Study on soil mechanics and frost resistance of fly ash–metakaolin geopolymer

Aiming at the economic and environmental protection of fly-ash-metakaolin-based polymer concrete, the frost resistance of fly-ash-metakaolin-based polymer concrete is studied. Concrete polymers were prepared by mixing 1:1 mass ratio fly ash with metakaolin and using potassium silicate excitation. According to the content of fly ash and metakaolin, water-binder ratio, sand ratio, and bone cement ratio, the soil-cement concrete blocks were divided into 7 groups. The effects of saturation volume absorption of vacuum water, mass loss of freeze-thaw cycle, and relative dynamic elastic modulus on the frost resistance of concrete specimens were tested. The results show that after curing for 3 days and 7 days, the compressive strength of soil polymer concrete increases by 93.7% and 134.4% respectively. The increase of metakaolin content of fly ash can effectively improve the structural compactness of soil-polymer concrete. When the water-cement ratio is 0.4%, the sand ratio is 0.25–0.30%, and the bone cement ratio is 3.5%, the compressive strength and splitting tensile strength of geopolymer concrete are better. The incorporation of fly ash and metakaolin can effectively reduce the vacuum saturation volume absorption rate and the freezing-thawing water content of geopolymer concrete.