The excessive extraction of natural river sand and stockpiling of coal bottom ash on landfills significantly caused many
problems related to the environment and humans. The present study is aimed to investigate the effect of using coal bottom ash to partially or fully replace natural river sand in concrete. Five concrete mixtures were designed with a fixed water-to-binder ratio of 0.45. The bottom ash was used to replace 0, 30, 50, 70, and 100% river sand in the concrete mixture. Test results showed that the maximum compressive strength value of about 24 MPa was obtained with the concrete sample containing 30% bottom ash. In addition, the water absorption, porosity, and electrical resistance of concrete were found to be increased, whereas ultrasonic pulse velocity and thermal conductivity of concrete decreased with increasing bottom ash content. Further increasing the replacement level (over 30%) caused the adverse effects on the concrete’s properties. In real practice, the replacement of natural river sand in concrete by bottom ash is suggested at a maximum level of 30%.