Asphalt Mixtures Using the Semi-wet Method of Reacted and Activated Rubber from Recycled Tires

The wet method technology of using crumb rubber from recycled tires as a modifier of asphalt (bitumen) binder started to be used in Arizona and California in the 1970s. The crumb rubber wet process is a practical means of providing environmental, economic, sustainable, and safety benefits from using crumb rubber from recycled tires using the wet method technology widely used for societal benefits. New imaginative and innovative engineering technology concepts have led to the development of a new crumb rubber semi-wet method material. The new semi-wet method employs reacted and activated rubber (RAR). The RAR semi-wet method has demonstrated a product capable of matching and surpassing the performance of traditional hot mix asphalt and the traditional crumb rubber wet method asphalt. Basically, RAR consists of pre-treated and pre-reacted rubber that can be used directly in a mix plant just like a “filler”, thus it is easy to handle and requires no special equipment for blending crumb rubber and asphalt and no additional heat source. The RAR dry filler when it meets hot asphalt amalgamates in such a way as to become like the traditional crumb rubber method asphalt rubber. This paper provides the concepts and some experiences of mixes with RAR and presents how the added flexible fatigue cracking resistance of these mixes leads to great environmental and sustainability benefits.