Effect of crumb rubber as coarse and fine aggregates on the properties of asphalt concrete

This research has used crumb rubber in asphalt mixture as a part of the coarse and fine aggregate. Three sieve sizes of crumb rubbers were used in asphalt mixture No. 4, No. 8 and No. 50, with five percent of asphalt cements (4, 4.5, 5, 5.5 and 6%) by weight and four percent of crumb rubbers (10, 20, 30 and 40%) by weight used as an aggregate for preparing asphalt mixture specimens. The Hot Mix Asphalt (HMA) Marshal test method for asphalt mixture specimens was used; 72 specimens were prepared for evaluation of Marshall Properties (flow, Stability, bulk density, air void percentage and void in mineral aggregate). Previous studies showed that the crumb rubber has further effects on the performance of asphalt mixture by increasing its Marshall flow, stability, air voids and decreasing the bulk density. It is concluded that the crumb rubber as a fine aggregate improves the stability and flow with respect to a crumb rubber as a coarse aggregate.