Optimizing durability and performance in high-volume fly ash-based alkali-activated mortar with palm oil fuel ash and slag: A response surface methodology approach

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While extensive research has been conducted on the production of binary or ternary binders incorporated into alkali-activated mortars (AAMs), significant efforts continue to be directed towards determining the optimal blends that not only address strength requirements but also durability criteria. The present study seeks to optimize highly durable AAMs subjected to harsh conditions that would most likely occur in the mortar during service, through both experimental and optimization modeling. A ternary binder system was developed with a high proportion of fly ash (FA) at 50%, 60%, and 70%, combined with ground granulated blast furnace slag (GBFS) and palm oil fuel ash (POFA) at varying levels from 0% to 30%. Visual inspection, compressive strength loss, and microstructure tests were used to evaluate the performance of the proposed AAMs with exposure to freezing-thawing cycles, wet-dry cycles, and an acidic environment for up to one year. Results indicated that the acid, wet-dry, and freezing-thawing resistances of the proposed mortar were satisfactory at the binder level (60% FA, 10% POFA, and 30% GBFS). Furthermore, the response surface methodology model's accuracy and robustness were attained, with mean absolute percentage error (MAPE) and scatter index (SI) values less than 0.11. It is recommended that a ternary binder of high-volume FA incorporating POFA and GBFS should be used in AAMs to minimize environmental problems, enhance durability performance, and reduce natural resource depletion.