Masonry Mortar with Carbide Sludge and Limestone for Enhanced Hydration and Carbonation Performance

This investigation utilized carbide sludge, predominantly composed of calcium hydroxide, with or without ground limestone, to partially replace portland cement for masonry mortar applications. Accelerated carbonation was employed to simulate the long-term environmental exposure of the resulting composites. The inclusion of carbide sludge was found to improve water retention, thereby improving the spreadability and finishability of the associated mortar. It delayed the hydration peak of C 3 A due to the inherent presence of sulfate. While the combination of carbide sludge and limestone reduced the composite strength under moist curing, carbonation elevated the strength to levels comparable with those of mortar containing limestone alone. Limestone promoted the formation of monocarboaluminate, whereas carbide sludge reduced it. The primary crystalline carbonation products were calcite, vaterite, and aragonite. Drying shrinkage decreased with the addition of limestone but increased with carbide sludge both with and without limestone. The results demonstrate that carbide sludge improves key fresh and hardened properties of masonry mortar, offering a promising route for waste valorization in construction materials.