Effect of filler on the bitumen-aggregate adhesion in asphalt mix

The loss of adhesion is one of the primary mechanisms of physical distress in asphalt mixes since it negatively affects the durability of asphalt mix. The effect of filler on this mechanism was explored by analyzing active and passive adhesions between the aggregates and the bitumen that constitute asphalt mix. As part of the analysis, the measurement of mixing times and Boiling Water Tests were conducted. Five types of fillers of different sources, constituting of conventional (natural stone dust) and waste fillers (glass powder from glass industry, bauxite residue from aluminum industry, Kota stone dust from dimension stone industry and copper tailings from mining industry) were added at variable compositions (4, 5.5, 7 and 8.5% by weight of aggregates) in mixes to generalise the conclusions. The statistical analysis of results confirmed that type of filler and their quantity in asphalt mixes, significantly affect both active and passive adhesion. The results also indicated that use of calcium-based fillers (natural stone dust and Kota stone dust) result in significant improvement in both adhesions. Whereas, use of silica-based glass powder filler results in the worst active and passive adhesions and should be used judiciously.