Compatibilizers play a critical role in resolving compatibility issues between styrene–butadiene–styrene (SBS) modifiers and asphalt systems. These additives enhance the uniform dispersion of SBS modifiers and stabilize their cross-linked network structure within the asphalt matrix. This study employed molecular dynamics (MD) simulations via Materials Studio (MS) to investigate the effects of a compatibilizer on compatibility mechanisms and diffusion behavior in SBS-modified asphalt (SBSMA). Model validation was conducted through density and glass transition temperature (Tg) analyses. The cohesive energy density (CED) and solubility parameters were quantified to assess the impact of compatibilizer dosage on system compatibility. Radial distribution function (RDF) and mean square displacement (MSD) analyses elucidated molecular diffusion dynamics. The results indicate that compatibilizers enhance cohesive energy density by 12.5%, suppress irregular intermolecular motion, and reduce system instability. The synergistic interaction between aromatic and saturated components in compatibilizers effectively disperses asphaltene aggregates and inhibits π–π stacking. Additionally, strong solubility interactions with hydrocarbon mixtures facilitate the diffusion of asphaltene gum molecules. These findings provide molecular-level insights for optimizing compatibilizer design in SBSMA applications.

This study aims to investigate the restorative effects and rejuvenation mechanisms of two rejuvenators on ultraviolet (UV)-aged SBS modified asphalt binder. Two types of rejuvenators were developed. The rheological properties of aged and rejuvenated asphalt were systematically evaluated using a dynamic shear rheometer (DSR), bending beam rheometer (BBR), and multiple stress creep and recovery (MSCR) tests. Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were employed to analyze the rejuvenation mechanisms. The results demonstrate that UV aging significantly deteriorates both the high- and low-temperature performance of SBS modified asphalt binder. Oil-rich rejuvenator A effectively restores UV-aged asphalt’s high-temperature performance and low-temperature stiffness. Polymer-based rejuvenator B better repairs PAV-aged cross-linked networks with superior chemical dilution, but over-dilutes large molecules. Both comparably restore aged low-temperature performance, with rejuvenator A favoring stiffness recovery and rejuvenator B favoring m-value recovery. FTIR analysis reveals that aging significantly increases the carbonyl and sulfoxide indices of SBS modified asphalt binder, especially after PAV and UV aging. Rejuvenator B exhibits superior chemical dilution, reducing these indices nearly to their original levels. GPC analysis demonstrates an aging-induced molecular weight increase and large molecular size (LMS) formation. The recovery effect of rejuvenator A is quite limited (reducing LMS by 2%). Conversely, rejuvenator B aggressively reduces LMS but causes over-dilution. Overall, rejuvenator B is recommended to be used for aged SBS modified asphalt binder, especially after UV aging.

In the seasonally frozen regions, during the grouting of prestressed bridge ducts in low-temperature environments, incompletely cured grout materials undergo volumetric changes due to freeze–thaw cycling, resulting in structural cracks along the prestressing ducts of the bridge, thereby diminishing the bridge’s operational lifespan. In order to investigate the freeze–thaw characteristics of grouting materials under the influence of freeze–thaw cycles and propose improvement measures, the influence of various additives on the freeze–thaw stress characteristics of mortar under freeze–thaw cycle conditions was elucidated through freeze–thaw stress tests. The mechanisms for improving the freeze–thaw characteristics of grouting materials were explored through analyses of free water content, setting time, compressive strength, XRD, and SEM. In light of the requirements for comprehensive performance of grouting materials, composite additives are employed to enhance the freeze–thaw performance of the grout. The results indicate that reducing the water-cement ratio, incorporating calcium formate, sulfoaluminate cement, air-entraining agents, and carbamide all have a positive impact on mitigating frost-heaving stress in grout materials. However, the improvement mechanisms differ, and employing a single measure alone is insufficient to effectively reduce frost-heaving stress while meeting performance criteria such as compressive strength, setting time, and flowability. Free water content emerges as a crucial indicator determining the magnitude of frost-heaving stress in grout materials, with 11.5% of free water content representing the critical threshold for frost heaving in grout materials. Utilizing composite admixtures can simultaneously decrease free water content, lower the freezing point of free water, and alleviate frost-heaving deformation, resulting in a more efficient reduction of frost-heaving stress. When the admixture content reaches 9.9%, frost-heaving stress is eliminated, and the comprehensive performance parameters, including compressive strength, setting time, and flowability, meet the specified requirements. Overall, the conclusions of this research will offer a scientific foundation for the choice of cold-resistant grouting materials, the mitigation of grout material freeze–thaw risk, and the improvement of quality assurance levels in bridge construction within seasonally frozen areas.

In order to solve the limitations of the existing bridge pier damage detection equipment, a rope-driven bridge pier damage detection robot (RDBPDR) is proposed. Firstly, the composition of the RDBPDR system was introduced. Secondly, the kinematical and dynamical model of the RDBPDR was established, and the optimization model of rope tension was given. Based on the dynamic model, the evaluation method and index of the stability of the RDBPDR were given. Finally, the distribution of the stability evaluation index of the RDBPDR in the workspace was clarified with an example calculation and analysis. The results show that the stability of the RDBPR gradually decreases from the geometric center to the boundary area in the horizontal section. With the increase in the height of the damage detection platform, the stability of the RDBPDR gradually increases in the vertical direction, but this change is not significant. It provides a basis for detection task planning, overall structure configuration, and prototype testing in the future.

The objective of this study is to investigate the friction performance between tire rubber and rubberized asphalt mortar. The friction force and dynamic friction coefficient (DFC) were selected as the characterization indexes for the friction performance between the tire and the rubberized asphalt mortar, and the tests were carried out using a friction coefficient tester. The variations in material parameters, namely crumb rubber content (CRC), filler-to-binder ratio (F/B), filler particle sizes and aging conditions of rubberized asphalt mortar on friction properties were analyzed, for which significance analysis was carried out. Results show that rubberized asphalt mortar composed of different material parameters exhibit different friction properties. Filler-to-binder ratio and crumb rubber content were identified as significant predictors of the friction properties in rubberized asphalt mortar, and as these factors increase, the friction coefficient between rubber asphalt mortar and tire rubber is increased. Higher crumb rubber content (30%) reduces the temperature sensitivity of friction. In contrast, an increase in F/B exacerbates the temperature-induced variation in DFC, with F/B = 1.2 showing 2.1% DFC increase from −20 °C to −10 °C versus 0.6% for F/B = 0.6. Filler particle sizes, aging degree, and temperature showed no statistically significant effects on DFC (p > 0.1).

This study aims to systematically evaluate the balancing mechanism between road performance, carbon emissions, and economic cost when selecting asphalt materials for severe cold regions, filling the gap in multi-criteria decision-making for composite chemical modifications. To address alternating temperatures, heavy traffic, and modified asphalt transport difficulties, this study presents a novel evaluation framework focusing on the performance–environmental–cost nexus of a desulfurized rubber powder composite SBS-modified asphalt mixture, which provides a clear technological breakthrough for high-ratio scrap tire recycling in seasonal frost zones. Two reference mixtures serve as comparisons: a conventional rubber powder composite SBS (styrene–butadiene–styrene triblock)-modified asphalt mixture (CR-SBS) and an SBS-modified asphalt mixture (SBS). A comparative experiment was conducted between the two materials and the SBS-modified asphalt mixture (ACR-SBS) compounded with desulfurized rubber powder. High-temperature stability was tested by the rutting test, low-temperature crack resistance by the beam bending test, and water stability by the immersion Marshall and freeze–thaw splitting tests. Life cycle carbon emissions and economic costs were quantified from raw material acquisition to construction. The results show that desulfurized rubber powder composite with ACR-SBS delivers the most superior overall road performance. However, it also generates the highest life cycle carbon footprint. Its total carbon emission reaches 162,800 kgCO₂eq, which is 13.7% (19,600 kgCO₂eq) higher than SBS (143,200 kgCO₂eq) and 7.7% (11,600 kgCO₂eq) higher than CR-SBS (151,200 kgCO₂eq). The total cost of ACR-SBS is 391,000 CNY, which is 1.5% (6000 CNY) higher than SBS (385,000 CNY) and 1.3% (5000 CNY) lower than CR-SBS (396,000 CNY). These findings provide a basis for the selection of high-performance, low-carbon, and economical composite-modified asphalt in severe cold regions.