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, work-ability, 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.