This paper evaluated the effects of sawdust ash on the characteristics of asphaltic concrete with a view to investigating its suitability as an additive in asphaltic concrete. The sawdust was obtained from Alekuwodo in Osogbo, Osun state, Nigeria. The bitumen, coarse aggregates, fine aggregates, and mineral filler were obtained from Espro Asphalt Plant, Ife-Ibadan Road, Osun state, Nigeria. The sawdust was burnt into ash using a furnace at a temperature of 800°C, allowed to cool and sieved through 75 µm BS sieve (No.200). The properties of the materials were determined using standard procedures. Asphaltic concrete samples were prepared with sawdust ash at 0, 5, 10, 15, 20, and 25 % by weight of the granite filler. The samples were subjected to Marshall Stability test. The stability, flow, density, voids filled with bitumen (VFB), air voids (AV) and voids in mineral aggregate (VMA) were determined. The values of stability, flow, bulk density, voids filled with bitumen, air voids and voids 3 filled in mineral aggregates at 15 % optimum sawdust content were, 18.2 kN,3.40 mm, 2.36 g/cm , 77.13 %, 4.05 % and 17.71 %, respectively. The result showed that, the inclusion of sawdust ash in asphaltic concrete improved its properties.

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The effect of coal bottom ash (CBA) on the characteristics of asphaltic concrete was investigated with a view to assess its suitability as a partial replacement of fine aggregate. Coal procured from Lafia-Obi coal mines was burnt in a fixed bed combustor until a sand size residual was produced. The properties of the materials used for the study were characterize using standard procedures. The CBA was introduced in the asphalt mix at an increasing rate of 10, 15, 20 and 25% content by weight of the fine aggregate and test samples of asphaltic concrete were prepared. The samples were subjected to Marshall stability test. Results showed that the specific gravity and absorption test for granite dust were 2.45 and 0.25%, respectively, while those of the CBA were 2.86 and 0.58% respectively. The result of stability, flow, bulk density, voids filled in bitumen (VFB), air voids (VA) and voids in mineral aggregate (VMA) of the asphaltic concrete at 0% CBA were 12.02 kN, 3.04 mm, 2.491g/cm3, 66.0%, 4.3%, 12.7% respectively; while the values at 20% CBA content were 16.97 kN, 3.51mm, 2.514g/ cm3 , 71.2%, 3.4%, 11.9% respectively. The result showed that coal bottom ash in asphaltic mix improved its properties.