Study on the Effects of SBR and Cement on Cold-Mix Emulsified Asphalt Mixture

Cold-mix asphalt mixture (CMA) is gaining increasing attention for sustainable pavement construction because of its low energy consumption and environmental benefits. However, its low early strength, poor high-temperature stability, and limited durability restrict its application in high-grade pavements. This study proposes a synergistic modification approach by incorporating styrene-butadiene rubber (SBR) latex and cement into emulsified asphalt to enhance the mechanical and durability performance of cold-mix emulsified asphalt mixture (CMEA). The effects of different SBR contents on emulsified asphalt properties were evaluated through penetration, softening point, ductility, and residue content tests. Microstructural analyses, including particle size distribution, X-ray diffraction (XRD), and scanning electron microscopy (SEM), were conducted to investigate the interaction between SBR and cement during curing. The performance of the modified mixture was assessed through rutting, immersion Marshall, freeze–thaw splitting, four-point bending fatigue, and skid resistance tests. The results indicate that increasing the SBR content enhances both the high- and low-temperature properties of the asphalt residue. The addition of cement significantly improves the early strength and moisture resistance. A curing protocol of 110°C for 24 h was identified as optimal, promoting rapid demulsification without excessive binder aging. The SBR–cement system forms a flocculated and cohesive microstructure, balancing flexibility and stiffness and delivering superior rutting resistance, water stability, fatigue life, and surface friction. For high-polymer-modified emulsified asphalt and CMEA, strength enhancement measures provide a reference.