JP2008026020A - Compression strength test control method of concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method contributing to the enhancement of precision by sensing eccentric loading during a test and correcting it, in a compression strength test of concrete. <P>SOLUTION: In the compression strength test of concrete, longitudinal strains at a plurality of places in a test piece at the time of loading are measured and the eccentric loading is sensed on the basis of the measured longitudinal strains at a plurality of places to be corrected. That is, the eccentric loading is sensed on the basis of the difference between the longitudinal strains at a plurality of places during the test to be corrected. Concretely, loading is performed while recognizing the longitudinal strains at two points or more at the time of the compression strength test (for example, the longitudinal strains are measured on two lines parallel and symmetric to the axis of the test piece at a position 1/2 the height of the test piece) and, in the case where the difference between the longitudinal strains becomes large, loading is interrupted and the installation state or the like of the test piece is confirmed to again perform the test. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a management method for compressive strength test of concrete.

Nondestructive compressive strength tests on concrete formations and the like have been performed by various methods (see, for example, Patent Document 1).
In the concrete compressive strength test (JIS A 1108), in order to prevent eccentric loading on the specimen under test, “clean the specimen's upper and lower end surfaces and the compression surfaces of the upper and lower pressure plates” or “test specimen diameter. The center axis is set so as to coincide with the center of the pressure plate with an error within 1%. These methods reduce the possibility of eccentric loading during the test before the test, and do not sense the eccentric loading after the start of the test.
JP 2002-181677 A

  In the concrete compressive strength test, when loaded on the specimen, if there is a minute substance on the upper and lower end surfaces of the specimen and the compression surface of the pressure plate, or the center axis of the specimen is slightly shifted from the center of the pressure plate In some cases, the load is decentered and results in a strength lower than the actual strength.

  The subject of this invention is providing the management method which contributes to a precision improvement by detecting and correcting the eccentric load under test in the compressive strength test of concrete.

  In order to solve the above-mentioned problems, the present invention measures the longitudinal strain at a plurality of locations in a specimen when loaded in a compressive strength test of concrete, and detects the eccentric loading by the difference between the measured longitudinal strains at the plurality of locations. It is characterized by correction.

That is, the eccentric load is detected and corrected by the difference in longitudinal strain at a plurality of locations during the test.
Specifically, at a compressive strength test, two or more longitudinal strains (for example, the longitudinal strain is measured at two positions parallel to the axis of the specimen and symmetrical on the half of the height of the specimen. Load) while confirming the difference of (Yes). If the difference in longitudinal strain becomes large, stop loading, check the installation status of the specimen, and perform the test again.
Note that loading is suspended when the difference in longitudinal strain becomes large by about 1/3 of the design reference strength.

  According to the present invention, in the compressive strength test of concrete, the eccentric load under test is sensed and corrected by the difference in longitudinal strain, so that an improvement in accuracy can be achieved.

  Hereinafter, embodiments of the present invention will be described with reference to tables and drawings.

  Table 1 and FIGS. 1 to 3 show the compressive strength test results of ultra-high strength concrete. Table 1 shows the compressive strength test results corresponding to the differences in age and specimen. 1 to 3 show the compressive strength test results (stress-strain curves) corresponding to differences in specimens for each age. In addition, the stress-strain curve at the time of performing based on the static elastic modulus test method of the concrete prescribed | regulated to JISA1149 is used.

  As shown in Table 1 and FIGS. 1 to 3, the compressive strength at the age of 182 was lower than the compressive strength at the age of 91 days. Looking at the measurement results of the longitudinal strain at the age of 182 days, the difference in the longitudinal strain of all the specimens is large, which seems to have influenced the compressive strength test results.

In the compressive strength test on the age of 365 days, loading was performed while confirming the difference in longitudinal strain. When the difference in longitudinal strain exceeded 300μ at a stress of 40 N / mm ² or less, loading was interrupted, and the specimen was installed. Etc. were confirmed and the test was performed again. As a result, the difference in longitudinal strain is smaller than the age of 182 days, and the compressive strength is higher than the age of 91 days and 182 days, so that it can be judged that good test results were obtained.

  From the above, it is considered effective to measure and manage the longitudinal strain during the compressive strength test of ultra high strength concrete.

It is the figure (ac) which showed the compressive strength test result (stress-strain curve) corresponding to the difference of the test body of 91 days of age. It is the figure (ac) which showed the compressive-strength test result (stress-strain curve) corresponding to the difference of the test body of 182 days of age. It is the figure (ac) which showed the compressive strength test result (stress-strain curve) corresponding to the difference of the test body of the material age 365 days.

Claims (1)

In the compressive strength test of concrete,
A compressive strength test management method for concrete, characterized by measuring longitudinal strain at a plurality of locations in a specimen at the time of loading, and detecting and correcting eccentric loading based on the difference between the measured longitudinal strains at the plurality of locations.

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