Improvement of the performance and microstructural development of alkali-activated slag blends

This study investigated the performance and microstructural development of alkali-activated slag (AAS) blends containing hydromagnesite seeds. AAS blends with and without seeds were assessed by isothermal calorimetry, porosity, setting time and compressive strength measurements. The formation of hydrate phases was further investigated via XRD, TGA-DSC, FTIR and SEM analyses. AAS blends incorporating 2% hydromagnesite seeds revealed the best performance in terms of hydration kinetics, strength and microstructural development. The positive influence of seeds was highlighted via increased hydration rates and degrees, shortened setting times, higher compressive strengths and denser microstructures. These improvements were attributed to the provision of additional nucleation sites in the presence of seeds that enabled the increased formation of hydrate phases (e.g. C-(A)-S-H with more crosslinks forming between adjacent silicate chains) within the pore structure.