Effect of Locust Bean Pod Ash as Filler on Hot Mix Asphalt Mixtures

At present, the conventional sources for mineral filler in asphaltic concrete mixes are the chemical element of lime, cement, quarry dust and fly ash which has some health hazards. This study presents a laboratory investigation on the effects of locust bean ash as filler in Hot Mix Asphalt (HMA) production for a wearing course in order to find a cost-effective, environmentally friendly and less hazardous alternative to the traditional mineral filler of cement or lime. A total of 90 trials of bituminous mixtures with two types of mineral filler (locust bean ash and ordinary Portland cement) at 4 loading rates of 0, 2.5, 5 and 10% were evaluated for mechanical (strength) and workability performance properties according to standard asphalt mix Marshall Method of design. The Marshall stability, flow, density and void properties were developed for each mineral filler contents and the corresponding optimum binder content were determined for the general specification for roads and bridges in a subtropical region. The 2.5% for the two types of mineral filler was found to produce best performance of the HMA at optimum binder content of 5.5%. Also, the use of locust bean ash was found to be hazardous-free. Similarly, mineral filler from biomass was found to be advantageous for use as mineral filler source in asphalt mix production. Its application in the subtropical region where the biomass wastes are mostly abundant was recommended for HMA.