Characterization of aged bitumen recovered from in-situ polymer-modified HMA and WMA using advanced technologies

The growing attention of public opinion towards the environment has prompted, in the last decades, to find eco-sustainable and economic alternatives to the traditional productions of hot-mix asphalt (HMA). Under theseauspices, the use of warm mix asphalt (WMA) technology applied to mixtures containing reclaimed asphalt (RA)has grown, also due to the well-proven advantages in terms of plant odor emissions and improved workingconditions. In addition, it is now known that the mechanical performance of WMAs is completely comparable,even superior in some cases, to that of HMAs. However, to date, there is no comparison in terms of long-termperformance of bitumens used in full-scale pavements laid with the two different technologies. Therefore, theaim of this research is to evaluate the oxidative and rheological state of four bitumens recovered from differentlayers of a full-scale pavement prepared with WMA and HMA technologies and set up a methodology tool set forinvestigating the physicochemical properties of bitumens. An in-depth laboratory investigation, carried outthrough physicochemical and rheological tests, has shown that the bitumens used in WMA mixtures are char-acterized by less oxidation than HMA ones (which are characterized by longer relaxation and glass transitiontimes) and the Styrene-Butadiene-Styrene (SBS) polymers inside them are less degraded and still contributepositively to the rheological response even after five years in service, demonstrating the ability of the chemicaladditive to act as possible “sacrificial agent”, safeguarding the rheological characteristics of polymer modified bitumens (PMBs).