Determination of Dynamic Youngs Modulus of Concrete at Early Ages by Impact Resonance Test

Abstract

Youngs modulus of concrete increases with hardening of the concrete at early ages. Youngs modulus measured statically has been widely used to assess the variation of modulus with curing ages. However, this method is costly because the numerous test specimens are required. The dynamic testing technique has an advantage of performing the measurement nondestructively without breaking specimens. Furthermore, the perceived difference between static and dynamic moduli is becoming smaller due to the improvement of accuracy in the static measurement. In this paper, the impact resonance method, which is a dynamic Youngs modulus measurement technique, is briefly described. Dynamic Youngs modulus of concrete of 28-day compressive strength ranging from 35 MPa to 65 MPa is evaluated at early ages by the impact resonance test. Based on the test results, it is found that the resonance frequency increases significantly even in the early curing age of concrete and the dynamic Youngs modulus correlates quite well with early-age concrete strength, showing the possibility of using this dynamic testing technique in the evaluation of concrete strength.