EVALUATION OF LOCUST BEAN POD ASH AS MINERAL FILLER IN HOT MIX ASPHALT

Abstract

An increase in the consumption of agricultural products generates large quantities of waste daily. The husks of the locust bean seeds when removed from the plant are littered in the environment which negatively affects the environment. In this research, locust bean pod ash (LBPA) was used as a mineral filler in hot mix asphalt. Physical and chemical tests were done on the aggregate, bitumen and LBPA, showing adequacy for use in asphalt concrete production. All tests were conducted in accordance with relevant standards. LBPA was admixed with granite dust from 0–50% (at intervals of 10%) with varying bitumen content from 4–7% (at 0.5% intervals). For this experiment, the Marshall mix design method was used. The Marshall stability of samples containing LBPA improved by 19%, from 8.16kN to 9.67kN. Similarly, Marshall flow decreased by 19% from 3.4 mm to 2.75 mm. The density-void analysis of the asphalt samples also revealed an improvement. The microstructural examination revealed an enhanced structural arrangement due to the flocculation of the LBPA particles. Overall, the hot mix asphalt samples meet the Federal Ministry of Works and Housing specifications for flexible pavement-wearing courses. It was determined by the study that adding 40% LBPA with 60% granite dust at 5% bitumen content would improve the performance of hot mix asphalt.