Influence of Cassava Peel Ash on Bruce Marshall Properties of Asphalt Concrete under Submergence

The use of agricultural waste materials in highway construction has gained attention due to growing concerns about environmental sustainability and material scarcity. This study evaluates the influence of cassava peel ash (CPA) as a mineral filler on Bruce Marshall properties of asphalt concrete under submergence. CPA was incorporated at varying rates (0%, 2.5%, 5%, 7.5% and 10%) by weight of aggregate, and the resulting mixes were tested for stability, flow, density, air voids (Va), voids in mineral aggregate (VMA), and voids filled with asphalt (VFA). Results revealed that the inclusion of CPA up to 7.5% enhanced all Marshall properties by exceeding its minimum specification when submerged in water for up to 3 days. With an overall improvement of approximately: 49.34 - 59.60% in stability, 9% in flow, 0.8% in density, 20.93 - 26.02% in Va, 3.37 - 3.7% VMA and 10.80 - 11.11% in VFA as compared to the control mix, while higher percentages beyond 7.5% led to a decline in all Marshall properties due to excess CPA content. The optimal CPA replacement level was identified at 7.5%, and it is suitable when the pavement is under submergence for not more than 3 days. These findings demonstrate that cassava peel ash is a viable supplementary material for improving asphalt performance while promoting sustainable waste management practices in tropical regions.