Lime mud waste from the paper industry as a partial replacement of cement in mortars used on radiant floor heating systems

In order to mitigate climate change, reductions of energy consumption are required on heating systems for residential and non-residential buildings. Despite radiant floor heating systems are being widely used due to their high thermal efficiency and comfort, further improvements are necessary to reduce the carbon footprint of the mortars used. This paper studies the use of lime mud, a by-product of the paper industry, as a partial replacement of cement to reduce the environmental impact of the resulting mortar. For that purpose, a reference cement mortar is compared to mortars with 10%, 20%, 30% and 40% of cement replacement by weight. Physical, thermal and mechanical properties showed that up to 20% of cement could be replaced by lime mud while maintaining thermal properties of the mortar. Despite the reduction of the mechanical resistance, mortars with up to 20% of cement replacement fulfilled the requirements of EN 1264-4:2010 standard. Finally, tests on laboratory-made radiant floor heating slabs proved that slabs with reference mortar had a similar stationary behaviour to that of the slabs with mortar containing 20% of lime mud, but the latter reach stationary faster due to the lower thermal inertia of its mortar.