Use of Waste Tyre Rubber Crumbs in Stone Mastic Asphalt: Potential Use in Pervious Pavements

This study aimed to evaluate the performance of Stone Mastic Asphalt containing 6%, 8% and 10% waste tyre rubber crumbs. The study results revealed that the density decreased with the increase in the percentage of waste tyre rubber crumbs (6% addition of tyre crumbs with conventional asphalt resulted in a 1.52% reduction in density; 8% addition resulted in a 2.28% reduction and 10% addition resulted in a 2.6% reduction). Consequently, water absorption increased with the increase in the percentage of waste tyre rubber crumbs (6% addition of tyre crumbs with conventional asphalt resulted in an 8% increase in water absorption; 8% addition led to a 12% increase and 10% addition resulted in a 15% increase). As percentage of tyre increased, so did the load to penetrate an equal distance on the cone used in the penetration test (6% addition of tyre crumbs with conventional asphalt resulted in a 10.6% increase in penetration resistance in terms of loads; 8% addition resulted in a 14% increase, and 10% addition resulted in a 15% increase in penetration resistance). Tensile strength decreased with the increase in % waste tyre rubber. Tensile strength ratio (TSR) of the mixtures decreases with the addition of waste tyre rubber crumb; however, TSR values were above 70% indicating that all mixes may have adequate resistance against damage induced by moisture. The use of waste tyre rubber in asphalt is a waste reduction practice. Stormwater management; urban and traffic runoff management has provisions for low-density pervious bituminous pavements and surfaces where these Stone Mastic Asphalt can find their use.