In this paper, the effect of rice husk ash (RHA), as silicate impurities, on the microstructure and mechanical properties of calcium aluminate cement concrete (CACC) is explored. Various mechanical tests, including tests for obtaining the compressive, splitting tensile, flexural strengths and elastic modulus, were performed on different mixture designs containing different volume percentages of RHA (0, 2.5, 5, 7.5, and 10%) at W/Cs of 0.4 and 0.5. Furthermore, the impact of RHA on the microstructure of this concrete was examined through careful analysis of the scanning electron microscope (SEM) images and energy dispersive X-ray spectroscopy (EDS) results. The results demonstrate that, At W/C of 0.5, the microstructure and mechanical properties were improved, with the greatest improvement for the RHA substitution percentage of 5%. However, at W/C of 0.4, the addition of RHA showed no positive effect, which can be attributed to a higher specific surface area of RHA than cement.