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Solid waste recycling and reuse have attracted great interest as environmentally friendly modifiers for asphalt pavements in recent years, and phosphogypsum whiskers (PSWs) synthesized by phosphogypsum (PSP) wastes were used as the main modifying material to develop an environmentally friendly asphalt binder in this study. PSWs could significantly enhance the deformation resistance and fatigue performance of asphalt binder but were prone to cracking at low temperature. To alleviate this problem, the novel idea of developing a PSW composite modified asphalt binder was proposed in this study. The organic coating method was used to surface modify PSWs by using surfactants and ultrasonic vibrator to enhance the compatibility of PSWs with asphalt binder. Then a composite modifier containing modified PSW (MPSW) was developed by the uniform design method (UDM), and the preparation process of the modifier was investigated by response surface method (RSM) on this basis. The physical performance of modified asphalt binder was investigated by conventional performance tests; the high-temperature performance, rutting resistance, and fatigue performance were investigated by several rheological tests; and the low-temperature performance was evaluated by the force ductility test (FDT). The microstructure and modification mechanism were characterized by the Fourier transform infrared spectroscopy (FTIR) test and differential scanning calorimetry (DSC) test. The results showed that the self-developed modifier (MPGJ-I) could effectively reduce the negative effects of MPSW on conventional physical properties, and it exhibited a significant aging resistance compared with other commonly used modifiers. In addition, the modified asphalt binder showed a significant enhancement in high-temperature performance, rutting resistance, and fatigue performance. The MPGJ-I not only solved the adverse effect of MPSW on low-temperature performance, but also enhanced the low-temperature performance to a certain degree. The MPGJ-I was only physically mixed with asphalt binder and did not change its chemical structure. The MPGJ-I reduced the influence of MPSW on glass transition temperature (Tg) and improved the thermodynamic properties of asphalt binder at low temperatures. The comparison study revealed that the MPGJ-I could comprehensively enhance the service performance of virgin asphalt binder, and the recommended dosage of MPGJ-I was 6%. [ABSTRACT FROM AUTHOR]

The study of the adhesion properties between asphalt and aggregate plays a critical role in deciphering the fracture behavior and damage characteristics in asphalt mixtures. This research is dedicated to exploring the impact of various aging behaviors on adhesion properties and the reinforcing effects of modifiers. In this context, a novel composite modifier (MPM), was synthesized from phosphogypsum whisker, derived from phosphogypsum waste. Asphalt specimens, encompassing both virgin and modified asphalt with the different dosages of MPM, were prepared under a spectrum of eight aging conditions. The mechanical properties of these specimens were meticulously analyzed using multiscale tests to assess the adhesion properties under diverse aging conditions and modifier dosages. Furthermore, the study delved into the microscopic effects of aging and modification on adhesion properties. The results highlighted that aging detrimentally impacts the adhesion properties of asphalt, with this negative effect progressively intensifying over time. In contrast, the enhancement of adhesion properties by MPM exhibited variation in accordance with its dosage. Limestone, characterized by a rougher external interface and a higher prevalence of high-valent cations, demonstrated more pronounced adhesion properties to asphalt compared to granite. The aging process introduced new diffraction patterns and characteristic peaks in the asphalt, with their intensities showing a direct correlation with the duration of aging. The MPM modification was found to effectively mitigate the deterioration in the structural stability of the virgin asphalt. Overall, this study offers comprehensive insights into the aging and modification mechanisms affecting adhesion properties between asphalt and aggregate, contributing significantly to the resource utilization of solid waste. [ABSTRACT FROM AUTHOR]

The study of the reaction mechanism of sea salt solution (SSS) on asphalt binder was important for the development of perpetual asphalt pavements in coastal areas. For this, a novel modifier (MPGJ-I) was developed in this study using phosphogypsum whiskers (PSW) synthesized from phosphogypsum (PSP) wastes, then the prepared composite-modified asphalt binders and base asphalt binders were immersed in the SSS with six concentrations. Then, the surface free energy (SFE) test, rheological tests, and Fourier transform infrared spectroscopy (FTIR) test were used to investigate the function mechanism of SSS on the surface properties, rheological properties, and chemical structure. The results showed that the salt in SSS would gradually transfer to the inside of asphalt binder, and with the increase in SSS concentration, the mass accumulation rate of base asphalt binders increased by 0.84% and 0.72%, whereas the modified asphalt binders only increased by 0.64% and 0.61%, respectively. The MPGJ-I effectively alleviated the decline trend of surface properties, with the incorporation of MPGJ-I, the SFE and cohesive work of base asphalt binders increased by 29.14%–32.83% and 5.23%–48.63%, respectively. In addition, with the increase in SSS concentration, the rutting factor (G*/sinδ), and creep recovery rate (R) of base asphalt binders increased by 15.44%–57.69% and 7.58%–22.34%, respectively, and the fatigue life (Nf) decreased by 6.08%–47.24%. Whereas G*/sinδ and R of modified asphalt binders increased by 10.07%–50.77% and 2.15%–19.35%, respectively, and Nf decreased by 1.79%–8.89%, which meant that the incorporation of MPGJ-I effectively restrained the attack action of SSS on base asphalt binders. There was a chemical reaction between SSS and asphalt binder, and the peak intensity of the new characteristic peaks in asphalt binder was positively correlated with SSS concentration, the incorporation of MPGJ-I could reduce the increasing rate of peak intensity to a certain degree. In addition, the principal component analysis (PCA) model showed that the surface properties and fatigue performance were closely related to the SSS concentration, and this correlation was not affected by the modification effect of MPGJ-I. [ABSTRACT FROM AUTHOR]