Influence of slag composition on the hydration of alkali-activated slags

This study investigates the hydration properties of different blast-furnace slags activated with sodium metasilicate and NaOH. The objective is to compare the strength development and microstructural characteristics of these systems over time. Methodologically, the research involved experiments to assess compressive strength at various hydration ages, alongside analysis of microstructural differences between the activation methods. Results demonstrate that while sodium metasilicate leads to poor strength after 1 day, it achieves significantly higher strength after 7 days compared to NaOH activation, which results in rapid early strength but slower later development. Furthermore, the study reveals that sodium metasilicate produces a denser hydration product, resulting in a less porous microstructure compared to NaOH. Additionally, variations in slag composition, particularly magnesium oxide (MgO) and aluminum oxide (Al2O3) contents, were found to influence hydration kinetics and compressive strength. Higher MgO levels enhanced hydration speed, while increased Al2O3 slightly hindered strength development. These findings underscore the importance of slag composition in optimizing the performance of alkali-activated systems.