A Laboratory Study on the influence of Coffee Husk Ash and Slag Ash Fillers on the Performance of Bituminous Concrete Mixes

This study investigated the influence of coffee husk ash (CHA) as a filler in bituminous asphalt concrete mixes containing basaltic stone dust (BSD), slag ash (SA), and coffee husk ash (CHA). The performance of bituminous concrete mixes containing various wastes on the mechanical properties of bituminous asphalt concrete for heavy traffic roads, such as Marshall stability, flow, volumetric properties, indirect tensile strength, and tensile strength ratio, has been evaluated, and their comparison was made with the conventional mix containing basaltic stone dust (BSD) filler. A total of forty-five (45) bituminous asphalt concrete specimens were prepared with basaltic stone dust (BSD), slag ash (SA), and coffee husk ash as fillers with bitumen content between 4.5% and 6.5% at varying increments of 0.5%, and the Marshall stability test was performed to determine the optimum bitumen content (OBC) of the mixtures. From the test results, it is observed that specimens made with coffee husk ash, slag ash, and basaltic stone dust are found to have satisfactory Marshall parameters, and moisture susceptibility showed that mixes using CHA filler provide better resistance to moisture effect than mixtures using both SA and BSD filler. The BSD shows reduced optimum bitumen content (OBC) by 14% compared to CHA. The values for Marshall stability of the bituminous asphalt concrete mixture using CHA, SA, and BSD were 10.25 kN, 14.58 kN, and 14.60 kN, respectively, which satisfy the limiting value of 8.0 kN. The findings indicated that the tensile strength ratio (TSR) of the paving mixes using basaltic stone dust was 89.50%, slag ash was 95.96%, and coffee husk ash was 100%, which satisfied the criteria provided in the minimum values of 80% TSR as per the Asphalt Institute Standard Specifications. Hence, it is generally decided that coffee husk ash can successfully replace the most popular fillers, such as basaltic stone dust and slag ash, in pavement mixtures. Coffee husk ash is used as a filler in hot-mix asphalt concrete, which helps to partially address the enormous environmental problem of disposing of agricultural waste.