Granitic quarry sludge waste in mortar: Effect on strength and durability

Granitic quarry sludge is an abundant waste from granite rock processing, causing serious environmental concern. The use of this waste could become a valuable resource if properly engineered into a successful solution as a partial cement replacement in concrete. The effect of granitic sludge from a quarry in northern Portugal was analyzed as a partial cement replacement in mortar in terms of strength and durability, so as to envisage its use in concrete. The experimental program included chemical analyses, laser particle size distribution and scanning electron microscopy of granitic quarry sludge, as well as mechanical strength, expansion due to alkali silica reaction and chloride penetration resistance on mortars containing different dosages of cement replacement with granitic quarry sludge waste ground to different fineness levels. Results showed that granitic quarry sludge waste, if ground to sufficient fineness, produces a denser matrix promoting up to 38% reduction in expansion due to ASR and almost 70% improvement in resistance to chlorides, without compromising workability and strength. This surprising improvement in terms of chloride resistance seems to derive from captivation of chlorides by aluminates present in the waste with formation of chloroaluminates. Finally, a properly engineered use of granitic waste in cement-based composites, leading to enhanced durability can turn granitic quarry sludge, an abundant waste, into a valuable resource and therefore contribute to sustainable construction. (C) 2013 Elsevier Ltd. All rights reserved.