Current practices on the recycling of bituminous mixtures

Current concerns with a sustainable development have lead pavement engineers and practitioners to focus on recycling techniques and incorporation of industrial by-products in the production of asphaltic mixtures. The present paper focused on the study of different mixtures with the incorporation of Reclaimed Asphalt Pavement (RAP) and other waste materials like used motor oil. One of the main objectives of this work was the study of asphalt mixtures with high recycling rates (between 50 and 100 per cent), taking into consideration that this may lead to the need to modify production procedures, in order to maintain the asphalt plant productivity above an acceptable level. A selection of a few recycled asphalt mixtures was comprehensively evaluated through performance tests in order to make them available to be applied on the field. Their performance should not be compromised by the incorporation of the recycled materials, in comparison to a conventional Hot Mix Asphalt (HMA) mixture. In order to assure an adequate performance of the studied mixtures, the use of special additives (with rejuvenation or temperature reduction characteristics) may be necessary, as discussed in the present paper. The performance tests carried out, including water sensitivity, wheel tracking, stiffness and fatigue cracking tests, showed that it is possible to produce recycled mixtures with high recycling rates without compromising their performance.