Optimum Blending Requirements for EVA Modified Binder

Abstract

Increase in traffic, new axle configurations and high temperature, demands the use of modified binders for resisting the stresses induced. The primary goal of modifier is to increase the stiffness at high temperature while maintaining its flexibility at lower temperatures. It tends to increase the effective visco-elastic response of the binder. Among different modifiers, polymers have been very promising in improving the properties of binder.Ethylene Vinyl Acetate (EVA) is a plastomer, obtained by co-polymerization of ethylene and vinyl acetate. Depending on the percentage of vinyl acetate, the properties of the co-polymer changes, low vinyl acetate showing similar behavior to that of low density polyethylene (LDPE). EVA is characterized by its melt flow index (MFI) and vinyl acetate content.Though a potential modifier, problems of phase separation have been encountered, attributable to the presence two separate phases of bitumen and polymer which are incompatible with each other. Apart from the properties of base binder and the amount of polymer, the blending temperature, time and shear rate play an important role in obtaining a homogenous mix.This paper focuses on obtaining the optimum blending temperature, time and shear rate for EVA co-polymer. VG 10 is modified with EVA at varying combination of the three parameters and a total of 80 combinations is being obtained. Storage stability and Fluorescence microscopy is used for characterizing the phase separation of the modified binder.