Hardening performance and mechanism of hydraulic fluorgypsum-based binding material

Hardening,hydration performance and mechanism of the hydraulic fluorgypsum-based binding material were studied in this paper. The fluorgypsum-based binding material were mixed 60% fluorgypsum with other chemical activators contained 1% K₂SO₄, 5% clinker and 35% blast furnace slag. The 28-day compressive strength of the the fluorgypsum-based binding material could reached 41.25MPa, the softening coefficient was 0.936, and the concentration of fluoride reduced to 0.0701 ug/ml. Microscopic analyses using XRD, SEM and FTIR revealed that: bar-like ettringite crystals and board-like dihydrate gypsum crystals contacted each other as structural framework.The rest round-flake anhydrite crystals and unreacted CaF₂ crystals were embedded by a great deal of network and filamentous C-S-H gel, they sticked and filled in structural framework and formed compacted body. lt was main reason that fluorgypsum-based binding material strength improved, water resistance increased and leaching toxicity decreased.