Rheological and performance characterisation of the bitumen recovered from different emulsions for cold mixtures

In recent years, over-stabilized polymer-modified bitumen emulsions have been widely used to improve the mechanical properties of cold bituminous mixtures. However, the effect of the polymer modification process on the emulsion performance have not been investigated. The present paper deals with the analysis of the binders recovered from a reference unmodified bitumen emulsion and two polymer-modified emulsions, respectively including SBR-latex added after bitumen emulsification (post-blending) and SBS added before bitumen emulsification (pre-blending). The laboratory investigation included the linear viscoelastic characterisation and the evaluation of the resistance to permanent deformations and damage. The results showed that the polymer-modified bitumen emulsions have a more pronounced elasticity with respect to the unmodified emulsion, allowing achieving a higher performance against permanent deformations and fatigue. In addition, the SBS modified bitumen emulsion (pre-blending) has better properties than the latex modified emulsion (post-blending), as a consequence of the different chemical structure that the modification process produces.