Effect of cement additives on unconfined compressive strength of warm and ice-rich frozen soil

The effect of nine cement additives on the unconfined compressive strength (UCS) of warm and ice-rich frozen soils was analyzed. After 7 days of curing at −1 °C, the UCS at −1 °C, the freezing-point depression and changes in the water content of soil samples were measured to explore the additive effect and mechanism. The optimum additive dosage was determined to improve engineering applications. The conclusions were: (1) attapulgite, metakaolin, nano-silicon dioxide (SiO2), silica fume and hardener accelerator increased the UCS by reducing the water content of frozen soils; (2) sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and sodium lignosulfonate thawed the ice and reduced the UCS of frozen soil samples; (3) when frozen soil with a water content of 30% and 90% was mixed with 15% cement, the optimum dosages were 2% and 8% metakaolin and 0.49% and 0.62% hardening accelerator, respectively.