Appraisal of Asphalt Concrete with Coal Bottom Ash as Mineral Filler

Abstract

This study was conducted to access the performance of asphalt concrete produced with coal bottom ash as partial replacement of cement in the mineral filler. The Marshal Mix design method of hot mix asphalt (HMA) samples preparation and testing was adopted. Fifteen (15) samples of HMA compacted and used for volumetric and stability testing at a varying percentage of bitumen contents (5.0, 5.5, 6.0, 6.5, and 7.0%,) following the Asphalt Institute and Nigeria General Specification for Road and Bridges (NGSRB) approach for determining optimum bitumen content (OBC). An Optimum bitumen content of 5.5 % was obtained and used throughout the study. Another set of 15 samples of the HMA were prepared and compacted at varying percentage replacement of cement with CBA in the order of 15, 20, 25, 30, and 35% by volume of cement to determine the optimum dosage of the coal bottom ash that will satisfy the requirements for the strength and durability of wearing course of flexible pavement. The Marshall Stability, flow, and the volumetric properties test results obtained indicated that the samples prepared with 25% CBA as filler with OBC of 5.5% satisfied the requirements of the NGSRB for wearing course of flexible pavement. Hence, the addition of up to 25% CBA by volume of cement in asphalt concrete can reduce the consumption of cement and provide a proper means of CBA disposal.