Hydration and rheology of activated ultra-fine ground granulated blast furnace slag with carbide slag and anhydrous phosphogypsum

Abstract

In this study, two different ultra-fine ground granulated blast furnace slag referred to as GS (i.e., by dry-winnowing method) and WS (i.e., by wet-grinding method) were obtained, and the hydration and rheology of activated ultra-fine ground granulated blast furnace slag (activated-BFS) with carbide slag and anhydrous phosphogypsum (AG) as combined activator were systematically investigated by means of setting time, workability, rheological behavior, compressive strength, autogenous shrinkage, electrical resistivity, SEM, XRD and TG-DTG. The results showed that the limiting factor is the BFS type, and not the AG dosage in terms of setting time, and their rheological behavior fitted with H–B model. WS and increase in AG dosage significantly reduced the plastic viscosity, shear stress and yield stress of activated-BFS pastes. The WS presented higher initial reaction activity that generated more hydrates in the early age, restricting the further hydration of BFS particles especially when AG dosage exceeded 10%, thus leading to the different compressive strength development trends between mixtures containing WS (WS/A) and GS (GS/A). The compressive strength of GS/A mixtures increased with increasing AG dosage and reached 39.9 MPa at 3 days, while WS/A first increased and then decreased. The activated-BFS with carbide slag and AG is technically feasible to be employed as cementitious materials in the production of concrete.