Preliminary studies on the cutting wastes from Sicilian stone industries: a resource for Alkali-Activated Materials.

Sicily is a Region extremely rich in natural stones suitable for different uses in building construction, flooring, etc. For this reason, the extraction, sawing and processing activities are widely developed. However, the cutting process inevitably causes large quantities of sludge, a mixture of rock powder and machines cooling water. Globally, the stone industries are responsible for producing about 1000 Kg of cutting waste per 2500 Kg of natural stone (Almeida et al., 2007). The disposal of this waste is regulated by European Waste Codes 010413. Sadly, the sludge is often abandoned indiscriminately in open areas causing a real environmental problem. Therefore, the cutting waste recovery is an ecological challenge: the reuse of these waste materials as construction materials appears to be a viable solution to this problem generating cost reduction, while preserving natural resources. The utilization of stone sludge in alkali activation process has been recently reviewed (Occhipinti et al., 2021). In this work, three residues of rocks cultivations were selected to determine their potential as precursors in the alkali activation process. The precursors were sampled from local cutting industries and includes Etnean basalts, metamorphic rocks and quartzarenite. To investigate their chemical and mineralogical compositions, these raw materials were characterized by means of X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Fourier Transform-InfraRed spectroscopy (FT-IR). In particular, the behaviour towards alkali activation process of these sawing sludges either alone or in binary mixtures with metakaolin, a Numidic clay and a common industrial waste such gypsum, was evaluated. Sodium hydroxide and sodium silicate were used in different proportions for the activation process and the binders were cured at room temperature for 28 days. The promising AAMs were characterized through XRD, FT-IR, and Scanning Electron Microscope (SEM) techniques, to access their mineralogical and microstructural features. Flexural and uniaxial compressive tests were carried out to evaluate their mechanical strength. The obtained results are satisfying the perspective of their potential reuse in the building and restoration fields.