Energy performance and calorimetric behaviour of cements bearing granite sludge

Blending supplementary cementitiousmaterialswith portland cement is one of the current strategies for producingmore eco-efficient binders by lowering the energy consumption and CO2 emissions intrinsic to OPCmanufacture. The effect of such additions on heat of hydration and energy performance is a subject of particular interest, for higher heatmay reduce the service life of a concrete structure,whilst energy consumption per tonne of binder or megapascal may prove not to be energy-efficient. This paper explores the energy performance of granite sludge (GS) as an active addition to clinker and the effect of this by-product on heat of hydration and ecoefficiency. The findings show that maximum heating and total heat released are lower in the additioned than in the conventional material, with the difference widening at higher replacement ratios. At 35% GS, maximum heating was 36% lower than in OPC and total heat released 24% lower. Optimal energy performance is observed at ratios of 15% to 30% (both inclusive), with the experimental materials requiring less energy (−1.6 kW·h·t−1/MPa – 0.8 kW·h·t−1/MPa) than ordinary cement per megapascal (MPa) of strength. Cements with 15% to 30% granite sludge are consequently eco-efficient. With 15% GS they can be classified as ordinary (N270 J/g at 41 h),with 20% to 30% as lowheat cements (b270 J/g at 41 h) andwith 35% as very lowheat cements (b220 J/g at 41 h).
This research was funded by the Spanish Ministry of Economy and Competitiveness (BIA2016-76643-C3-1-R) (MINECO/ERDF), as well as by the Government of Extremadura and the European Regional Development Fund (ERDF) under grant GR 18122 awarded to the MATERIA research group.