Application of waste materials as fillers in bituminous mixes

This study investigates the suitability of seven different waste materials as fillers in place of conventional material in dense graded bituminous macadam mix. Waste materials under consideration are glass powder, limestone dust, red mud, rice straw ash, brick dust, carbide lime and copper tailings. Ordinary Portland cement was adopted as a conventional filler. Detailed physical, geometrical and chemical characterization of fillers was carried out. Thereafter, bituminous mixes were prepared using waste materials and their strength, volumetric properties and performance against various distresses (rutting, cracking and moisture susceptibility) were assessed. At similar bitumen content, all waste modified mixes delivered satisfactory mechanical and volumetric performances as demanded by paving specifications. Mixes with finer fillers (red mud and limestone dust) displayed superior stiffness and cracking resistance. Similarly mixes having filler with a predominance of calcium minerals (carbide lime and limestone dust) displayed superior adhesion and moisture resistance.