ABSTRACT
The compressive stress-strain relationships of concrete exposed to elevated temperatures were studied at a macro-level (Castillo & Durrani, 1990; Khoury et al., 2002; Cheng et al., 2004). However, these test results cannot identify the main contributor to the thermal degradation. It has been reported that using a SEM technique the thermal decomposition and the thermal cracks could be correlated to the degradation, but most of the previous observations were conducted under cool conditions so that they were suitable for understanding the residual properties of concrete after high temperatures. As for the thermal damage of concrete during a heating up process, it is of interest to observe the change of the microstructure of the cementitious materials in a real-time mode.
