To address the deficiencies of traditional emulsified asphalt-pavement maintenance material in cohesive strength, high-temperature rutting resistance, as well as adhesion to aggregates, this study developed waterborne epoxy resin-modified emulsified asphalt (WEA) binders using a two-component waterborne epoxy resin (WER) and systematically investigated their modification mechanisms and pavement performance. The results indicated that WER emulsions and curing agents could polymerize to form epoxy resin within the emulsified asphalt dispersion medium, with the modification process dominated by physical interactions. When the WER content exceeded 12%, a continuous modifier network structure was established within the emulsified asphalt. The epoxy resin formed after curing could significantly increase the polarity component of the binder, thereby increasing the surface free energy. The linear viscoelastic range of the WEA binder exhibited a negative correlation with the dosage of the WER modifier. Notably, when the WER content exceeded 6%, the high-temperature stability (rutting resistance and elastic recovery performance) of the binder was significantly enhanced. Concurrently, stress sensitivity and frequency dependence gradually decrease, demonstrating superior thermomechanical stability. Furthermore, WER significantly enhanced the interfacial interaction and adhesion between the binder and aggregates. However, the incorporation of WER adversely affects the low-temperature cracking resistance of the binder, necessitating strict control over its dosage in practical applications.

As a typical thermosetting material, viscosity is critical in the compaction process of thermosetting polyurethane (PU)-modified asphalt (TPUA) pavement systems. However, limited research on the key factors governing TPUA viscosity has hindered the precise control of its allowable construction time. In this study, a TPUA binder was synthesized using modified hexamethylene diisocyanate (HDI) as the main agent, polytetramethylene ether glycol (PTMG) as the soft segment, and 1,4-butanediol (BDO) as the chain extender. The effects of external factors (preparation methods, curing temperature, PU content) and internal factors (soft segment molecular weight, hard segment content, reactive group ratio) on the viscosity growth of modified asphalt were systematically investigated. The results showed that Both two-component and three-component preparation methods exhibited negligible differences in viscosity growth and allowable construction time of TPUA binders. Higher curing temperatures accelerated viscosity growth rates, significantly shortening the allowable construction window. When the curing temperature increased by 5 °C, the allowable construction time decreased by 6 to 10 min. Moreover, A viscosity-temperature evolution model was proposed, effectively simulating the initial viscosity changes of TPUA binder. Increased soft segment molecular weight, hard segment content, and reactive group ratio accelerated viscosity growth and reduced allowable construction time. Allowable construction time correlated positively with PU content, with a recommended minimum PU dosage of 30 wt% to ensure workability. Comprehensive analysis identified hard segment content, PU dosage, and curing temperature as the most critical parameters governing viscosity growth and allowable construction time. These results provide critical insights for optimizing TPUA formulations and curing protocols to balance processability and performance in pavement engineering applications.

A new thermosetting polyurethane modified asphalt (TPUA) pavement material was developed to solve the unbalanced performance of traditional bridge deck pavement materials. Compared with the conventional bridge deck pavement materials, this work comprehensively evaluates the pavement performance of the TPUA binder and its mixture. The results indicate that the TPUA binder gradually shows elastic material properties at high temperatures and has excellent deformation resistance. The low-temperature flexibility of the TPUA binder is much better than that of SBS asphalt and epoxy asphalt (EA) binders. The TPUA binder is a viscoelastic material at low temperatures, and its creep meets the Burgers constitutive model. Moreover, the TPUA binder also has excellent mechanical properties and flexibility. In addition, the TPUA mixture has excellent mechanical properties, high-temperature deformation resistance and moisture stability. Its crack resistance at room temperature and low temperature is much better than those of SBS asphalt and EA mixture. This work will help us continue the development and performance research of TPUA pavement materials.

The silty fine sand and rounded gravel layers are widely distributed in Nanning City, China. Due to the low clay content, the silty fine sand and rounded gravel layers are prone to disturbance during sampling and transportation, which affects the shear strength test results. The reasonable determination of their shear strength is significant and imperative to the project. The rail transit project in Nanning is under large-scale construction. This work obtained the shear strength of the silty fine sand and the rounded gravel layers by conducting laboratory tests on undisturbed samples from deep foundation pits, combined with large-scale direct shear in situ tests. In addition, geotechnical investigation reports for typical projects in Nanning City were compiled, and the test data for the silty fine sand and the rounded gravel layers were comparatively analyzed using the empirical value. The results show that the shear strength test values of the fine sand layer are consistent with the current standard empirical values, and empirical values can be used for reference. The shear strength test value of the rounded gravel layer has significantly improved compared to the current standard empirical value, with a cohesion (c) value of 06.8kPa and an increase in internal friction angle (φ) of 012.5. It is recommended to determine the shear strength of the rounded gravel layer based on the actual situation.