Giampiero Montesperelli

Due to global environmental concerns related to climate change, the need to improve the service life of structures and infrastructures is imminently urgent. Structural elements typically suffer service life reductions, leading to poor environmental sustainability and high maintenance costs. Graphene oxide nanosheets (GONSs) effectively dispersed in a cement matrix can promote hydration, refine the microstructure and improve interfacial bonding, leading to enhanced building materials’ performance, including mechanical strength and transport properties. Cement-based nanocomposites engineered with GONSs were obtained using two commercial nanofillers, a GO water suspension and a free-flowing GO nanopowder, characterized by fully comparable morphology, size and aspect ratio and different oxidation degrees (i.e., oxygen-to-carbon molar ratio), 0.55 and 0.45, respectively. The dosage of the 2D-nanofiller ranged between 0.01% and 0.2% by weight of cement. The electrical and thermal properties were assessed through electrochemical impedance spectroscopy (EIS) and a heat flow meter, respectively. The results were discussed and linked to micrometric porosity investigated by micro-computed tomography (μ-CT) and transport properties as determined by initial surface absorption test (ISAT), boil-water saturation method (BWS) and chloride ion penetration test. Extra-low dosage mortars, especially those loaded with a lower oxidation degree (i.e., 0.45GO), showed decreased permeability and improved barrier to chloride ion transport combined with enhanced thermal and electrical conductivity with respect to that of the control samples.

The increase in concrete structures’ durability is a milestone to improve the sustainability of buildings and infrastructures. In order to ensure a prolonged service life, it is necessary to detect the deterioration of materials by means of monitoring systems aimed at evaluating not only the penetration of aggressive substances into concrete but also the corrosion of carbon-steel reinforcement. Therefore, proper data collection makes it possible to plan suitable restoration works which can be carried out with traditional or innovative techniques and materials. This work focuses on building heritage and it highlights the most recent findings for the conservation and restoration of reinforced concrete structures and masonry buildings.

The impact of extra-low dosage (0.01% by weight of cement) Graphene Oxide (GO) on the properties of fresh and hardened nanocomposites was assessed. The use of a minimum amount of 2-D nanofiller would minimize costs and sustainability issues, therefore encouraging the market uptake of nanoengineered cement-based materials. GO was characterized by X-ray Photoelectron Spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), and Raman spectroscopy. GO consisted of stacked sheets up to 600 nm × 800 nm wide and 2 nm thick, oxygen content 31 at%. The impact of GO on the fresh admixtures was evaluated by rheology, flowability, and workability measurements. GO-modified samples were characterized by density measurements, Scanning Electron Microscopy (SEM) analysis, and compression and bending tests. Permeability was investigated using the boiling-water saturation technique, salt ponding test, and Initial Surface Absorption Test (ISAT). At 28 days, GO-nanocomposite exhibited increased density (+14%), improved compressive and flexural strength (+29% and +13%, respectively), and decreased permeability compared to the control sample. The strengthening effect dominated over the adverse effects associated with the worsening of the fresh properties; reduced permeability was mainly attributed to the refining of the pore network induced by the presence of GO.

The preservation of archaeological sites, often considered as open-air museum, is a priority and a challenge due to their exposure to environmental actions and natural hazards. Every day, the artifacts populating these sites, which can have either structural or decorative functions, are subjected to continuous degradation processes, related to frost-thaw cycles, humidity and temperature variations, causing a deterioration of the materials mechanical properties. Anthropogenic pressure (visitors, human actions) can acts towards his direction, as well. In order to evaluate the ongoing process of degradation affecting a specific site, the study of the actual conditions of the materials is typically one of the first steps of the analysis. With this perspective, in this work, the results of the investigations carried out on the constituent materials of the Knossos Palace in Crete are presented. The Knossos Palace is one of the most important archaeological sites in Crete. The main excavation work took place at the beginning of the 20th century, directed by Sir Arthur Evans. The importance of this site led him and his collaborators to design and perform preservation actions, which included the reconstruction of relevant parts of the Knossos Palace. In addition for preserving the site, reconstructions were a way of highlighting the palace magnificence and the importance of the Minoan civilization. At that time concrete was already one of the most widely used building material. Considered a durable material, the concrete was used in the construction of reinforcement structures and new architectural elements, often placed in direct contact with the original ones. Nevertheless, the restoration/reconstruction made by Evans, using concrete, is nowadays considered an integral part of the monument and its history, to be studied and protected.In the context of the HERACLES Project [1], samples of stones and concrete used in the Palace of Knossos were analysed to determine their morphological and chemical characteristics and their mechanical properties. For this purpose, an integrated approach, i.e. the use of several analytical techniques, was considered essential to support the material preservation actions.[1]European Project HERACLES has received funding from the European Union Framework Programme for Research and Innovation HORIZON 2020 under GA n° 700395 

The corrosion resistance features of two different Metal Matrix Composites based on 6061 and 2618 aluminium alloys reinforced by 20% Al₂O₃ particles by stir casting process, were studied in 3.5% NaCl and compared. The composites and their respective base alloys were characterised in terms of microstructure by optical and scanning electron microscopy and in terms of corrosion resistance by polarisation curves and electrochemical impedance. Results show how the presence of Al₂O₃ has different effects depending on matrix composition. In 6061 MMC, Al₂O₃ promotes the formation of Mg₂Si which has a cathodic behaviour altering the pitting susceptibility of the composite. In 2618 MMC, the high content of Cu induces a strong uniform attack. The subsequent increase in the Open Circuit Potential caused a pitting attack.

Good conservation and restoration practices of cultural heritage assets rely on the knowledge of original materials. In the framework of the HERACLES Project (HERACLES—HEritage Resilience Against CLimate Events on Site, H2020 Grant Agreement 700395), dealing with the effects of climatic actions and natural hazards on built heritage, a set of important heritage sites are currently under study to improve their resilience against climate events. Among these are the medieval Gubbio Town Walls in Italy. The present work focuses on the mortars and binders of this monument and collected samples related to different parts of the Walls, corresponding to various historical periods of construction and interventions. They were characterized to determine their minerochemical composition, thermal behavior, and morphology. For that purpose, ex-situ laboratory techniques, such as X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), polarized light microscopy (PLM), scanning electron microscopy (SEM), and simultaneous differential thermal analysis and thermogravimetry (TG-DTA) were used to discern trends in different sampling areas due to construction/reconstruction periods and building techniques.

TiO₂ coatings on AA6082 aluminium alloy were obtained at low temperature (80 and 100°C) by the sol–gel dip-coating technique starting from titanium tetra-isopropoxide solution in ethyl alcohol. The preparation was carried out in the presence of acetic acid with both functions of catalyst and chelating agent. The curing temperatures used for these coatings are between 80 and 100°C, low enough to make such coatings suitable to incorporate additives such as organic inhibitors or polymeric nanoparticles. The coated samples were characterised by scanning electron microscopy and energy-dispersive spectroscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy (EIS). Compact coatings with a thickness of 500 nm, consisting of amorphous and nearly stoichiometric titanium dioxide, were obtained. EIS results revealed an effective corrosion protection of the substrate for more than 120 h of immersion in 3.5 wt-% NaCl aqueous solution.