Performance of self-compacting mortars with granite sludge as aggregate

Waste produced in the extraction and processing of granite stone severely damages the environment when it is deposited in landfills. This research aims to use granite sludge as an alternative to conventional aggregates (natural sand and siliceous filler) in self-compacting mortars production. In a previous stage, the granite sludge was characterised by chemical and mineralogical composition, specific gravity, scanning electron microscopy, particle size distribution and environmental evaluation by leaching test. Subsequently, three replacement percentages (0%, 20% and 40%) by volume of conventional aggregate with granite sludge were evaluated for their self-compactability properties. Compressive and flexural strength at 7, 28 and 91 curing days were measured. The mineralogical phases using X-ray diffraction techniques, microstructure by mercury intrusion porosimetry, shrinkage and mass loss, water absorption by capillarity, water absorption capacity, bulk and skeletal density, open porosity for water and wettability of hardened mortar specimens were all studied. The granite sludge incorporation did not affect the cement hydration phases, although the microstructure of the self-compacting mortars was slightly modified. The morphology of the granite sludge particles reduced the filling effect of pores and required a slight increase in the w/c ratio to maintain the self-compacting parameter. This fact justifies the slight increase in porosity, the lower bulk density and the slight decrease in the mechanical strength of mortars with granite sludge. The durability properties were also slightly affected compared to the selfcompacting reference mortar. From an engineering point of view, the results show the feasibility of incorporating up to 40% of granite sludge in self-compacting mortar. This study explores a sustainable alternative to conventional aggregates in the manufacture of self-compacting mortar by reducing the consumption of raw materials and avoiding granite sludge landfill. (C) 2020 Elsevier Ltd. All rights reserved.