Asphalt-Rubber by “Dry” Method – Design of an Open-Graded Mixture Complying with Portuguese Specifications

Asphalt-rubber can be produced following three main types of methods: the “wet method”, the “dry method” and the more recent “semi-wet” method, each one with their own variations. As long as an adequate technical and economical assessment is performed, these methods of asphalt-rubber production might have their own space, as they have different costs and specific equipment demands that might suit different projects' characteristics. Traditionally, the “dry” method has been less used worldwide and the present specifications for asphalt-rubber mixtures from the Portuguese road administration authorities don't take it into consideration. The main objective of this work is improving the knowledge of asphalt-rubber production in Portugal by presenting the mix design of an open-graded asphalt-rubber mixture by “dry” method complying with all the same properties listed in the specifications for the equivalent mixture by the prescribed “wet method” (the same mixture by “dry” and “wet” method will also be compared). All the different factors impacting the interaction between rubber and bitumen that were defined and taken into consideration in the “dry” method design are presented so that further studies can be compared with the present one.