EXPOSURE TO ELEVATED TEMPERATURES AND COOLED UNDER DIFFERENT REGIMES - A STUDY ON BLENDED CONCRETE

Abstract

Fire is one of the most destructive powers to which a building structure can be subjected, often exposing concrete elements to elevated temperatures. The relative properties of concrete after such an exposure are of great importance in terms of the serviceability of buildings. Unravelling the heating history of concrete and different cooling regimes is important to forensic research or to determine whether a fire-exposed concrete structure and its components are still structurally sound or not. Assessment of fire-damaged concrete structures usually starts with visual observation of colour change, cracking and spalling. Thus, it is important to know the effect of elevated temperatures on strength retention properties of concrete. This study reports the effect of elevated temperature on the mechanical properties of the concrete specimen obtained by replacing 30% OPC by GGBS and cooled differently under various regimes. In the heating cycle, the specimen were subjected to elevated temperatures ranging from 150 0 C to 550 0 C, in steps of 100 0 C with a retention period of 1 hour. Then the cooling regimes studied include, furnace cooling, air cooling and sudden cooling. After exposure to elevated temperatures and cooled differently, the weight loss, residual compressive and split tensile strengths retention characteristics are studied. Test results indicated that weight and both strengths significantly reduce with an increase in temperature and are strongly dependent on cooling regimes adopted.