Experimental evaluation of rice husk ash and fly ash as alternative fillers in hot-mix asphalt

Ever-growing concern to protect the environment concentrated the attention of the society on the possible re-use of different agricultural and industrial wastes in road construction. This research study depicts the effect of using wastes like rice husk ash (RHA) and fly ash (FA) as a replacement of conventionally used hydrated lime (HL) as fillers in hot-mix asphalt (HMA). Primarily, the dense graded bituminous macadam (DBM) mix specimens were made in the laboratory with varying proportions ranging from 2% to 8% of HL, RHA and FA by following design mixes according to the Marshall method and compared the results with control mix as prepared by utilising 2% HL. The performances of the said mixes were studied through the Marshall quotient, indirect tensile strength and tensile strength ratio. Results of investigation show better performance of HMA with the addition of RHA and FA and also proved to be economical as the optimum bitumen content is reduced by 7.5% from that of control mix when added at 4% filler ratio. Further, RHA shows a greater affinity to the bitumen attributing the highest stiffening effect of the bituminous mastic droplets compared to that of other used fillers with good compatibility at the micro level by satisfying the essential criterion.