This work involved the use of neutron imaging for the study of the mechanism and rate of capillary water uptake within alkali-activated materials (geopolymers) synthesized starting from natural and industrial waste precursors of the Sicilian territory, to be applied to the conservation of cultural heritage. In detail, the materials were produced starting from Mt. Etna Volcanic ash, basalt cutting sludges and industrial ceramic tiles wastes; the starting formulations were also enriched with different types of additives (calcium-rich or reinforcing fibres); furthermore, all the samples were investigated both as such and after preliminary weathering treatment inducing sodium chloride crystallization. The aqueous solutions transfer capability of the products was investigated, with important implications in the possible formation of efflorescence. This is vital when prospecting a conservation intervention and evaluating the suitability of the materials for this scope. The study during water uptake was conducted by means of neutron radiography continuously acquiring images integrated on 10 s, while the wet samples of the ceramic-based geopolymers group were studied also by means of neutron tomography with the aim of observing the porous structures/the formed fractures in 3 dimensions. The data were treated and the sorptivity of the materials was obtained, giving some indications about the advisable formulations (e.g. with calcium-based additive) and those to be avoided for cultural heritage conservation (e.g. ceramic-based without additive).

This study explores the feasibility of utilizing granite sawing sludge (FC) as a precursor to produce alkali-activated materials (AAMs). To enhance the reactivity of the system, metakaolin (MK) was added and binary mixtures were synthetized. A multidisciplinary approach, including mineralogical, chemical and mechanical analysis, was employed to assess the suitability of these precursors to produce AAMs. X-Ray diffraction (XRD) and Fourier-Transform Infrared spectroscopy (FT-IR) confirmed the occurred activation reaction with the consequent increase in the amorphous content. Raman spectroscopy was used to further explore the mineralogical composition of the consolidated specimens, helping in the detection of salts, whose formation is ascribed to secondary carbonatation processes. Morphological analysis (SEM-EDS) displayed relatively uniform microstructures for all specimens. Compressive strength tests revealed that MK rich samples achieved best values compared to FC rich formulations, which exhibited reduced strength resistance. This study highlights, for the first time, the benefits of incorporating Cuasso al Monte granite sawing sludges into alkali-activated binders. Results suggested that the incorporation of FC is recommended for both environmental and economic advantages.

This study evaluates the influence of natural and synthetic fibres on the physical–mechanical performance of volcanic ash-based alkali-activated materials (AAMs). Volcanic ash from Mt. Etna (Italy) blended with metakaolin was used as a precursor and activated with 8 M sodium hydroxide and sodium silicate solutions. Prickly pear, palm trees and carbon fibres were added up to 1 wt.% in short (~10 mm) and long (~40–70 mm) configurations. FTIR analysis showed chemical modifications of the natural fibres after alkaline exposure, including the reduction or disappearance of bands associated with lignin, hemicellulose, and some cellulose-related functional groups. Mechanical tests demonstrated a dependence on fibre type and geometry. Short carbon fibres provided the highest flexural strength (23.19 MPa), corresponding to an increase of about 197% compared with the unreinforced binder. Long palm fibres yielded the highest stiffness, with a Young’s modulus of 12.16 GPa. In contrast, prickly pear fibres reduced flexural strength due to weak fibre–matrix adhesion and fibre pull-out. Water absorption tests showed that palm fibres exhibited the highest absorption rate (~20%) and mass loss (~1.9%), while prickly pear fibres proved to be less prone to absorb water. Microstructural analysis demonstrated good fibre–matrix adhesion, with localised interfacial gaps. Overall, carbon fibres ensure the best mechanical performance, while natural fibres remain a promising alternative for non-structural and restoration applications.