Quantitative damage estimation of concrete by acoustic emission

Damage estimation of structural concrete from concrete samples is developed, combining acoustic emission (AE) measurement with damage mechanics. The AE activity of a concrete sample during a uniaxial compression test is quantitatively analyzed, based on the rate process theory. AE activity under compression is very high from low stress level in the concrete sample which contains a number of microcracks. In contrast, AE activity of sound concrete remains low until impending final failure. This discrepancy of AE activity is quantitatively estimated from the rate. Empirically, it is confirmed that the rate is substantially associated with pore volume that is responsible for the damage in concrete. Then, the damage is quantitatively defined by damage mechanics. Correlating the rate with the damage parameter, quantitative estimation of the damage is proposed. The applicability of the procedure is confirmed in concrete samples of controlled damage due to freezing and thawing. Furthermore, the procedure is applied to concrete-core samples taken from an existing bridge. The results suggest that the damage of concrete at the current (initial) state could be readily estimated from AE rate process analysis without knowing the original state of the concrete at construction. (C) 2001 Elsevier Science Ltd. All rights reserved.