Understanding the early reaction and structural evolution of alkali activated slag optimized using K-A-S-H nanoparticles with varying K2O/SiO2 ratios

Abstract

So far, little is known about the manner the synthesized K-A-S-H (K2O–Al2O3–SiO2–H2O) nanoparticles affects the hydration of alkali-activated slag (AAS). To understand the effects of adding K-A-S-H nanoparticles with two distinct K2O/SiO2 ratios on reaction and microstructural development of AAS, heat evolution, TGA, MIP and SEM-BSE analyses were measured. Results revealed that incorporation of synthesized K-A-S-H nanoparticles can not only be used as seeding to induce nucleation, thereby significantly promoting the hydration of slag and manipulating the chemical composition of the hydrate phases, but also as fillers to increase the density of alkali-activated slag pastes; then microstructure analysis found that incorporation of synthetic K-A-S-H nanoparticles in AAS could optimize the pore size distribution, leading to a dense matrix structure. Furthermore, the effect of K-A-S-H particles with varying K2O/SiO2 ratios was mainly related to their specific surface area. These important findings provide possible practical implications for controlling the late-stage performance of alkali-activated binders.