Öz This paper aims to study strength properties, UPV, and weight changes exposed to sulfate attack, and microstructural properties of geopolymer mortar prepared using metakaolin and red-mud as binder materials by mixing with river sand replaced partially by limestone, marble and basalt powder with different ratios (25%, 50%, and 75%) as filler materials, the mix proposed were activated by sodium silicate and sodium hydroxide solutions (12mol). The proposed samples were exposed to 10% of magnesium and sodium sulfate solutions for various periods of 60, 120, and 180 days to investigate the durability properties of the manufactured geopolymer mortar. The experimentally obtained results uncover that the prepared geopolymer mortar’s strength properties increase at 60 days for all the proposed mixes, while at 180days, the geopolymer mortar suffers a significant loss. Change in weight increase obviously between 10.83% and 13.65% for 60 days and decrease gradually for 120 days between 9.22% and 10.19% to reach a stable value between 120 and 180 days. Furthermore, to evaluate this work, the Scanning Electron Microscopy and X-ray Diffraction methods were investigated.
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