Nurwidayati, R., Haryanti, N.H., Chairunnisa, N., Pratiwi, A.Y., Krasna, W.A. and Rahmadania, N. 2025. Investigating the Impact of Fly Ash Replacement with Portland Cement on Porosity, Water Absorption, and Compressive Strength of Geopolymer Mortars in a Tidal Acid Environment. Engineering, Technology & Applied Science Research. 15, 6 (Dec. 2025), 28829–28835. DOI:https://doi.org/10.48084/etasr.13667.