Title: Evaluation of maize cob ash as partial replacement for mineral filler in hot-mix asphalt concrete production

Abstract

The effect of maize cob ash as a partial replacement of conventionally used filler material in hot mix asphalt for binder course was evaluated. All the volumetric properties and the physical properties of the asphalt mixture were evaluated to determine the optimum replacement of MCA in the production of binder courses for heavy traffic roads. The content of crushed stone dust (CSD) filler was replaced with MCA at a rate of 0% (control), 25%, 50%, 75%, and 100% by weight of CSD. A total of thirty (30) mix specimens prepared, fifteen asphalt concrete samples were prepared by a 6% of crushed stone dust as filler by weight of aggregate with bitumen content between 4.5% and 6.5% at varying increments of 0.5% by total weight of the mix to determine the optimum bitumen content. The remaining specimen was prepared at 5.30% OBC to find out the optimum replacement rate of maize cob ash (MCA). The stability, flow, unit weight, voids filled with asphalt (VFA), air voids, and voids in mineral aggregate (VMA) were determined. The values of stability, flow, unit weight, air voids and voids in mineral aggregate and voids filled with asphalt at 75 % replacement of crushed stone dust with maize cob ash were, 11.7 KN, 3.13 mm, 2.360 g/cm3, 4.0 %, 14.58 %, and 72.56 %, respectively. Research findings indicated an optimum value of maize cob ash could be replaced the crushed stone dust is 75% by weight of CSD filler or 4.5% by weight of aggregate in the production of hot mix asphalt binder course for heavy-trafficked roads. Hence, the maize cob ash is recommended to use as a replacement for CSD fillers in the hot mix asphalt binder course.