Yavuz, D.2025-09-032025-09-0320252075-530910.3390/buildings151425262-s2.0-105011671417https://doi.org/10.3390/buildings15142526https://hdl.handle.net/20.500.14720/28402This research explores the effectiveness of eggshell powder (ESP) and polypropylene (PP) fiber in geopolymer (GP) mortars. It examines how various doses of ESP, ranging from 0% to 25%, and two volumes of PP fibers, at 0.1% and 0.2% (by volume), impact the workability, mechanical and physical characteristics, and microstructure of GP mortars. Assessments were made for workability, apparent porosity, water absorption, and flexural and compressive strengths, along with microstructural evaluations. Using ESP as a substitute for metakaolin (MK) at 15% and 25% (by weight) improved the flexural and compressive strengths by 22.9%, 22.5%, 37.1%, and 50.7%, respectively. Using PP fiber resulted in flexural strength improvements of up to 97%. These findings deepen the understanding of ESP’s potential as a partial replacement for MK in geopolymer mortar, provide insights on material enhancement, and demonstrate superior mechanical and durability properties. © 2025 by the author.eninfo:eu-repo/semantics/closedAccessEggshell PowderFiberGeopolymer MortarMetakaolinArticle1514Q2Q2