JP3705683B2 - Durability test method for concrete specimen, concrete specimen container for ultrasonic measurement used in the method, and freeze-thaw test automatic measurement apparatus using the container - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention makes it easy to perform a durability test of concrete specimens by automatically measuring deterioration with time using an ultrasonic generator by repeatedly freezing and thawing concrete specimens rapidly and alternately. In addition, the present invention relates to a durability test method for a concrete specimen that can be accurately performed over time, a concrete specimen container for ultrasonic measurement used in the method, and a freeze-thaw test automatic measurement apparatus using the container.
[0002]
[Prior art]
As a conventional test method for durability of concrete, there is a freeze-thaw test method (JIS A6204) for testing the resistance of concrete to freeze-thaw action by rapid repetition of freeze-thaw in water. One of the major factors affecting the durability of concrete is considered to be damage caused by freezing and thawing of water present in the concrete. In the conventional durability test method defined by the above JIS, the upper limit of the freeze-thaw cycle is 200 cycles, and the deflection of the concrete specimen immediately after the end of the thawing process is once within 36 cycles. The durability index is obtained by measuring the primary resonance frequency of vibration (JIS A1127).
[0003]
Specifically, first, a cooling and heating apparatus necessary to give a predetermined freeze-thaw cycle to concrete, a test tank cooled and heated by the apparatus, and a cross-section cured under a certain condition is 100 mm on a side. A test specimen container for storing a rectangular concrete specimen having a rectangular shape of 400 mm in length is prepared, and the test specimen container is placed in a test tank filled with a refrigerant, and the concrete specimen in the container is placed. Is repeatedly frozen and thawed by the above cooling and heating apparatus to forcibly cause deterioration of the concrete specimen. Next, after such a freeze-thaw cycle is continued for a certain number of times, the primary resonance frequency of the flexural vibration of the concrete specimen immediately after thawing is measured. Then, by performing this frequency measurement operation at regular intervals of the freeze-thaw cycle, changes in deterioration with time caused by freeze-thaw in the concrete specimen are measured, and this is used as a test method for the durability of concrete.
[0004]
[Problems to be solved by the invention]
However, in the conventional method, when measuring the primary resonance frequency of flexural vibration, the concrete specimen is manually removed from the concrete specimen container filled with water, and the surface of the concrete specimen is removed. After the surface is cleaned with a brush or the like, the measurement is performed after wiping off the water, and therefore, the work requires a great deal of labor. Further, after measuring the vibration frequency in this way, immediately return the concrete specimen to the concrete specimen container, repeat the freeze-thaw cycle again, and measure the primary resonance frequency of the flexural vibration again after the end of a certain cycle. Although it is necessary to perform the operation, it is also necessary to rinse the inner wall of the concrete specimen container and replace it with fresh water. As described above, the conventional method for testing the durability of concrete has a problem that it is very complicated and requires a lot of labor and time.
[0005]
In JIS, the frequency is measured once every 36 cycles, but in order to measure the deterioration of concrete specimen caused by freezing and thawing more accurately and accurately, freeze and thaw. However, it is difficult to measure every cycle by the above-described conventional manual measurement method, and it is almost impossible to measure deterioration over time over every cycle. there were. In addition, when performing manually, there is a problem that it is difficult to measure the primary resonance frequency of the flexural vibration, which is repeatedly performed, with the measurement conditions always constant, and the measurement accuracy is inferior. .
[0006]
On the other hand, in recent years, environmental protection on a global scale has been screamed, and recycled aggregate concrete that has been used after being crushed and reused has begun to be used. It is known that it is inferior in durability to concrete using When constructing a structure, if concrete that is less durable than desired is used, the strength and durability of the structure may be impaired, and there may be a serious problem in terms of safety. is there. Therefore, it is desired to develop a test method that can easily and accurately confirm the resistance (durability) to the freeze-thaw action of concrete when recycled aggregate concrete is mixed. Furthermore, not only for concrete using natural aggregate, but especially for recycled aggregate concrete that has almost never been used so far, the physical condition of the concrete against the change in durability (degraded state) Development of a test method that can be confirmed chemically is desired.
[0007]
Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and the same concrete specimen as used in JIS can be rapidly and alternately repeatedly cooled and frozen and heated and thawed. By repeatedly forcing this freeze-thaw, the degree of resistance change (that is, the state of deterioration) generated in the concrete specimen can be accurately and accurately quantified, and the heavy concrete object is provided. The test time can be measured very easily without taking the sample in and out of the test sample container every time, and the time required for the test can be greatly reduced compared to the conventional method. It is another object of the present invention to provide a durability test method for a concrete specimen that can be continuously and automatically measured. Furthermore, the object of the present invention is to provide a concrete specimen container for ultrasonic measurement for realizing the durability test method for a concrete specimen having the above-mentioned excellent effects, and an automatic measuring apparatus for freeze-thaw test using the container. There is to do.
Another object of the present invention is not only to continuously and automatically measure deterioration over time caused by repeated freezing and thawing, but also to provide concrete with a history similar to that in which deterioration has occurred. An object of the present invention is to provide a durability test method for a concrete specimen, which can also compare the deterioration state of the concrete with other characteristics by simultaneously performing a destructive test such as a strength measurement test on the specimen.
[0008]
[Means for Solving the Problems]
The above object is achieved by the present invention described below. That is, in the present invention, the cooling and freezing and heating and thawing of the concrete specimen stored in the concrete specimen container are repeated alternately, and the concrete specimen is held in the concrete specimen container every fixed cycle of freezing and thawing. It is characterized by measuring the propagation speed of the ultrasonic wave propagating through the concrete specimen immediately after melting using an ultrasonic generator and automatically measuring the deterioration of the concrete specimen due to repeated freezing and thawing. A concrete test specimen durability test method, a concrete specimen container for ultrasonic measurement used in the method, and a freezing and thawing test automatic measurement apparatus using the container.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As a result of diligent research to solve the above-mentioned problems of the prior art, the present inventors have measured the deterioration of concrete specimens caused by repeated and forced freezing and thawing to measure the concrete supply from the container. By measuring the propagation speed of ultrasonic waves propagating through the concrete specimen while it is stored in the concrete specimen container without taking the specimen outside, the deterioration state caused in the concrete specimen can be accurately and accurately determined. The inventors have found that it can be quantified and have arrived at the present invention. According to the inventor's study, it was found that the above-described effects can be easily obtained particularly when a concrete specimen container having a specific structure and a freeze-thaw test automatic measuring device are used. That is, by adopting the above configuration, it is not necessary to take in and out a heavy concrete specimen from the specimen container every time it is measured, so it is very easy to know the deterioration state of the concrete specimen. In addition, the time required for the test can be remarkably reduced as compared with the conventional method. In addition, since it is possible to continuously measure the deterioration of the concrete specimen over time for each cycle of freeze-thawing, it is possible to obtain a test result with more accuracy and accuracy. Furthermore, according to a preferred embodiment of the present invention, the strength test result of the concrete specimen can be obtained simultaneously with the deterioration state of the concrete specimen, so that more useful analysis can be performed in the same test. .
[0010]
Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a schematic explanatory schematic view of a freeze-thaw test automatic measuring apparatus according to the present invention to which a concrete specimen durability test method according to the present invention is applied. The apparatus shown in FIG. 1 mainly includes an ultrasonic generator a, a freeze / thaw tank b, and a control unit that controls these apparatuses. The control unit includes a control unit d that controls cooling and heating of the freeze / thaw tank b and a system controller s that controls the whole. And it is required that at least the concrete specimen container is accommodated in the freeze / thaw tank b of the freeze / thaw test automatic measuring apparatus of the present invention. In the apparatus illustrated in FIG. A specimen container c1 is disposed, and a concrete specimen container c2 for temperature measurement and a concrete specimen container c for various tests are disposed on both sides thereof. In addition, the apparatus shown in FIG. 1 has means for supplying and draining water into these concrete specimen containers, and is provided with a water supply and drainage section e which can be controlled so that each container is filled with water as needed. It has been.
[0011]
First, a concrete specimen container for ultrasonic measurement, which is a main part of the automatic freeze / thaw test automatic measuring apparatus of the present invention as illustrated in FIG. 1, will be described.
(1) Concrete specimen container for ultrasonic measurement
The concrete specimen container of the present invention has a storage case for storing a concrete specimen, an ultrasonic oscillator x, and an ultrasonic receiver y, and the ultrasonic oscillator x and the ultrasonic receiver y; These are characterized in that they are arranged so as to be placed in pressure contact with the two surfaces facing each other of the concrete specimen in the storage case via a highly adhesive member. According to such a concrete specimen container, as shown in FIG. 3, the concrete specimen f is necessary on the upper and lower surfaces of the concrete specimen f in a state where the concrete specimen f is accommodated in the storage case (2). Accordingly, since the ultrasonic oscillation x and the ultrasonic transducer y can be press-contacted via the high adhesion member (3), the ultrasonic oscillation x and the ultrasonic transducer y are not shown. It is possible to propagate the ultrasonic waves generated by the ultrasonic generator into the concrete specimen under stable conditions. As a result, the ultrasonic propagation velocity propagating through the concrete specimen can be automatically measured with the concrete specimen contained in the container, and the ultrasonic propagation velocity can be continuously measured every cycle of freezing and thawing. It is also possible to automatically measure the aging degradation that occurs in concrete specimens by freezing and thawing, and to accurately and accurately measure the durability test of concrete specimens in a short time and accurately. be able to.
[0012]
Here, a method of placing the ultrasonic oscillation x and the ultrasonic transducer y in pressure contact with each other on the two faces facing the concrete specimen will be described. That is, it is preferable to measure under a certain condition in order to accurately and accurately measure the state of deterioration generated in the concrete specimen by freezing and thawing using an ultrasonic generator. The ultrasonic oscillation x and the ultrasonic transducer y are pressed against the surface of the concrete specimen f with some force, and the ultrasonic oscillation x and the ultrasonic transducer y are stably adhered to the surface of the concrete specimen. It is good to measure in fixed pressure conditions.
[0013]
The concrete specimen container for ultrasonic measurement of the present invention illustrated in FIG. 3 is of a type in which the concrete specimen container is installed in the vertical direction. In this case, the ultrasonic oscillator x is placed at the bottom of the container. Since the ultrasonic oscillator x is set by the weight of the concrete specimen, the ultrasonic specimen x is pressed against the concrete specimen via the high adhesion member (3). There is no need to provide the member (4) for press-contact like the vibration receiving element y. In the example of FIG. 3, a spring-like pressure contact member is used as a pressure contact member (4) that presses the ultrasonic wave transducer y against the concrete specimen surface. Due to the elasticity of the spring, the ultrasonic wave transducer x is supplied to the concrete sample. It is in close contact with the surface of the specimen. Further, in the example of FIG. 3, in order to improve the adhesion with the concrete specimen, a buffer material (5) is provided under the ultrasonic oscillator x, but in the present invention, the buffer material (5) Not necessarily required. As a material for forming the buffer sheet (5) used at this time, for example, a material having a certain degree of flexibility and strength such as various rubbers and elastomers may be used.
[0014]
On the other hand, in the container illustrated in FIG. 3, the ultrasonic ultrasonic transducer y at the upper portion is placed at a constant pressure on the concrete specimen through the high adhesion member (3) by the force of the pressure welding member (4). With pressure contact. As the high adhesion member (3) used at this time, the ultrasonic oscillator and the receiver are not slippery and can be attached to the surface of the concrete specimen stably and with a certain pressure. It is preferably formed of a material that propagates sound waves well, has a certain degree of flexibility and strength, and is excellent in water resistance, cold resistance, and pressure resistance. For example, a silicone rubber plate is preferable, but the present invention is not limited to this.
[0015]
The concrete specimen container for ultrasonic measurement of the present invention illustrated in FIG. 4 is of a system in which the concrete specimen is installed in a horizontal direction unlike the case shown in FIG. Both the oscillator x and the transducer y are brought into close contact with the surface of the concrete specimen through the high contact member (3) by the force of the spring-like pressure contact member (4). As a result, the ultrasonic wave velocity x propagating through the inside of the concrete specimen f was always stabilized by bringing the ultrasonic oscillation x and the ultrasonic transducer y into contact with the surface of the concrete specimen f under a certain pressure condition. It becomes possible to measure in a state. In the example shown in FIGS. 3 and 4, a coil spring is used as the pressure contact member (4). However, the present invention is not limited to this, and the ultrasonic oscillator x and / or the ultrasonic wave is used. Any method may be used such as pressing with a plate spring or an elastic body, screwing, etc., as long as it can be stably pressed against the surface of the concrete specimen with a constant force.
[0016]
JIS A6204 stipulates that the entire surface is always covered with approximately 3 mm thick water during the freezing and thawing process. Therefore, in the example shown in FIG. 3, according to this regulation, when the concrete specimen and the storage case (1) for storing the specimen are stored and the concrete specimen is stored, the outer wall of the concrete specimen is It is preferable that the space between the inner wall of the storage case {circle around (1)} is about 3 mm so that the portion can be filled with water. In this case, in order to easily and appropriately fill the gap with the water supply / drainage as described above, as shown in FIG. 3, the storage case (1) has a water supply / drainage port (6). It is preferable to provide a water supply / drainage means so that water supply / drainage from these water supply / drainage ports can be automatically performed by a water supply / drainage section e controlled by the system controller s.
[0017]
Moreover, in the concrete specimen container for ultrasonic measurement of the present invention having the above-described configuration, the concrete specimen can be easily put in and taken out, and the entire surface of the concrete specimen is covered with water. In order to prevent water leakage from the container, as shown in FIG. 3, it is preferable that both ends of the storage case (1) have a flange shape and are sandwiched by metal plates matched to the flange shape to have a bolt screw fastening structure. Moreover, as a forming material of the storage case (1), water is filled, the concrete specimen stored in the storage case (1) is heavy, and the concrete specimen is stored in the storage case (1). Freeze-freezing and heat-thawing are repeatedly performed, so it has excellent water resistance, cold resistance and heat resistance. Furthermore, volume expansion and contraction occur due to freezing and thawing, so it is more flexible and stretchable than rigid materials. It is preferable to use a material excellent in tensile strength. Examples of such a material include natural rubber and synthetic rubber such as IR, SBR, BR, and EPDM. In particular, the rubber may be formed from natural rubber. Of course, the present invention is not limited to this.
[0018]
As for the shape of the concrete specimen container for ultrasonic measurement of the present invention, the shape of the concrete specimen for freezing and thawing specified in JIS A6204 is a square section with a side length of 100 mm and a length of 400 mm. Therefore, what is necessary is just to set it as the specimen container which can accommodate the concrete specimen of the dimension according to this. However, the present invention is not limited to this, and for example, a cylindrical specimen having a diameter of 100 mm and a length of 200 mm used for a strength test, or a specimen container having a shape and size adapted to various tests may be used. it can.
[0019]
Next, other components constituting the freeze / thaw test automatic measuring apparatus of the present invention will be described.
(2) Ultrasonic generator
It is used to measure the ultrasonic velocity propagating through the concrete specimen, detect the damage inside the concrete specimen caused by repeated freezing and thawing, and grasp the deterioration of concrete. Since this method is a non-destructive inspection method, it is possible to measure deterioration over time of the same concrete specimen continuously over a long period of time. According to the study by the present inventors, for example, when damage such as cracks or voids occurs in a concrete specimen due to repeated freezing and thawing, it varies depending on the degree of damage, but exceeds 5 to 30% compared to healthy concrete. The sound wave propagation speed becomes slow. If the damage is even greater, there will be a further delay.
[0020]
The ultrasonic velocity propagating through the concrete specimen is measured in the storage case {circle around (1)} of the ultrasonic measurement specimen container c1 of the present invention having the structure as shown in FIG. 3 or FIG. Specify the shape and curing concrete specimen f according to JIS standard, and specify the freeze-thaw by using the ultrasonic oscillator x and the ultrasonic transducer y connected to the ultrasonic generator. The ultrasonic wave propagation velocity can be measured immediately after the concrete specimen is melted every cycle or every cycle. By measuring every cycle, deterioration with time can be continuously monitored.
[0021]
(3) Freezing and thawing tank
The freeze-thaw tank b for repeatedly freezing and thawing the concrete specimen used in the freeze-thaw test automatic measuring apparatus of the present invention is capable of stably freezing and thawing the concrete specimen in an appropriate cycle. Any of them may be used. For example, as in JIS 6204, a system using a heat medium system may be used, but a forced air circulation system may be used. Recently, the performance of refrigerators and thermostats has improved, and it can be adequately handled by forced air circulation.
If the heat medium method is adopted, the heating and cooling efficiency is superior to the forced air circulation method. However, since it is necessary to immerse the concrete specimen container in the heat medium, the material for forming the ultrasonic oscillator x and the receiver y must be a type that can withstand the heat medium to be used. For this reason, the complexity of the handling operation of the concrete specimen container and the maintenance of the thermostat is inferior to that of the forced air circulation method.
[0022]
Regarding freezing and thawing conditions, JIS A6204 stipulates that the center temperature of the concrete specimen is in the range of −18 ° C. to 5 ° C. (± 2 ° C.). The temperature of the heat medium in the freeze / thaw tank is in the range of -25 ° C to 20 ° C. Since the time required for one cycle of freezing and thawing is 3 hours or more and within 4 hours, it is necessary to set the control conditions for the freezing and thawing tank according to this. At this time, when the forced air circulation method is used, since the inside of the freeze-thaw tank is air, the heat conduction is inferior compared to the case where the heat medium method is adopted, and the cooling and heating conditions are mild. It is necessary to extend the temperature control range to a range of -30 ° C to 30 ° C. However, even if constituted in this way, there is little problem on the freezing and thawing conditions of the concrete specimen, and there is no problem.
[0023]
(4) Water supply / drainage means
The water in the container filled so as to cover the entire surface of the concrete specimen described above is contaminated with elution or crushed material from the concrete specimen while the freeze-thaw cycle is repeated. Replacement may be necessary. In the freeze / thaw test automatic measuring apparatus of the present invention, as described above, in such a case, it is preferable to provide a water supply / drainage means in order to enable water to be replaced appropriately and easily. In addition, when there is little dirt of water and there is no trouble in ultrasonic measurement, long-term cycle measurement is possible without replacing water.
[0024]
As described above, the freeze-thaw test automatic measurement apparatus of the present invention is composed of the above-described components, and the ultrasonic test concrete specimen container c1 of the present invention is disposed at least in the freeze-thaw tank b. In the freeze-thaw tank b, the concrete specimen f is configured to be repeatedly frozen and thawed at a constant cycle. In the present invention, as shown in FIG. It is preferable that a concrete sample container for temperature measurement c2 different from the concrete specimen container for ultrasonic measurement c1 is arranged in the inside. If it does in this way, temperature control of the freezing and thawing tank b is performed by the temperature information from the temperature sensor provided in the concrete specimen container c2 provided in the freezing and thawing tank b together with the concrete specimen container c1 for ultrasonic measurement. It becomes possible to carry out more accurately. Hereinafter, the concrete specimen container c2 for temperature measurement used in this case will be described.
[0025]
(5) Concrete specimen container for temperature measurement
As shown in FIG. 5, the concrete specimen container for temperature measurement c2 is configured in substantially the same manner as the concrete specimen container for ultrasonic measurement c1 described above, but the supersonic wave for measuring the propagation speed of ultrasonic waves. Instead of the sound wave oscillation x and the ultrasonic wave transducer y, the element of the temperature sensor t is installed so as to be located at the center of the concrete specimen. As a result, the temperature information of the concrete specimen that can be used for the control management of the cooling temperature in the cooling freezing process for the concrete specimen performed in the freeze thaw tank b, and the control management of the heating temperature in the heating and melting process, It is output to the system controller s, and it becomes possible to perform the temperature control of the freeze / thaw tank b and the timing of measuring the ultrasonic wave propagation speed more accurately.
[0026]
Furthermore, in the freeze / thaw test automatic measuring apparatus of the present invention, as shown in FIG. 1, various tests such as a strength test other than the ultrasonic measurement concrete specimen container c1 are provided in the freeze / thaw tank b. It is also preferable to place various test concrete specimen containers for obtaining concrete specimens to be used in the above. That is, the ultrasonic measurement concrete specimen cannot be subjected to a destructive test, but in this way, a concrete specimen having a history similar to that of the ultrasonic measurement concrete specimen can be obtained. It can be taken out from the specimen container and used for a destructive test such as a strength test. At this time, as shown in FIG. 1, if a plurality of test specimen containers for various tests are arranged, the specimen is taken out from the concrete specimen container in accordance with the change in the value of ultrasonic propagation velocity measurement. Since various destructive tests can be performed and various characteristics can be known, more useful analysis can be performed. Hereinafter, various test concrete specimen containers c used in this case will be described.
[0027]
(6) Concrete test specimen containers for various tests
As shown in FIG. 6, the various test concrete specimen containers c are configured in substantially the same manner as the ultrasonic measurement concrete specimen containers c1 described above, but are used for measuring the ultrasonic propagation velocity. The container is not provided with the sound wave oscillation x and the ultrasonic wave transducer y, and only freezes and thaws the concrete specimen.
As shown in FIG. 1, if a plurality of concrete test specimen containers for various tests are provided, for example, the concrete specimen is appropriately frozen in accordance with the change in the ultrasonic propagation velocity measured for each freeze-thaw cycle. After taking out from the melting tank b and examining the dimensions, mass, appearance of the specimen, etc., it may be used as a specimen for a destructive test such as a strength test. Accordingly, the shape and dimensions of the various test concrete specimen containers may be those which can give a specimen having the same shape as the ultrasonic measurement concrete specimen, but more preferably suitable for various tests. It can be determined according to the test piece of any shape. For example, when used for a compressive strength test, a specimen container having a shape capable of accommodating a cylindrical specimen having a diameter of 100 mm and a length of 200 mm may be used.
[0028]
(7) System controller
In the freeze / thaw test automatic measurement apparatus of the present invention, it is preferable that the above-described constituent members are configured to be collectively controlled by the system controller s. As a result, according to a particularly preferable aspect of the present invention, the temperature management in the freeze / thaw tank b is performed under the optimum conditions based on the temperature information from the temperature sensor t arranged in the concrete specimen container for temperature measurement. It is possible to freeze and thaw the concrete specimen rapidly and stably in a constant cycle. Furthermore, the ultrasonic propagation speed of the concrete specimen can be measured under a certain condition immediately after the concrete specimen is melted at the best timing for each cycle, and the measurement is performed with high accuracy. Moreover, the water supply / drainage part e can be controlled so that the water covering the entire surface of the concrete specimen can be taken in and out automatically.
[0029]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples of the durability test method for concrete specimens of the present invention.
Example 1
<Measurement of deterioration with time by combination of ultrasonic method and strength test>
In this example, the freeze-thaw test automatic measuring apparatus of the present invention shown in FIG. 1 was used. That is, using the apparatus shown in FIG. 1, a plurality of concrete specimens for freezing and thawing simultaneously under the same conditions were produced under the same conditions with respect to the blending ratio and the like. And one of them is left as a specimen for strength test before freezing and thawing, and one of the other specimens is stored as a specimen for ultrasonic measurement in a concrete specimen container c1 for ultrasonic measurement. The container is housed in a case (see FIG. 3), and an ultrasonic oscillator and a receiver are attached to the facing surfaces of the concrete specimen, respectively, and one of them is a concrete specimen container for temperature measurement with a hole in the center. It was housed inside and installed so that the element of the temperature sensor t was positioned at the center of the concrete specimen (see FIG. 5). Further, the remaining concrete specimens were respectively stored in storage cases of various test concrete specimen containers c for use as strength test specimens (see FIG. 6). And the ultrasonic wave propagation velocity inside the concrete was measured up to 200 cycles per cycle for the concrete specimen for ultrasonic measurement.
[0030]
In the apparatus shown in FIG. 1, the temperature information of the concrete specimen provided by the temperature sensor t is configured to be output to the system controller s, and the temperature control of the freeze / thaw tank b can be performed based on this. Thus, the temperature control of the freeze / thaw tank b is accurately performed. Furthermore, based on the above temperature information, it is possible to measure the ultrasonic propagation velocity of the concrete specimen immediately after thawing while confirming that one cycle of freezing and thawing has been completed. As a result, the amount of information obtained by this example was much larger than that of the conventional method, and the degradation state could be analyzed accurately and accurately.
Further, in accordance with the change in the ultrasonic velocity generated in the freeze-thaw cycle obtained above, one of the strength test specimens was taken out from the freeze-thaw bath as appropriate, and the strength test was performed. As a result, the deterioration with time can be directly determined by the value of the breaking strength, and the correlation between the ultrasonic propagation speed and the strength can be determined.
[0031]
On the other hand, in the conventional method of freezing and thawing concrete, since it is not possible to perform a strength test that destroys the specimen, the primary resonance vibration of the flexural vibration just before the start of freezing and thawing for one specimen, The primary resonance vibration of the flexural vibration at every fixed freeze-thaw cycle is measured, and the durability index is obtained indirectly by the calculation formula to determine the deterioration with time. In addition, since it is necessary to measure the primary resonance vibration after the complicated work of taking out the concrete specimen from the concrete specimen container filled with water and cleaning the surface each time it is measured, As in the case of the embodiment, it is difficult to measure vibration every cycle, and rough measurement is performed once every 36 cycles. Therefore, there is a case where sufficient analysis cannot be performed with such an amount of information.
[0032]
Example 2
<Measurement of deterioration with time by ultrasonic method>
In this example, the freeze-thaw test automatic measuring apparatus of the present invention shown in FIG. 2 was used. Then, a plurality of specimens having different blending ratios and blending materials are prepared, and one of them is opened in the center of the concrete specimen container c2 for temperature measurement, and the other specimens are ultrasonicated. Each was set in a concrete specimen container c1 for measurement, and the change in ultrasonic propagation velocity was continuously measured for each freeze-thaw cycle. As a result, it is possible to continuously measure changes in the ultrasonic propagation speed for each freeze-thaw cycle in parallel for a number of concrete specimens with different production conditions, and for multiple concrete specimens with different concrete blending ratios and blending materials. Was able to be tested quickly and easily.
[0033]
Example 3
<Application example of ultrasonic method to recycled aggregate concrete>
In this example, the automatic measuring apparatus for freeze-thaw test of the present invention shown in FIG. 2 similar to that used in Example 2 was used. Then, durability tests were conducted on natural aggregate concrete and recycled aggregate concrete (recycled aggregate) which is currently attracting attention. Four types of concrete specimens were produced in the same manner as in Example 1 using natural aggregate concrete A and recycled aggregate concrete B, C and D having different production methods. These are set in the ultrasonic measurement concrete specimen container c1, respectively, and in the temperature measurement concrete specimen container c2, the same specimens as the natural aggregate concrete A are put, and each is subjected to each freeze-thaw cycle. The change of ultrasonic propagation velocity was measured continuously. The results are shown in FIG.
As is clear from FIG. 7, in the natural aggregate concrete A, the propagation speed of the ultrasonic wave inside the concrete did not change up to 100 cycles, but in the recycled aggregate concrete B, the propagation speed gradually increased after 20 cycles. The measurement was delayed, and measurement was impossible in 84 cycles, and measurement was impossible in recycled aggregate concrete C in 46 cycles and recycled aggregate concrete D in 13 cycles. When the specimens of these recycled aggregate concrete that became impossible to measure were taken out and observed, collapse was observed on the outside and inside.
[0034]
【The invention's effect】
According to the present invention described above, a concrete specimen similar to that used in JIS is rapidly and stably and alternately repeatedly cooled, frozen and heated to melt, thereby forcibly deteriorating the concrete specimen. Therefore, the degree of deterioration can be quantified accurately and accurately, and the time required for the test can be compared with the conventional method very easily without taking out a heavy concrete specimen from the specimen container. There is provided a durability test method for a concrete specimen that can be measured by being significantly shortened, and that can automatically measure the state of deterioration over time over the entire cycle.
In addition, according to the present invention, not only continuous automatic measurement of the deterioration over time caused in the concrete specimen by repeatedly forcibly freezing and thawing, but also the concrete specimen having the same history as the deterioration has occurred. As a result of being able to perform destructive tests such as strength measurement tests at the same time, it is possible to compare the deterioration state of concrete with other characteristics, and durability of concrete specimens that can obtain useful analysis results Sex test methods are provided.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory schematic view of an automatic measuring apparatus for freeze / thaw test according to the present invention.
FIG. 2 is a schematic explanatory schematic view of an automatic measuring apparatus for freeze / thaw test according to the present invention.
FIG. 3 is a cross-sectional view showing a specific example of a concrete specimen container for ultrasonic measurement according to the present invention.
FIG. 4 is a cross-sectional view showing another specific example of a concrete specimen container for ultrasonic measurement according to the present invention.
FIG. 5 is a cross-sectional view showing a specific example of a concrete specimen container for temperature measurement used in the automatic measuring apparatus for freezing and thawing test of the present invention.
FIG. 6 is a cross-sectional view showing one specific example of various test concrete specimen containers used in the freeze / thaw test automatic measuring apparatus of the present invention.
FIG. 7 is a measurement result of ultrasonic propagation velocity for various specimens measured every cycle by the freeze / thaw test automatic measuring apparatus of the present invention.
[Explanation of symbols]
▲ 1 ▼: Storage case
▲ 2 ▼: Bolt
(3): High adhesion material
(4): Pressure contact member
(5) Buffer material
(6): Water supply / drainage port
(7) Drain outlet
a: Ultrasonic generator
b: Freezing and thawing tank
c: Concrete specimen container for various tests
c1: Concrete specimen container for ultrasonic measurement
c2: Concrete specimen container for temperature measurement
d: Cooling and heating control unit
e: Water supply / drainage section
f: Concrete specimen
g: Cooler
h: Heater
s: System controller
t: Temperature sensor
p: Water supply / drainage pump
v1: Water supply valve
v2: Drain valve
x: ultrasonic oscillator
y: Ultrasonic transducer

Claims (6)

The cooling and freezing and heating and thawing of the concrete specimen stored in the concrete specimen container are repeated alternately, and the ultrasonic wave is ultrasonicated with the concrete specimen held in the concrete specimen container at every freeze-thaw cycle. Using a generator, the propagation speed of ultrasonic waves propagating in the concrete specimen immediately after melting is measured, and the deterioration of the concrete specimen over time caused by repeated freezing and thawing is automatically measured. Durability test method. A concrete specimen container for ultrasonic measurement used in the durability test method for a concrete specimen according to claim 1, comprising a storage case for storing the concrete specimen, an ultrasonic oscillator x, and an ultrasonic receiver. A pendulum y, and the ultrasonic oscillator x and the ultrasonic receiver y are arranged so as to be pressed against two opposing surfaces of the concrete specimen in the storage case. A concrete specimen container for ultrasonic measurement, characterized by comprising: Furthermore, the concrete specimen container for ultrasonic measurement of Claim 2 with which the water supply / drainage means for supplying and draining water is provided in the storage case. An ultrasonic generator and a freeze / thaw tank for alternately repeating cooling and freezing and heating and thawing of the concrete specimen stored in the concrete specimen container, and for each cycle in which the concrete specimen is frozen and thawed Furthermore, in the freeze / thaw test automatic measuring device configured to continuously and automatically measure the ultrasonic wave propagation speed at which the ultrasonic waves generated by the ultrasonic wave generating device propagate through the concrete specimen during melting, the freeze / thaw tank An automatic measuring apparatus for freeze-thaw testing, comprising one or more concrete specimen containers therein, wherein at least one of the concrete specimen containers is the concrete specimen container for ultrasonic measurement according to claim 1. In addition to the concrete specimen container for ultrasonic measurement, a concrete specimen container for temperature measurement having a temperature sensor for measuring the temperature inside the concrete specimen is stored in the freeze-thaw tank, and according to the obtained temperature information 5. The freeze / thaw test automatic measurement apparatus according to claim 4, wherein the temperature control of the freeze-thaw tank and the control of the ultrasonic generator are performed. The freeze / thaw test automatic measuring device according to claim 4 or 5, wherein a concrete specimen container for various tests is housed in the freeze-thaw tank separately from the concrete specimen container for ultrasonic measurement.

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