Age influence on compressive strength for concrete made with different types of aggregates after exposed to high temperatures

Abstract

This study investigates the influence of concrete age and the type of coarse aggregate on compressive strength after exposure to high temperatures. Three coarse aggregates were used: crushed clay bricks as recycled aggregates, expanded glass as lightweight aggregates, and normal quartz aggregates. Specimens were initially cured in water for seven days, and then kept in laboratory conditions for different durations (28 days, 120 days, and 240 days). On the age of 120 and 240 days, specimens were exposed to high temperatures ranging from 200 °C to 1000 °C, and their residual compressive strength was determined.Results indicate that the compressive strength tests for the unheated specimens revealed an increase in strength with age, which can be attributed to the hydration of cement and the formation of a denser microstructure. The results of the residual compressive strength tests for concrete with quartz aggregates (M1-QZ) at 120 and 240 days showed a decline with increasing temperature and age. At 120 days, the strength ranged from 74.3% to 16.9%, and at 240 days, it ranged from 83.5% to 23.8%. Similarly, concrete with expanded glass aggregates (M2-EG) demonstrated decreased compressive strength with increasing temperature and age. The strength ranged from 94.3% to 8.6%, and 88.9% to 10.3% at 120 and 240 days, respectively. In contrast, concrete with crushed clay bricks (M3-CB) exhibited more favourable resistance to high temperatures, with a lower compressive strength reduction. The values ranged from 97.9% to 23.1% at 120 days and from 98.7% to 22.2% at 240 days. The reduced compressive strength after exposure to high temperatures can be attributed to the differences in thermal expansion and aggregates and the moisture loss.These findings demonstrate that the coarse aggregate type significantly influences the concrete's residual compressive strength after exposure to high temperatures.