Evaluation of Maize Cob Ash as Filler in Hot-Mix Asphalt Concrete Production

Increased production of wastes from different companies and agricultural areas creates severe surrounding trouble in terms of management and removal in Ethiopia. The utilization of agricultural waste products and residue in construction work is an excellent alternative solution in reducing the solid waste disposal problem of the environment. In this research, the application of maize cob ash (MCA) in asphalt concrete production is investigated as filler material in hot mix asphalt for binder course. Physical and chemical tests were investigated for MCA. Asphalt specimen prepared using crushed stone dust (CSD) as filler without maize cob ash used as a control material. The content of CSD filler was replaced with MCA at a rate of 0%, 25%, 50%, 75%, and 100% by weight of CSD. A total of thirty (30) mix specimens were prepared, fifteen asphalt concrete samples were prepared by a 6% of CSD 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 (OBC). The remaining specimen was prepared at 5.30% OBC to find out the optimum replacement rate of MCA. The values of Marshall stability, flow, unit weight, air voids, and voids in mineral aggregate and voids filled with asphalt at 75% replacement of CSD with MCA 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 MCA could be replaced the CSD 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. Results also indicated that agriculture waste materials used in this investigation can be constructively used as partial replacement of CSD fillers in the hot mix asphalt binder course. Overall, it is established that MCA is a viable agriculture waste product that can be used as filler materials at a specified percentage in the production of asphaltic binder courses for heavy-trafficked roads.