Abstract:  This study examines the mechanical properties of metakaolin-based geopolymer-modified soil under freezing construction conditions. Using silty clay from Fuzhou, the effects of freezing temperature, activator modulus, the water glass to metakaolin mass ratio (S-MK ratio), geopolymer content, and curing age on the uniaxial compressive strength were analyzed. The relationship between strength development and these factors was explored through soil stress-strain curves and failure modes. Scanning electron microscopy (SEM) was used to analyze the microstructure of geopolymer and cement-modified soils with varying activator moduli, providing insights into the micro-level strength development mechanism. The results indicate that the compressive strength of metakaolin-modified soil is significantly higher under freezing conditions compared to normal temperatures. The unconfined compressive strength declines with increasing alkali activator modulus, accompanied by brittle failure at low modulus levels. With the rise of the S-MK ratio, the strength exhibits an initial increase followed by a subsequent decrease. Additionally, the strength improves as geopolymer content increases, yet the enhancement trend gradually levels off once the dosage exceeds 25%. The optimal mix was found to be an activator modulus of 1.3, an S-MK ratio of 1.4, and 25% geopolymer content. 

Key words: metakaolin, geopolymer, frozen, modified soil, compressive strength, activator modulus, S-MK ratio, silty clay ,