Static and impact behaviour of recycled aggregate concrete under daily temperature variations

Concrete continuously suffers from impact loading and variations in daily temperature. In this study, tests on static compressive, static flexural, and impact compressive concrete specimens with different replacement percentages of recycled coarse aggregate (RCA), additional water, and cyclic temperatures were carried out to investigate the mechanical behaviour of recycled aggregate concrete (RAC). The static tests were conducted using a universal mechanical testing machine, and the impact tests were then applied using a 100-mm diameter split Hopkinson pressure bar facility. The failure mode, compressive strength, flexural strength, brittleness coefficient, strain-strain curve, and dynamic increase factor (DIF) were analysed and discussed. The results showed that (1) the influence of the replacement percentage of RCA and additional water on the static behaviour of RAC mainly depend on the effective water-to-cement ratio, RCA strength, and bond strength between the mortar and RCA, (2) the strain rate has a significant effect on the impact performance of RAC, and (3) the cyclic temperature significantly weakens the material properties of RAC. Finally, based on an empirical formula given by Comite Euro-International du Beton (CEB), a modified CEB model was proposed to accurately estimate the relationship between the strain rate and DIF of RAC.