Innovative Use of Polyurethane Precursor to Facilitate the Reaction-Rejuvenation of Aged SBS-Modified Asphalt

Abstract

The high-quality reutilization of waste styrene-butadiene-styrene (SBS) modified asphalt (SBSMA) mixtures has been a focus area for researchers in recent times. Commonly used rejuvenators are generally unsatisfactory to fully restore their overall properties because it has no effect on the SBS modifier in aged binders. A significant research gap still exists regarding the restoration of the molecular structure and properties of aged SBS to instigate the performance recovery of aged SBSMA binders that will concurrently lead to enhancement of mixture performance. On this basis, this study considered the adoption of reactive organic materials, namely, polyurethane (PU) precursor and 1, 4-butanediol diglycide ether (BUDGE) for the investigation of the reaction-rejuvenation of aged SBSMA binders and mixtures. For the binder study, conventional rheological tests such as softening point, penetration, ductility, and infrared spectra spectroscopy were employed to evaluate the rejuvenation of the collective use of PU precursor and BUDGE on aged SBSMA binder. For the mixture study, two rejuvenator addition approaches, namely, carrier-free method and carrier-support method, were applied for aged SBSMA mixtures, and the high-temperature property, moisture-induced damage resistance, and low-temperature crack resistance were comparatively analyzed. The results indicated that PU precursor contributes to improving the softening temperature of aged SBSMA binder, and in combination with BUDGE, increased low-temperature ductility and flexibility can be attained. From the mixture performance results, the carrier-supported rejuvenation method can recover the permanent deformation resistance of the rejuvenated SBSMA mixture to similar levels as that of the fresh SBSMA mixture. Additionally, it can also effectively improve the moisture-induced damage resistance of the aged SBSMA mixture as well as providing a superior resistance to low-temperature cracking compared to the carrier-free rejuvenation method.