Comprehensive Selection of Base Asphalt Binders for Effective Formulation of Polymer-Modified Asphalts

Polymer-modified asphalts (PMAs) are known to improve the rutting, cracking, and durability of pavements, especially creating better resistance to aging susceptibility. Although the properties, benefits, and performance of PMAs overall are fairly well known and talked about in the asphalt industry, the key aspect of selecting a good base binder for effective styrene–butadiene–styrene compatibility and enhanced performance still remains largely unexplored, and is generally based on trial-and-error methodologies. The main objective of this study was to perform in-depth physical, chemical, rheological, and microstructure characterization of base (neat/unmodified) and corresponding PMA binders to understand and quantify important aspects of their composition that would contribute to developing robust and better-performing PMAs. The experimental matrix included three base asphalt binders from different sources but similar SuperpaveTM performance grades (PG) and three corresponding PMAs. A comprehensive characterization effort was carried out on these binders that included PG grading, Black Space analysis, G* master curves, determination of ΔTc, determination of saturates, aromatics, resins, and asphaltenes fractions, differential scanning calorimetry, size-exclusion chromatography, Fourier transform infrared, and microscopy. The key outcome of this study is a set of guidelines and recommendations for preferable characteristics of base binders that contribute to formulating effective PMAs and certain “dos and don’ts” with respect to the interpretation of data and/or the analysis approach. It is expected that the outcome of this study will become an important tool for formulating well-performing PMAs that will be useful to asphalt and additive suppliers as well as contractors, agencies, or both, that procure, handle, and use PMAs for pavement applications in general.