Mazzoleni, Paolo

Geopolymers are synthetic materials, which attract increasing interest because they represent a supplementary cementitious material as an alternative to Portland cement. Geopolymers are considered as environmentally friendly materials, due to the low processing temperature and the absence of CO2 gas emissions. These ecological features, linked to their technical properties, such as high strength, high acid resistance, and/or high-temperature resistance, make them very innovative technological materials. In addition, geopolymers show good performance if realized by the utilization of secondary raw materials (industrial wastes like fly ash or slag), thus improving strong interest in such technology from countries with growing industrialization. Here, in order to reduce global impacts and to stimulate the Sicilian green economy, we provide the evaluation of the Life Cycle Assessment (LCA) through the employ of local raw materials to produce geopolymers in Sicily. To reach this aim, geopolymers have been produced in collaboration with a Sicilian cement industry, through the use of local raw materials (furnace blast slag from Sicilian steelworks and Calabrian kaolinite) and the construction of a pilot plant. The obtained results show, for different scenarios, a considerable reduction of both CO2 emissions and energy consumption, but also a general improvement of the environmental indicators.

The results of a petrographic and geochemical study carried out on archeological grindstones allow to provide new constraints on protohistoric commercial exchanges over the Mediterranean area. Eleven grindstones, discovered in an archeological site located in Milazzo (Messina, Sicily) and dated from the Early Bronze Age, have been investigated by geochemical and petrographic techniques. The raw materials are mainly volcanic rocks characterized by calc-alkaline and K-alkaline affinities with volcanic arc geochemical signature. Only one sample, made of basalt belonging to the Naalkaline series, shows an intraplate signature. The comparison with the available literature data for similar rocks allowed constraining the volcanic origin of the exploited lavas. While the intraplate-type raw material came from Mt. Etna Volcano (Sicily), the arc-type volcanic rocks are mostly trachyandesites, basaltic andesites, and one rhyolite. Although most of them come from the Aeolian Arc, a provenance of some samples from the Aegean Arc cannot be excluded. This last region could represent the most probable provenance area for the rhyolite sample.

Ashes emitted during volcanic explosive activity present peculiar surface chemical and mineralogical features related in literature to the interaction in the plume of solid particles with gases and aerosols. The compositional differences of magmas and gases, the magnitude, intensity and duration of the emission and the physical condition during the eruption, strongly influence the results of the modification processes. Here we report the characterization of the products emitted during the 2013 paroxysmal activity of Mt. Etna. The surface features of the ash particles were investigated through X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM) allowing the analysis at nanometer scale. TEM images showed on the surface the presence of composite structures formed by Ca, Mg and Na sulphates and halides and of droplets and crystals of chlorides; nanometric magnesioferrite and metallic iron dendrites are observable directly below the surface. From the chemical point of view, the most external layer of the volcanic glassy particles (<5 nm), analysed by XPS, presents depletion in Si, Mg, Ca, Na and K and strong enrichment in volatile elements especially F and S, with respect to the inner zone, which represents the unaltered counterpart. Below this external layer, a transition glassy shell (thick 50–100 nm) is characterized by Fe, Mg and Ca enrichments with respect to the inner zone. We propose that the ash particle surface composition is the result of a sequence of events which start at shallow depth, above the exsolution surface, where gas bubbles nucleate and the interfaces between bubbles and melt represent proto-surfaces of future ash particles. Enrichment of Ca, Mg and Fe and halides may be due to the early partition of F and Cl in the gas phase and their interaction with the melt layer located close to the bubbles. Furthermore the formation of volatile SiF4 and KF explain the observed depletion of Si and K. The F enrichment in the external 50 nm thick layer of the glassy particles suggests the resorption of this element during the rise from depth less than 400 m below the summit vent. During the eruption, the gas/ash interaction persists inside the plume where further changes on the particle surface occurs. Gaseous S, Cl and F react causing the formation of solid Ca, Mg, Na and K compounds, while SiF4 was released as volatile phase and HF was physisorbed. Finally, in the low temperature plume zone, halides previously formed continuously react with gases producing sulfates. 2015 Elsevier Ltd. All rights reserved.