Search

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.

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 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.

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.

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.

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.

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.].

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.

Surface coatings made of hydroxyapatite (HAP) have been proposed to protect marble artworks from dissolution in rain, originated by the aqueous solubility of calcite. However, HAP coatings formed by wet chemistry exhibit incomplete coverage of marble surface, which results in limited protective efficacy. In this study, electrodeposition was explored as a new route to possibly form continuous coatings over the marble surface, leaving no bare areas. Electrodeposition was performed by placing marble samples in poultices containing the electrolyte (an aqueous solution with calcium and phosphate precursors) and the electrodes. The influence of several parameters was investigated, namely the role of the working electrode (cathode or anode), the distance between the marble sample and the working electrode, the deposition conditions (potentiostatic or galvanostatic), the electrolyte composition and concentration, the applied voltage, and time. The coating morphology and composition were assessed by SEM/EDS and FT-IR. The protective ability of the most promising formulations was then evaluated, in all cases comparing electrodeposition with traditional wet synthesis methods. The results of the study suggest that electrodeposition is able to accelerate and improve formation of HAP coatings over the marble surface, even though the obtained protective efficacy is not complete yet.

The aim of this work was to evaluate the durability, in real pedestrian traffic condition, of lapped porcelain stonewares with surface protective treatments able to fill up pores opened by the lapping process. In recent years, the durability of ceramic surfaces has become a key factor during the design process. The knowledge of the material durability is important to define the behavior of tiles in use. Standard procedures for indirectly assessing durability are already available (ie, abrasion tests, staining resistance, chemical resistance), however, a standard method of aging in real condition is still lacking. In this study, a durability test was performed in real pedestrian traffic condition by fixing tiles on floors to evaluate the surface characteristics after 6 and 12 months. The surface characteristics were analyzed before and after the durability tests and in terms of microstructural observations and determination of surface porosity. In particular a durability index has been estimated as ratio of pores filled by dirtiness respect to the original surface porosity (before aging). Results of durability index showed good correlation between aging duration and kind of treatments (industrially applied and/or manually applied).

This work focuses on an in-depth investigation of the formation of pores in the structure of lightweight geopolymer cements and mortars using rice husk as a foaming agent. The hardener used in this study was sodium waterglass. Metakaolin was replaced by 0, 10, 20, 30 and 40 % by mass of husk and the obtained powders were used to produce lightweight geopolymer cements and mortars. The formation of pores in the lightweight geopolymer cements was monitored using X-ray diffractometry and infrared spectroscopy while those in the mortars were assessed using apparent density and compressive strength measurements, mercury intrusion porosimetry and optical and scanning electron microscopy. The values for the compressive strength and apparent density were in the ranges of 28.92–0.75 MPa and 1.88–1.70 g/cm 3 , respectively. The results indicated that the values for the compressive strength and apparent density of geopolymer mortars decreased while those of the cumulative pore volume increased with increases in the metakaolin replacement level. Stereomicroscopic and scanning electron microscopic images showed the presence of rice husk and fibres of rice husk, respectively, in the networks. It was found that rice husk can be used as a foaming agent for producing sustainable lightweight geopolymer mortars. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of The Korean Ceramic Society and The Ceramic Society of Japan.

The objective of this paper is to review the current knowledge on the development of nanostructured zirconia-based ceramics and composites suitable for application in dentistry. Isi Web of Science, Science Direct, Scientific.net databases, and Google were searched electronically for the period of 1980 to the present, matching the keywords “nano” with the keywords: “Zirconia, ZrO2, Y-TZP, and dental, dentistry”. A total of 74 papers were found, with the majority coming from Asia, indicating a more active scientific interest on the topic in this geographic area, followed by Europe, South America, and North America. The research shows, even though the scientific activity on nanostructured ceramics was intense in the last fifteen years, the development of fully dense zirconia-based nanoceramics is yet at an initial stage, most of all from the point of view of the clinical applications. It has been demonstrated that nanostructured ceramics can show improved properties because of the reduction of the grain size to the nanoscale. This is also true for zirconia-based nanoceramics, where some improvements in mechanical, optical, as well as resistance in low-temperature degradation have been observed. Potential applications of this class of material in the dental field are discussed, summarizing the results of the latest scientific research.

The sustainable microcomposites with different molar ratios CaO/SiO2 such as 0, 0.4, 0.6, 0.8, 1.0 and 1.2 were prepared using calcined brown chicken eggshell, rice husk ash and distilled water. 10 wt% of each microcomposite was used to substitute metakaolin and the obtained calcium aluminosilicate materials were used for investigating the effects of the molar ratios CaO/SiO2 in the microcomposites on the physical, mechanical and microstructural properties of (Ca, Na)-poly (sialate-siloxo) networks. Commercial sodium waterglass and sodium waterglass from rice husk ash with a molar ratio SiO2/Na2O kept constant at 1.6 were used as chemical ingredients. Each (Ca, Na)-poly (sialate-siloxo) network was obtained by mixing each calcium aluminosilicate material with each hardener. The final products were characterized by infrared spectroscopy and X-ray diffractometry. The determination of the apparent density, compressive strength and scanning electron microscopy analysis were done. The results show that the compressive strength values of geopolymer cements using hardener from rice husk ash and microcomposites containing the molar ratios CaO/SiO2 equal to 0, 0.4, 0.6, 0.8, 1.0 and 1.2 are 64.01, 67.97, 66.15, 65.09, 60.73 and 49.40 MPa, respectively. Whereas, those from commercial sodium waterglass are 64.75, 69.03, 64.64, 56.73, 36.47 and 28.30 MPa, respectively. It was found that the most convenient molar ratio CaO/SiO2 in the structure of microcomposite required for producing (Ca, Na)-poly (sialate-siloxo) networks with higher mechanical properties is around 0.4.

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 represents the “state of the art” on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.

Dicalcium phosphate dihydrate (DCPD) and hydroxyapatite (HAP) were prepared from oyster shell powder and phosphoric acid solution as raw materials using sol-gel process in order to study the influence of calcium phosphate compounds on the mechanical and microstructural properties of metakaolin-based geopolymer cements. The synthesized DCPD and HAP with molar ratio Ca/P equal to 1.00 and 1.65, respectively, were used as additives for replacement of metakaolin (0, 2, 4, 6, 8 and 10 wt%) and the resulting powders were used for producing geopolymer cements. The compressive strengths of geopolymer cements containing DCPD were in the range 40–48 MPa with increasing DCPD content, but when 10 wt% was used, the strength fell to 26 MPa. Similar results were obtained for HAP addition with a decrease of the compressive strength at 8 wt%. The ESEM images of geopolymers containing 4–10 wt% of HAP showed some non-reacted or partially reacted particles that do not well connect to the matrix. Samples of geopolymer with 4–8 wt% of DCPD present a lower number of unreacted particles and the matrix appeared denser than that of the control geopolymer cements. The use of calcium phosphate compounds such as brushite and hydroxyapatite led to the overall improvement in compressive strength and contribute to the densification of the structure of geopolymer cements. On the other hand, the addition of 4% of HAP and 10% of DCPD resulted in a large amount of hydroxyapatite and brushite, respectively in the systems. The matrix appear less dense indicating that a fraction of calcium phosphate addition at the aforementioned level was excessive.

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.

This paper reports on the diagnostic investigations on the bronze panel in the Church of San Moise in Venice (Italy), aiming at the identification of materials and causes of corrosion. Both the bulk metal and surface layers were investigated by a wide range of techniques: alloy composition and microstructure were determined by VP-SEM/EDS, the corrosion products by Raman spectroscopy and XRD. The organic compounds were analysed by pyrolysis gas chromatography mass spectrometry (Py-GC-MS). The adjacent mortars were analysed in terms of mineralogical composition and soluble salts content, in order to highlight their role in the degradation processes at the contact areas between the masonry and the bronze panel. The alloy is a quaternary bronze (Cu-Sn-Zn-Pb): high-relief figures were cast separately then mechanically joined to the panel. Traces of the clay core were detected in the back of the panel. The bronze surface was artificially patinated by potassium sulphide. The organic protective layer consisted of stearin and paraffinic wax. However, siccative oil was detected at the interface with the metal, likely corresponding to the original protective treatment. Also pine resin traces were detected. The corrosion products mainly consisted of basic copper chlorides (paratacamite, atacamite) and mixed copper/sodium carbonates (chalconatronite), deriving from the interaction with mortar.

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.

Steel fiber reinforced geopolymer matrix (S-FRGM) composites are explored as a new tool in strengthening applications of reinforced concrete (RC) structures. The suitability of fly ash geopolymers as the matrix employed in S-FRGMs is investigated in this paper. Geopolymer matrix is used to embed galvanized steel fibers and bond the composite to a concrete substrate. By varying the molar concentration of the NaOH activating solution, three different geopolymer matrices are obtained and the influence of the alkaline environment on the bond behavior between fibers and matrix is examined. Physical, mechanical, and microstructural properties of the three matrices are measured and related to the interfacial bond behavior of S-FRGM-concrete joints. Results show that the decrease of the molar concentration of the NaOH activating solution leads to an increase of the interfacial bond behavior between matrix and fibers, which in turn improves the effectiveness of the composite action of the strengthening system.

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.

International audience; In order to bring the treatment of historical bronze monuments in line with proper engineering practice and cultural heritage regulations, the standardisation of artificially aged surfaces that are comparable with natural ones is still to take place. In this aim, this investigation reports a comparative study of corroded quaternary bronze samples produced by accelerated ageing tests, simulating the unsheltered and sheltered exposure conditions mainly affecting outdoor bronze monuments. The effects of run off in a dropping test (unsheltered simulation) and the exposure to stagnant acid rain in a wet & dry test (sheltered simulation) on a bronze surface were studied. A multi-analytical approach was performed including conventional analytical methods, such as a microscopy examination coupled with elemental and structural analyses of the surface. In addition, a focused ion beam (FIB) was used to produce cross sections in the size range up to a few tens of nanometres. It is evidenced that the corrosion layers, forming a nano-porous structure, are linked to a decuprification process marked by the preferential dissolution of Cu and Zn and the formation of a Sn-O species network within the barrier layer. A correlation between the tin content of the alloy and the corrosion amplitude is shown: the anodic areas are related to the lowest tin-content part of the alpha phase (in the centre of the dendrite), while the eutectoid areas (including the delta phase) are cathodic and therefore not attacked. The corroded samples artificially aged are well representative of natural corrosion structures observed on outdoor bronzes. (C) 2017 Elsevier B.V. All rights reserved.

Present concerns about global warming due to the greenhouse emissions in the atmosphere have pushed the cement industry to research alternatives to ordinary Portland cement (OPC). Geopolymer binder may constitute a possible breakthrough in the development of sustainable materials: understanding the effectiveness and the influences of superplasticizers on geopolymer systems is one of the essential requirements for its large-scale implementation. This study aims to investigate the possibility of using commercially available chemical admixtures designed for OPC concrete, to improve fresh properties of fly ash-based geopolymers and mortars. A special emphasis is laid upon evaluating their influence on mechanical and microstructural characteristics of the hardened material realized under room-temperature curing conditions. Results indicate that the addition of a polycarboxylic ether-based superplasticizer, in the amount of 1.0 wt. % by mass of fly ash, promotes an improvement in workability without compromising the final strength of the hardened material. Moreover, the addition of the polycarboxylic ether- and acrylic-based superplasticizers induces a refinement in the pore structure of hardened mortar leading to a longer water saturation time.

International audience; Gilded bronzes are often affected by severe corrosion, due to defects in the Au layer and Au/Cu alloygalvanic coupling, stimulated by large cathodic area of the gilded layer. Galvanic corrosion, triggered by gilding defects, leads to products growth at the Au/bronze interface, inducing blistering or break-up of the Au layer. In this context, fire-gilded bronze replicas prepared by ancient methods (use of spreadableAu–Hg paste) was specifically characterised by compiling complementary spectroscopic and imaging information before/after accelerated ageing with synthetic rain. Fire-gilded bronze samples were chemically imaged in cross-section at nanometric scale (

This study concerns the corrosion behavior of steel in different room temperature cured alkali-activated fly ash mortars exposed to chloride solution. The corrosion process was monitored by polarization resistance and corrosion potential measurements and the results were interpreted in the light of a complete microstructural, mechanical and chemical characterization of the mortars. The most compact alkali-activated mortars have higher porosity and lower mechanical properties than a cement-based mortar (CEM), but the protectiveness afforded to the rebars is slightly higher than that obtained in CEM. The reason for this discrepancy is connected to a lower chloride content accumulated in the former mortar type and to a specific inhibition of the rebar corrosion afforded by the pore electrolyte in alkali-activated mortars.

Surface and building runoff can significantly contribute to the total metal loading in urban runoff waters, with potential adverse effects on the receiving ecosystems. The present paper analyses the corrosion-induced metal dissolution (Fe, Mn, Cr, Ni, Cu) from weathering steel (Cor-Ten A) with or without artificial patinas, exposed for 3 years in unsheltered conditions at a marine urban site (Rimini, Italy). The influence of environmental parameters, atmospheric pollutants and surface finish on the release of dissolved metals in rain was evaluated, also by means of multivariate analysis (two-way and three-way Principal Component Analysis). In addition, surface and cross-section investigations were performed so as to monitor the patina evolution. The contribution provided by weathering steel runoff to the dissolved Fe, Mn and Ni loading at local level is not negligible and pre-patination treatments seem to worsen the performance of weathering steel in term of metal release. Metal dissolution is strongly affected by extreme events and shows seasonal variations, with different influence of seasonal parameters on the behaviour of bare or artificially patinated steel, suggesting that climate changes could significantly influence metal release from this alloy. Therefore, it is essential to perform a long-term monitoring of the performance, the durability and the environmental impact of weathering steel.

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.

This paper presents the comparative results obtained from X-ray and neutron pair distribution function (PDF) analysis aimed at determining the variability in aluminosilicate glass chemistry in five types of class F fly ash (FA). Results have been discussed in light of the complementary information provided by the two methods in order to give a comprehensive overview of FA structure at the nanoscale. The analysis of short range correlations reveals that the bulk glassy structure of FA sources differing in chemical composition are relatively similar, but some specific distinctions in atomic structure are visible in those containing high levels of amorphous VI-coordinated aluminum (e.g., amorphous mullite/alumina), iron and/or carbon (with similar local bonding environment to graphite). The obtained experimental results fill a deficit in literature in the atomic structure and associated variability for class F FA, which is extensively used in several industrial applications including as raw material in alkali-activated cements.

Application of a protective coating is the most widely used conservation treatment for outdoor bronzes (cast Cu-Sn-Zn-Pb-Sb alloys). However, improving coating protectiveness requires detailed knowledge of the coating/substrate chemical bonding. This is particularly the case for 3-mercapto-propyl-trimethoxy-silane (PropS-SH) applied on bronze, exhibiting a good protective behaviour in outdoor simulated conditions. The present work deals with X-Ray Photoelectron Spectroscopy (XPS) and Electron Microscopy (FEG-SEM + FIB (Focused Ion Beam)) characterization of a thin PropS-SH film on bronze. In particular, in order to better understand the influence of alloying elements on coating performance, PropS-SH was studied first on pure Cu and Sn substrates then on bronzes with increasing alloy additions: Cu8Sn as well as a quinary Cu-Sn-Zn-Pb-Sb bronze. Moreover, considering the real application of this coating on historical bronze substrates, previously artificially aged (''patinated'') bronze samples were prepared and a comparison between bare and ``patinated'' quinary bronzes was performed. In the case of coated quinary bronze, the free surface of samples was analysed by High Resolution Photoelectron Spectroscopy using Synchrotron Radiation (HR-SRPES) at ANTARES (Synchrotron SOLEIL), which offers a higher energy and lateral resolution. By compiling complementary spectroscopic and imaging information , a deeper insight into the interactions between the protective coating and the bronze substrate was achieved. (C) 2017 Elsevier B.V. All rights reserved.