Effect of palm oil fuel ash on the hydration and microstructural properties of limestone calcined clay cement (LC ³ ) utilizing prehydrated-carbonated Portland cement

This study evaluates synergistic use of prehydrated/carbonated ordinary Portland cement (OPC) and palm oil fuel ash (POFA) in limestone calcined clay cement (LC3), with emphasis on hydration behavior, microstructural evolution, mechanical performance, and embodied carbon. Different dosages of POFA were incorporated into LC3 system. The incorporation of POFA modified early hydration, as isothermal calorimetry revealed reduced initial reactivity and delayed main hydration peaks due to porous POFA structure. POFA exhibited a pronounced filler and nucleation effect, enhancing later-age hydration. TG–DTG analysis confirmed the consumption of portlandite beyond 28 days of hydration, indicating relatively slow POFA’s pozzolanic reactivity. This mixture showed increased formation of C(A)SH, AFt, and AFm phases, corresponding to continuous strength development up to 57 days. Higher POFA contents limited gel formation due to portlandite depletion. Environmentally, POFA significantly reduced embodied carbon through clinker substitution and low processing energy. Overall, 10% POFA provided optimal balance between strength and carbon efficiency.