Thermodynamic Stability and Dissolution of Calcium Fluoride of Phosphogypsum Solidified in Cement-Based Cementing Materials in Bicarbonate Solution

Cement-based cementitious materials present an alkaline environment and mainly exist in the form of Ca(OH)2. Phosphogypsum, as a retarder materials, is often added to cement instead gypsum, fluorine by-product phosphogypsum also fixed CaF2. These cement-based serve environments containing carbonate groundwater, which changes stability solidified This paper studied solid liquid Ca(OH)2-CaF2, Ca(OH)2-CaF2-HCO3, CaF2-HCO3-OH systems, therefore solubility CaF2 groundwater HCO3- anion after curing system through experiments thermodynamic equation simulation. The results showed that dissolved Ca2+ Ca(OH)2 led dissolution CaF2, significant reduction F- concentration. However, with increase concentration Ca(OH)2-CaF2-HCO3 increased, main product formed phase was calcium carbonate; anions increased Therefore, influence should be considered when using gypsum materials.