This study focuses on investigating the use of cement-grouted bituminous mix (CGBM) as a composite pavement material. CGBM is composed of an open-graded porous bituminous mix with an air-void content ranging from 25 to 35%. The main objective of this research is to determine the optimal proportion of cement and fly ash in CGBM to achieve enhanced performance and sustainability. To achieve this objective, various proportions of fly ash-based cementitious grout were used in the preparation of CGBM samples. The fly ash replacement levels included 0, 20, 25, 30, and 50%. The experimental investigation involved conducting tests for compressive strength, Marshal stability, and modulus of rupture to evaluate the effects of partial cement substitution with fly ash on the characteristics of CGBM. The results of the study indicate that the 75:25 mix proportion of cement and fly ash exhibits acceptable strengths in CGBM. This means that the desired performance requirements can be met by replacing 25% of the cement with fly ash. Furthermore, the incorporation of fly ash in the mix offers additional benefits beyond strength enhancement. It reduces construction costs by minimizing the need for cement and contributes to the environmental sustainability of CGBM pavements. This substitution not only decreases the carbon footprint associated with pavement construction but also promotes the utilization of industrial waste, aligning with sustainable practices.