Changes in fractional compositions of PPA and SBS modified asphalt binders

Asphalt binders are complex chemical composites of various organic molecules. They are often modified chemically to obtain some rheological and physical superiority over the unmodified neat binders. The chemical compositions they inherit from their crude origins determine the suitable modification methodologies, which eventually lead to their rheological changes. The changes in chemical compositions due to the modifications of selected asphalt binders with Polyphosphoric Acid (PPA) and Styrene Butadiene Styrene (SBS) were observed in this study. The percentage fractions of Saturates, Aromatics, Resins, and Asphaltenes (SARA) were measured for binders modified with different amounts of PPA and SBS. The Asphaltenes content was found to increase linearly with the addition of PPA and SBS, and so did their viscosity values. Unlike acidic binders (pH < 7.0), basic binders (pH > 7.0) demonstrated a distinctive decline of pH with PPA modifications. The Aromatics and Resins contents had a sharp change after a certain amount of PPA that demonstrated a demarcation point beyond which further addition of PPA would result in no desirable benefits. The demarcation points were different for two different (crude origin) binders. The addition of SBS did not contribute in changing the Asphaltenes content. Rather, SBS changed the Aromatics and Resins contents to yield the desired paving grade binder.