The aim of this research is evaluating the flow behavior of slag cement paste depending on various types of gypsum and their replacement ratio. In this research, gypsum was added for the slag cement to induce ettringite formation and thus achieve improved and stable strength. Although natural anhydrite gypsum is primarily used for this purpose, various other types of gypsum have been studied as potential additives for slag cement. However, these studies have focused on the reaction mechanisms or hardened properties. Hence, in this research, using workability measurement methods and a rheological test method, six-different types of gypsum were evaluated: anhydrite, α, and β hemihydrate, dihydrate, desulfurized gypsums and combined gypsum of desulfurized and anhydrite gypsums. Experiment results showed that the dissolution rate of different gypsums can significantly influence the fluidity of the pastes.

Keywords: Slag cement paste, Gypsum type, Gypsum replacing ratio, Rheology.