Review of the potentials for quantitative microstructural analysis of polymer-modified bitumen

The objective of this article is to provide a critical synthesis and review of the potentials of the most relevant techniques and analysis procedures for styrene-butadienestyrene (SBS)- and epoxy-modified bitumen based on fluorescence microscopy. This analysis considers SBS-modified bitumens with the mass fractions of SBS from 1.5 to 6 % and epoxy-modified bitumens with 10 to 90 % of epoxy. The content of polymeric phases plays a main role in the morphological characteristics and the percolation of microstructure. The SBS-modified bitumen shows a tendency towards distortion of droplet shapes into complex microencapsulated structures, thus significantly increasing particle?s bulk volume. This also seriously questions the assumption of continuum used in the linear viscoelastic testing and modelling. The microstructure of the epoxy-modified bitumen gradually evolved from an even dispersion of epoxy droplets to almost bimodal dispersion of bituminous particles within epoxy. By approaching the phase inversion, epoxy gradually encapsulates bituminous nuclei. Future research should focus on how microstructure affects the non-linear viscoelasticity of bitumen, especially regarding the formation of large polymeric agglomerations. Besides, an involvement of infrared microscopy is critical for understanding the interfacial chemical interactions of polymer and residual bitumen.