Estimation of Concrete Strength by Nondestructive Methods

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We have studied and carried out the experiments on the estimation of strength of massive concrete test piece by non-destructive methods from 1989. In 1995 and 1996, we carried out the following two experiments ;(]SY.encircleda.[) The estimation of massive concrete strength by ultrasonic pulse velocity for the massive test pieces with height*width*depth = 70*60*40,70*40*40 and 70*20*40cm at the ages 7,14,28 and 56 days. And at the end of age, the compressive strength of concrete cores bored from massive test pieces were measured.(]SY.encircledb.[) The influences of diameter and length of test piece on the ultrasonic pulse velocity. The sizes of test piece were 3 diameters (10,15,20cm) and 5 lengths (20,30,40,50,60cm). At the ages 7,14,28 days, ultrasonic pulse velocity was measured.From these experiments, the following results were obtained ;(1) The strength development in a massive concrete test piece with nearly same size of actural structural member is estimated by ultrasonic pulse method fairly accurately.(2) To estimate the compressive strength and the density in a massive concrete test piece, the bored concrete cores with 7.5 cm diameter is fairly better than those with 10cm.(3) The ultrasonic pulse velocity through the concrete test piece decreases with the increasing of diameter and length of test pieces. As compared with the length of test piece, the diameter greatly influences the decreasing of ultrasonic pulse velocity.