VARIATION OF CONCRETE COMPRESSIVE STRENGTH DATA OBTAINED BY USING SMALL DIAMETER CORE

Abstract

specimen, the larger the variation of the compressive strength test value, and the loading method also affects the variation of the compressive strength test value, too.
In this research, a compressive strength test using small diameter core (φ25mm and φ33mm) with h/d=2.0 is focused on the purpose for obtaining compressive strength test value with less deviation. To reduce the deviation of compressive strength test value of small diameter cores, arranging the obtained test value by using the statistical method and testing method should be based on the viewpoint of the friction influence on the end edge surface of the specimen and the loading plate was experimentally considered. The end face of the core specimens was polished, and compressive strength tests conducted under both with friction (without Teflon sheet) and without friction (two overlapped Teflon sheets with a thickness of 0.1 mm as an antifriction material on both end faces inserted between the end faces and the loading plate)
As a result, it is clarified that the deviation of compressive strength becomes small in the condition of loading without friction on φ33mm diameter small cores. In addition, when the allowable error range of the compressive strength of the small diameter core is 5.0 N/mm2, the required number of specimen to satisfy this condition is from 4 to 10, and the obtained test value of small core is found around from 80 to 90% compared to the φ100mm core strength.
Furthermore, applicability trial test of compressive strength test by using small core specimen collected from demolished T-girder of PC Bridge is conducted. The obtained result indicates that it is possible to obtain a test value of about 90% compared to φ100mm strength in case of the condition of φ33mm small core without friction loading. Then, it is clarified that its deviation use can control small diameter core strength for practical.