Energy & Fuels, Vol.18, No.2, 357-364, 2004
Linear viscoelasticity of recycled EVA-modified bitumens
The aim of the present work is to study the rheology in the linear viscoelasticity range of polymer-modified bitumens with recycled EVA. In this way, blends of bitumens having two different penetration grades (60/70 and 150/200) and recycled EVA were prepared, ranging from 0 to 9 wt % polymer. Oscillatory shear tests were carried out at different temperatures, from -10 to 75 degreesC. From them, "empirical" master curves for polymer concentrations up to 7 wt % were obtained in a wide frequency range. Nevertheless, empirical superposition could not be carried out on the system having 9 wt % polymer. This fact suggests that a change in the binder microstructure takes place at this polymer content, although, as shown by optical microscopy, phase inversion (i.e., a continuous polymer-rich phase) is not yet achieved. In addition, MDSC measurements made evident that a significant decrease in the polymer melting point occurs as EVA is blended with bitumen, probably related to smaller polymer crystallites. Bitumen modification with recycled EVA enhances bitumen behavior in the pavements, at both low and high in-service temperatures, as well as makes it an interesting environmental alternative for disposing of waste plastics.