• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.49-55
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• 2017

In the seventies, a number of researchers carried out experiments on pullout tests with prototype equipment, and the pullout test was certified as a reliable nondestructive testing(NDT) method for determining the strength of concrete. To estimate the strength of high-strength concrete, we propose a simplified pullout test that uses as a break-off bolt a standard 10mm bolt with a groove on the shaft, an insert nut, and a pullout instrument that includes a hydraulic oil pump without a load cell. To verify the advantages of the simplified pullout test(low cost, simplicity, and convenience), four wall specimens were tested with two levels of concrete strength, 30 MPa and 50 MPa, using a simplified pullout tester with a load cell. The pullout load and concrete compressive strength were measured every day until day 7, day 14, day 21 and day 28. It was found that the pullout load was very similar to the compressive strength. Therefore, we have verified that a simplified pullout test can be used to evaluate the in-place strength of high-strength concrete in structures. The prediction equation of the groove diameter of the break-off bolt(y) with the concrete strength(x) was derived as y=0.05x+3.79, with a coefficient of determination of 0.88 found through regression analysis.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.3
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• pp.314-321
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• 1995

Experiments were conducted to obtain information on separation of nonviable seeds from seed lots of rape, Chinese cabbage and radish, by nondestrutive ways. Seeds were artificially aged at 90% relative humidity(RH) and 45$^{\circ}C$ to get different seed qualities. Large amounts of amino acids, proteins and sinapine were leaked from the dead seeds into water in the course of 4~8 hours soaking, while high quality seeds did not leak in all crops. Percentage of normal seedlings from nonfluorescent cellulose coated seeds of rape, Chinese cabbage and radish under ultraviolet light was 96, 96 and 74%, while that of fluorescent seeds was 8, 9 and 1%, respectively. Cellulose coating and storage of Chinese cabbage and rape seeds at 60 and 75% RH for 3 months and 90% RH for 2 months did not deteriorate seed quality. But percentage of normal seedlings from nonfluorescent radish seeds stored at 60, 75 and 90% RHs for 3 months was 63, 64 and 2%, respectively.