Determining optimum fly ash content for Stabilized subbase materials in road pavements

ABSTRACT The investigation of fly ash content for stabilized subbase materials in road pavements was presented in this study. The effects of partial replacement of cement by 17%, 33%, 50% of fly ash contents by total weight of mixture were investigated to evaluate mechanical properties of stabilized subbase materials using the unconfined compressive strength (UCS) test, indirect tensile (IDT) test, and resilient modulus test. It was found that the replacement of cement by 33% of fly ash can use for stabilized subbase material. In addition, a strong relationship between IDT and UCS strength, and resilient modulus and UCS is given which is the coefficient of determination of developed correlation to be 0.9 and 0.82, respectively. It was suggested that the IDT strength or the resilient modulus can be estimated from a UCS test. Finally, the performance of cement replacement with fly ash was evaluated using mechanistic empirical pavement design guide (MEPDG) program. Based on the results of the study, it can be concluded that the cement replacement with 33% fly ash can enhance the performance life significantly and the construction cost reduction can be around 23%, compared to using conventional subbase material.