AN EXPERIMENTAL INVESTIGATION OF BOND AND COMPRESSIVE STRENGTH OF CONCRETE WITH MINERAL ADMIXTURES AT HIGH TEMPERATURES

The effects of high temperature on the mechanical properties of concrete have been investigated since the middle of the 20th century [1–7]. A number of research studies have indicated that the addition of silica fume to concrete densifies the pore structure of concrete, which can result in explosive spalling due to the build-up of pore pressure by steam [6]. The evaporation of physically absorbed water in concrete starts at 80°C, which induces thermal cracks due to thermal shrinkage. Concrete at elevated temperatures therefore shows inferior performance as compared to concrete at normal temperatures [7]. The physical changes and chemical decomposition of major concrete constituents at elevated temperatures is demonstrated in widely spread cracks, explosive spalling or both. In reinforced concrete members, such changes are reflected by a reduction in the mechanical properties, increase in the permeability of concrete, and weakening of the bond strength between embedded steel and concrete [8–9]