Effect of Extraction Solvents on Rheological Properties of Recovered Asphalt Binders

Abstract

This study examined the effect of three extraction solvents [trichloroethylene (TCE), toluene, and nPB] on the rheological properties of recovered asphalt binders when used with four binders of different performance grades (PG 58-28, PG 64-22, PG 64-28, and PG 70-22) that have been subjected to various levels of aging (unaged, short-term aged, and long-term aged). A dynamic shear rheometer (DSR) was used to characterize the viscoelastic properties of the original and recovered binders at high and intermediate temperatures, whereas a bending beam rheometer (BBR) was used to evaluate the rheological behavior at low temperatures. The test results showed a significant reduction in the dynamic shear modulus (G*) and a slight increase in the phase angle when TCE was used, with recovered to original G* ratios ranging between 30% and 75%. On the other hand, Toluene and nPB did not follow a clear trend for either G* or phase angle. In general, toluene resulted in recovered G* values within 20% of the original, whereas nPB resulted in recovered G* values within 40%. By comparing the high-temperature and low-temperature continuous PGs of the original and recovered binders, it was observed that toluene resulted in a minor change in both PGs, whereas the effect of TCE and nPB was more pronounced, especially on the low-temperature PG.