EVALUATION OF HIGH-TEMPERATURE-INDUCED DAMAGE TO CONCRETE

The evaluation of high-temperature-induced damage to an ordinary Portland cement concrete was carried out. Results showed that the uniaxial compressive strength of the concrete linearly decreased with the increasing exposure temperature. After a high-temperature exposure, the concrete was more easily deformed under loading. The as-received cement was dense and free of obvious holes. The cement and the aggregate were bonded tightly, and no cracks were observed. Above 200 degrees C, dehydration and decomposition of calcium silicate hydrate during the high-temperature exposure led to small holes, formed in the cement, and microcracks at the bonding aggregate/cement interface. With the increasing exposure temperature, the small holes formed in the cement grew up and the microcracks located at the aggregate/cement interface gradually expanded into a coherent crack network. Above 600 degrees C, the cement was significantly locally pulverized and the microcracks at the aggregate/cement interface were further broadened. Below 400 degrees C, detected phases of the exposed mortar sample were the same as those of the as-received mortar. After exposures to 600 degrees C and 800 degrees C, peaks of CaO were also detected besides the pre-existing phases. The reaction between CaO and SiO2 enhanced the decomposition of CaCO3 while promoting the formation of Ca2SiO4.