The vulnerability of cementitious materials to acidic environments, combined with the high carbon footprint of cement production, poses significant challenges for sustainable construction. This study investigates acid resistance of Portland Limestone Cement (PLC) mortar incorporating four iron ore tailings (IOT) types as sand replacements, at levels of 10%−40%. Specimens were exposed to 5% sulphuric (H2SO4) and citric (C6H8O7) acid solutions for nine weeks, with performance evaluated through visual inspection, mass loss and residual compressive strength. The optimum replacement level for the different IOT types ranged between 20% and 30%, with 28-day compressive strength of optimum mixes increasing by 6.4% to 23.0% compared to the control mix. Under sulphuric acid exposure, optimum IOT mixtures exhibited up to 10.6% higher strength retention and 4.7% lower mass loss than the control, while under citric acid exposure, they achieved up to 13.0% higher retention and 44% lower mass loss. Scanning electron microscopy/energy-dispersive spectroscopy and X-ray diffraction analyses confirmed that IOT incorporation produced a denser microstructure, restricting acid ingress and reducing dissolution of hydration products. These findings demonstrate the effectiveness of IOT as a fine aggregate alternative, promoting waste utilisation and reducing natural sand reliance. Further studies are recommended under long-term combined exposure and more severe acidic conditions.
El-Maghawri et al. (Sun,) studied this question.
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