Micro-Structure Analysis and Mechanical Behaviour of Hot Mix Asphalt Modified with Reclaimed Asphalt Pavement Using Palm Kernel Shell Ash as Mineral Filler

Abstract

In pavement construction and production of hot mix asphalt HMA, the use of industrial and agricultural waste has gained much relevance because of its economic and environmental benefits. This research examined the effects of palm kernel shell ash PKSA on the physical and volumetric properties of HMA modified with reclaimed asphalt pavement RAP. All preliminary test conducted on the modified asphalt mixture in accordance with relevant standards showed adequacy for use in production of HMA. Marshall method of mix design was adopted for the HMA production. The bitumen content was varied from 4.5 to 6.5% (at intervals of 0.5%). The palm kernel shell ash was varied from 25% to 75% (at interval of 25%). A maximum stability of 7.1kN was recorded at 5.5% bitumen content which is a little increment in strength but good significance in material (virgin bitumen) when compared to the maximum stability of 6.9kN at 6% bitumen obtained from the control mix. The microstructural analysis of the hot mix asphalt done on the palm kernel shell ash PKSA showed a rough surface texture needed in flexible pavement construction and when comparison was done between the control specimen and the modified specimen, it shows an improvement in the interlocking arrangement of aggregates resulting in a denser mixture for the modified hot mix asphalt. In conclusion this study confirms that a blend of a 50% RAP and 50% virgin aggregates with 50% palm kernel shell ash PKSA as mineral filler at 5% bitumen content can improved strength performance of HMA, hence, the effect of PKSA as a mineral filler in HMA containing RAP is significant.