Relationship between fractal, viscoelastic, and aging properties of linear and radial styrene-butadiene-styrene polymer-modified bitumen

The present study is aimed at evaluating the morphological and interfacial properties of the polymer and bitumen (BIT) in linear styrene-butadiene-styrene (SBS-L) block copolymer and radial SBS (SBS-R) block copolymer-modified BIT (PmB) by fractal analysis. Fluorescence microscopy technique coupled with image analysis was used to measure the particle size distribution and fractal dimension of PmB morphology formed in mixtures. Fractal analysis approach was proposed as quantitative description method to evaluate nonuniformity of phase-separated SBS polymer particles/fibrils in PmB. Fractal-like structures in fluorescence micrographs of PmB morphology with the polymer phase-separated particles/fibrils were quantified using interface D[BW], BIT-rich phase D[B+BW], and SBS-rich phase D[W+BW] box-counting fractal dimensions. The overall morphological structure became more compact or more fibril organized as the polymer content attained overcritical values. The relatively high values for the BIT-rich phase D[B+BW] fractal dimension suggests that the PmB mixtures have a structure with extremely high space-filling capacity. Polymer-BIT mixture properties by the conventional laboratory performance tests and by the rheological measurements before and after the Rolling Thin Film Oven Test have been correlated with the PmB mixtures fractal dimensions.