In this paper, mathematical models were developed using stress strain relations to predict the compressive strength of concrete produced with partial replacement of cement with rice husk ash. The water absorption property was also predicted but based on the assumption that the amount of water absorption in concrete is dependent on the volume fraction of rice hush ash used as partial replacement. Both the compressive strength and water absorption compared favourably with the experimental values and both decreased with increase in rice husk content. The coefficient of correlations were very high for both the compressive strength and water absorption (0.934, 0.946) showing that the proposed model can be used as a tool in the prediction of mechanical properties of concrete produced with replacement of cement with rice husk ash.