Effect of Using Coal Dust as Filler in Bituminous Mix Design

Abstract

Bituminous concrete, also known as asphaltic concrete, is among the most advanced and expensive types of flexible pavement layers used in surface courses. Due to its high-cost specifications, bituminous mixtures are carefully engineered to meet the required standards of strength and longevity. The mix consists of densely graded coarse aggregate, fine aggregate, and mineral filler, all coated with a bitumen binder. The mineral filler passing through a 0.075 mm sieve plays a vital role in the performance of bituminous mixes. Marshall stability improves with an increase in filler content. The Asphalt Institute suggests incorporating 4 to 8% filler in asphalt concrete. Conventional filler materials such as cement, limestone, and granite powder are not readily or economically obtainable in Bangladesh. However, coal dust is more cost-effective and abundantly available in the country. This study explores the impact of different filler types on the properties of bituminous mixtures. It investigates and compares the characteristics of bituminous mixes using coal dust with those using conventional filler materials like fine sand and stone dust mixtures. The Marshall mix design method was employed for this comparison. The Marshall stabilities of mixes containing fine sand and coal dust were found to be 2.15 kN and 1.42 kN, respectively, all near the minimum requirement of the Marshall Design criteria. The findings highlight the potential of using coal dust as a filler in bituminous concrete.