Residual Mechanical Response of Recycled Aggregate Concrete after Exposure to Elevated Temperatures

A considerable number of investigations have been conducted on the mechanical and material properties of concrete made with recycled concrete aggregate (RCA), as these properties can often be different than those of conventional concrete. However, relatively little attention has been directed at studying the performance of concrete made with RCA at elevated temperatures. This is despite the fact that coarse aggregates play an important role in the behavior of concrete under fire exposure. To address the lack of knowledge, an experimental program was conducted in which six different concrete mixes were prepared with different combinations of coarse aggregates made from recycled concrete aggregate, river gravel, and crushed limestone aggregates. A total of 204 concrete cylinders ($100\times 200\mathrm{mm}$) were cast and heated under four different temperatures: 20°C (ambient temperature), 250, 500, and 750°C. The residual compressive and tensile strengths, moduli of elasticity, and damage and failure patterns of the concretes were observed and analyzed. The results indicate that concrete with aggregate both fully and partially replaced with RCA exhibits good performance under elevated temperatures and it can be considered comparable to conventional concrete. No concrete disintegration was observed when RCA concrete was heated up to 750°C. The results of tests of residual mechanical properties show some variation among concretes made with different replacement percentages of RCA.