Study on Preparation and Polymerization Mechanism of CFB Fly Ash Geopolymer

In this study, CFB fly ash was used as raw material for alkali excitation, and the geopolymer was studied. Through a series of physical and mechanical tests, the influences of water-cement ratio, sodium silicate and quicklime on the fluidity and unconfined compressive strength of the net slurry of CFB fly ash were analyzed, and the condensation and hardening mechanism of CFB fly ash geopolymer was discussed. The results show that: the net slurry fluidity of CFB fly ash geopolymer ranges from 90 to 320 mm, and the 28-day curing strength ranges from 2 to 35 MPa. The balance points suitable for CFB fly ash geopolymer are: water-cement ratio 0.6–0.65, sodium silicate modulus 1.7, sodium silicate content 14–19%, and lime content 0–5%. The strength of CFB fly ash geopolymer comes from C–S–H gel generated by hydration. When the alkali content in the environment is too low, it is difficult to stimulate the active substance of fly ash vitreous, and thus cannot generate strength. When the amount of calcium in the environment is too large, Ca is more likely to break, and the diffusion rate is faster, resulting in the rapid synthesis of gelling substances in a short time, which inhibits the subsequent depolycondensation process.