Influence of different types and contents of gypsum on mechanical properties and porosity of sulphate activated binder

Abstract

Fly ash (FA) is pozzolanic, while blast furnace slag (GGBS) is latent hydraulic. These two materials react slowly in the presence of water to harden. Adding an alkali activator such as strong hydroxide could boost the hardening process, but the safe handling of highly corrosive materials is the primary concern. Therefore, the present work prescribed various types of gypsum to activate FA and GGBS as a binder phase for making mortar. It aimed to investigate the influence of different types and contents of gypsum on the mechanical properties and porosity of sulphate-activated binder. Gypsum is a less corrosive material to provide calcium and sulphate ions for activating GGBS and FA. The main component of gypsum was calcium sulphate. Gypsum provides calcium sources that promote more C-S-H to be formed. A few types of gypsum were studied with their effect on FA/GGBS blended mortar. Furthermore, the mechanical strength and porosity of gypsum-activated GGBS/FA blended mortar were assessed. The mortar containing white gypsum exhibited the best mechanical performance among all types of gypsum. On the other hand, red gypsum and dental gypsum were established to be more effective in pore refinements, lowering the mortar’s total porosity. In conclusion, white gypsum is the most suitable material for activating the FA/GGBS blend among the various types of gypsum examined.