This document presents the results of an experimental study investigating the effects of partially replacing coarse aggregate with cinder in concrete. M30 concrete mixes were designed using the ISI method. Cubes and cylinders were cast with 0%, 20%, 40%, 60%, 80%, and 100% replacement of coarse aggregate with cinder and tested for compressive strength, split tensile strength, and flexural strength at 7 and 28 days. The results showed that compressive strength, split tensile strength, and flexural strength generally decreased as the cinder replacement ratio increased. The highest strengths were obtained with 40-60% cinder replacement. Overall, partially replacing coarse aggregate with cinder produced lightweight concrete with reasonably good strength.