Rice husk consists of a huge amount of silica when it is burned properly, and cement can be partially replaced by rice husk ash (RHA) to make concrete. In the present experimental research, flexural strength (FS), workability, compressive strength (CS), and indirect split tensile strength (STS) of M30 grade concrete are investigated by partially replacing cement with RHA with an increment of 5%. The influence of the various percentages of RHA as a cement substitution material on the workability, CS, STS, and FS is compared with that of normal M30 grade concrete. The water-cement ratio is 0.55, which is maintained constant. The test results also concluded that the CS, STS, and FS of concrete decreased with an increase in RHA above 15%. The findings of the experimental research show that the optimum percentage of RHA was 15%, at which point the CS, STS, and FS were at their maximum, and any additional RHA addition beyond 15% causes a significant decrease in the CS, STS, and FS, and that it is recommended to replace cement with RHA in the range of 5–15% to achieve an effective and high strength of concrete.1 © 2022