USE OF GRANITE SAWING WASTES IN FUNCTIONAL CEMENT BASED MORTARS: COLOUR AND PHOTOCATALYTIC PROPERTIES

摘要

Appropriate waste management is one of the main requisites for sustainable development at present. This task is nowadays tackled by the material construction industry. This work focused on the valorisation of granite sludge (GS) wastes through their incorporation, as fillers and/or functional additions, into cement based mortar formulations. These wastes had a high proportion of SiO2 (52–62 %) and Al2O3 (10.5–13.5 %). Other significant components included Fe2O3 (6.8–27.9 %) and CaO (3.4–5.9 %). The composition, morphology and particle size distribution of GS wastes warrant their use by the mortar industry. An interesting improvement in mechanical properties was obtained by gradually replacing CaCO3 filler with GS, increasing the compressive strength values from 5.2 to 6.25 N·mm-2. Conversely, 10 % cement can be replaced with GS without loss of compressive strength. The amounts of Fe2O3 present were large enough to obtain an effective reddish pigment simply by calcination at 700–900 oC for a short time. The colour coordinates of the resulting products correspond to a middle-intensity yellow-orange colour. This is an additional benefit of these residues with a view to preparing coloured mortars with good mechanical properties. The ability for this waste to act as photocatalytic material is considered by the presence of iron compounds. We have tested this property when the GS waste has been introduced in a mortar. The previous results concerning to the photocatalytic degradation of organic dyes were promising.