Physicochemical and mechanical changes of thermally damaged cement pastes and concrete for re-curing conditions

Thermally damaged concrete recovers its material properties under specific post-heating curing conditions. Among the previous studies to investigate the effects of post-heating curing, the nonlinear resonance vibration method was recently proposed to evaluate contact-type defects of concrete induced by high temperature although the use of physicochemical analysis is not reported to investigate the rehydration products of concrete on post-damage curing conditions. This study performed destructive and nondestructive tests, such as the measurement of tensile strength, dynamic elastic modulus, and hysteretic nonlinear parameter, to evaluate the degree of thermal damage of concrete and its restoration. Various types of concrete samples were prepared according to the different exposures of high temperature and relative humidity for re-curing. In addition, XRD analysis of heated cement pastes was performed to identify the formed and disappeared hydration products, and physicochemical characteristics of thermally damaged concrete was discussed with respect to various exposed temperature and re-curing conditions.