Solvent-Based Cold-Mix Asphalt for Pavement Pothole Repair: Mechanisms, Performance, Challenges, and Future Perspectives

Solvent-based asphalt cold patching materials, commonly used for pothole repair, offer advantages such as ease of application, low carbon emissions, cost-effectiveness, and year-round applicability. However, they face issues such as environmental pollution from volatile solvent emissions, long curing times, and limited durability. This review focuses on the mechanisms of strength development, performance evaluation, and improvement strategies for solvent-based cold patching materials. First, the composition and gradation characteristics of various solvent-based cold patching materials are reviewed. Subsequently, the strength formation mechanism is examined within the Mohr–Coulomb theoretical framework from multiple perspectives, including intermolecular interactions, chemical bonding, and interfacial adhesion theories, such as mechanical interlocking and surface energy theory. A comprehensive assessment of their mechanical properties and road performance also is provided. Finally, strategies for optimizing the performance of solvent-based cold patching materials are discussed, together with an evaluation of their cost-benefit performance and environmental impacts. The analysis demonstrates that the volatile organic diluent (e.g., diesel or biodiesel), as a key component, directly affects performance characteristics, including strength, moisture resistance, and storage stability, through its volatility, solubility parameters, and residual content. The introduction of chemical structures or reactions involving modifiers and additives leads to the formation of peaks, such as carbon–carbon double bonds, ester groups, and carboxylic acids. These changes alter the polarity, cross-linking density, and interfacial activity of diluted asphalt, thereby enhancing the strength, thermal performance across high and low temperatures, and moisture resistance of cold patching materials. Despite these improvements, long-term service performance remains a challenge in the industry, with most research focusing on incorporating modifiers [such as styrene-butadiene-styrene (SBS) polymers, polyurethane, and waste rubber powder] and fillers (for example, cement, fibers, and epoxy resin) into diluted asphalt. A multiperformance optimization model is needed for the synergistic design of material and performance, and further studies should clarify material degradation mechanisms and diluent migration under different environments.