Study on multiscale low temperature performance evaluation of new cold stone matrix asphalt using lime and deicing agents for cold climatic regions

Cold climatic regions impose severe challenges on asphalt pavements due to prolonged sub-zero temperatures, freeze–thaw cycling and repeated application of chemical deicing agents, leading to premature cracking, ravelling and moisture-induced damage. This study presents a comprehensive multiscale evaluation of the low-temperature performance of a newly developed Cold Stone Matrix Asphalt (CSMA) incorporating hydrated lime and commonly used chloride-based deicing agents. CSMA mixtures were prepared using two aggregates (basalt and granite), two cationic slow-setting (SS) emulsions based on VG10 and VG30 binders (SS10 and SS30), hydrated lime (4%), NaCl, CaCl₂ and MgCl₂ at varying dosages. Mixture-scale performance was assessed through indirect tensile strength and TSR, IDEAL-CT, semicircular bending and Cantabro tests after extensive freeze–thaw conditioning. Binder–mortar-scale interactions were quantified using contact angle measurements, surface free energy–based adhesion parameters, energy ratios and FTIR-derived hydration indices, while FESEM–EDS analysis elucidated lime–silica hydration through Ca/Si ratios. Results demonstrate that CSMA performance in deicing environments is governed by coupled effects of binder rheology, aggregate mineralogy, salt chemistry and lime-driven hydration. Calcium chloride consistently enhanced silicate polymerisation, adhesion, fracture resistance and moisture durability through stable Ca–Si interactions and C–S–H formation, whereas magnesium chloride suppressed effective hydration and durability. Multiscale correlation and grey relational analyses identified SS30–basalt–lime systems with optimised CaCl₂ content as the most durable configuration. The findings establish hydration-controlled interfacial chemistry as the key mechanism governing CSMA performance and provide a scientific basis for durable cold-region pavement design.