Evaluation of slag-blended alkaline-activated palm oil fuel ash mortar exposed to the sulfuric acid environment

The performance of alkaline activated ground slag/ultrafine palm oil fuel ash (AAGU) mortars upon their exposure to 6% of H₂SO_4aq (acid) for 60 days was investigated. The mortars were prepared with NaOH_aq of varied concentrations and Na₂SiO_3aq (Ms-SiO₂/Na₂O=3.3) activators and then cured at a temperature of 60°C for 24 h. The findings through strength, microstructural examination, and product characterization revealed that sulfuric acid attack could cause the disintegration of microstructure through the removal of the key elements-Ca, Mg, Na and Al-which resulted in the formation of gypsum, expansive shrinkage cracks, and a reduction in strength retention. Maintaining the slag content, concentration of NaOH_aq, Na₂SO_3aq/NaOH_aq ratio, and the mixing water content in the range of 20-40 wt.%, 8-10 M, 1.0-2.5, 5-10 wt.% of the pozzolanic materials (PMs), respectively could enhance the resistance of AAGU mortar subjected to sulfuric acid attack.