Research On The Ion Immobilization Capability Of High-calcium Fly Ash Geopolymer And Properties Of Solidified Body

Geopolymers have special space framework structures which make it has advantages in the field of heave metal ions solidification.This applied prospect attracts people’s widespread attention.Aluminum silicate minerals with little or no calcium are main choices for producing immobilizing geopolymers.Nowadays,the researches in this field mainly focus on the preparation of solidified body and its mechanical properties Less researches is executed on the solidification capability of geopolymer and the properties of solidified body.In this paper,high-calcium fly ash was chosen as a substitution precursor instead of traditional precursor,coordinated with silica fume,for geopolymer preparation.Effects of different factors on the mechanical pro perties and frost resistance of geopolymer were investigated and the mixing proportion of matrix was designed based on the optimal comprehensive properties.The solidified body was prepared according to the mixing proportion.The solidification effects and influences of heave metal ions（Cu2+、Cr3+）on the properties of solidified body were analyzed.The results showed that the optimal performance of high-calcium fly ash geopolymer can be achieved according the following mixing proportion: SiO₂/Na₂O=1.2,the dosages of Na₂O and silica fume are 8 wt.% and 10 wt.% of binder materials,respectively.The samples should be cured for 24 h at 80℃ after demolding.A higher strength increasing rate can be achieved in geopolymer with high Na₂O content,while the ratio of SiO₂ to Na₂O in activator kept in a low level.For geopolymer with low Na₂O content,the higher strength increasing rate can be gained when the ratio of SiO₂ to Na₂O in activator kept in a high level.The addition of heave metal ions postponed the extent of reaction of high-calcium fly ash geopolymer.Raising the ratio of water to binder appropriately is beneficial to enhancing the compressive strength and heave metal ion stability of solidified body.The solidified body of chromium ions is more porous than the solidified body of calcium ions.With a rational pore size distribution,the solidified body of chromium ions showed weak sensitivity to low temperature.