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Alkali activated materials and geopolymers have attracted a lot of attention in the last 20 years thanks to their excellent mechanical performances, durability and sustainability properties, especially for civil applications. These materials also exhibit promising properties as fire- and corrosion-resistant protection systems. In a previous study, a 20-mm coating based on light-weight alkali activated mortar (LWAAM) suitable for the protection of steel structures against fire was successfully developed. To understand if the same coating is also able to ensure corrosion protection to steel structures, this study reports the results obtained in two different chloride-rich environments. The corrosion performance of the new system based on steel coated by LWAAM (using expanded perlite and hydrogen peroxide in the mix) was compared with a steel coated by a traditional alkali activated mortar (NWAAM). Electrochemical tests on steel samples immersed in an alkaline solution simulating the pore environment of the binder or embedded in the two different types of mortars were carried out in presence of different chloride concentrations. It was found that the alkaline environment is able to passivate the steel surface, however, the increasing of chloride ions concentration, affects passive film stability and promotes steel corrosion. In presence of low chloride concentration (i.e., 0.2M NaCl), the increased porosity of the LWAAM did not impair the steel corrosion protection, when compared with NWAAM.

Lo sviluppo sostenibile è diventato il motore di tutte le politiche odierne che guidano gli aspetti ambientali, economici e sociali. Il settore delle piastrelle di ceramica ha promosso, fin dagli anni ’70, un percorso strategico atto ad applicare concretamente i principi dello sviluppo sostenibile. Il presente articolo riassume le diverse strategie intraprese fino all’introduzione, nel 2021, della norma sulla sostenibilità (ISO 17889-1) per le piastrelle di ceramica.

The topic of sustainability of reinforced concrete structures is strictly related with their durability in aggressive environments. In particular, at equal environmental impact, the higher the durability of construction materials, the higher the sustainability. The present review deals with the possible strategies aimed at producing sustainable and durable reinforced concrete structures in different environments. It focuses on the design methodologies as well as the use of unconventional corrosion-resistant reinforcements, alternative binders to Portland cement, and innovative or traditional solutions for reinforced concrete protection and prevention against rebars corrosion such as corrosion inhibitors, coatings, self-healing techniques, and waterproofing aggregates. Analysis of the scientific literature highlights that there is no preferential way for the production of “green” concrete but that the sustainability of the building materials can only be achieved by implementing simultaneous multiple strategies aimed at reducing environmental impact and improving both durability and performances.

The application of protective coatings for the conservation of outdoor metallic artworks is currently considered the best approach actively employed. This paper focuses on the evaluation of the protectiveness of an optimised fluorosilane (FA-MS) coating with low occupational hazard impact and high inhibition efficiency. FA-MS coating was applied on a typical historical as-cast bronze (Cu-Sn-Zn-Pb), artificially patinated by synthetic acid rain dropping, to simulate natural unsheltered patinas. Subsequently, the patinated bronze was coated by brushing and then artificially aged by synthetic rain dropping. In order to investigate the coating-patina system, a multi-analytical approach was applied including scanning electron microscopy coupled with elemental analysis (FEG-SEM with EDS), microstructural analysis of cross-sections produced by Focused Ion Beam milling (FIB) and X-ray Photoelectron Spectroscopy (XPS). The coating homogenously covered the whole patinated surface producing a transparent layer few μms thick. The weathering solutions were also analysed for the assessment of metallic cations release. FA-MS showed excellent protective performances for the patinated bronze exposed to simulated outdoor conditions. Very high values of inhibiting efficiency in terms of metal release in the weathering solutions (up to 99%) were measured. In order to investigate all the necessary requirements for application in conservation field, the durability of FA-MS was also tested on a real bronze artistic casting, in terms of limiting the alloy composition changes (measured by in situ XRF) over time. A good durability of the coating was observed during the ongoing field exposure test. Lastly, reversibility of FA-MS was investigated by applying different mechanical cleaning methods, such as brushing and blasting. The reversibility was assessed by the evaluation of the morphology (colour change, surface roughness and optical microscopy) and the composition (SEM-EDS and Py-GC-MS chromatography) of the cleaned surfaces. Cleaning by brushing proved to be an efficient method for removing this coating without significantly altering the bronze patina.

This work aims to prepare low-cost nanocomposite and microcomposite with lower molar ratio CaO/SiO2 (0.4). Nano-silica, rice husk ash and calcined chicken eggshell have been used as silica and calcium sources. Metakaolin has been separately replaced by 0, 10 and 20 wt% of each composite in order to study their behavior on the properties of geopolymers. The hardener used is sodium waterglass from rice husk ash. The surface area of nano-silica and rice husk ash was 54.40 and 4.08 m2/g, respectively. The cumulative volumes of the control geopolymer, the ones containing 10 wt% of microcomposite and nanocomposite are 119.71, 89.92 and 110.49 mm3/g, respectively. The compressive strength of the control specimen is around 64.02 MPa. The one using 10 wt% of microcomposite was 68.97 MPa. It drops to 42.88 MPa when metakaolin was replaced by 20 wt % of microcomposite. Whereas the one using 10 wt% of nanocomposite was 30.03 MPa and it decreases to 26.05 MPa when metakaolin was substituted by 20 wt% of nanocomposite. It can be concluded that 10 wt% of microcomposite could be mixed to metakaolin for strength development and nanocomposite does not recommend to use as an additive for producing high strength of geopolymer cements. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

While cast geopolymers are deeply investigated, geopolymers shaped by pressing are still rather unexplored. This work aims at developing one-part pressed geopolymers investigating the influence of parameters such as Na/Al molar ratio, water content and pressure load on the physical, microstructural and durability properties of the hardened geopolymers. Geopolymers were prepared by dry mixing and cured at 70 °C for 24 h and at room temperature for further 6 days. Density, water absorption, porosity features, microstructure and durability have been determined for all the samples. The results show that Na/Al molar ratio, water content and pressure load are key parameters to control the properties of one-part geopolymers. Their optimization can allow to obtain geopolymers suitable for microfiltration flat membrane support. Finally, the best performances in terms of durability are obtained when using the highest pressure load (20 MPa) and water content (15%).

One-part or “just add water” alkali activated materials (AAMs) have attracted a lot of attention thanks to the use of solid alkaline activators that makes these materials more suitable to commercialization compared to conventional AAMs (two-part). This is mainly because large quantities of caustic solutions should be handled for producing conventional AAMs. So, one-part AAMs have a great potential for in-situ applications. However, heat curing (

Le piastrelle in gres porcellanato, prodotto industriale di altissima qualità, si qualificano come scelta ottimale anche per le pavimentazioni in esterno date le elevate prestazioni tecnico-funzionali. Nel contributo se ne analizzano le principali caratteristiche con riferimento anche ai sistemi di caratterizzazione delle piastrellature.

Alkali activated materials and geopolymers have attracted a lot of research interests in the last 20 years thanks to their excellent performances in terms of mechanical, thermal and durability properties. In addition, these materials show promising properties in terms of sustainability when compared to traditional binders commonly used in the building sector (i.e., ordinary Portland cement) and to traditional and advanced ceramics (i.e., membranes, adsorbents, and catalysts). Sustainability in geopolymers can be reached by using a broad variety of industrial by-products as raw materials and by ambient or low temperatures (< 100 °C) consolidation. The aim of the present study was the optimization of microstructural properties of one-part geopolymers, based on flash-sintered metakaolin and anhydrous sodium silicate, for microfiltration membrane support in wastewater treatments. Investigated geopolymers were shaped by uniaxial pressing and cured at 70 °C for 24 h. Several parameters in terms of mix design optimization (i.e., alkali concentration and water content) and pressing pressure were investigated to obtain a microstructure suitable for the preparation of the support of flat asymmetric membranes. Assessment of the total open porosity and the pore size distribution was carried out by mercury intrusion porosimetry, while microstructural observations were performed by field emission gun-scanning electron microscopy (FEG-SEM) coupled with energy dispersive spectroscopy (EDS). It was found that pressing is a particularly suitable shaping method for one-part geopolymers thanks to the use of low water amount for the activation of the mix. In addition, increasing the water content (up to 15 wt%) and pressing pressure (up to 20 MPa) allowed the formation of a dense geopolymeric gel, while alkalis concentration, ranging between Na/Al = 0.7 and 1.1, did not strongly influence the microstructure. Finally, the optimized parameters for producing flat support for microfiltration membranes are a Na/Al molar ratio equal to 1.0, 12 wt% water content and 2 MPa of pressing pressure. These conditions allowed to obtain the same range of open porosity and pore size distribution characteristic of ceramic membrane support used for the same purpose.

The replacement of natural aggregates with recycled ones for concrete production is of vital importance in view of increasing the sustainability of construction materials in accordance with the Circular Economy. The use of crushed Recycled Asphalt Pavement (RAP) as aggregates for concrete will allow the production of more sustainable materials in the construction field. However, chemical, physical and mechanical characteristics of RAP aggregates shall be investigated to optimise their use for concrete production. This issue is one of the tasks of the research project “Sustainable concrete made with recycled asphalt pavement (RAP-CON)” granted by Fondazione Cariplo, currently ongoing. This study reports the first results on the characterization of five types of RAP collected from different Italian Highways. Several properties of RAP as aggregates for concrete were investigated in terms of microstructure, dimensional stability and durability. In particular, morphological observation was carried out by optical and scanning electron microscopy, while open porosity and pore size distribution was evaluated by mercury intrusion porosimetry. Dimensional stability was assessed by preparing cementitious mortar and concrete samples, following the accelerating curing described in EN 1367-4. Lastly, durability was investigated in terms of resistance to freeze and thaw cycles performed in accordance with EN 1367 (parts 1 and 6) in presence of distilled water and salts (1 wt% NaCl solution), respectively. It was found that RAP is a suitable material for aggregates in concrete. Depending on the adhesion between the bituminous binder and the natural aggregates, different durability performances can be achieved. Finally, different results have been obtained as function of types of RAPs, indicating that their characterization before concrete preparation is an important step to ensure the performance of the final product.

This chapter deals with innovative applications of photocatalytic TiO2 in different building materials, with particular reference to cement-based materials (concrete, mortars, and pavements) and tiles, which are omnipresent materials in constructions. The possibility of manufacturing materials with antipollution, self-cleaning, and antimicrobial surface is extremely attractive in buildings, while the use of embedded titania nanoparticles is expected to improve the mechanical strength of concrete, which is desirable for structural applications. Two further applications of TiO2 are considered in the present chapter. The first one is in geopolymers, a new class of binders that received great attention in recent years, due to their much lower environmental impact and higher resistance to aggressive agents and high temperatures, compared to ordinary Portland cement. The second application is in the field of cultural heritage, where TiO2-based treatments may contribute to fight the chemical and biological deterioration processes threatening ancient building materials, thus helping one to preserve our national identities and economic prosperity.

Microfiltration membranes are widely used in wastewater treatment and are typically made of ceramic or polymer materials. Despite the great durability of ceramic membranes, polymeric membranes are very often preferred due to production costs. By using geopolymers, however, it is possible to obtain microfiltration membranes with durability characteristics similar to those of ceramic materials, but with considerably reduced production costs since geopolymers do not require a sintering treatment. In this study, a geopolymer support for asymmetric microfiltration membranes is characterized in terms of porosity and hydraulic permeability. The support was obtained by uniaxially pressing a dry mixed powder consisting of metakaolin and anhydrous sodium silicate, sprayed with 12 wt% of water. Curing was carried out at 70 °C for 24 hours and 6 more days at room temperature. The porosity of samples pressed using 2 MPa (total open porosity of 39 % and a modal pore size of 23 μm) are comparable to those of ceramic membranes for microfiltration [1]. The support permeability was measured in a dead-end apparatus at a trans-membrane pressure varying from 0.2 to 0.5 bar, with pure water and ethanol-water solutions. Hydraulic permeability of 30500 ± 3090 L/(h·m2·bar) was obtained with 4 samples, whereas the use of 100 and 200 g/L ethanol-water solutions showed a reduction in permeability to 26140 ± 2640 and 20820 ± 1430 L/(h·m2·bar) respectively. Further tests performed on less porous samples obtained by pressing the powder at 5 MPa (total open porosity and modal pore size of 27% and 15 μm, respectively) led to similar results. These initial characterizations highlight the potential of this new material in the treatment of wastewater by membrane separation. Future studies are ongoing to develop geopolymer selectives layer by dip coating to be applied on geopolymer supports.

In the last twenty years a new class of materials known as geopolymers has rapidly grown in interest in order to reduce the CO2 emissions for cement and ceramic materials productions. Geopolymers are based on alkali activation of precursors able to consolidate at room or slightly higher temperatures. One of the main advantages of geopolymers is the possibility to use waste-based powders, such as coal fly ashes, thus promoting a circular economy approach. Nevertheless, the scope to classify geopolymers as a new binder for the construction sector can be obtained only by a good knowledge of both differences and similarities between this new class of materials and ordinary portland cement. As known, shrinkage is a critical aspect to take into account for a proper characterization of a new material in the construction industry. Indeed, shrinkage has a crucial importance for both durability aspects and structural long-term maintenance, due to possible cracks formation. At the present state, only a few researches on engineering properties and shrinkage of geopolymers have been made. In this work, three different coal fly ash-based geopolymer mortars were studied with an attempt to investigate their drying shrinkage behavior (as opposed to chemical or autogenous). For comparison sake, an ordinary portland cement mortar was used as reference. Consistency at the fresh state and physical properties (i.e., bulk density, water absorption and total open porosity) of the mortars were determined. Then, two different behaviors were studied on specimens: 1) the first shrinkage during the first months of curing; 2) the dimensional variations related to humidity change after a long period of time. All tests have been made at a constant temperature and varying the relative humidity: weight change and shrinkage of all specimens were measured regularly. Preliminary obtained results could be useful for the future set up of a predictive model for the shrinkage of geopolymer that at the present state does not exist.

This work investigates the state of the art on innovative and sustainable self-compacting concrete (SCC) prepared with coarse and fine recycled concrete aggregates (RCAs) (up to 100% of total amount of aggregates). Fresh-state behavior is presented and related to the hardened state and durability characteristics of the conglomerate. Studies on this new research topic in the field of construction industry highlight that self-compacting properties can be maintained when RCAs are used and their good qualities enhance effective mechanical properties thus promoting its successfully use not only for nonstructural elements, but also structural and highly reinforced structures which hinder the vibration procedures.

In the present work the microstructural characterization of the powder-metallurgy X190CrVMo20-4-1 has been performed and correlated with its corrosion properties. The martensitic stainless steel was hardened at different austenitizing and tempering temperatures. Microstructural analyses were carried out using Scanning Electron Microscopy (SEM–EDS) to define the carbide distribution in the steel matrix. Carbides morphology and retained austenite content were evaluated and correlated to the corrosion behaviour of the different heat-treated steels, investigated by means of electrochemical tests. The results show the presence of M23C6 and M7C3 Cr-V based carbides homogenously dispersed in the matrix in annealed and quenching-and-tempering conditions. The carbides dissolution was evaluated by image analysis in every different heat treatment condition. When low tempering temperature was applied, an increasing in retained austenite content was defined by high austenitizing temperature and elevated carbides solubilization. At high tempering temperature, retained austenite content was not up to 5% nor affected by austenitizing temperature. Contrary to the expectations, HRC hardness was not influenced by the heat treatment conditions and retained austenite content. Corrosion resistance of the different heat-treated samples was found to be mainly influenced by retained austenite volume fraction and the tempering temperature. In particular, high austenitizing temperature and low tempering temperatures allowed the best corrosion resistance among the different heat treatment parameters investigated. The results obtained in the experimentation can provide support to the heat treatment optimization of the steel, widely used in tool and mould applications. Graphical Abstract: [Figure not available: see fulltext.].

Purpose: Alkali-activated materials, also known as geopolymers, are considered promising assets in the sustainable materials industry. Given the excellent properties in terms of thermal stability and low thermal conductivity, geopolymer-based matrices can effectively substitute cementitious binders in the preparation of passive fire protection (PFP) systems. The present study aims at evaluating the environmental footprint of a newly proposed geopolymer-based fireproofing material. The results are compared to a reference commercial lightweight cement-based coating with equal PFP performance. Methods: The boundaries of the system assessed were based on a cradle-to-grave life cycle. A preliminary scale-up of the laboratory protocol allowed the evaluation of the industrial production of the geopolymer-based PFP mix. An ancillary life cycle analysis was performed, comparing the environmental footprint of a geopolymer-based concrete block to the relevant literature studies for the same system in order to validate the approach of the present study. The functional unit of the main study was defined, taking into account the material performance in terms of resistance to heat exposure, allowing a functional comparison with lightweight cement-based PFP. The impact assessment phase used the CML-IA methodology as a characterization method. Results and discussion: The ancillary LCA confirmed the alignment of the assumptions of the current study with previous analyses. The analyzed geopolymer-based fireproofing material exhibited a life cycle impact which is 27% lower than the lightweight concrete reference in terms of the global warming indicator, mainly thanks to the avoided CO2 emissions from the clinker process in cement manufacturing. Therefore, the greenhouse gas reduction described in previous studies on geopolymer application as a strong environmental advantage of the geopolymer technologies is also confirmed in this case. However, the other considered impact categories, such as resource depletion, acidification, eutrophication, and human toxicity, resulted in indicator values higher than the reference, as a consequence of the energy-intensive production process for the alkali activators (in particular, sodium silicate). Conclusions: Though the reduction of greenhouse gas emissions is confirmed, the overall sustainability of geopolymers for PFP applications is hindered by the relevant environmental footprint of the sodium silicate production process. However, a substantial reduction of the impacts could be achieved by selecting the production process of sodium silicate which takes advantage of renewable energy supplies (e.g., hydrothermal route) or by reducing the amount of sodium silicate in the geopolymer recipe in favor of waste-based alkali activators.

International audience; A 3-mercapto-propyl-trimethoxysilane coating (PropS-SH) applied on Cu-Si-Mn bronze, patinated by “liver of sulphur”, was investigated as a non-toxic alternative to Incralac®, usually applied on outdoor artistic bronzes. Electrochemical testing was performed in synthetic acid rain. Exposure to temperature/UV cycles and accelerated corrosion test simulating unsheltered exposure to rainwater was also carried out. The exposed samples were characterised by FEG-SEM coupled with EDS on FIB cross-sections and XPS on free surfaces. The black patina without protective coating was scarcely protective against bronze corrosion and easily transformed into cuprous oxide. PropS-SH coating fully preserved the black patina microstructure and phase constituents (cuprous oxide and cuprous sulphide). The PropS-SH coating also resulted more protective than Incralac® when aged under run-off conditions. Selective dissolution of copper from the silicon bronze alloy was observed on both uncoated and Incralac®-coated bronze, leading to the formation of an internal Si-rich corrosion layer.

Alkali activated lightweight mortars, obtained by room temperature activation of coal fly ash, were studied as passive fire protection systems for steel elements. Physical, mechanical and thermal properties were investigated as a function of the compositional Si/Al molar ratio and of the amount of lightweight aggregate and foaming agent. Experimental findings were used as input data to assess their fire resistance by finite volume simulations. Results pointed out that the optimized alkali activated lightweight mortars are able to outperform alternative commercial cement-based mortars, thus representing a promising technology.

This chapter deals with innovative applications of photocatalytic TiO2 in different building materials, with particular reference to cement-based materials (concrete, mortars, and pavements) and tiles, which are omnipresent materials in constructions. The possibility of manufacturing materials with antipollution, self-cleaning, and antimicrobial surface is extremely attractive in buildings, while the use of embedded titania nanoparticles is expected to improve the mechanical strength of concrete, which is desirable for structural applications. Two further applications of TiO2 are considered in the present chapter. The first one is in geopolymers, a new class of binders that received great attention in recent years, due to their much lower environmental impact and higher resistance to aggressive agents and high temperatures, compared to ordinary Portland cement. The second application is in the field of cultural heritage, where TiO2-based treatments may contribute to fight the chemical and biological deterioration processes threatening ancient building materials, thus helping one to preserve our national identities and economic prosperity.

This research reports on the influence of particle size and distribution on the physical, mechanical and microstructural features of solid solutions (feldspathic materials) based inorganic polymer composites (IPCs). Both granite and pegmatite were ground to different degree of finess making four different granulometry with particles of 63, 80, 125 and 200 μm. The respective mixes receive 15 wt% of metakaolin and were activated with a well designed alkaline solution. Matrices obtained showed high compressive and flexural strengths in the range 101.2–131.3 MPa, and 29–35.5 MPa, respectively. It was observed that the optimum mechanical performance of these matrices can be achieved through a mix-design of different grades of granulometry. This was suggested by mechanism combining reactivity and particles packing. In fact, although it can be expected that the finess of the combination of the particles size under 63 μm might present the better reactivity, it is showing that the combination of fine, medium and coarse particles is efficient in achieving denser and tougher microstructure. Lower cumulative pore volume (17 mL g−1) of the composites based on pegmatite, value not far from that of natural stones, resulted in a higher impact resistance of 3.03 J. It was concluded that designing the feldspathic rock-based composites with high strengths appear as sustainable, low energy consumption and environmentally-friendly materials for the structural construction.

Five different alkali activators were prepared by mixing sodium hydroxide with molar concentrations of 8, 10, 12, 14 and 16M and sodium silicate, Na2SiO3 in volume ratio 1:1. The obtained alkaline activators were used for producing metakaolin/feldspathic rock-based geopolymer composites. These geopolymer composites were obtained by mixing different solid precursors of natural solid solutions (trachyte, pegmatite and granite) in the range of 70 to 85wt% with metakaolin and adding each alkaline solution at a liquid/solid mass ratio of 0.37. The pastes were cured at room temperature for 28days before testing. The influence of NaOH concentration on structural modifications was investigated using Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). Water absorption for open porosity, Environment Scanning Electron Microscope (ESEM) and compression tests were adopted to observe the morphology and mechanical properties. The results indicate that the NaOH concentration of 12M was optimum for solid solution of trachyte with 98–106MPa due to content of higher amorphous phases compared to solid solutions of pegmatite (94–105MPa) or granite (101–108MPa) where the better results were achieved at 10M.

Ceramic tile production is an industrial process where energy efficiency management is crucial, given the high amount of energy (electrical and thermal) required by the production cycle. This study presents the preliminary results of a research project aimed at defining the benefits of using combined heat and power (CHP) systems in the ceramic sector. Data collected from ten CHP installations allowed us to outline the average characteristics of prime movers, and to quantify the contribution of CHP thermal energy supporting the dryer process. The electric size of the installed CHP units resulted in being between 3.4 MW and 4.9 MW, with an average value of 4 MW. Data revealed that when the goal is to maximize the generation of electricity for self-consumption, internal combustion engines are the preferred choice due to higher conversion efficiency. In contrast, gas turbines allowed us to minimize the consumption of natural gas input to the spray dryer. Indeed, the fraction of the dryer thermal demand (between 600–950 kcal/kgH2O), covered by CHP discharged heat, is strictly dependent on the type of prime mover installed: lower values, in the range of 30–45%, are characteristic of combustion engines, whereas the use of gas turbines can contribute up to 77% of the process’s total consumption.

According to UNESCO Institute for Statistics (UIS) data (UIS fact sheet, 2019), less than 30% of researchers worldwide are women. Long-standing biases and gender stereotypes are discouraging girls and women away from science related fields. In particular, STEM (science, technology, engineering and mathematics) research is traditionally male dominated and women remain underrepresented. As UNESCO has highlighted, both science and gender equality are, however, essential to ensuring sustainable development. In order to change traditional mindsets, gender equality must be promoted, stereotypes defeated, and girls and women should be encouraged to pursue careers in STEM. Throughout history, the contributions of female researchers to scientific progress have been extremely important. Yet, whereas the extraordinarily talented Nobel laureate Marie Sklodowska-Curie is often mentioned as a role model, it is nowadays well established that countless women such as Lise Meitner have received less recognition and acknowledgement for their research findings than their male counterparts (so-called Matilda effect (Rossiter, 1993)). Also, women traditionally publish less than men according to the European Commission She Figures, the ratio of women to men among authors of scientific publications in the EU being on the average one to two (EU, 2018), and recent surveys are highlighting a further drop in academic submissions from female scientists since the start of the Covid-19 pandemic early 2020. Role models are definitely extremely important to show to younger generations the growing impact of female researchers to science. Therefore, continuing the spirit of the International Day of Women and Girls in Science, Frontiers in Materials is proud to offer this platform to promote the work of female scientists, across the breadth of materials science and engineering. This inaugural ‘Women in Science: Materials’ collection (Fig.1) aims to highlight the impact of women researchers working in materials science and engineering. It gathers a selection of original articles with the lead author and/or corresponding author being a woman. 32 contributions (3 reviews, 1 brief research report and 28 original research articles) present advances in theory, experiment and methodology with applications to compelling problems, across almost all sections of the journal:  Mechanics of materials (Bouquerel et al., Jeong et al., TerMaath et al., Zhu et al.);  Smart materials (Duc et al.);  Polymeric and composite materials (Badji et al., Berzin et al., Brunella et al., Hostettler et al., Martins and Gil, Mirbaha et al., Padhan et al., Quintana et al., Raj et al., Saffar et al.);  Carbon-based materials (Kato et al., Moulefera et al., Xu et al., Zhang et al.);  Structural materials (Bonoli et al., Boyer et al., Korat and Ducman, Manzi et al., Masi et al.);  Colloidal materials and interfaces (Garcia-Hernando et al., Pucci et al.);  Energy materials (Castro-Gutierrez et al.);  Ceramics and glass (Giosue et al.);  Environmental materials (Bassi et al.);  Biomaterials (Criado-Gonzalez et al., Kebaili et al.); The Guest Editorial team hope that this collection of papers will be the foundation of an international network of women researchers working in materials science and engineering, and a starting point for future collaborations and discussions.

Sustainable development has recently become the driving force of all the policies leading environmental, economic, and social aspects of our life. In the construction sector, a large number of technological innovations has been introduced thus leading to an assessment of the environmental impact of the production processes. In the present study, the environmental impact of the Italian ceramic tiles production is analyzed and discussed. The evolution trends of the main atmospheric pollutants and the management of water and solid wastes of ceramic tile plants have been investigated over a period greater than 10 years, considering three different layouts of production cycles. The current evaluation shows that the Italian ceramic tiles industry has considered the environmental assessment as a fundamental practice for its development since the late 1980s. The reported data prove the high level of excellence reached by the Italian ceramic tile production and demonstrate how attention to the environmental impact is a fundamental key for the ceramic tile sector.

In this paper, three different coal fly ash-based alkali activated mortars are studied. The three different mortars are obtained using the same binding system but different types (i.e. silica sand or expanded perlite) and sizes of aggregates. Small-scale beams are constructed together with additional specimens for material characterization. The small-scale beams are notched and loaded in a three-point bend setup to investigate the fracture properties of the three mixtures. The setup utilized follows the draft of the ACI 446 report on the fracture testing of concrete. The fracture energy is determined from the work of fracture and results highly dependent on the type of aggregate rather than its dimension. Digital image correlation is employed to obtain the displacement and therefore strain components on the side surface of the specimens in order to investigate the crack propagation and determine the size of the fracture process zone, which appears to be similar to the one of a cement-based mortar.

This study aims at investigating the use of coal fly ash-based alkali activated mortars as passive fire protection system for steel structures. These systems are used to slow down the temperature rise of the steel substrate in case of fire. In addition, the protective system should guarantee the ability to prevent and/or mitigate steel corrosion phenomena. The behavior of a light-weight mortar was compared to that of a normal-weight mortar. Density and porosity were measured to better characterize the physical properties of the mortars. The degree of protection in case of fire was assessed by performing medium-scale fire tests. Acoustic emission measurements were conducted to analyze cracking phenomena during the high temperature exposure. The corrosion process was evaluated using an electrochemical approach in order to monitor the durability of the developed material. Preliminary results show that a 20 mm- thick layer of light-weight mortar is able to protect the steel substrate from reaching the critical temperature of 500 °C for 38 minutes in case of cellulosic fire. In addition, alkali activated mortars provide protection for carbon steel in presence of aggressive environment (i.e. presence of chlorides). The corrosion resistance is strictly related to the physical properties of the developed mortars.

Application of protective coatings is the most widely used conservation treatment for outdoor bronzes. Eco-friendly and non-hazardous coatings are currently needed for conservation of outdoor bronze monuments. To fulfil this need, the M-ERA.NET European research project B-IMPACT (Bronze-IMproved non-hazardous PAtina CoaTings) aimed at assessing the protectiveness of innovative coatings for historical and modern bronze monuments exposed outdoors. In this project, two bronze substrates (historical Cu-Sn-Zn-Pb and modern Cu-Si-Mn alloys) were artificially patinated, by acid rain solution using dropping test and by “liver of sulphur” procedure (K2S aqueous solution) to obtain black patina, respectively. Subsequently, the application of several newly developed protective coatings was carried out and their performance was investigated by preliminary electrochemical tests. In the following steps of the work, the assessment of the best-performing coatings was carried out and their performance was compared to Incralac, one of the most widely used protective coatings in conservation practice. A multi-analytical approach was adopted, considering artificial ageing (carried out in representative conditions, including exposure to rain runoff, stagnant rain and UV radiation) and metal release, as well as visual aspect (so as to include aesthetical impact among the coating selection parameters) and morphological and structural evolution of the coated surfaces due to simulated outdoor exposure. Lastly, also the health impact of selected coatings was assessed by occupational hazard tests. The removability and re-applicability of the best-performing coatings were also assessed. The best alternatives to the conventional Incralac exhibited were: (i) fluoroacrylate blended with methacryloxy-propyl-trimethoxy-silane (FA-MS) applied on patinated Cu-Sn-Zn-Pb bronze and (ii) 3-mercapto-propyl-trimethoxysilane (PropS-SH) applied on patinated Cu-Si-Mn bronze.

Research in alkali-activated materials (AAMs) is an innovative and dynamic material science topic. This is due to the relevant performances in terms of physico-mechanical properties comparable to traditional construction materials (e.g., ordinary Portland cement). The sustainability of AAMs is often highlighted since they can be developed by using many natural or industrial by-products–based precursors. This leads to challenges with the optimization of AAM production due to their different performances, availability, and costs. However, they are flexible and locally adapted materials. The research interest in AAMs has rapidly increased in the early 2000s. In recent years, about 1,000 international articles have been published each year. This study aims at assessing the gender balance of this specific research topic to investigate the relevance of women’s participation. Author lists of the published articles were analyzed throughout the Scopus database, applying “alkali-activated material” and “geopolymers” as keywords in the titles, abstracts, and keywords search. The last 10 years (2009–2019) were taken into account. The gender of the most prolific authors was analyzed, and a focus of European authors on this topic was considered, as more than 25% of the research in AAMs have been carried out in Europe. The analysis of 5,900 publications in the last decade shows that there is currently a shift toward men in the gender balance in this specific research, and female authors only covered 22% of the most productive authors worldwide. Considering European authors, a more equal gender distribution is reached, when the first author is considered, with a concentration of women in the range of 36–56%, recorded over 1,396 articles.

The RILEM technical committee TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ conducted a round robin testing programme to determine the validity of various durability testing methods, originally developed for Portland cement based-concretes, for the assessment of the durability of alkali-activated concretes. The outcomes of the round robin tests evaluating sulfate resistance, alkali-silica reaction (ASR) and freeze–thaw resistance are presented in this contribution. Five different alkali-activated concretes, based on ground granulated blast furnace slag, fly ash, or metakaolin were investigated. The extent of sulfate damage to concretes based on slag or fly ash seems to be limited when exposed to an Na2SO4 solution. The mixture based on metakaolin showed an excessive, very early expansion, followed by a dimensionally stable period, which cannot be explained at present. In the slag-based concretes, MgSO4 caused more expansion and visual damage than Na2SO4; however, the expansion limits defined in the respective standards were not exceeded. Both the ASTM C1293 and RILEM AAR-3.1 test methods for the determination of ASR expansion appear to give essentially reliable identification of expansion caused by highly reactive aggregates. Alkali-activated materials in combination with an unreactive or potentially expansive aggregate were in no case seen to cause larger expansions; only the aggregates of known very high reactivity were seen to be problematic. The results of freeze–thaw testing (with/without deicing salts) of alkali-activated concretes suggest an important influence of the curing conditions and experimental conditions on the test outcomes, which need to be understood before the tests can be reliably applied and interpreted.

A ready-to use, highly sustainable solution for large scale exhausts catalytic abatement was developed: the active bricks. An environmentally-friendly composite was synthesized by depositing La0.6Sr0.4Ga0.3Fe0.7O3, by combustion synthesis, on a fly ash-based geopolymer improved to bear the high temperatures (> 900°C) required for synthesis. The geopolymer was obtained using by-products and was synthesized at RT: its production is sustainable and cost efficient. Prepared composites have been tested for methane oxidation and show good, durable activity above 400°C. Thermal stability was also proved. Composites are a good solution for oxidation of fuel residues in industrial processes. Graphic Abstract: [Figure not available: see fulltext.].

Results of three-point bending tests on notched beams cast with three alkali-activated mortars that differ by the type and size of the aggregates are presented. Digital image correlation is used to estimate the size of the fracture process zone. The fracture energy is computed by means of the work-of-fracture method and found to be strongly dependent on the type of aggregate used and does not differ whether the LDVT or DIC load-deflection curves are used. Finally, low values of the fracture energy in alkali-activated mortars might be associated with the presence of unreacted fly ash.

Bone grafts and bone-based materials are widely used in orthopedic surgery. However, the selection of the bone type to be used is more focused on the biological properties of bone sources than physico-chemical ones. Moreover, although biogenic sources are increasingly used for deposition of biomimetic nanostructured coatings, the influence of specific precursors used on coating&rsquo, s morphology and composition has not yet been explored. Therefore, in order to fill this gap, we provided a detailed characterization of the properties of the mineral phase of the most used bone sources for allografts, xenografts and coating deposition protocols, not currently available. To this aim, several bone apatite precursors are compared in terms of composition and morphology. Significant differences are assessed for the magnesium content between female and male human donors, and in terms of Ca/P ratio, magnesium content and carbonate substitution between human bone and different animal bone sources. Prospectively, based on these data, bone from different sources can be used to obtain bone grafts having slightly different properties, depending on the clinical need. Likewise, the suitability of coating-based biomimetic films for specific clinical musculoskeletal application may depend on the type of apatite precursor used, being differently able to tune surface morphology and nanostructuration, as shown in the proof of concepts of thin film manufacturing here presented.

The aim of this work is to evaluate the cleanability performances of lapped porcelain stoneware surfaces with and without protective treatments. The knowledge of the material cleanability is an important selection parameter in buying tiles. However, an objective basis for testing and assessing this property still is lacking. In this study, standardized and laboratory tests to evaluate the cleanability performance of lapped porcelain stoneware products have been carried out and compared. Cleanability tests were performed by applying two different soiling suspensions, optimized for tile surfaces and reproducing chemical and mechanical actions simulating the working conditions and traditional cleaning operations. Surface characteristics (microstructure, topography, roughness) were analyzed before and after cleanability tests. The results showed a good correlation between different behavior in terms of cleanability and the microscopic and topographic characteristics of lapped tile. Respect to international standardized tests specific for ceramic tiles, such as stains resistance test, the laboratory procedures to evaluate the surface cleanability are able to better show cleanability improvements of lapped tiles with protective treatments.

The technological behavior of porcelain stoneware bodies during deposition and pressing of large slabs depends on the rheological properties of spray-dried powders and the way they affect compaction. Although the literature offers some insights into the characteristics of spray-dried powders for ceramic tiles, no data are available on bodies utilized by novel technologies for large slabs (>4 m2). In order to fill this gap, a systematic approach to properties and behavior of spray-dried powders for porcelain stoneware slabs was carried out. For this purpose, twenty industrially-manufactured spray-dried powders were characterized for intrinsic features (particle size and agglomerate size distribution; shape and moisture distribution in function of agglomerate size) and rheological properties (mass flow, static and dynamic angles of repose, poured and tap density, Hausner ratio). The effect of intrinsic characteristics on the flowability of powders was appraised, as the mutual relationships between the rheological parameters, in order to unveil the best parameters to be used in ceramic tile production. Two broad classes of spray-dried powders occur with a finer and a coarser agglomerate size distribution. Results reveal that ceramic powders are free-flowing, with rheological properties fluctuating in a rather narrow range of values, which makes hard to see significant relationships among the various methods (the only strict correlation is between mass flow rate and tap density). Flowability mainly depends on the occurrence of coarser aggregates, particularly those irregular in shape, stemming from coalescence of three or more individual agglomerates. A phenomenological description of how the spray-dried powders behave in the deposition on tape and the early stage of compaction is outlined.

A mild chelating agent treatment was performed on the residuals of the sorting processes of separately collected urban glass, which is currently landfilled. This fraction, that represents about the 10 wt% of the overall collected glass, has a very heterogeneous composition and contains relatively high amounts of lead and barium and consequently cannot be used to produce new glass containers. This contaminated material shows, when used as fine aggregate in Portland Cement based composites, an expansive behaviour due to the alkali silica reactions. The expansion can only be partially reduced by using finely ground soda lime glass, showing pozzolanic activity. However, after the chelating agent treatment, because of heavy atoms surface depletion, the synergic effect of pozzolan addition leads to a suppressed expansion, thus allowing the use of waste in the formulation of cement composites. Graphical Abstract: [Figure not available: see fulltext.].

The standards for the ceramic tiles certification were developed for traditional-sized products, when large size ceramic tiles had not reached current market volumes. Consequently, the applicability of these test methods, tuned up to characterise a product according to a standard, in some cases is arduous. It occurs, for example, when measuring the dimensional characteristics (as stated in the standard ENISO 10545-2) of ceramic tiles having dimensions larger than 60x60 cm. In order to fill the gap between the test methods usually used in the laboratories and the need to certificate these novel products, some techniques, new to the ceramic field, but widely used in other industrial fields, were analysed. To this aim two new instruments were used to perform the measurements, a coordinate measuring machine CMM and a portable three-dimensional measuring arm, comparing the results with those obtained with a data-plucometer, traditionally used to perform the test. The analysis was conducted on tiles having dimensions lower than those usually named as “large size tiles”, with the aim to demonstrate the possibility to use these new techniques also for the ceramic purposes. The work done to set up the software used to elaborate the data acquired allowed the testingto be conducted following exactly the abovementioned ISO standard. The experimental campaign conducted showed a good agreement between the data-plucometer results and the results obtained with the new techniques, confirming the possibility to use these last ones to perform the tests on large size ceramic slabs. Moreover, the work highlighted some insights to open discussion on normalisation tables.

The technological behaviour of porcelain stoneware bodies during deposition and pressing of large slabs depends on the rheological properties of spray-dried powders and the way they affect compaction. Although the literature offers some insights into the characteristics of spray-dried powders for ceramic tiles, no data are available on bodies used by novel technologies for large slabs (>4 m2). In order to fill this gap, a systematic approach to properties and behaviour of spray-dried powders for porcelain stoneware slabs was carried out. For this purpose, 11 industrially-manufactured spraydried powders were characterised for their intrinsic features (particle size and agglomerate size distribution; shape and moisture distribution in function of agglomerate size); rheological properties (mass flow, static and dynamic angles of repose, poured and tapped density); compaction behaviour (curves of bulk density, intergranular and intragranular porosity in function of applied load); and firing behaviour, in order to reveal any effect of dry bulk density on shrinkage and bulk density of fired samples. The effect of these intrinsic characteristics on the flowability and compressibility of powders was appraised, as was the mutual relationships between the rheological parameters. Two broad classes of spray-dried powders occur with a finer and a coarser agglomerate size distribution. Results reveal that ceramic powders are free-flowing, with rheological properties fluctuating in a rather narrow range of values, which makes hard to see strict correlations between the various methods. Flowability mainly depends on the occurrence of coarser aggregates, particularly those irregular in shape, stemming from coalescence of three or more individual agglomerates. The features of green compacts are somehow inherited by the fired bodies, especially in terms of shrinkage and densification kinetics, even though the starting differences are damped during firing. The performance of spray-dried bodies during compaction is crucial to control uniformity, in terms of porosity and bulk density, which has important repercussions on the properties of final slabs, especially considering that residual stresses may be related to differential shrinkages during firing due to density gradients.

In this study, considerations for design and valorization of sustainable restorative materials for applications in the developing countries are investigated. The paper deals with several preliminary requisites leading to mortar design for conservation of built environment of these countries with numerous cultural heritage elements in need of conservation. Different forms of compatibility are discussed that does not exclude conceptual, physical, chemical, and aesthetical considerations. Where practicable, reversibility is a demanding property expected from such a restorative material. Moreover, sustainability of the restorative materials project is highly dependent on the environmental considerations. The suggested policies leads to significant reduction in use of materials with high carbon dioxide production and landfills. Economic considerations will also play an important role in the frame of conservation plan as their development potentially broadens the domain of conservation possibilities. This is an important value for developing countries with loads of historic buildings in need of restoration. The designation of waste-based strategy in design of restoration materials and their answer to requisites of the conservation plan are discussed. The conceptual suitability of low impact and waste-based restorative materials for treating the built environment in developing countries is justified and discussed. However, the sensetiveness of these countries in application of economic materials for restoration should be dealt with. An economic, high performance, and compatible restoration respects the feature of historic elements and is in-line with many historic material design strategies.

Air lime mortars with addition of two types of sesame cooking oil were synthesized and cured in two different conditions: laboratory and natural climatic conditions of the Pasargadae and Persepolis World Heritage Sites. For the mortars cured in the laboratory, addition of oils in the mortar induced hydrophobic effects, but it adversely affected on permeability values and carbonation rates. However, the air lime mortars cured in the site conditions demonstrated increment in their hydrophobicity and superficial durability without retarding their setting time and adverse effects on their calcium carbonate formation values, due to various climatic parameters existing in natural outdoor conditions.

Porcelain stoneware tiles are industrially processed by using high sintering temperatures and fast firing cycles that result in products characterized by an almost impervious surface layer surrounding a rather porous bulk material. Since mechanical properties are affected by porosity, the knowledge of the material stiffness is an important parameter to define the service behavior of tiles. In the present investigation, porcelain stoneware samples having different closed porosity were investigated in order to understand the influence of the porosity on the elastic constants of the materials. Based on the quantitative XRD phase composition, elastic constants have been calculated via Voigt-Reuss-Hill averaging, and the influence of porosity has been taken into account via power-law and exponential relations. It is shown that the effective elastic constants predicted by exponential and power-law relations are in agreement with experimental values. It may be concluded that for this class of materials, in the porosity range below 14–16%, both exponential and power-law relations are helpful tools to design tiles with controlled microstructure and tailored mechanical properties.

The response to thermal variations is the primary cause of marble deterioration in ancient and modern buildings. In this study, the thermal behavior of Carrara marble after consolidation by an innovative hydroxyapatite-based treatment was investigated in comparison with ammonium oxalate and ethyl silicate. Samples were subjected to heating-cooling cycles up to 80 °C. All the consolidating treatments were found to be fairly compatible, as in no case the residual strain after the thermal cycles was found to increase compared to the unweathered untreated marble. Anyway, the hydroxyapatite-treatment has the advantage of causing the highest increase in marble cohesion and the lowest residual strain, besides being more chromatically compatible and durable than the alternative commercial consolidants. Keywords: Hydroxyapatite, Calcium oxalate, Thermal expansion coefficient, Residual strain, Dilatometry

International audience; When attempting to sufficiently protect outdoor bronze monuments from corrosion, searches for an effective solution are usually based on coating applications which have a high anticorrosive efficiency. In order to correctly assess the level of protection provided by such coatings, adherence (practical adhesion) measurements need to be performed for the proper evaluation of the deterioration of coating systems with aging. Although a coupled study of adherence with aging would be of great interest, very few such studies are available. In this work, a methodological approach is proposed for the evaluation of coatings applied to metallic cultural heritage monuments of, based on the use of a three-point bending test. Adherence characterization of different protective coatings has been performed both on bare and on traditionally black-patinated bronze coupons (Cu–Sn alloy with 5.9 wt% Sn), which were used as basic model substrates. The investigated coatings were Incralac®, silane, sol–gel oxysilane, and a silane-modified polymethacrylate (an adhesion promoter for fluoropolymer). The results of measurements which were obtained before and after accelerated aging in concentrated acid rain made it possible to more easily differentiate between the various adherence levels of different coating systems. Coupled with adherence measurements, the results of systematic optical and SEM observation of the different failure morphologies are also presented. In the case of the coated bare alloy, adhesive failures were mainly observed. The silane (PropS-SH) coating showed the best adherence. In the case of the patinated bronze test specimens, only cohesive failures occurred. Adherence is directly related to the cohesion of the black patina rather than that of the applied coating. It was observed that aging reduces the level of the adherence.