The Influence of Al2O3on the Properties of Alkali-Activated Slag Cement

This research investigates the influence of ground granulated blast furnace slag (GGBFS) composition on the alkali-activated slag cement (AASC). Aluminum oxide (Al2O3) was added to GGBFS binder between 2% and 16% by weight. The alkaline activators KOH (potassium hydroxide) was used and the water to binder ratio of 0.50. The strength development results indicate that increasing the amount of Al2O3 enhanced hydration. The 2M KOH + 16% Al2O3 and 4M KOH + 16% Al2O3 specimens had the highest strength, with an average of 30.8 MPa and 45.2 MPa, after curing for 28days. The strength at 28days of 2M KOH + 16% Al2O3 was 46% higher than that of 2M KOH (without Al2O3). Also, the strength at 28days of 4M KOH + 16% Al2O3 was 44% higher than that of 4M KOH (without Al2O3). Increase the Al2O3 contents of the binder results in the strength development at all curing ages. The incorporation of AASC tended to increases the ultrasonic pulse velocity (UPV) due to the similar effects of strength, but increasing the amount of Al2O3 adversely decreases the water absorption and porosity. Higher addition of Al2O3 in the specimens increases the Al/Ca and Al/Si in the hydrated products. SEM and EDX analyses show that the formation of much denser microstructures with Al2O3 addition.