SettingTime and Strength of Concrete Using the Impact-Echo Method

Abstract

Tests were performed to evaluate the feasibility of using the impact-echo method to determine setting time and to monitor strength development of concrete. In the impact-echo method, the test object is subjected to point impact and the surface displacement is monitored at a point adjacent to the impact. From the measured displacement waveform and the thickness of the object, the P-wave velocity is determined. Changes in the P-wave velocity with time reveal information about the development of mechanical properties as the concrete matures. The results are discussed of setting-time tests on concrete mixtures of two water-cement ratios both with and without set-controlling admixtures. The results are also discussed of tests that examined the relationship between P-wave velocity, as determined by the impact-echo method, and the compressive strength of concrete. It is concluded that the impact-echo method is a promising nondestructive technique for monitoring the development of mechanical properties in concrete from initial setting to ages of several days.