Polymer-modified bitumen recovery: evaluating solvent effects on bitumen and polymer phases

Abstract

Efficient reuse of reclaimed asphalt pavement (RAP) requires accurate assessment of the aged binder, especially for polymer-modified bitumen (PmB), whose performance depends on its polymer network. However, current European binder extraction and recovery standards were developed for unmodified bitumen and offer limited guidance for PmBs, leaving polymer network behaviour during recovery unclear. This study evaluated the influence of solvent types, binder-to-solvent ratios, and recovery conditions on the chemical, rheological, and morphological properties of recovered PmBs. Two PmBs were recovered using six chlorinated, aromatic, ether-based, and bio-based solvents. Fourier-transform infrared (FTIR) spectroscopy indicated only mild oxidative aging. Rheological results confirmed minor stiffening without polymer degradation, supported by fluorescence microscopy. Tetrahydrofuran and limonene yielded rheological properties closest to the original. Limonene demonstrated good recyclability over multiple reuse cycles. Nitrogen-assisted recovery, required by American standards, showed no consistent benefit. The findings support rational solvent selection, improved recovery standards, and sustainable, high-quality RAP reuse.