2001 Volume 41 Issue 5 Pages 513-518
Immobilization of fluorine in aqueous solution with 2CaO · SiO2(C2S) and 3CaO · SiO2(C3S), and the effect of C2S and C3S on the fluorine immobilization with 3CaO · Al2O3(C3A) and 12CaO · 7Al2O3(C12A7) have been studied. The hydration products are identified by X-ray diffraction method and the fluorine-substituted compounds are confirmed by electron microprobe analysis. It is found that C3S appears more effective to immobilization of fluorine than C2S and (OH-) site in calcium silicate hydrates is substituted with F- ion. The behavior of fluorine immobilization by calcium aluminates changes with the addition of calcium silicates because calcium silicates affect the formation of Ca3Al2(OH)12-xFx, which is the most effective calcium aluminate hydrate in view of the incorporation of F- ion. The fluorine immobilization with C12A7 can be promoted in the presence of appropriate amount of C2S or C3S.