Performance evaluation and optimization of emulsified asphalt cold recycled mixtures using dual-recycled RAP and RAI materials

In recent years, the amount of waste generated during milling has increased dramatically, and improper disposal poses a significant environmental challenge. To mitigate environmental pollution and enhance the road performance of emulsified asphalt cold recycled mixtures (ECRM), this study employed recycled asphalt pavement (RAP) and reclaimed inorganic binder stabilized aggregate (RAI) as dual recycled materials for ECRM preparation. The blending ratios of reclaimed base and surface layer mixtures significantly influence ECRM's performance, with adjusted proportions substantially improving compressive strength and dynamic modulus. Firstly, three distinct proportioning options were developed for the recycled materials. Mix designs incorporating varying RAP/RAI ratios were used to determine the optimal mix parameters: moisture content, cement dosage, and emulsified asphalt content. Subsequently, comprehensive performance evaluations were conducted through high-temperature wheel tracking tests, freeze-thaw splitting tests, uniaxial compression tests, and dynamic modulus measurements to analyze the pavement characteristics of the three ECRM formulations. Experimental results demonstrate: Compared with ECRM with a blending ratio of RAP:RAI:new aggregate = 30:50:20 (Option 1), the dynamic stability, freeze-thaw splitting strength ratio, compressive strength, and compressive resilient modulus of ECRM under Option 3 (RAP:RAI:new aggregate = 50:30:20) decreased by 31.8%, 5.2%, 16.4%, and 13.1%, respectively. This indicates that increasing RAP content while reducing RAI proportion enhances the tensile strength of ECRM, yet adversely affects its high-temperature stability, moisture resistance, and compressive performance. This work not only addresses the challenge of jointly utilizing asphalt pavement waste and base waste, but also provides a cost-effective and sustainable method for the stable application of milling material resources in road engineering. • Dual-layer recycling (RAP+RAI) overcomes single-source limits in emulsified asphalt cold mixes. • Optimizes moisture, cement and asphalt content for emulsified asphalt cold recycling. • RAP enhances water stability and tensile strength. • Synergistic RAP-RAI interaction achieves rigidity-flexibility balance.