Mechanical Characterisation of Hot Mix Recycled Materials PAULO A.A. PEREIRA a, *, JOEL R.M. OLIVEIRA a and LUI ´ S G. PICADO-SANTOS b a Department of Civil Engineering, University of Minho, Azure ´m P 4800-058, Guimara ˜es, Portugal; b Department of Civil Engineering, Faculty of Science and Technology of the University of Coimbra, Po ´lo II, Pinhal de Marrocos P 3030-231, Coimbra, Portugal Among the available techniques for pavement maintenance/rehabilitation, recycling of pavements is becoming more acceptable. It is based on sustainable development, by reusing materials reclaimed from the pavements and reducing the disposal of asphalt materials. Based on the results of an earlier study of asphalt mixtures containing 30 to 50% recycled asphalt, using the Marshall mix design methodology, additional mixtures of identical composition, containing 50% recycled asphalt, were produced at a range of bitumen contents and were all tested in more detail for permanent deformation and fatigue behaviour. The results from both investigations were analysed, with the objective of verifying if the Marshall mix design method was suitable to design bituminous mixtures with 50% reclaimed material. However, it is important to mention that this study is still not finished and that, it will evolve towards the validation of the manufacturing processes and the mechanical properties of the mixture using tests related with the field performance. A conventional mixture of identical gradation and material composition, made of 100% virgin aggregates, was also studied to compare with the recycled mixtures’ behaviour. Keywords:Recycling, Reclaimed materials, Rehabilitation, Planings, Fatigue, Permanent deformation. INTRODUCTION Q2 Modern trends in the industrial sector tend towards the elimination of waste materials and by-products, through the optimisation of their use in all the industrial processes. Existing deteriorated material can be reused; its characteristics can be rehabilitated, recycled and improved. The old material can be used in the same application that it was initially used for, or as part of a new material. The process of reuse can be carried out through the regeneration of the material by means of simple physical processes, such as its homogenisation, reclassi- fication and filtration, or mixture with other new or reused materials. In other cases, its original nature and behaviour can be modified by using additives of several types (Ferna ´ndez del Campo, 2003). Bituminous mixtures obtained from hot recycling of flexible pavements demonstrate similar characteristics to new hot mixtures, as long as the recycled materials are correctly characterised and the mix design is properly done. In a study carried out by Potter and Mercer (1997), several trials on public roads and full-scale accelerated load testing facilities, were evaluated in order to assess the performance of the recycled materials used in their construction. One of the main conclusions of the study was that the performance of the recycled materials was as good as that of equivalent conventional materials. Servas et al. (1987) have studied the mechanical properties after the incorporation of reclaimed material in hot mixtures in different percentages (0, 30, 50 and 70%). In that study no clear correlation was found between the percentages of recycled material and the properties of the resulting mixture. Therefore, given an adequate mix design, the amount of recycled material to be included depend upon other factors, related to the material itself, the type of plant and even economic and ecological policies. In 2002, a study was carried out by Picado-Santos and Baptista (2002a), in order to use materials reclaimed from the top layers (mainly the surface course) of one major road in Portugal, as part of new bituminous mixtures to be used in base courses. In that study, different Recycling Ratios, † (R R ), were used and the amounts of new aggregate and bitumen were calculated according to the properties of the recycled material. Further investigations were carried out to determine the mix design (Picado- Santos and Baptista, 2002b), which was done in accordance with the Marshall mix design method. In that second study, three R R were used (30, 40 and 50%) ISSN 1029-8436 print/ISSN 1477-268X online q 2005 Taylor & Francis Ltd DOI: 10.1080/10298430412331333668 *Corresponding author. E-mail: ppereira@civil.uminho.pt † Recycling ratio is the ratio between the amount of reclaimed material and the total amount of material used in the final mixture. The International Journal of Pavement Engineering, 2004 Vol. 5 (4), pp. 211–220 GPAV41029—10/2/2005—RSIVAKUMAR—129860