Role of Modifiers in the Modulus and Cracking Behavior of Emulsified Asphalt Cold-Recycled Mixtures

The use of emulsified asphalt cold-recycled mixtures presents several advantages, including the ability to mix at ambient temperatures, enhanced construction workability, excellent capacity for incorporating reclaimed asphalt pavement, reduced energy consumption, and economic benefits. However, due to their relatively poor resistance to cracking, these mixtures are primarily employed in base layers of pavement. This study aims to improve the fracture characteristics of emulsified asphalt cold-recycled mixtures through the incorporation of various modifiers. The investigation examines the behavior of these additives under intermediate and low-temperature conditions, revealing their distinct behavioral characteristics. The results show that performance optimization is temperature-dependent. Styrene–butadiene–styrene modifiers provide the most significant improvement in fracture resistance at low temperatures, superplasticizers perform optimally at intermediate temperatures, and recycling agents offer the best overall performance across both temperature ranges. Notably, the superplasticizer additive achieves substantial improvements in fracture properties, making it a cost-effective solution for practical pavement construction applications. Further, a linear correlation exists between the newly proposed peak poststrain index and the flexibility index.