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International audience; 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 Skłodowska-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-Gutiérrez et al.); Ceramics and glass (Giosuè 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.

The present study aims to investigate the use of geopolymer mortars as passive fire protection system for steel structures. Coal fly ashes were used as aluminosilicate source and perlite was employed as aggregate to obtain a lightweight system. In addition, a geopolymer mortar containing quartz aggregate was produced for comparison. The geopolymer mortars were applied on stainless steel plates and exposed to both, cellulosic and hydrocarbon standard fire curves, according to ISO 834-1 and EN 1363-2, respectively. Acoustic emission measurements were conducted to analyze cracking phenomena during the high temperature exposure. The resulting temperature-time curves showed that the investigated system is effective in retarding the temperature rise of the steel plates. When the cellulosic fire curve was applied, a 20 mm [0.79 in.] thick layer of lightweight geopolymer mortar protected the steel substrate from reaching the critical temperature of 500 ?C [932 ?F] for at least 30 minutes, avoiding the rapid decrease of its mechanical properties and thus representing an important safety measure against accidental fires. No spalling phenomena on heating were detected; however, significant cracking was observed on cooling.

Since the arrival of lapped porcelain stoneware tiles on the market, several studies have been focused on the improvement of the technical characteristics of the surfaces of these products. Surface lapping induces aesthetical improvements, but can at the same time deteriorate the performance of porcelain stoneware tiles. To overcome this problem, it is possible to protect the lapped surface with commercial waterproofing materials. In this work, lapped commercial porcelain stoneware tiles with protective stain proofing agents (FILA PD15 and FILA 1239 Plus) were evaluated. The stain resistance and chemical resistance results were correlated to the morphological surface characteristics of the products with and without protection. A systematic study of the surface porosity of the tiles was carried out. Results showed that unprotected surface pores tend to fill with dirt that is hardly removable by ordinary maintenance. If the pores are protected, the dirt from foot traffic is deposited only superficially and can be removed.

Cement production is responsible for approximately 9.5% of global anthropogenic CO2 emissions and as a consequence the increasing attention to sustainability issues has promoted research in alternative materials to cement paste, such as geopolymers. Current studies on geopolymers mainly focus on mechanical strength but research on their long-term mechanical performance and durability is still limited. Reducing the uncertainties around geopolymer durability requires a better understanding of the microstructural features and microscopic mechanisms that govern their chemo-mechanical behaviour. This can be pursued using simulations based on High Performance Computing (HPC), as previously experienced in the field of traditional cement. The aim of this study is to combine results from experimental analysis with HPC-based theoretical understanding of the fundamental mechanisms of material’s reactivity and ageing. The molecular structure of N-A-S-H (sodium aluminosilicate hydrate) geopolymer is considered as a model of metakaolin geopolymers. First results on molecular simulations based on a simplified crystalline version of N-A-S-H with hydrosodalite structure and Al/Si = 1 are discussed. The simulations indicate a path to develop a more fundamental understanding of Na-Si and Na-OH concentration effect on the porous structure and on the skeletal density.

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.

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 (

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.

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.

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.

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 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.].

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

This work investigates the effects of the structure, the bulk chemical composition and amount of the aluminosilicate fines on the strength development, pore refinement, water permeability, moisture control capacity and the microstructure of inorganic polymer concretes (IPC). The amorphous fines, one from pumice and another from recycled glass, presented sponge-like microstructure with tortuous pore network that maintained the presence of fine capillary pores while semi-crystalline feldspar sludge, the third type of fine aggregates used for this study, showed more dense and compact microstructure that explain the higher strength enhancement. Both amorphous and semicrystalline fines contributed to decrease the porosity, improve the strength and microstructure. However, based on the moisture control capacity and the durability indicators, the fine aggregate derived from semicrystalline feldspar was found to be more appropriate and efficient for the development of IPC at short time scale of curing. Pumice fine aggregate was found to be effective only with a long term curing. (C) 2015 Elsevier Ltd. All rights reserved.

Geopolymers are hydrated aluminosilicates with excellent binding properties. Geopolymers appeal to the construction sector as a more sustainable alternative to traditional cements, but their exploitation is limited by a poor understanding of the linkage between chemical composition and macroscopic properties. Molecular simulations can help clarify this linkage, but existing models based on amorphous or crystalline aluminosilicate structures provide only a partial explanation of experimental data on the nanoscale. This paper presents a new model for the molecular structure of geopolymers, in particular for nanoscale interfacial zones between crystalline and amorphous nanodomains, which are crucial for the overall mechanical properties of the material. For a range of Si–Al molar ratios and water contents, the proposed structures are analyzed in terms of skeletal density, ring structure, pore structure, bond-angle distribution, bond length distribution, X-ray diffraction, X-ray pair distribution function, elastic moduli, and large-strain mechanics. Results are compared with experimental data and with other simulation results for amorphous and crystalline molecular models, showing that the newly proposed structures better capture important structural features with an impact on mechanical properties. This offers a new starting point for the multiscale modeling of geopolymers.

Air- and formulated lime mortars with pulverized brick waste were synthesized with addition of two organic waste-based additives: spent cooking oil and albumen. The addition of spent oil in the mortar induced significant hydrophobic effects, but decreased permeability values and setting kinetics. Parallel additions of oil and albumen in lime mortars significantly increased their hydrophobicity and superficial durability without retarding their setting time thanks to role of fatty acids and unfolded proteins under alkaline conditions. The parallel valorization showed high potentials in synthesis of restorative mortars design with low environmental impact and high respect to the feature of historic mortars. (C) 2018 Elsevier Ltd. All rights reserved.

The paper describes part of the preliminary results of the of the MATERSOS project, funded by the Emilia Romagna Region, Italy. This research project aims at implementing circular economy processes in the constructions industry, through the usage of secondary raw materials. The present paper focuses on structural concrete. After an analysis of locally available waste materials, those with the highest potential as concrete components were identified. Normal and self-compacting concrete mixes containing powder from ceramic tile grinding, shell powder, and construction demolition waste aggregates, were then developed. Ceramic powders were used both as replacement for a fraction of cement and as filler while shell powders were used as filler only. The paper presents the results of various experimental tests that were carried out to evaluate the mechanical properties of these concretes. In particular, their compressive and flexural-tensile strengths, elastic moduli, shrinkage and creep deformations were evaluated and compared with traditional concretes. The results of the experimental tests indicated that the mechanical properties of some of the concretes containing secondary raw materials were comparable to those of traditional concretes suggesting that their adoption in real world applications is possible.

This review presents “a state of the art” report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1—the present paper—focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

The suitability of new lime mortars for restorative rendering applications was investigated. Air-, formulated- and hydraulic-lime mortars were synthesized with inclusion of two different types of spent sunflower cooking oils and, when necessary, brick waste powder as pozzolanic addition. The results of spent cooking oils addition in the mortars exhibited promising hydrophobic effects, such as sorptivity reduction up to 60 times and improvement of superficial durability. Addition of high-oleic acid cooking oil in 13 wt% in the formulated and hydraulic lime mortars significantly increased their hydrophobicity without worsening their mechanical strengths. All the investigated mortars exhibited appropriate indexes as restorative materials.

Glass with different chemical compositions, deriving from separate collection, has been used as fine aggregate to formulate cementitious mortars, substituting natural sand. Glass coming from cathode-ray tube monitors, fluorescent lamps, and crystal glass (from production of home decor items) along with glass deriving from soda-lime glass containers, which has been taken as a reference, have been investigated. Glass solubility has been determined in alkaline environment similar to the one inside the cementitious composite. Alkali silica reaction has been tested on glass modified cement mortar in different accelerated conditions. Mortar samples containing glass with chemical composition different with respect to soda-lime glass are subjected to alkali silica reaction. This behaviour is largely dependent on the ratio among modifier and stabilizer oxides in the glass. The same ratio affects glass solubility and consequently composition of expanding gels when alkali silica reactions take place.

This paper aims at evaluating how the FRP/brick debonding force is influenced by brick mechanical properties (compressive, tensile and flexural strength) and physical-microstructural properties (surface roughness, porosity, pore size distribution, rate of water capillary suction). The depth of epoxy resin penetration into bricks and the thickness of brick layer detached at the end of bond test were also determined, in order to investigate the role of resin penetration into the brick on the FRP performance. All the tests were carried out on different brick surfaces (namely “bed” and “face”), to account for possible brick anisotropy. The results of the study point out that brick mechanical properties alone are not sufficient to accurately predict the maximum debonding force, but a better estimation can be achieved taking into account also brick surface roughness and resin penetration depth. If brick anisotropy is not considered, in some cases a remarkable overestimation of the maximum debonding force may be found.

This paper investigates the shrinkage and creep of self-compacting concrete prepared with coarse and fine recycled concrete aggregates (up to 40% of total amount of aggregates). Physical properties and porosity measurements are studied and related to the mechanical properties. Results highlight that self-compacting characteristics are maintained when recycled aggregates are utilized and their good quality promotes high mechanical properties. Creep behavior and pores size distributions are more influenced by the content and assortment of recycled aggregates, although their effect is more limited compared to what occurs in traditional concrete with recycled aggregates.

Alkali-activation of brick waste has recently been proposed as a sustainable route to develop pastes/mortars with tailored mechanical properties and pore system. In this study, the suitability of using pastes from brick waste alkali-activation for repointing existing masonries (i.e., filling the most external part of mortar joints, lost due to deterioration processes) was investigated. Five different formulations (having SiO 2 /Al 2 O 3 molar ratio ranging from 1.4 to 0.4) and two different curing temperatures (room temperature and 50 °C) were investigated. Open porosity and efflorescence formation were found to decrease for decreasing SiO 2 /Al 2 O 3 ratio. Curing at high temperature generally favored geopolymerization and reduced efflorescence formation. Pastes with SiO 2 /Al 2 O 3 =0.8 and 0.9 exhibited open porosity and water vapor permeability fairly similar to those of historic lime-based mortars, thus proving to be potentially compatible with them. Further optimization of the mix design seems however necessary to reduce the formation of efflorescence.

Recent work on the elastic constants of plagioclase feldspars is reviewed. Based on the 21 elastic constants (stiffnesses) reported in the literature for triclinic plagioclase monocrystals of different composition, the effective elastic constants of dense, single-phase, polycrystalline plagioclase aggregates with isotropic microstructure are calculated via standard Voigt- Reuss-Hill averaging. Master curves show the good agreement of the constants obtained via the two approaches (experiment and simulation) and recall the fact that values reported in the older literature have been underestimated. Fit relations are given for the calculation of Young's modulus, shear modulus, bulk modulus, Poisson ratio and density in dependence of the composition. These fit relations may serve as handy tools for obtaining relevant input information for the calculation of effective elastic constants of multiphase ceramics produced with Ca and Na containing raw materials.

This research investigates different kinds of waste as possible new binder components for the production of cement based mortar and concrete. Waste types have been selected on the basis of availability in the Emilia Romagna Region. In particular, three different wastes (i.e., waste from rectified porcelain gres tile, sea shell fragments and eggshell waste from agri-food industry) are explored as a possible substitution of a certain fraction of cement in order to evaluate their effect. Chemical properties and physical behavior of the waste are studied, and the activity index of the waste is investigated. A series of mortar specimens with normalized silica sand and a binder compositional ratio of cement (CEM I) at 75 wt.% and waste at 25 wt.% is prepared. The physical and mechanical behavior of the mortar is investigated at different curing time (i.e., 2, 7, 28 and 90 days). This research shows first preliminary results of the MATER-SOS Project, funded by the Emilia Romagna Region, Italy (POR FESR 2014-2020), aimed at implementing circular economy processes in the constructions industry.