Effect of Polymer Dispersion on the Rheology and Morphology of Polymer Modified Bituminous Blend

Increase in axle wheel load and traffic volume has led to the use of polymer modified bitumen (PMB) on roads as it offers better rutting, thermal and fatigue performances. In this paper the viscosity function of PMB obtained at 135°C was studied in the context of polymer dispersion in the bitumen blend. Polypropylene (PP) was used as the modifier for 80/100 pen bitumen. The morphological analysis using Scanning Electron Microscopy (SEM), Atomic force Microscopy (AFM) and Field Emission Electron Microscopy (FESEM) were presented. It was found that although the polymer resin was not fully digested by the virgin bitumen, there was evidence of a significant alteration of the Newtonian behavior of virgin bitumen to non-Newtonian behavior by the addition of the polymer.Presence of thixotropic behavior in the blend can be considered benefical in recovery of stress related deformation. SEM examination of PP resin revealed that partial breakage of the periphery of the resin was sufficient to enhance the viscosity of the PMB significantly. AFM phase images revealed that up to 2% polymer concentration in bitumen significantly enhances the viscoelastic property of the final PMB blend.The phase separated layer in PMB blend with sufficient stiffnesss and viscoelastic property of PP also acts as stress relaxant surface. Thus the PMB benefited by the incorporation of the polymer as it induces phase separated layer in the blend that can potentialy offer better fatigue and cracking properties to the resulting mix.