Neutralization Performance by Using Geopolymer Mortars Incorporating Unground Black Rice Husk Ash and Fly Ash
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Abstract
This study aimed to investigate the acid neutralization performance and compressive strength of geopolymer mortars incorporating unground black rice husk ash and fly ash at a ratio of 35:65 by weight. Sodium hydroxide (NaOH) solutions with concentrations of 10, 12, 14, and 16 M were used as alkaline activators. The specimens were cured and tested for compressive strength at the ages of 3, 14, 28, and 56 days. The acid neutralization performance was evaluated by immersing the geopolymer mortar specimens in a hydrochloric acid (HCl) solution with an initial pH of approximately 3. The results showed that the compressive strength of the geopolymer mortars increased with curing age and NaOH concentration, with the mixture activated by 14 M NaOH exhibiting the highest compressive strength at all curing ages. In addition, the geopolymer mortars rapidly increased the pH of the acidic solution during the initial stage and maintained effective acid neutralization performance throughout repeated immersion cycles, with the 14 M NaOH mixture providing the best overall performance. However, an excessively high NaOH concentration (16 M) may reduce aluminosilicate dissolution and hinder the geopolymerization process, resulting in decreased compressive strength and acid neutralization performance. The findings of this study indicate that geopolymer mortars exhibit significantly superior long-term acid neutralization performance compared with conventional cement mortars.
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