Workability, compressive strength, and efflorescence characteristics of one-part mix alkali-activated circulating fluidised bed combustion fly ash-based mortars

In this study, one-part alkali-activated mortars are formulated using circulating fluidised bed combustion (CFBC) fly ash, derived from lignite (brown coal) combustion, as the precursor, and sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) as the solid activators. Experimental findings indicate that an increase in solid activator-to-precursor ratio correlates with improved workability and compressive strength of the mortars. The influence of Na2SiO3-to-NaOH ratio on the compressive strength of the mortars is apparent only in mixes with a high solid activator-to-precursor ratio of 0.4 and 0.5, indicating its relatively lesser significance compared to the solid activator-to-precursor ratio. The mechanism through which an increase in the solid activator-to-precursor ratio improves the compressive strength of the mortars is elucidated using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. The results indicate that increasing the solid activator-to-precursor ratio enhances the degree of alkali-activation for fly ash, thereby improving the compressive strength with increasing solid activator-to-precursor ratio.