Optimizing the use of reactive terpolymer, polyphosphoric acid and high-density polyethylene to achieve asphalt binders with superior performance

Abstract

Styrene-butadiene-styrene (SBS) is the most widely used polymer in asphalt binders because of its success in mitigating pavement rutting and cracking distresses. However, the asphalt industry has been searching for alternatives that provide equivalent or possibly better performance. This study investigated the individual and combined effects of reactive terpolymer (etylene/metilacrilate/glycidyl metacrylate (EMA-GMA)), polyphosphoric acid (PPA) and high-density polyethylene (HDPE) on binder rheological properties with the goal of formulating new binders to replace a PG 76–22 SBS binder. The PPA and HDPE were found to only increase binder stiffness (i.e., reduced penetration number, non-recoverable compliance and increased high temperature performance grades) whereas the EMA-GMA also improved the binder elasticity (i.e., increased elastic recovery and strain recovery values). Binders with single modifier failed to meet the strain recovery requirement indicating insufficient elasticity, which is known to be positively correlated with binder cracking performance at intermediate temperatures. Conversely, the combined use of EMA-GMA with PPA or with PPA plus HDPE not only increased binder stiffness but also induced sufficient elasticity. Moreover, PPA as a catalyst, promoted the chemical reaction between EMA-GMA and base binder, better than HDPE did. Finally, comparisons were made in abovementioned properties between the PG 76-22 SBS binder and selected new binders. It was concluded that both PPA and HDPE enhanced the efficiency of EMA-GMA to achieve binders with equivalent or potentially better performance than a standard PG 76-22 SBS binder.