Effect of Coconut Fibre Ash on the Performance Asphalt-Modified Concrete

This research explores the use of coconut fibre ash (CFA) as a partial replacement of filler (Stone dust) in asphalt concrete to promote  sustainable  and  eco-friendly  road  construction  in  Nigeria,  where  coconut fiber  waste  is in abundant. The study utilized conventional materials such as aggregates and 60/70 penetration grade bitumen, Stone dust was partially substituted with CFA at varying proportions of  5%, 10%, 15%, 20%, 25%, and 30% to assess its effects on asphalt concrete properties. The physical properties of aggregates and fillers were evaluated through Sieve Analysis, Moisture Content, Aggregate Crushing test, Aggregate Impact Value, and Specific Gravity tests. The basic property of 60/70 bitumen used was assessed. The chemical and mineralogical properties of CFA were analyzed via X- Ray Diffraction (XRD) and X-Ray Fluorescence (XRF). The asphalt mixture composition was produced with varying proposition of coconut fibre ash as a replacement of stone dust and marshal stability and flow result were obtained. Thereafter the microstructural analysis of modified asphalt concrete mixture were analysed using  scanning electron microscope test (SEM) to determined in the microstructure image. The result showed that the fundamental properties of aggregate and bitumen were within the American standard for testing material and federal Government of Nigeria for road and bridges. XRDand XRF result revealing notable silica content and crystalline phases including quartz, urea, graphite, silvialite, and marialite. Marshall stability results showed that the highest value of 14.77 KN occurred at 5% CFA, while the lowest value of 11.33 KN was obtained at 30% CFA, indicating optimum mechanical performance at 5% CFA. The SEM result proves uniform CFA distribution and better interfacial bonding for the lower CFA percentages. The findings show that CFA at 5-15% optimises mechanical and volumetric properties of asphalt concrete, which is a sustainable and cost-effective approach to road construction and also addresses agricultural waste management in Nigeria.