WASTES: Solutions, Treatments and Opportunities 1 St International Conference September 12th – 14th 2011 WASTE POLYMERS RECYCLING IN HIGH PERFORMANCE ASPHALT MIXTURES H.M.R.D. Silva 1 , A.V. Machado 2 , J.R.M. Oliveira 3 and L.M.B. Costa 4 1 C-TAC, University of Minho, 4800-058 Guimarães, Portugal, hugo@civil.uminho.pt 2 I3N / IPC, University of Minho, 4800-058 Guimarães, Portugal, avm@dep.uminho.pt 3 C-TAC, University of Minho, 4800-058 Guimarães, Portugal, joliveira@civil.uminho.pt 4 Dpt. Civil Eng., University of Minho, 4800-058 Guimarães, Portugal, a48253@alunos.uminho.pt ABSTRACT Building a road pavement requires large amounts of constituent materials, whose extraction can lead to the devastation of natural resources and causes negative impacts on the environment. As aggregates comprise nearly 90% of asphalt mixtures, their partial substitution by waste thermosetting polymers (12 million tons of waste polymers are presently mislaid into landfills, every year, in Europe) can be considered as a sustainable technology, given that an equivalent performance can be assured. Thus, this study aims on evaluating possible advantages of introducing polyethylene based wastes in asphalt mixtures, namely high density polyethylene (HDPE) and cross-linked polyethylene (PEX), incorporating HDPE as a bitumen modifier and PEX as partial substitute of the aggregates. The laboratory tests carried out in this work showed that the use of HDPE significantly improves the behavior of the asphalt binder/mixture. The use of PEX considerably decreases the density of the mixtures, which can be attractive to lighten structures. The mixtures with PEX have similar performance to the conventional one in terms of water sensitivity, improving the permanent deformation resistance and reducing the temperature susceptibility. In brief, the mixtures incorporating waste polymers could be considered a good technical and environmental alternative for paving works. Keywords: Waste polymer recycling; Polyethylene; Polymer modified binder; Asphalt performance INTRODUCTION Presently, in Europe, 12 million tons of waste polymers are mislaid into landfills every year [1]. Most of these polymers have a very simple process of recycling, but the mechanical recycling generally does not work for thermosetting polymers and elastomers, because these polymers do not melt. Since they cannot be reprocessed, their reuse may be possible by taking advantage of their potential as aggregates that can be incorporated in road pavements. In fact, building a road pavement requires a large amount of constituent materials, whose extraction can lead to the devastation of natural resources and cause negative impacts on the environment. As aggregates comprise nearly 90% of asphalt mixtures, their partial substitution by waste thermosetting polymers can be considered as a sustainable technology, given that an equivalent performance can be assured [2]. Thus, this study aims on evaluating the possible advantages of introducing polyethylene based wastes in asphalt binders and mixtures by using different processes of incorporation. The materials used were high density polyethylene (HDPE) and cross-linked polyethylene (PEX), the first as a bitumen modifier and the second as partial substitute of the aggregates. Polymers can be applied in asphalt mixtures as bitumen modifiers or as partial substitute of the aggregates, and they could also be used as an aggregate coating layer [3]. Among polymers that may be used in asphalt mixtures, the most used are thermoplastics and elastomers [4], namely polyethylene based polymers, as well as EVAs, SBS and SBR polymers. According to several authors [5, 6] the use of recycled polymers or waste polymers rather than new is possible and most valuable, which leads to ecological and possibly to economic benefits.