Comparative Study of Different Subbase Materials

California Bearing Ratio (CBR) and static and cyclic triaxial tests were conducted on the four most frequently encountered local materials—fly ash, coarse sand, stone dust, and river bed material (RBM)—for their use in the subbase layer of a flexible pavement. The CBR of stone dust was the maximum value of all, but its behavior under dynamic load in triaxial tests was inferior to that of the other materials. Fly ash has low CBR, but better stress-strain behavior than stone dust. The results show that RBM is the best material for use in the subbase layer as it had good CBR, high E-value and resilient modulus, and low permanent strain values compared to other materials used in this study.