Influence of recycled rice husk ash filler on the mechanical performance of asphalt mixtures: A mortar scale analysis

Abstract

Using industrial or agro-industrial wastes as alternative raw materials to manufacture asphalt mixtures brings advantages such as conserving natural resources and reducing environmental problems. Among these wastes are (a) rice husk ash (RHA) and (b) recycled rice husk ash (RRHA), obtained by controlled and uncontrolled combustion of rice husks, respectively. Previous studies have shown a high potential for RHA to be used as a filler in asphalt mixtures. However, the existing literature on RRHA usage and its corresponding applications is limited. Based on this background, the main objective of this study was to investigate the effects of RRHA when used as a filler on the mechanical properties of asphalt mortars/mixtures. For this purpose, the behavior of asphalt mortars (a combination of asphalt binder blended with sand and RRHA filler) was evaluated using the dynamic mechanical analyzer (DMA) with the three-point bending test. The test results suggest that RRHA reduces the workability and ductility of asphalt mortars. Furthermore, while RRHA indicated superior moisture-damage tolerance, brittle RRHA asphalt mortars with reduced fatigue strength were also produced. The optimum RRHA dosage for optimizing the asphalt mortar's mechanical properties/performance should not exceed 13.5% on the total weight of the mortar for the materials and test conditions. As a supplement to this study's findings, further research involving the combination of RRHA with conventional fillers and different materials (i.e., asphalt binders and aggregate types) is suggested to quantitatively assess the scaled-up mechanical performance of the asphalt mortars and their subsequent validation in asphalt mixtures.