Combined effects of curing conditions and cement bypass dust addition on the compressive strength of fly ash-based alkali-activated materials

This study aimed to ascertain the possibility of replacing fly ash in alkali-activated materials (AAMs) with residues obtained through the extraction of chlorine from cement bypass dust (CBPD ex ). The effects of different cement bypass dust contents (5, 10, 15 and 20%) on the early-age compressive strength and structure of fly ash-based AAMs were investigated. Samples were cured in an oven at temperatures of 80 °C for 24 h and under two different sets of humidity conditions (“dry” and “wet” system). A mixture of sodium silicates and hydroxides was used as the alkaline activator. The results demonstrate that AAMs containing 5% CBPD ex content and cured under high humidity exhibited ~ 20–30% higher compressive strength compared to the reference sample. An FTIR analysis confirmed the formation of a strong polymer network in all the series, reflected in the shift of the Si-O-Si band from 1012 cm − 1 toward lower wavenumbers. The presented work is the first step in research efforts concerning the recycling of cement bypass dust as a calcium-rich addition for AAMs.