Durability of SAP-modified concrete for pavements under multi-field coupling: wheel loading, hydrodynamic pressure and temperature effects

Rapid deterioration of pavement concrete under wheel loading, hydrodynamic pressure, temperature and sulphate attack threatens traffic safety. This study investigated the role of Super-absorbent Polymer (SAP) in mitigating the deterioration of impermeability and sulphate resistance in concrete under multi-field coupling. Rapid chloride migration and sulphate solution dry‒wet cycling tests were used to evaluate the chloride migration coefficient (DRCM), mass loss, and relative compressive strength (Rc), and mercury intrusion porosimetry was used to characterise pore structure. The results indicate that SAP incorporation reduced the DRCM by 30.90%–33.21% and decreased its growth rate by 39.66%–41.16% after 200,000 coupling cycles across 0.40–0.70 stress levels, with the peak regulatory effect at 100,000 cycles. Following 50,000–150,000 pre-damage cycles and 180 dry‒wet cycles, the SAP reduced mass loss by 17.08%–26.61% and increased Rc by 9.95%–13.17%. SAP mitigated durability deterioration by refining the pore structure and inhibiting the development of connected transport pathways, with pore parameters reduced by 1.54%−6.40% after 150,000 coupling cycles. These results demonstrate that SAP is an effective strategy for improving the durability of pavement concrete under multi-field coupling.