Damage mechanism of foamed asphalt mixture under the coupling effect of salt-water-temperature base on CT technology

To investigate the damage mechanism of foamed asphalt mixture in seasonal freeze zones,Three types of foamed asphalt mixture were selected and subjected to varying numbers of salt-freeze-thaw cycles.The splitting tensile strength of all specimens was determined by the splitting test. Based on CT scanning and AVIZO software, three-dimensional micro-pore structure models were reconstructed for the three mixtures under various operating conditions, systematically extracting their equivalent network characteristics.The results show that under the coupling effect of salt - water - temperature, the microstructure of the foamed asphalt mixture deteriorates significantly. Porosity and pore volume increase continuously with the number of freeze-thaw cycles, exhibiting a highly negative correlation with splitting tensile strength.The decrease in pore sphericity and increase in tortuosity collectively indicate that pore morphology progressively evolves towards irregularity within coupled environments. Analysis reveals that the damage evolution of foamed asphalt mixture within coupled environments can be divided into three stages, namely the "crack propagation" dominant period, the "connection" dominant period and the "fusion" dominant period in sequence.At the same time, it is found that the variation in foaming water content directly influences the damage accumulation rate and evolution pathway of materials subjected to salt freeze-thaw cycles.This study provides crucial theoretical support for the durability assessment and performance optimisation of foamed asphalt mixture in permafrost regions. • The damage mechanism of foamed asphalt mixture under the coupling effect of salt-water-temperature are investigated. • Porosity and pore volume increase progressively with the number of freeze-thaw cycles, exhibiting a strong negative correlation with splitting tensile strength. • Pore morphology is evolving towards greater irregularity under the coupled effects of salt-water- temperature. • The damage evolution of foamed asphalt mixture can be divided into three stages under the coupled effects of salt-water- temperature. • The variation in foaming water content directly influences the damage accumulation rate and evolution pathway of materials subjected to freeze-thaw cycles.