Long-Term Aging Behaviour of Asphalt Mixtures Modified with Crumb Rubber Using the Dry Process

Abstract

The use of crumb rubber from waste tires as additive for asphalt mixtures has several environmental benefits in comparison with traditional options such as landfill disposal and energy recovery. Moreover, several studies have shown better performance in asphalt mixtures modified with crumb rubber compared to conventional asphalt. In this sense, crumb rubber can be incorporated by wet or dry processes. In the wet process, crumb rubber is added and blended into an asphalt binder prior to adding the heated aggregates. The major advantage of the dry process is related to the manufacturing procedure. Here, the crumb rubber is added into the mixer together with the aggregates and no additional equipment is required. Afterwards, once the asphalt mixture is prepared, a conditioning time must be allowed to ensure a proper interaction between crumb rubber and the binder. Many research and practical works have shown that this conditioning time along with the type, size and quantity of the crumb rubber added, bitumen content or air voids content has a significant influence on short-term performance of the modified mixtures. Our study aims to further investigate the ageing effect and the long-term performance of asphalt mixtures modified with crumb rubber using the dry process. To do this, semi-dense asphalt (SDA) mixtures with 12% air void content were prepared incorporating two different types of crumb rubber. Then, the performance of these mixtures was evaluated before and after a long-term aging treatment and compare to a conventional polymer modified mixture. The obtained results confirm that the incorporation of crumb rubber using the dry process can lead to mixtures with adequate long-term performance as well as less aging than a conventional polymer modified mixture.