Phase transformation and physical properties of binding materials fabricated from solid waste FGD gypsum by oil bath heating and the micromorphology and formation mechanism of their hydration products

Abstract

This work provides a novel approach to fabricate binding materials from flue gas desulfurization (FGD) gypsum. Results show that high performance binding materials composed of 96% hemihydrate gypsum (HH) and 4% anhydrite are prepared by calcining FGD gypsum at 190 ℃ for 90 min. They present low setting times and high mechanical strength, because HH promotes the saturation of [SO4]2- and Ca2+ ions in solution, leading to increases in their hydration activity and arrangement tightness of hydration product. Moreover, their hydration product dihydrate gypsum displays a stick-like structure with smooth surface and grows along [001] orientation by screw dislocation mechanism.