Optimization, Modelling and Evaluation of Marshall Stability of Asphaltic Concrete with Agricultural and Industrial Wastes Through Response Surface Method

Currently, there is a significant focus on utilizing agricultural and industrial waste products as partial or full replacement for asphaltic concrete materials. This study investigated the effect of replacing conventional filler material with bamboo leaves ash and steel slag powder on the Marshall stability of the binder course in asphaltic concrete. The assessment of Marshall stability serves as a measure of strength performance to demonstrate the behaviour of the developed mixture when subjected to vehicular loads. Using central composite design, Marshal stability was selected as the response, while the percentage composition of bitumen (5.0–6.1%), coarse aggregate (27–70%), fine aggregates (5–45%), quarry dust (2–7%), bamboo leaves ash (2–7%) and steel slag powder (2–7%) were provided as process factors for the experimental design. Results showed that all the process variables were significant, and a quadratic model with an R-squared value of 0.9812 was obtained for the prediction of the Marshall stability of the asphaltic binder course. Additionally, it was revealed that the utilization of bamboo leaves ash has the potential to improve the Marshall stability of asphaltic concrete provided it does not exceed 1.44%. However, optimal range of values for Marshall stability (15.38 to 18.22 kN) was achieved through a combination of 61.1% CA and 2.0% SSP, while maintaining centre point values for the remaining components of the mixture. Therefore, the study concluded that the utilization of steel slag powder as a filler material exhibited greater enhancement in the Marshall stability of asphaltic concrete in comparison with bamboo leaves ash.