Physical-Rheological Properties and Performances of Rejuvenated (Styrene-Butadiene-Styrene) Asphalt with Polymerized-MDI and Aromatic Oil

Traditional asphalt rejuvenators, like aromatic oil (AO), are known to be effective in improving the low-temperature properties and fatigue performances of aged SBS (styrene-butadiene-styrene) modified asphalt (SBSMA) binders and mixtures. However, these rejuvenators inevitably compromise their high-temperature properties and deformation resistances because they dilute asphalt binder but do not fix the damaged structures of aged SBS. In this study, a highly-active chemical called polymerized 4,4-diphenylmethane diisocyanate (PMDI) was used to assist the traditional AO asphalt rejuvenator. The physical and rheological characteristics of rejuvenated SBSMA binders and the moisture-induced damage and rut deformation performances of corresponding mixtures were comparatively evaluated. The results showed that the increasing proportion of AO compromises the hightemperature property and hardness of aged SBSMA binder, and an appropriate amount of PMDI works to compensate such losses; 3% rejuvenator at mass ratio of AO:PMDI = 70:30 can have a rejuvenated SBSMA binder with a high-temperature performance similar to that of fresh binder, approximately at 71.4 degrees C; the use of AO can help reduce the viscosity of PMDI rejuvenated SBSMA binder for improving its workability; PMDI can help improve the resistance of AO rejuvenated SBSMA binder to deformation, especially at elevated temperatures, through its chemical reactions with aged SBS; moisture induction can enhance the resistance to damage of rejuvenated mixtures containing AO/PMDI or only PMDI; and the rejuvenator with a mass ratio of AO:PMDI = 70:30 can lead the rejuvenated mixture to meet the application requirement, with a rut depth of only 2.973 mm, although more PMDI can result in a higher resistance of rejuvenated mixtures to high-temperature deformation.