In recent years, semi-flexible pavement surfaces have been identified as one of the alternatives to conventional rigid and flexible pavements due to its advantages over both the pavements. In semi-flexible pavement surfaces, the cementitious grouts are spread on the surface of a porous asphalt skeleton and allowed to penetrate through the depth. The cementitious grouts contribute to the durability (in terms of resistance to oil, water and adverse weather conditions) and the performance of semi-flexible pavement surfaces. The physical and performance properties of semi-flexible pavement depend on the voids in the porous asphalt skeleton and suitable compositions of cementitious grouts. This paper presents the design and optimization of compositions of cementitious grouts using Response Surface Methodology (RSM) technique. Similarly, statistical models are developed to predict the flow and compressive strength properties of grouts using RSM. Water-cement ratio (w/c) and Superplasticizer (SP) were chosen as two independent variables, and their effect on flow and compressive strength properties were investigated. Based on RSM analysis, the adjusted R2 was in reasonable agreement with predicted R2 because the difference was less than 0.2, and the models were found to be significant. Finally, the optimized compositions of grouts were validated by performing experimental program. © 2020 IOP Publishing Ltd. All rights reserved.