Highly Stable Self-Cleaning Paints Based on Waste-Valorized PNC-Doped TiO2 Nanoparticles.

Adding photocatalytically active TiO2 nanoparticles (NPs) to polymeric paints is a feasible route toward self-cleaning coatings. While paint modification by TiO2-NPs may improve photoactivity, it may also cause polymer degradation and release of toxic volatile organic compounds. To counterbalance adverse effects, a synthesis method for nonmetal (P, N, and C)-doped TiO2-NPs is introduced, based purely on waste valorization. PNC-doped TiO2-NP characterization by vibrational and photoelectron spectroscopy, electron microscopy, diffraction, and thermal analysis suggests that TiO2-NPs were modified with phosphate (P=O), imine species (R=N-R), and carbon, which also hindered the anatase/rutile phase transformation, even upon 700 °C calcination. When added to water-based paints, PNC-doped TiO2-NPs achieved 96% removal of surface-adsorbed pollutants under natural sunlight or UV, paralleled by stability of the paint formulation, as confirmed by micro-Fourier transform infrared (FTIR) surface analysis. The origin of the photoinduced self-cleaning properties was rationalized by three-dimensional (3D) and synchronous photoluminescence spectroscopy, indicating that the dopants led to 7.3 times stronger inhibition of photoinduced e-/h+ recombination when compared to a benchmark P25 photocatalyst.

In the Direction of an Artificial Intelligence-Enabled Monitoring Platform for Concrete Structures.

In a seismic context, it is fundamental to deploy distributed sensor networks for Structural Health Monitoring (SHM). Indeed, regularly gathering data from a structure/infrastructure gives insight on the structural health status, and Artificial Intelligence (AI) technologies can help in exploiting this information to generate early warnings useful for decision-making purposes. With a perspective of developing a remote monitoring platform for the built environment in a seismic context, the authors tested self-sensing concrete beams in loading tests, focusing on the measured electrical impedance. The formed cracks were objectively assessed through a vision-based system. Also, a comparative analysis of AI-based and statistical prediction methods, including Prophet, ARIMA, and SARIMAX, was conducted for predicting electrical impedance. Results show that the real part of electrical impedance is highly correlated with the applied load (Pearson's correlation coefficient > 0.9); hence, the piezoresistive ability of the manufactured specimens has been confirmed. Concerning prediction methods, the superiority of the Prophet model over statistical techniques was demonstrated (Mean Absolute Percentage Error, MAPE < 1.00%). Thus, the exploitation of electrical impedance sensors, vision-based systems, and AI technologies can be significant to enhance SHM and maintenance needs prediction in the built environment.

Damage Identification in Cement-Based Structures: A Method Based on Modal Curvatures and Continuous Wavelet Transform.

Modal analysis is an effective tool in the context of Structural Health Monitoring (SHM) since the dynamic characteristics of cement-based structures reflect the structural health status of the material itself. The authors consider increasing level load tests on concrete beams and propose a methodology for damage identification relying on the computation of modal curvatures combined with continuous wavelet transform (CWT) to highlight damage-related changes. Unlike most literature studies, in the present work, no numerical models of the undamaged structure were exploited. Moreover, the authors defined synthetic damage indices depicting the status of a structure. The results show that the I mode shape is the most sensitive to damages; indeed, considering this mode, damages cause a decrease of natural vibration frequency (up to approximately -67%), an increase of loss factor (up to approximately fivefold), and changes in the mode shapes morphology (a cuspid appears). The proposed damage indices are promising, even if the level of damage is not clearly distinguishable, probably because tests were performed after the load removal. Further investigations are needed to scale the methodology to in-field applications.

New Materials and Technologies for Durability and Conservation of Building Heritage.

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.

Operando monitoring of a room temperature nanocomposite methanol sensor.

The sensing of volatile organic compounds by composites containing metal oxide semiconductors is typically explained via adsorption-desorption and surface electrochemical reactions changing the sensor's resistance. The analysis of molecular processes on chemiresistive gas sensors is often based on indirect evidence, whereas in situ or operando studies monitoring the gas/surface interactions enable a direct insight. Here we report a cross-disciplinary approach employing spectroscopy of working sensors to investigate room temperature methanol detection, contrasting well-characterized nanocomposite (TiO2@rGO-NC) and reduced-graphene oxide (rGO) sensors. Methanol interactions with the sensors were examined by (quasi) operando-DRIFTS and in situ-ATR-FTIR spectroscopy, the first paralleled by simultaneous measurements of resistance. The sensing mechanism was also studied by mass spectroscopy (MS), revealing the surface electrochemical reactions. The operando and in situ spectroscopy techniques demonstrated that the sensing mechanism on the nanocomposite relies on the combined effect of methanol reversible physisorption and irreversible chemisorption, sensor modification over time, and electron/O2 depletion-restoration due to a surface electrochemical reaction forming CO2 and H2O.

Soil fertility in slash and burn agricultural systems in central Mozambique.

Slash and burn is a land use practice widespread all over the world, and nowadays it is formally recognized as the principal livelihood system in rural areas of South America, Asia, and Africa. The practice consists of a land rotation where users cut native or secondary forest to establish a new crop field and, in some cases, build charcoal kilns with the cut wood to produce charcoal. Due to several socio-economic changes in developing countries, some scientists and international organizations have questioned the sustainability of slash and burn since in some cases, crop yield does not justify the soil degradation caused. To estimate the soil quality in agricultural and forest soils at different ages of the forest-fallow period (25, 35, and 50 years), this survey investigated rural areas in three locations in Manica province, central Mozambique: Vanduzi, Sussundenga, and Macate. Soil profiles were trenched and sampled with a pedological approach under crop fields and forest-fallow. The chronosequence was selected to test the hypothesis that the increase in forest-fallow age causes an improvement of soil fertility. Results highlighted discrete variations among locations in mineralogy, Al- and Fe-oxyhydroxides, sand, silt, pH, total organic carbon, humic carbon, total nitrogen, available phosphorous, chloride, nitrate, fluoride, and ammonium. Few differences in mineralogy, Fe-oxyhydroxides, available P, chloride, and nitrate were detected between crop fields and forest-fallow within the same location. Such differences were mostly ascribed to intrinsic fertility inherited from the parent material rather than a longer forest-fallow period. However, physicochemical soil property improvement did not occur under a forest age of 50 years (the longest forest-fallow considered), indicating that harmonization of intrinsic fertility and agronomic practices may increase soil organic matter and nutrient contents more than a long forest-fallow period.

Transformation of industrial and organic waste into titanium doped activated carbon - cellulose nanocomposite for rapid removal of organic pollutants.

Production of cost-efficient composite materials with desired physicochemical properties from low-cost waste material is much needed to meet the growing needs of the industrial sector. As a step forward, the current study reports for the first time an effective utilization of industrial metal (inorganic) waste as well as fall leaves (organic waste), to produce three types of nanomaterials at the same time; "Titanium Doped Activated Carbon Nanostructures (Ti-ACNs)", "Nanocellulose (NCel)", and combination of both "Titanium Doped Activated Carbon Cellulose Nanocomposite (Ti-AC-Cel-NC)". X-ray diffraction (XRD), transmission electron microscopy (TEM) and microanalysis (EDXS) measurements reveal that the Ti-ACNs material is formed by Ti-nanostructures, generally poorly crystalized but in some cases forming hexagonal Ti-crystallites of 15 nm, embedded in mutated graphene clouds. Micro- Fourier transform infrared spectroscopy (micro-FTIR) confirms that the chemical structure of NCel with bond vibrations between 1035 to 2917 cm-1 remained preserved during Ti-AC-Cel-NC formation. The prepared materials (Ti-ACNs, Ti-AC-Cel-NC) have demonstrated rapid removal of organic pollutants (Crystal Violet, Methyl Violet) from wastewater through surface adsorption and photocatalysis. In the first 20 min, Ti-ACNs have adsorbed ≈87% of the organic pollutants and further photocatalyzed them up to ≈96%. When Ti-ACNs are combined with NCel, their efficiency is increased of about four times. This performance originates from the adsorption by mutated graphene-like carbon and assisted photocatalysis by Ti nanostructures as well as the good supporting capacity of NCel for the homogenous Ti-ACNs distribution.

Pilot scale cellulose recovery from sewage sludge and reuse in building and construction material.

The recovery of cellulose in toilet paper from municipal wastewater is one of the most innovative actions in the circular economy context. In fact, fibres could address possible new uses in the building sector as reinforcing components in binder-based materials. In this paper, rotating belt filters were tested to enhance the recovery of sludge rich in cellulose fibres for possible valorisation in construction applications. Recovered cellulosic material reached value up to 26.6 gm-3 with maximum solids removal of 74%. Content of cellulose, hemicellulose and lignin was found averagely equal to 87% of the total composition. Predictive equation of cellulosic material was further obtained. The addition of recovered cellulose fibres in mortars bring benefits in terms of lightness, microstructure and moisture buffering value (0.17 g/m2%UR). Concerning mechanical properties, flexural strength was improved with the addition of 20% of recovered cellulose fibres. In addition, a simplified economic assessment was reported for two possible pre-mixed blends with 5% and 20% of recovered fibres content.

Influence of Binders and Lightweight Aggregates on the Properties of Cementitious Mortars: From Traditional Requirements to Indoor Air Quality Improvement.

Innovative and multifunctional mortars for renders and panels were manufactured using white photocatalytic and non-photocatalytic cement as binder. Unconventional aggregates, based on lightweight materials with high specific surface and adsorbent properties, were adopted in order to investigate the possible ability to passively improve indoor air quality. The reference mortar was manufactured with traditional calcareous sand. Results show that even if the mechanical properties of mortars with unconventional aggregates generally decrease, they remain acceptable for application as render. The innovative mortars were able to passively improve indoor air quality in terms of transpirability (70% higher), moisture buffering ability (65% higher) and depolluting capacity (up to 75% higher) compared to traditional ones under the current test conditions.

Durability assessment to environmental impact of nano-structured consolidants on Carrara marble by field exposure tests.

The EU policy of reducing the emissions of combustion generated pollutants entails climate induced deterioration to become more important. Moreover, products applied to preserve outdoor built heritage and their preliminary performance tests often turn out to be improper. In such context, the paper reports the outcomes of the methodology adopted to assess the durability and efficiency of nano-based consolidating products utilized for the conservation of carbonate artworks, performing field exposure tests on Carrara marble model samples in different sites in the framework of the EC Project NANOMATCH. Surface properties and cohesion, extent and penetration of the conservative products and their interactions with marble substrates and environmental conditions are here examined after outdoor exposure for eleven months in four different European cities and compared with the features of undamaged and of untreated damaged specimens undergoing the same exposure settings.

Assessment of air pollutant sources in the deposit on monuments by multivariate analysis.

A proper recognition of the pollutant sources in atmospheric deposit is a key problem for any action aiming at reducing their emission, being this an important issue with implications both on human health safeguard and on the cultural heritage conservation in urban sites. This work presents the results of a statistical approach application for the identification of pollutant sources in deposits and damage layers on monuments located in different European sites: Santa Maria del Fiore, Florence (Italy), Cologne Cathedral, Cologne (Germany), Ancient ramparts, Salè (Morocco), National Museum, Cracow (Poland) and National Gallery, Oslo (Norway). For this aim, the surface damage layers on monuments and historical buildings of the selected sites were collected and analyzed, in terms of ionic and elemental composition, through application of ion chromatography and induced coupled plasma-optical emission spectroscopy. The achieved results were processed by multivariate analyses such as correlation matrix and principal component analysis in order to identify the possible origin of pollutants affecting the state of conservation of the monuments. This allowed us to assume that in all case studies the traffic emission is the main pollutant source. In the case of Ancient ramparts, Salè (Morocco), and National Gallery, Oslo (Norway), the surfaces are also under influence of marine aerosols. Moreover, concerning the Cologne Cathedral, the strong impact of the pollutants emitted by railway station was also revealed.