An investigation on blast-furnace stag as fine aggregate in alkali-activated slag mortars subjected to elevated temperatures

In this study, the possibility of using granulated blast-furnace slag (GBFS) as partial or full natural silica sand replacement in alkali-activated slag (AAS) mortar was investigated. The ratio of binder to fine aggregate was 1:2. Natural sand was replaced with GBFS at levels of 0%, 25%, 50%, 75% and 100%, by weight. Compressive strength at ages of 7 and 28 d was measured. The behaviour of the investigated mortar mixtures after exposure to 200, 400, 600 and 800 degrees C for 2 h was evaluated quantitatively by measuring the residual compressive strength and qualitatively by visual inspection. The various decomposition phases formed and the morphology of formed hydrates were identified by using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results indicated that the compressive strength of the mortar specimens before and after firing increased with increasing GBFS sand content. (C) 2015 Elsevier Ltd. All rights reserved.