The aim of this paper is to investigate the aging mechanism of asphalt in the sea salt erosion environment from a rheological point of view. In order to simulate the real pavement aging process in the sea salt erosion environment, base asphalt and Styrene−Butadiene−Styrene (SBS)-modified asphalt were selected for salt environment aging tests. The asphalt samples were aged via a thin film oven test (TFOT) and a pressure aging vessel (PAV) test. Then, thermo-oxidizing conditions were created after the samples were immersed in salt solution, mixed with four different concentrations of sodium chloride (NaCl) and sodium sulphate (Na₂SO₄), to investigate the aging state of asphalt. Temperature scan (TS), frequency scan (FS), and multiple stress creep and recovery (MSCR) tests performed using a Dynamic Shear Rheometer (DSR) were used to investigate the effects on the rheological properties of aged asphalt in a salt environment. The results showed that both base asphalt and SBS-modified asphalt were aged to different degrees under mixed salt solutions. The two asphalt samples aged in a salt environment showed increased hardness. SBS-modified asphalt exhibited higher aging resistance compared with base asphalt in the sea salt environment. However, due to the degradation of the SBS modifier and the aging of base asphalt, the properties of the SBS-modified asphalt showed more obvious complexity with changes in salt solution concentrations.

Studying the mechanisms and effects of rejuvenators on SBS-modified bitumen is crucial for repairing degraded SBS and recycling aged SBS-modified bitumen (ASMB), thereby contributing to the sustainable development of bitumen pavements. This research examines the roles of mono-epoxy Alkyl (C12-C14) glycidyl ether (AGE) and di-epoxy 1,6-Hexanediol diglycidyl ether (HDE) under the catalysis of N,N-dimethyl benzyl amine (BDMA) in repairing degraded SBS chains. Aromatic oil (ORSMB)-, AGE–aromatic oil (ARSMB)-, and HDE–aromatic oil (HRSMB)-rejuvenated bitumen are analyzed for their chemical structures, physical properties, and rheological properties. Fluorescence microscopy (FM) and Fourier transform infrared spectroscopy (FTIR) reveal that HDE chemically reconnects degraded SBS chains, enhancing ASMB properties, while AGE improves ASMB properties through physical softening. HDE balances high-temperature properties and improves mid-temperature fatigue resistance through a rigid repair effect and flexible chain structure. AGE enhances mid-temperature fatigue resistance but significantly reduces high-temperature rutting resistance due to a softening effect. The findings demonstrate that HDE restores ASMB ductility chemically, while AGE improves crack resistance through physical softening. These differences in rejuvenation mechanisms provide a theoretical basis for optimizing rejuvenator design and advancing bitumen pavement recycling.

Rejuvenating aged asphalt is critical for sustainable road construction and resource utilization. This paper systematically reviews the current research on rejuvenators, focusing on their classification and the micro-, and macro-properties of rejuvenated asphalt. Rejuvenators are categorized into mineral oil-based, bio-based, and compound types. Each type offers distinct advantages in recovering the performance of aged asphalt. Mineral oil-based rejuvenators primarily enhance low-temperature cracking resistance through physical dilution, while bio-based rejuvenators demonstrate superior environmental sustainability and stability. Compound rejuvenators, particularly those incorporating reactive compounds, show the best results in repairing degraded polymer modifiers and improving both low- and high-temperature properties of aged, modified asphalt. Atomic Force Microscopy (AFM), Fluorescence Microscopy (FM), and Scanning Electron Microscopy (SEM) have been applied to analyze the micro-properties of rejuvenated asphalt. These techniques have revealed that rejuvenators can restore the microstructure of aged asphalt by dispersing agglomerated asphaltenes and promoting molecular mobility. Functional groups and molecular weight changes, characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Gel Permeation Chromatography (GPC), indicate that rejuvenators effectively reduce oxidation products and molecular weight of aged asphalt, restoring its physicochemical properties. Macro-property evaluations show that rejuvenators significantly improve penetration, ductility, and fatigue resistance. Finally, this review identifies the key characteristics and challenges associated with rejuvenator applications and provides an outlook on future research directions.

The application of hot in-place recycling asphalt mixtures (HIRAMs) is gaining increasing attention in highway maintenance due to its environmental and economic benefits. This paper comprehensively reviews and discusses the state-of-the-art studies in the field of hot in-place recycling (HIR). Firstly, different HIR technologies are introduced, including surface recycling, remixing, and repaving. Then, this paper provides a detailed description of the key factors influencing the road performance of HIRAMs in terms of both materials and production, such as reclaimed asphalt pavement (RAP), rejuvenators, virgin asphalt, virgin asphalt mixtures, preheating temperature, and mixing time. Furthermore, the environmental and economic benefits of HIR are compared with other preventative maintenance and recycling technologies. Finally, some challenges for the investigation of HIR are further discussed, and the corresponding suggestions are recommended for future investigation.

This paper aims to explore the influences of the content and gradation of mineral powder on the rheological properties of styrene-butadiene-styrene (SBS) modified asphalt mastic at different aging stages and temperatures. In the experiment, SBS modified asphalt mastic samples with different powder-to-binder ratios (0.6, 0.8, and 1.0) and different mineral powder gradations (500 mesh passing rates of 76.89% and 100%) were prepared. Following aging periods of 5, 25, and 45 h in the pressure aging vessel (PAV), the asphalt underwent comprehensive rheological characterization using a dynamic shear rheometer (DSR). The research shows that mineral powder can boost mastic’s deformation resistance and elastic effect. When aged by PAV for 45 h, the powder-to-binder ratio increased from 0.6 to 1.0, and its complex modulus increased by nearly 2.5 times at 58 °C. For SBS modified asphalt mastic of PAV 0 h, the powder-to-binder ratio increased from 0.6 to 1.0 and its phase angle was reduced from 59.6 to 53.2, which indicated that the elasticity of mastic was improved. However, this accelerated the degradation rate of SBS, making the aging process more complex. Fine-grained mineral powder is more effective in enhancing mastic’s deformation resistance than coarse-grained mineral powder. The fine-graded mastic had better rutting resistance after 45 h of aging than after 25 h of aging because the mineral powder compensated for the SBS loss-induced elasticity reduction. Smaller mineral powder particles lead to better a mastic anti-aging effect. After 45 h of aging, fine-grained mineral powder offered a better elastic effect. But the ways in which mineral powder and SBS boost mastic elasticity differ greatly. The results of this study provide a reference for optimizing the design of asphalt mixtures.