Silvia Portale

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 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).

The Cathedral of Cefalù (Sicily, Italy), a UNESCO World Heritage Site since 2015, was built during the Norman rule and is famous for its magnificent mosaic. The mosaic apparatus, located in the apsidal area of the Cathedral, recently underwent extensive conservation work. Besides the mosaic tesserae, this area of the Cathedral was subjected to interventions aimed at preserving the integrity of masonry plasters, mortars, stuccoes and coloured plasters. However, basic information such as the chemical and mineralogical composition and microstructural arrangement of original materials was still lacking. In this perspective, in situ and ex situ analyses were carried out for the first time on the masonry and decorative materials of Cefalù’s Cathedral apse. Chemical analyses were carried out on original mosaic tesserae by means of portable X-ray fluorescence, highlighting that their manufacture involved the recycling of glass, excluding the use of natural glass and identifying the chromophores responsible for the wide colour variety; X-ray diffractometry was performed on masonry plasters and mortars allowing to recognise the use of predominantly carbonatic binders and the presence of degradation products such as calcium oxalates and sodium chloride; finally, petrographic observations carried out on stuccoes enabled the identification of various types of aggregates (carbonatic, gypsum-based, and quartz-feldspathic) embedded in a carbonatic binder, while petrographic analysis of the coloured plasters allowed the identification of three pigmentation techniques. Overall, these analyses provided very useful information on the nature of building and decorative materials as well as their mineralogical composition and degradation products, laying the foundations for future conservation work that takes into account the characteristics of each material. Graphic abstract

This paper presents research into the feasibility of using stone sawing sludge-based Alkali Activated Materials (AAMs) for conservation of Cultural Heritage. Sawing sludges are a stone processing waste product resulting from the mixing of rock powder with the water used to cool down the cutting blades. The chemical composition of the sawing sludges, when aluminosilicatic, is suitable for acting as a precursor to produce AAMs. AAMs are known for their low environmental impact and versatility since their existence is drawn from recycling waste materials. One of their possible applications is in the conservation of Cultural Heritage objects. This work presents a preliminary investigation into three sawing sludge-based AAMs with different mineralogical compositions and contributes to formulating guidelines for applying them as fillers on modern and archaeological ceramic pottery based on the evaluation of their workability, appearance and physical properties over time from the moment of application and up to 30 days. Dynamic Vapor Sorption and X-Ray Diffraction results provided an overview of the structural and mineralogical changes under high RH conditions, where the tested AAMs showed a type II isotherm curve, as expected for concrete-like materials, as well as disappearance of thermonatrite after one isothermal cycle. Ultrasonic Pulse Velocity test demonstrated the general homogeneity of the AAMs despite the lower velocity exhibited by one of the formulations, probably due to its internal pore distribution and possible presence of microstratification. The Oddy tests, application tests and colourimetric measurements evidenced the advantages and weaknesses of the AAMs, with overall encouraging results ensuing investment in further in-depth studies of these innovative conservation materials in view of their future use in the field of conservation of Cultural Heritage as a result of a circular economy model.

The 2021 Tajogaite eruption was marked by intense pyroclastic fallout that covered a substantial portion of La Palma island, with maximum thicknesses in the central-western part. This, combined with lava flows, resulted in widespread damage to public and private properties. In this study, we investigated if volcanic ash from this eruption could serve as a raw material in the synthesis of alkali activated materials (AAMs) and contribute to the construction of eco-friendly buildings and the restoration of those damaged by the eruption. Volcanic ash-based AAMs were synthesized using NaOH and Na2SiO3 as alkaline solutions and by adding metakaolin to enhance ash reactivity and enable processing at ambient temperatures. Lightweight porous AAMs were also produced using H2O2 and metallic aluminum as foaming agents. Chemical, textural, physical, and mechanical analyses on the final products assessed their suitability as environmentally friendly materials to be used in the reconstruction of the island infrastructure, opening new perspectives on recovery actions that can be undertaken after disastrous eruptions. Of all the islands in the Canary Archipelago, La Palma has experienced the highest number of eruptions (8) in historical times, all of which showing considerable similarity in terms of eruptive mechanisms and composition to the most recent Tajogaite event. Although this study investigated fresh Tajogaite ash, similar perspectives can be envisaged for both other recent eruptions at La Palma and other similar volcanic scenarios worldwide.

Piton de la Fournaise is an active shield volcano located in the eastern area of the Réunion Island (Indian Ocean) whose activity is characterized by effusive and explosive episodes with the emission of scarcely differentiated magmas with mostly tholeiitic affinity. The presently active edifice has grown within the Enclos Fouqué caldera, a polylobate plain bounded on its western side by the 80–200 m high Bellecombe vertical cliffs. This escarpment exposes a vertical sequence of 12 lava flows cut by a dike with an age > 5.5 kyrs. In this work, the Bellecombe products were investigated by X-ray fluorescence, Inductively Coupled Plasma Mass Spectroscopy, a Scanning Electron Microscope and X-ray computed microtomography in order to characterize the evolution over time of the magmatic system feeding the eruptive activity prior to the Enclos Fouqué caldera collapse. The results indicate that lava flows share a geochemical affinity with the two main series documented at Piton de la Fournaise, namely, Steady State Basalts (SSB) at the bottom and top of the sequence and Abnormal basalt Group (AbG) with different degrees of differentiation in the central part. The emission of these two different products in both a restricted area and timespan testifies to the dynamic activity of the plumbing system, capable of shifting rapidly from central to eccentric activity in the recent past.