Experimental characterization of transparent synthetic binder mixes reinforced with cellulose fibres

The use of synthetic binders in wearing course mixes allows to integrate road pavements into urban surroundings. In fact, the mixes prepared with this binder mitigate the visual impact that common asphalt materials produce, allowing a pavement coloration depending on the aggregate dyes to be obtained. In this paper, the characterization of open graded mixes prepared with a synthetic binder, reinforced or not with cellulose fibres, was performed. In particular, nine mixes, with different binder and cellulose fibre contents, were investigated through several laboratory tests to find the ‘optimum’ mix in terms of both mechanical performance and durability. The study of all mixes was performed in two steps. In the first step, traditional tests were carried out: Marshall, Indirect Tensile and Cantabro tests. Moreover, to investigate the water effect on these open graded mixes, the traditional tests were also performed on specimens immersed in water for 15 days, and the results were compared. In the second step, the same nine mixes were investigated in terms of rutting behaviour by using Wheel Tracker Machine, and stiffness modulus and fatigue strength through Nottingham Asphalt Tester (NAT). Finally, the comparison with a traditional open graded mix (with SBS hard bitumen) was performed showing higher laboratory performance for the synthetic binder mix. This paper shows that specific synthetic binder and cellulose fibre contents provide an ‘optimum’ open graded mix.