Study on compressive strength and pore structure evolution of nano‐silica modified aeolian sand concrete under freeze–thaw cycle based on fractal dimension

Abstract This study investigates the deterioration patterns of nano‐SiO₂ modified aeolian sand concrete (NS‐ASC) under salt frost conditions. NS‐ASC was prepared using nano‐SiO₂ at dosages of 0%, 1%, 2%, 3%, and 4%, with 30% aeolian sand. The performance degradation and frost resistance mechanisms of NS‐ASC were analyzed through compressive strength tests (macroscopic) and microscopic tests (SEM and NMR) before and after freeze–thaw cycles (FTCs). Additionally, the pore fractal dimension D ( D min and D max ) of NS‐ASC under different FTCs was derived from NMR results. A model was developed to predict the compressive strength of NS‐ASC under salt frost conditions, using NS dosage and fractal dimension D as variables. The results indicated that the compressive strength of NS‐ASC gradually declined with increasing FTCs. After 200 FTCs, ANS‐1, ANS‐2, ANS‐3, and ANS‐4 exhibited strength increases of 31.1%, 36.92%, 105.49%, and 82.32%, respectively, demonstrating improved frost resistance compared to ASC without NS. The incorporation of NS effectively filled ASC's internal pores, reducing salt frost damage. Moreover, the pore fractal dimension showed a gradual decline with increasing FTCs, reflecting the progressive disruption of ASC's internal pore structure due to salt frost. The pore structure evolved from complex to simpler, with small pores gradually transforming into larger ones. Additionally, compressive strength increased with the fractal dimension D . A model based on fractal dimension D and the NS dosage contribution rate effectively described the variation of NS‐ASC in salt frost environments. This study provides a theoretical foundation for analyzing the damage and deterioration of NS‐ASC under salt frost conditions.