Composite Design of a Phosphogypsum Whisker–Based Rejuvenator Based on the RSM and Evaluation of the Rejuvenating Effect

This research aimed to develop a superior asphalt rejuvenator characterized by its resistance to aging by utilizing phosphogypsum whiskers (PSWs) derived from phosphogypsum (PSP) waste. Initially, the ratios of components in the rejuvenator were established through conventional performance evaluations. Subsequently, the rejuvenator components were structured using the response surface design method (RSM), and the formula for the novel PSW rejuvenator (PSWR) was derived using the corresponding model. The ideal amount of PSWR was determined through routine performance assessments. Following this, the aging resistance test and various rheological tests were conducted to assess the aging resistance trends and the high- and low-temperature performance, along with the fatigue performance of PSWR, compared to other rejuvenators. The results allowed for a detailed evaluation of PSWR application prospects. Furthermore, the interaction mechanism of PSWR with aged asphalt (AA) was analyzed using Fourier transform infrared spectroscopy (FTIR). The findings indicated that PSWR significantly restored the physical performance of AA and markedly enhanced its resistance to aging. The integration of this rejuvenator decreased the rutting factor of AA by 53.78%–66.28%, lowered the creep recovery rate by 78.06%–79.31%, and augmented the irrecoverable creep compliance by 34.09%–115.1%. These changes imply a slight reduction in AA’s resistance to high temperature and rutting. Moreover, PSWR substantially boosted the fatigue life and low-temperature performance of AA, with increases in fatigue life ranging from 99.73% to 131.73%, reductions in creep stiffness from 65.45% to 84.05%, and increases in creep rate from 49.1% to 87.72%. PSWR outperformed other rejuvenators in the rejuvenating effects on AA. The study found that PSWR was merely physically blended with AA, and a direct relationship was observed between the PSWR dosage and its rejuvenating effect, aligning with macroscopic observations. This investigation not only addressed the reuse of PSP resources but also supported the sustainable development concept in asphalt pavement.