This paper presents an experimental research on the influence of defects of recycled coarse aggregate on mechanical properties of recycled aggregate concrete (RAC).Concretes at two water/binder ratios (0.255 and 0.586) were broken into recycled aggregate (RA).A type of thermal treatment, i.e.heating to target temperature 620 C, which was maintained for 3 hr, was employed to remove mortar from gravel in RA.