Use of basic oxygen furnace slag fines in the production of cementitious mortars and the effects on mortar expansion

The purpose of this study was to examine the properties of ordinary Portland cement (OPC) and alkali-activated slag (AAS) mortars produced with basic oxygen furnace (BOF) slag fines, and to reveal the effects of BOF slag fines on the expansion of the cementitious mortars. The use of BOF slag fines in OPC mortars significantly reduced the compressive strength and slightly increased the volume expansion of the mortars. Significant changes in mineralogical composition were observed in the OPC mortars produced with BOF slag fines after autoclaving. On the other hand, the AAS mortars produced with BOF slag fines had compressive strength comparable to normal OPC mortars, and their volume expansion was much lower than the AAS-Control and all the OPC mortars. The mineralogical compositions of the AAC mortars before and after autoclaving were almost identical. The results of this study indicate that the BOF slag fines are suitable to partially replace the binder for the production of AAS mortars, and the resulting AAS mortars have high volume stability.