Utilization of coconut shell ash as filler for hot mix asphalt containing reclaimed asphalt pavement

Abstract

This research examined the strength properties of hot mix asphalt (HMA) containing a blend of reclaimed asphalt pavement (RAP) and virgin aggregates with granite dust was replaced with coconut shell ash. Physical test was carried out on the RAP and virgin aggregates. Chemical and geometrical test was done on the coconut shell ash (CSA). All preliminary test conducted in accordance with relevant standards showed adequacy for use in production of HMA.  Marshall method of mix design was adopted for the HMA production. Asphalt Institute blending charts was used to determine the quantity of RAP to be incorporated into the mixture. The bitumen content was varied from 4.5 – 7.5% (at intervals of 0.5%). The coconut shell ash was varied from 25% to 100% (at interval of 25%). A maximum stability of 6.8kN was recorded at 5% bitumen content which is a little increment in strength when compared to the maximum stability of 6.7kN obtained at the control.  The microstructural analysis of the hot mix asphalt done on the optimum coconut shell ash replacement showed a rough surface texture needed in flexible pavement construction and when comparison is done between the control sample and optimum replacement samples, it shows an improvement in the interlocking arrangement of aggregates resulting in a denser mixture for the modified hot mix asphalt. The study recommends a blend of a 70% RAP and 30% virgin aggregates with 50% coconut shell ash at 5% bitumen content for an improved strength performance of HMA