Influence of Corn Cob Ash as a Filler Material in Asphalt Concrete Mixes

In this study, an attempt has been made to assess the influence of Corn Cob Ash (CCA) as filler in asphalt concrete mix. The effect of corn cob ash on mechanical properties of the asphalt concrete such as Marshall stability, flow, volumetric properties, and indirect tensile strength of asphalt concrete for heavy traffic roads has been evaluated. A total of thirty (30) asphalt concrete specimens were prepared with basaltic stone dust (BSD) and corn cob ash as a filler with bitumen content between 3.5% and 5.5% at varying increments of 0.5% and the Marshall stability test was performed on full mixes to determine the Optimum Bitumen Content (OBC) of the mixtures. From the test results, it is seen that specimens made with corn cob ash and basaltic stone dust are found to have satisfactory Marshall properties and moisture susceptibility showed that mixes using CCA filler provide better resistance to moisture effect than mixtures using BSD filler. Optimum bitumen content of CCA, and BSD were found out as 4.69%, and 4.86%, respectively. It is seen that maximum stability is observed by CCA filler materials. The value of stability of the asphalt concrete mixture using CCA and BSD is 11.4kN and 10.9kN, respectively, which satisfies the limiting value of 8.006 kN. Research findings indicated that the Indirect Tensile Strength Ratio (ITSR) of the paving mixes using basaltic stone dust was 93.71%, and corn cob ash was 97.04% which satisfies the criteria provided in the Ethiopian Road Authority (ERA) and Asphalt Institute Standard Specifications. Hence, it is generally concluded that the corn cob ash can effectively be used as filler in paving mixes in place of the most commonly used filler such as basaltic stone dust. Corn cob ash is a viable agriculture waste product that can be used as filler materials in the production of asphaltic concrete for heavy-trafficked roads. Overall, the use of corn cob ash as filler in hot mix asphalt concrete partly solves the significant agricultural waste disposal problem of the environment.