The purpose of this paper is to evaluate the effects of volume of coal washery rejects (CWR) on the strength properties of concrete.0%, 20%, 30%, 40% and 50% in volume of natural aggregates in the concrete mixes were replaced by an equal volume of CWR aggregates. The compressive, splitting and flexural strength properties were determined at different curing periods and compared to M 25 grade of conventional concrete (CC). From the results, it is observed that the increase in CWR replacement level decreased the strength properties. The percentage decrease in compressive strength from 20% to 30% CWR replacement was 2.55%, 3.29% and 3.72% at 7, 28 and 56 days respectively. But beyond 30%, the decrease was very much significant. Hence, it is concluded that 30% CWR replacement is considered as optimum and can be recommended for safe structural concrete. During coal washing process, large quantities of impure coal so called coal washery rejects (CWR) are getting accumulated and posing disposal problems. As the construction industry is the feasible application to reuse waste materials, this investigation is mainly intended to introduce CWR as an alternative to coarse aggregate and study the mechanical properties of CWR based concrete.