Using agricultural residue sustainably: Enhancing asphalt properties with rice husk ash and analyzing its mixture performance using response surface methodology

The employment of agricultural waste in asphalt pavement has been advocated by scientists as a strategy for raising waste recycling proportions, conserving natural resources, and handling disposal difficulties. Rice husk is an agricultural waste product with a large volume that is often incinerated for energy generation or as a means of disposal. This study conducted an investigation into the impact of rice husk ash (RHA) on the physical performance properties of asphalt binder, which included parameters such as penetration, softening point, viscosity, ductility, and storage stability, along with several temperature performance indexes. The effect of RHA and asphalt concentrations on the strength and volumetric properties of the asphalt mixture was subsequently explored through the application of response surface methodology (RSM). The compacted mixtures were subjected to Marshall stability, flow, and indirect tensile strength (ITS) tests. Subsequently, the study analyzed the effects of preparation factors using RSM with the central composite design (CCD) approach. Mathematical modeling was then carried out to predict the responses. In addition, the microstructure of the modifier and modified asphalt was examined using a scanning electron microscope (SEM). Based on the findings, the inclusion of RHA was observed to have a significant beneficial impact on the physical properties of the asphalt. Additionally, it was observed that asphalt binders could be effectively modified using up to 10% RHA, without encountering any phase separation problems during high-temperature storage. The RSM analysis indicated that changes in the preparation factors significantly influenced the flow, stability, and tensile strength of the asphalt mixture as well as its volumetric properties. The proposed models demonstrated significant agreement with the empirical findings, demonstrating a substantial correlation. Additionally, the numerical optimization findings indicated that the optimal mixture proportions to achieve the desired maximum responses were 7.6% RHA and 5.3% asphalt content.