Shock vibration test of concrete

Abstract

A new test method for evaluating the effects of shock vibration on concrete has been developed. In this method, shock vibrations are applied to prismatic specimens by hammering each specimen at one end in the longitudinal direction. During the test, the shock vibration applied is measured by using an accelerometer, from which the signals are first digitized and then analyzed to yield the peak particle velocity of the pure vibration component, taken herein as the intensity of the shock vibration. The short- and longterm effects on the concrete are examined by: 1) visual inspection of cracks; 2) ultrasonic tests conducted before and after the hammer impact; and 3) direct tension and equivalent cube strength tests of hammered and control specimens at the age of 28 days. Test results obtained thus far revealed that the major damage caused by shock vibration was the formation of cracks. Even when cracks were not observed on the surfaces, however, there could be significant reductions in ultrasonic pulse velocity and tensile strength, probably due to the formation of internal cracks not observable on the surface. On the other hand, the effect on compressive strength appeared to be relatively small.