Acid and Sulfate Resistance of Alkali-Activated Ternary Blended Composite Binder

The aim of the study is to evaluate both acid and sulfate resistance of alkali-activated binders (AABs): (1) AAB-1 made up of slag, palm oil fuel ash, and rice husk ash alongside a 2.5 M NaOH solution; and (2) AAB-2 with the same binders except for palm oil fuel ash, which was replaced by fly ash. Acid and sulfate resistance of mortar specimens were evaluated by visual observation, weight change, compressive strength change, and microstructure analysis. AABs mortar specimens showed superior test results in terms of weight loss and compressive strength reduction compared with an ordinary mortar when immersed in 3% H2SO4 and 3% HCl solutions for 270 days. On the other hand, the AAB-1 mortar specimen showed a better sulfate resistance than those of AAB-2 and an ordinary mortar when immersed in 5% Na2SO4 and 5% MgSO4 solutions for 270 days. The microstructure analysis revealed a significant residual gel structure in case of AABs mortar specimens compared with an ordinary mortar specimen after 270 days in both acid and sulfate media.