A NEW LOOK AT RUBBER-MODIFIED ASPHALT BINDERS

The high-temperature theological characteristics and the low-temperatu re fracture properties of asphalt binders containing crumb and devulca nized rubber waste have been investigated. Asphalt binders containing crumb rubber of different mesh sizes, with and without surface modific ation, and a commercially available binder containing devulcanized rub ber, were tested and compared with an unmodified asphalt and three com mercially available polymer-modified binders. Interfacial modification of asphalt systems containing crumb rubber was found to give binders that were far superior in their low-temperature performance to commerc ially available products. The data suggest that a crack-pinning or cra ck-blunting mechanism is responsible for the increase in toughness fou nd in these systems. A commercially available binder containing devulc anized rubber showed reasonably good high-temperature properties; howe ver, its low-temperature fracture performance was disappointing in tha t it was not significantly better than that of unmodified asphalt bind ers.