Coal Bottom Ash as Partial Replacement of Fine Aggregate in Asphaltic Concrete

Abstract

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.