Effect of high temperature and cooling regimes on the compressive strength and pore properties of high performance concrete

This paper describes the behavior of high performance concrete (HPC), compared with normal strength concrete (NSC), after subject to different high temperatures (800 and 1100 degrees C) and cooling regimes (gradual and rapid cooling). Deterioration of compressive strength of the concrete was measured. The results obtained showed that the strength of both the HPC and NSC reduced sharply after their exposure to high temperatures. Thermal shock due to rapid cooling caused a bit more deterioration in strength than in the case of gradual cooling without thermal shock. However, thermal shock did not significantly increase the spalling of HPC. Mercury intrusion porosimetry (MIP) tests were carried out to measure changes in the pore size distribution in the concrete. Test results showed that the pore volume in the HPC increased much more than that in the NSC. A significant change in the cumulative pore volume was observed and the difference in cumulative pore volume between the two cooling regimes was less after subject to the peak temperature of 1100 degrees C when compared with that of 800 degrees C peak temperature. (C) 2000 Elsevier Science Ltd. All rights reserved.