Performance evaluation of coconut fiber ash as mineral filler in asphalt mixture

Agricultural waste materials are potentially dependable and affordable road construction materials that help to develop sustainable pavements, reducing nuisance waste and minimizing construction costs. To determine the suitability of coconut fiber ash (CFA) for use as a filler in asphaltic concrete, this study evaluates the effects of CFA as a filler on the properties of asphaltic concrete. According to ASTM requirements, tests to ascertain the physical and chemical properties of the bitumen, filler, and fine and coarse aggregate were conducted. Marshall specimens were created using varying percentages of 5%, 10%, 15%, 20%, and 25% of coconut fiber ash. To assess each sample’s effectiveness, six replacement rates of 5.0 to 7.5% at an interval of 0.5% by weight were used to determine the optimum bitumen content (OBC), and volumetric characteristics like flow test, stability, density, and air void in mineral aggregates were studied. It was observed that 15% of CFA filler replacement achieved the best values of OBC at 6.3%, maximum stability at 14.4 KN, flow at 3.8 mm, void filled with bitumen (VFB) at 84.9%, bulk density at 2.55 g/cm³, air void at 4.3%, and lastly marshal quotient value was 3.8 KN/mm which met all the requirement of the standard specification for medium-traffic roads in asphalt mixture. To ensure the optimum performance of the CFA-modified asphalt mixtures, a 15% CFA is recommended.