The properties of materials used in preparing concrete play an important role on the performance of concrete during its lifetime. Concrete generally provides adequate fire resistance for most applications. However, the strength and durability properties of concrete are significantly affected when subjected to elevated temperature. Terrorist attack, accidental fire breakout and different type of explosions produce a rapid change of temperature for a short period. This study was focused on improving the elevated temperature resistance of normal concrete by using Ground Granulated Blast Furnace Slag (GGBFS) as cement replacement and fine aggregate replacement and Brick Break (BB) as coarse aggregate replacement. Different replacement percentages of GGBFS and BB were used in this study (10%, 20% and 30%). Percentage of GGBFS replacement was calculated based on the dry weight of cement material, while the percentage of BB was calculated based on the weight of coarse aggregate. Nine mixes in additional to the reference concrete mix (25 MPa) considered in this study were exposed to high temperatures of 300, 600 and 800°C. Moreover, cooling system effect of heated concrete cubes have been investigated through two cooling procedure [Air cooling and Water cooling (quenching)].
Physical and mechanical properties of the developed mixes including residual compressive strength, mass losses, adsorption, and water absorption have been determined. Test data indicated that high temperature caused significant deterioration in the properties of concrete; the addition of GGBFS and BB could all effectively improve the residual compressive strength of concrete. For all series there is decrease in compressive strength with increase in temperature this decrease reached to 50% for control mix at 800°C in case of slow cooling in air, however the residual compressive strength was 65 and 60% for mixes containing GGBFS and BB respectively