Structural Investigation of Alkali-Activated Blast Furnace Slag

Abstract

Concrete production is associated with significant carbon dioxide emissions, primarily due to the the production of Ordinary Portland Cement (OPC), acting as the binder in conventional concrete. Alkali-activated materials (AAMs) have emerged as a promising alternative binder system with the potential to reduce the environmental impact of the construction industry. In alkali-activated systems, the chemistry and performance of the material are strongly influenced by the composition of the activator solution, particularly SiO2/Na2O ratio, also known as the water glass modulus. This thesis investigates the influence of water glass modulus on the reaction behavior, microstructure development, and mechanical properties of alkali-activated blast furnace slag systems. Samples were prepared using ground granulated blast furnace slag (GGBS) with alkali activator solutions of varying water glass moduli. The materials were characterized in terms of setting time, chemical composition, reaction kinetics, microstructure and mechanical properties. The results showed that the water glass modulus significantly affected setting time, porosity, structural development, and compressive strength. Modulus 1.0 exhibited the fastest structural development, highest compressive strength, and lowest surface area whilst still having an acceptable initial setting time (IST). This study demonstrates the importance of optimizing sodium silicate modulus in AAMs systems and contributes to the understanding of how activator chemistry governs reaction mechanisms and material performance in sustainable cementitious binders.