it is preferable that the temperature of the hardened cementitious body does not drop when moving the hardened cementitious body in this step. . Specifically, there is a method in which the cured cementitious material is placed in a synthetic resin bag and transported in a sealed state.

[Measurement process]
This step is a step of measuring the mechanical properties of the hardened cementitious material using a mechanical property measuring means at a location for testing the mechanical properties.
Mechanical property measuring means are instruments, machines, devices, etc. that are appropriately used in various tests for measuring the mechanical properties of hardened cementitious bodies.
Since the hardened cementitious body is heated at the second set temperature using the second heating means, the temperature of the hardened cementitious body is maintained at or near the target temperature in this step. .
In addition, in the measurement process, it is sufficient that the temperature of the cementitious hardened body is maintained at the target temperature or a temperature in the vicinity thereof. Heating of the cured body may be performed at any one or more points from the above-mentioned heating step to the measurement step (for example, after the movement step and before the measurement step).
In addition, in the measurement process, the temperature of the cementitious hardened body only needs to be maintained at or near the target temperature, so the set temperature of the second heating means in the measurement process is set lower than the second set temperature. Alternatively, the second heating means may not be used in the measurement step.

In addition, in the measurement process, the term "target temperature or a temperature near it" means that the temperature of the cementitious hardened body during the test completely matches the target temperature, which is the temperature indexed as the target during the test. This is because the numerical values have been given a wide range due to reasons such as the difficulty of
Further, the "target temperature or a temperature near it" is preferably a temperature within a range of ±3°C of the target temperature, more preferably within a range of ±2°C, particularly preferably within a range of ±1°C.
By measuring the mechanical properties of the hardened cementitious material within the above range, it is possible to more accurately evaluate the mechanical properties of the hardened cementitious material under a specific temperature.

The first set temperature in the first heating means and the second set temperature in the second heating means are set at the temperature of the cementitious hardened body in the measurement step (preferably all steps of the heating step, the moving step, and the measuring step). The temperature is determined to be maintained at or near the target temperature.
Hereinafter, an example of a method for determining the first set temperature and the second set temperature will be described.
For example, a cementitious hardened body (hereinafter also referred to as a "determining hardened body") for determining the first set temperature and the second set temperature may be prepared in advance and used as a substitute for the cementitious hardened body to be tested. Each step is carried out in the same manner as the heating step, moving step, and measuring step described above, except that the determining cured body is used, and in the measuring step (preferably all steps of the heating step, moving step, and measuring step). , a method for determining the first set temperature of the first heating means and the second set temperature of the second heating means such that the temperature of the determining cured body is maintained at or near the target temperature. Can be mentioned. In addition, when performing the above-mentioned heating process, moving process, and measuring process using the cured body for determination, since the first set temperature and the second set temperature have not yet been determined, the first set temperature and the second set temperature Instead, for example, after setting an arbitrary temperature within a range of ±8° C. of the target temperature, the temperature may be changed as appropriate based on the temperature of the determining cured body.
By determining the first set temperature and the second set temperature by the method described above, the mechanical properties of the hardened cementitious body can be measured more accurately at a specific temperature (especially at a high temperature).

As the hardened body for determination, the same thing (having the same manufacturing conditions and shape) as the cementitious hardened body to be tested is used. Moreover, a temperature measuring means is disposed in the determining cured body for the purpose of measuring the temperature of the determining cured body and determining whether the temperature is maintained at or near the target temperature.
The temperature measuring means disposed on the cured body for determination is not particularly limited as long as it can measure the change in temperature of the cured body for determination, and examples thereof include a thermocouple.
Moreover, from the viewpoint of accurately measuring the temperature of the cured body for determination, it is preferable that the temperature measuring means is embedded in the cured body for determination. The position where the temperature measuring means is embedded in the determining hardened body is preferably approximately at the vertical center of the installed determining hardened body when the determining hardened body is installed in the mechanical property measuring means. By embedding the temperature measuring means in the portion, the temperature of the cured body for determination can be measured more accurately.

Moreover, from the viewpoint of measuring the temperature of the determined cured body more accurately, it is preferable to use a plurality of temperature measuring means and take the average value of the plurality of obtained temperatures as the measured value. The number of temperature measuring means varies depending on the shape and size of the cured body for determination, but is preferably 2 or more, more preferably 2 to 8, particularly preferably 3 to 5.
Furthermore, from the viewpoint of being able to accurately grasp the temperature of the entire interior of the cured body for determination, a plurality of temperature measuring means are embedded in the cured body for determination, and the depth at which the plurality of temperature measuring means are buried ( The depth from the surface of the determining cured body to the temperature measuring means may be different.
For example, at a position near the surface of the cured body for determination, at the deepest position from the surface of the cured body for determination (approximately the central part of the cured body for determination), and at a position intermediate between the nearby position and the deepest position, Each temperature measuring means may be embedded.

In addition, when actually carrying out the test method for the desired type of mechanical properties, from the viewpoint of accurately measuring the temperature of the determinant cured body from the start to the end of the test, we have added the determination cure to the mechanical property measurement means. A plurality of temperature measuring means may be buried so as to be distributed and lined up in a direction perpendicular to the direction in which the mechanical characteristic means operates when the body is installed (for example, "b-" in FIG. 2). 1)). In particular, when the mechanical property test is a splitting crack initiation strength test or a notch bending strength test, the stress applied during the test increases in the part corresponding to the above-mentioned perpendicular direction, so a temperature measuring means is installed in that part. By embedding it and determining the first set temperature and the second set temperature, the mechanical properties of the determined cured body can be measured more accurately during the test.

Further, the first set temperature and the second set degree may be determined as appropriate depending on the target temperature, the type of testing method for the mechanical properties of the hardened cementitious body, the shape of the hardened cementitious body, and the like.
For example, from the viewpoint of setting the temperature of the cementitious hardened body at or near the target temperature, the first set temperature in the first heating means is preferably set to be higher than the target temperature and lower than or equal to the target temperature +8°C, more preferably , it is preferable to set the temperature within a range of not less than the target temperature and not more than the target temperature +6°C, more preferably not less than the target temperature and not more than the target temperature +4°C.
In addition, from the viewpoint of setting the temperature of the cementitious hardened body at or near the target temperature, the second set temperature in the second heating means is preferably within a range of ±8°C of the target temperature, more preferably, It is preferable to set the temperature within the range of ±6°C of the target temperature, more preferably within the range of ±4°C of the target temperature.

Furthermore, the magnitudes of the first set temperature and second set temperature determined in the first set temperature determination step and the second set temperature determination step are adjusted depending on the type of testing method for the mechanical properties of the cementitious hardened body. You can. By the above adjustment, the temperature of the hardened cementitious body can be easily brought to the target temperature or a temperature in the vicinity thereof.
Specific examples (i) to (iii) of adjusting the magnitude of the first set temperature and the second set temperature will be described below.
(i) Compressive strength test When the above-mentioned mechanical property test method is a compressive strength test, in the first set temperature determination step and the second set temperature determination step, for example, the first set temperature is lower than the second set temperature. The temperature may also be set to a higher value (preferably 1 to 6°C, more preferably 2 to 5°C higher).
An example of a compressive strength test is "JIS R 1108:2018 (Concrete compressive strength test method)".
(ii) Splitting crack initiation strength test When the above-mentioned test method for the mechanical properties is a splitting crack initiation strength test, in the first set temperature determination step and the second set temperature determination step, for example, the first set temperature is The temperature may be determined to be lower than the second set temperature (preferably 0.5 to 4°C, more preferably 1 to 3°C lower).
An example of a splitting crack initiation strength test is "JIS A 1113:2018 (Test method for splitting tensile strength of concrete)."

(iii) Notch bending strength test When the above-mentioned mechanical property testing method is a notch bending strength test, in the first set temperature determination step and the second set temperature determination step, for example, the first set temperature is The value may be determined to be less than or equal to the second set temperature (preferably from the second set temperature -4°C to the second set temperature, more preferably from the second set temperature -2°C to the second set temperature).
An example of a notch bending strength test is "Fiber-reinforced concrete ``Method for measuring load-displacement curves of notched beam test specimens''.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.
[Example 1]
[Compressive strength test method]
A compressive strength test of concrete at high temperature was conducted in accordance with "JIS R 1108:2018 (Concrete compressive strength test method)". This will be explained below with reference to FIG.
In the test, concrete was used as the cementitious hardened body, and as the concrete specimen 6, a cylindrical specimen with a diameter of 100 mm and 200 mm was used. “Digital temperature controller monoone-120” manufactured by Three High Co., Ltd. was embedded in the specimen 6 as temperature measuring means 1 to 3. Temperature measurement means 1 to 3 were buried at positions 100 mm vertically from the bottom of the specimen, and 5 mm, 25 mm, and 50 mm from the side surface of the specimen (Fig. 1 a- 1, a-2).

The specimen 6 was placed in a drying oven (first heating means), and the temperature inside the drying oven was raised at a rate of 3°C/hour from room temperature (approximately 20°C) to the first set temperature shown in Table 1. Heated at a temperature rate. Heating was performed with the specimen 6 placed in a sealed synthetic resin bag for the purpose of suppressing drying of the specimen 6. After the temperature in the drying oven reached the first set temperature, the specimen 6 was stored in the drying oven until the start of the test.
After taking out the specimen 6 from the drying oven, the compression testing machine 12 (JIS B 7721:2018 (Tensile testing machine/compression testing machine - Calibration method and verification method of force measurement system) 7. Testing machine grade) After setting the specimen to a specified grade 1 or higher; maximum load: 1,000 to 3,000 kN), immediately place two sheet heaters 9 (Three High Co., Ltd.) on the side surface of the specimen 6 as a second heating means. A "silicon rubber heater" (105 mm x 150 mm) manufactured by Co., Ltd. was attached to the position a-3 in FIG. 1, sandwiching the specimen. Note that the seat heater 9 was heated in advance to the second set temperature shown in Table 1. Further, the area where the seat heater 9 and the specimen 6 were in contact was 40% of the 100% surface area of the specimen.

Loading was started 1 minute and 30 seconds after the specimen 6 was taken out of the drying oven. Loading was carried out so that the increase in compressive stress was 0.6±0.4N/ ^mm2 , and after the specimen 6 started to undergo rapid deformation, the adjustment of the loading speed was stopped and the specimen 6 A load was applied until it broke.
Table 1 shows the temperature of the specimen 6 measured by temperature measuring means 1 to 3 at the end of the test (when the specimen 6 was crushed).

[Example 2]
[Splitting cracking strength test]
In accordance with "JIS A 1113:2018 (Test Method for Splitting Tensile Strength of Concrete)," a splitting crack initiation strength test of concrete at high temperatures was conducted. This will be explained below with reference to FIG.
As the concrete specimen 7, a cylindrical specimen measuring φ100×110 mm was used. The same temperature measuring means 1 to 3 as used in Example 1 were embedded in the specimen 7. Temperature measurement means 1 to 3 were buried at positions 5 mm, 27.5 mm, and 55 mm in the axial direction from the top surface of the cylindrical specimen, and 50 mm from the side surface of the specimen 7 (Fig. (See b-1 and b-2 of 2).

The specimen 7 was placed in a drying oven (first heating means), and the temperature inside the drying oven was raised at a rate of 3°C/hour from room temperature (approximately 20°C) to the first set temperature shown in Table 2. Heated at a temperature rate. Heating was performed with the specimen 7 placed in a synthetic resin bag and sealed. After the temperature in the drying oven reached the set temperature, the specimen 7 was stored in the drying oven until the start of the test.
After taking out the specimen 7 from the drying oven, the compression testing machine 13 (JIS B 7721:2018 (Tensile testing machine/compression testing machine - Calibration method and verification method of force measurement system) 7. Testing machine grade) After setting the specified grade 1 or higher; maximum load: 1,000 kN as shown in b-1 in Figure 2, two sheets were immediately placed on the side surface of the specimen 7 as a second heating means. The seat heater 10 ("Silicon Rubber Heater" manufactured by Three High Co., Ltd.: 105 mm x 115 mm) is placed between the specimen 7 and the specimen 7, avoiding the area where the compression tester 13 and the specimen 7 come into contact. (See b-2 in Figure 2). Note that the seat heater 10 was heated in advance to the second set temperature shown in Table 2. Further, the area where the seat heater 10 and the specimen 7 were in contact was 24% of the 100% surface area of the specimen.

Loading was started 1 minute and 30 seconds after the specimen 7 was taken out of the drying oven. The loading was such that the increase in tensile stress was 0.06±0.04 N/mm ² and the increase was maintained until the maximum load (1,000 kN) was reached.
Table 2 shows the temperature of the specimen 7 measured by temperature measuring means 1 to 3 at the end of the test (when the specimen 7 was crushed).

[Example 3]
[Notch bending strength test]
``Load-displacement of fiber-reinforced concrete notch beam test specimens'' described in ``Report of the Research Committee on Testing Methods for Fracture Characteristics of Concrete'' by the Japan Concrete Institute (currently the Japan Concrete Institute). A notch bending strength test was conducted at high temperatures in accordance with the Curve Measurement Method. This will be explained below with reference to FIG.
As the concrete specimen 8, a prismatic specimen measuring 100×100×400 mm was used. The same temperature measuring means 1 to 3 as used in Example 1 were embedded in the specimen 8. Temperature measuring means 1 to 3 were buried at a position 200 mm in the axial direction from the top surface of the prismatic specimen 8, and at positions 5 mm, 25 mm, and 50 mm from the side surface of the specimen (see Fig. 3). c-1, c-2).
In addition, a notch 4 with a length of 100 mm and a width of 5 mm or less is made to a depth of 30 mm in the center of one side of the specimen 8 (the surface that becomes the bottom surface when the specimen is set in a three-point bending tester). I put it in.

The specimen 8 was placed in a drying oven (first heating means), and the temperature inside the drying oven was raised at a rate of 3°C/hour from room temperature (approximately 20°C) to the first set temperature shown in Table 3. Heated at a temperature rate. Heating was performed with the specimen 8 placed in a synthetic resin bag and sealed. After the temperature in the drying oven reached the set temperature, the specimen 8 was stored in the drying oven until the start of the test.
After taking out the specimen 8 from the drying oven, set the members 14 and 15 of the three-point bending test device (not shown) as shown in c-3 in FIG. As a second heating means, eight sheet heaters 11 ("silicon rubber heater" manufactured by Three High Co., Ltd.: 100 mm x 120 mm) were prepared, and one of the specimens 8 was placed at the position shown in c-3 in FIG. Two pieces were attached to each side. Note that the seat heater 11 was heated in advance to the second set temperature shown in Table 3. Further, the area where the seat heater 11 and the specimen 8 were in contact was 53% of the 100% surface area of the specimen.
Next, a clip gauge (manufactured by Tokyo Sokki Kenkyusho Co., Ltd., clip-type displacement meter (UB-10S001)) for measuring opening displacement was attached.

After 3 minutes and 30 seconds had passed since the specimen 8 was removed from the drying oven, loading was started using a displacement-controlled precision universal testing machine ("Autograph AG-100KNG", manufactured by Shimadzu Corporation). The loading speed was controlled by the load point displacement, and the speed was 0.3 mm/min. During the test, the load and opening displacement were continuously measured, and the temperature of the cementitious hardened body was continued to be measured until the opening displacement reached 10 mm or more.
After calculating the average value of the temperature history measured during the test for each of the temperature measurement means 1 to 3, the average of the above average values of the temperature measurement means 1 to 3 (in Table 3, "average temperature during the test") ) was calculated. In addition, the difference between the maximum and minimum values of the average values of temperature measuring means 1 to 3 (indicated as "maximum temperature difference" in Table 3) was calculated.
The results are shown in Table 3.

From Tables 1 to 3, according to the present invention, the temperature of the hardened cementitious body is kept within the range of target temperature to target temperature + 0.6°C from the start to the end of the test for measuring the mechanical properties of the hardened cementitious body. It turns out that it can be maintained.

1, 2, 3 Thermocouple (temperature measurement means)
4 Notch 6, 7, 8 Specimen (hardened cementitious material)
9,10,11 Seat heater (second heating means)
12,13 Compression tester (mechanical property measurement means)
14,15 parts

Claims (7)

A method for testing the mechanical properties of a cementitious hardened body at a target temperature, the method comprising:
The first set temperature, which is the set temperature during heating of the first heating means disposed through the space for performing non-contact indirect heating on the cementitious hardened body, is set to be equal to or higher than the target temperature, a first set temperature determination step of determining within a range of the target temperature + 8°C or less ;
The second set temperature, which is the set temperature during heating of the second heating means disposed in contact with the cementitious hardened body to perform direct heating by contact , is within the range of the target temperature ± 8 ° C. a second set temperature determining step;
a heating step of heating the cementitious hardened body at the first set temperature using the first heating means;
A moving step of moving the cementitious hardened body that has been heated in the heating step to a place for testing mechanical properties;
a measuring step of measuring the mechanical properties of the hardened cementitious body using a mechanical property measuring means at a place for testing the mechanical properties, and
The hardened cementitious body is heated at the second set temperature using the second heating means, and in the measurement step, the temperature of the hardened cementitious body is maintained at or near the target temperature. A method for testing the mechanical properties of hardened cementitious materials. 2. The method for testing mechanical properties of a hardened cementitious material according to claim 1, wherein the first heating means is a heating furnace disposed to accommodate the hardened cementitious material. 3. The method for testing mechanical properties of a hardened cementitious material according to claim 1, wherein the second heating means is a sheet heater attached to the surface of the hardened cementitious material. The method for testing the mechanical properties of a hardened cementitious material according to any one of claims 1 to 3, wherein the target temperature or a temperature near the target temperature is within a range of ±3°C of the target temperature. The test method for the mechanical properties is a compressive strength test, and in the first set temperature determination step and the second set temperature determination step, the first set temperature is set to a value higher than the second set temperature. The method for testing the mechanical properties of a hardened cementitious material according to any one of claims 1 to 4, wherein the method is determined to: The test method for the mechanical properties is a splitting crack initiation strength test, and in the first set temperature determination step and the second set temperature determination step, the first set temperature is set to be lower than the second set temperature. The method for testing the mechanical properties of a hardened cementitious material according to any one of claims 1 to 4, wherein the mechanical properties are determined to be a low value. The test method for the mechanical properties is a notch bending strength test, and in the first set temperature determination step and the second set temperature determination step, the first set temperature is lower than or equal to the second set temperature. The method for testing the mechanical properties of a hardened cementitious body according to any one of claims 1 to 4, wherein the mechanical properties of a hardened cementitious body are determined to be a value.

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