Effects of red mud and Alkali-Activated Slag Cement on efflorescence in cement mortar

Recently AASC (Alkali Activated Slag Cement) is utilized for construction materials in order to reduce environmental load like abundant CO2 emission. Red mud which is a byproduct from Bauxite ores process has a strong alkali component containing 10.0-15.0% of Na2O, so that it can be used for an alkali activator or retarder for cement hydration. This work presents an evaluation of efflorescence characteristics in cement mortar with AASC and red mud. For the work, OPC (Ordinary Portland Cement) and AASC are used as matrix binder, and varying replacement ratios of red mud (0.0-30%) are prepared. In order to evaluate the efflorescence characteristics in the binders with red mud, analysis of water absorption and porosity are performed. The changing efflorescence areas with weight loss are also measured. The compounds in efflorescence are quantitatively analyzed through various techniques such as EDS, XRD, SEM, TGA, and alkali leaching test. In the work, the accelerated efflorescence mechanism and its characteristics are quantitatively evaluated considering the effects of binder types and red mud replacement ratios.