Influences of cooling regime on the residual strength of SCC incorporating PPF after fire

Abstract

This research aims at the effects of elevated temperatures and cooling regimes on the fire resistance of self-compacting concrete incorporating polypropylene fibre (SCCPPF) and normal self-compacting concrete (SCC). Both concretes were exposed to elevated temperature of 200 °C, 400 °C, 600 °C and 800 °C for a duration of one hour. After fire, the concrete specimens (f100×200mm) were cooled to room temperature using two methods of air cooling and water cooling. The results indicate that the SCC specimens exhibited explosive spelling at elevated temperature, which were dried previously for 3, 5 and 7 days before testing. On the contrary, the SCCPPF specimens without dried previously didn't present explosive spelling. The surface cracks of both kinds of concrete specimens become evident by increasing temperature. The surface cracks of specimens with water cooling were wider and concentrated each other compared with those of SCC. The strengths of both specimens decreased with increasing temperature. Different cooling regimes affect the residual compressive strength of concrete. When the temperature reached to 200 °C, the residual compressive strengths of the specimens with air cooling are higher than those of the specimens with water cooling. For the concrete specimens subjected to the temperatures of 200 °C and 400 °C, two cooling regimes resulted in almost the same residual compressive strength for the SCCPP specimens, but the SCC specimens presented lower residual compressive strengths with water cooling than those with air cooling.