Identification of undisclosed modifiers and their effects on chemical, thermal, and microstructural properties of unaged and aged industrial high polymer-modified asphalt binders

Abstract

This study employs thermo-chemical and microstructural analyses to identify undisclosed crystalline modifiers (UMs) in industrial high polymer-modified binders (HiPMBs) and evaluate their effects on aging phenomena. Chemical, thermal, and microstructural properties of several industrial HiPMBs were evaluated via Fourier-transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), fluorescence microscopy (FM), and atomic force microscopy (AFM). Results indicate that crystalline UMs, contained in most binders, can be readily identified by calorimetric analysis. In contrast to styrene–butadienestyrene (SBS) thermoplastic elastomers, UMs drastically alter the surface microstructure of all binders. Typical bee-like structures disappear, and undefined topographies emerge due to the interactions between UMs and bituminous waxes. No significant effects were noticed concerning the homogeneity of the binders’ amorphous phases. Aging processes affect the characteristics of base bitumen, SBS, and UMs. Oxidation of bitumen and degradation of SBS can be evaluated by semi-quantitative analysis of FT-IR absorption bands and glass transition temperature (Tg) values. At the same time, variations of DSC endotherms reflect the influence on the crystallinity of UMs.