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Traditional Portland cement-based composites have a great environmental impact. Alkali-activated binders can offer an alternative, particularly if they can be obtained even partially from waste. Two residuals derived from the finishing steps of the traditional ceramic industry have been used as possible polymerizable sources mixed with metakaolin. Moreover, to contrast the low dimensional stability of alkali-activated materials and their mechanical brittleness, natural fibers derived from the Arundo donax plant have been added to the mortars. The use of renewable natural fibers instead of synthetic ones can contribute a further environmental advantage. The fresh (consistency) and cured (mechanical) properties of composite materials prepared with residuals and metakaolin were analyzed here. For comparison's sake, a reference set of composite materials not loaded with fibers but with an identical binder/sand and liquid/binder ratio was cast. A room-temperature curing condition was selected that, although inadequate to promote the short-time reactivity of the wastes, has a minimal energy requirement and allows on-site applications. A small-scale decrease in the properties in the compression mode tests was observed in the waste-modified mortars, while the Arundo addition improved their flexural strength and dimensional stability. [ABSTRACT FROM AUTHOR]

This research reports the investigations of threshold reactivity limit of blends of pegmatite with different calcined clays as well as the influence of calcined clay source on the geopolymerization kinetic, microstructural, and physicomechanical properties of feldspathic mineral-based inorganic polymer composites. These composites were designed from 85 to 94 wt% of the solid solution of pegmatite and calcined clay. The three-point flexural and compressive strengths, porosity, and microstructure as well as heat evolution rate of geopolymerization reactions of resulting composites were affected by the type of calcined clay. The four calcined clays provided the highest mechanical properties of the composites when added in the range of 12-15 wt%. Specifically, the values of flexural and compressive strengths ranged from 32 to 34 MPa and 101 to 105 MPa, respectively, for geopolymer composites with 15 wt% of metakolin added, while they ranged from 38 to 42 MPa and 106 to 107 MPa with 12 wt% of meta-hallosyte added. The polycondensation/polymerization process of calcined clay developed sufficient amounts of N-A-S-H and polysialate geopolymer to cover the incongruently dissolved fine particles of pegmatite. The resulting microstructure was dense and compact with the lower cumulative pore volume at about 91 mm3/g. It was concluded that designing the pegmatite/clay-based geopolymer composites with high mechanical strengths and low porosity resulted in sustainable, low energy consumption and environmental-friendly materials for civil engineering. [ABSTRACT FROM AUTHOR]

Aluminum alloys are extensively used to manufacture mechanical components. However, when exposed to alkaline environments, like lubricants, refrigerants, or detergents, they can be corroded, reducing their durability. For this reason, the aim of this study is to investigate the influence of aggressive alkaline solutions (i.e., pH and presence of chlorides) on the corrosion resistance of three aluminum alloys (AA 5083-H111, AA 6082-T6, and AA 7075-T6) with and without anodizing treatments. Open circuit potential (EOCP) and anodic polarization measurements were carried out and typical corrosion parameters such as corrosion current density (icor) and corrosion rate (CR) were determined. Morphology of the corrosion attack and samples microstructure were investigated by scanning electron microscope. Results show that corrosion behavior of the three investigated alloys is influenced by (i) the aggressiveness of the testing environments; (ii) the thickness of the anodizing treatment; (iii) the alloy chemical composition; (iv) the distribution of intermetallic phases in the aluminum matrix. Moreover, three galvanic series have been built also testing other metallic alloys commonly used in mechanical applications, i.e., carbon steel (C40), stainless-steel (AISI 304), and Cu-based alloys (Cu-Ni alloy and CW 617 N, respectively). Results clearly indicate that galvanic series play a fundamental role when it is necessary to select an alloy for a specific environment, highlighting the thermodynamic conditions for corrosion occurrence. On the other hand, kinetic measurements and microstructural studies carried out on the three aluminum alloys stress the importance of the surface treatments and relevant thickness as well as the effect of metal exposure. Future work will involve the study of other surface treatments on aluminum alloys and the evaluation of their corrosion behavior in acidic environments. [ABSTRACT FROM AUTHOR]

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.

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 VoigtReuss-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 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.

Ceramic tile manufacturing is a highly energy-intensive process. Concerns about carbon emissions and energy costs make energy management crucial for this sector, which holds a leading role in Italian industry. The paper discusses the energetic and environmental performance of cogeneration (CHP) in the ceramic industry, where prime mover exhaust heat is supplied to a spray-dryer system, contributing to the satisfaction of the thermal demand and decreasing natural gas consumption. A thermodynamic model of a dryer unit, validated against real data, has been set-up to provide a detailed representation of the thermal fluxes involved in the process. Then, the thermal integration with two types of CHP prime movers of similar electric size (4 MW) is investigated. Energetic results show that the gas turbine can contribute up to 81% of dryer thermal consumption, whilst internal combustion engine contribution is limited to 26%. A methodology was ad-hoc defined for the environmental assessment of CHP, accounting for global (CO2) and local (CO and NOX) emissions. Results confirm that CHP units guarantee reduction of CO2 and NOX compared to separate generation, with maximum values equal to 81 g/kWhth and 173 mg/kWhth, respectively; CO emission is decreased only in the case of gas turbine operation, with savings equal to 185 mg/kWhth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 décor 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Alkali activation of fly ash can be considered as one of the more promising alternative systems to traditional hydraulic binders, particularly if the process can be carried out at room temperature. With the aim of finding the best solution chemistry for room temperature activation, two types of fly ash have been activated using Na 2 O/SiO 2 molar ratio ranging from 0.12 to 0.20. It was found that the behaviour of the resultant geopolymer and mortars in the fresh and hardened state is more influenced by the type of fly ash, in particular by their fineness and mineralogical composition, than by the increasing proportion of sodium silicate solution in the mix. [ABSTRACT FROM AUTHOR]

An abstract of the article "Recycling Waste For the Production of Sustainable Mortars for Brick Masonry" by Elisa Franzoni and colleagues is presented.

Abstract: The effects of bulk composition and microstructure on strengthening mechanisms and fracture resistance were investigated for metakaolin based geopolymers. Crack initiation and propagation under mechanical and environmental stresses were correlated to pore size distribution and bulk composition. Based on IR spectra and porosity analysis, it was observed that capillary pores and the nature of alkali-aluminosilicate hydrated named polysialates (H–M–A–S) determine cracks initiation site in the Al-rich geopolymer samples with low Si/Al molar ratio (range 1.23–1.5). These samples exhibited low flexural strength, Young modulus and Impact toughness as well as delayed failure under environmental stresses. Increasing the Si/Al molar ratio (range 1.79–2.42) improved the flexural strength and Impact toughness. Formation of more polymerized H–M–A–S phases contributed to strengthening the matrices and hinder axial cracks; consequence of toughening mechanisms developed by the coarsening on molecular scale of H–M–A–S. [Copyright &y& Elsevier]

Abstract: Recently, many efforts have been made to recycle waste of different nature as constituents of sustainable concrete. This practice produces large environmental benefits that can be further extended if deleterious chemical side-reactions, deriving from the use of some types of waste and/or raw materials, could be prevented and suppressed. This paper presents the combined action of different ceramic wastes partially replacing natural sand and cement, respectively. Alkali silica reaction (ASR) promoted by boron–silicate and lead–silicate glass used as fine aggregates (⩽4mm) is limited and controlled by using a new type of blended cement based on a siliceous residue coming from sludge produced by the polishing of porcelain stoneware tiles. The results of expansion tests carried out in accelerated conditions together with mechanical and microstructure characterisations of mortar samples highlight the combined action of the investigated wastes. Indeed, the blended cement containing porcelain stoneware polishing residue can be effectively exploited as valid alternative to pozzolan cement. [Copyright &y& Elsevier]

Abstract: The large amount of waste yearly disposed to landfill, the global impoverishing of natural resources and environment, the emergency of carbon dioxide emissions, are some of the motivations driving research institutes and industrial world to move towards sustainable solutions for civil engineering field. Accordingly, the use of sustainable materials for green buildings construction is an important goal that must be reached in short times. Sustainable cements can be designed by partially replacing clinker content with non hazardous waste. Indeed, recycling process can transform waste in secondary raw materials that work as new cement constituents usually leading to sustainable binders with peculiar environmental resistances. Details of cement manufacturing process and its effect on the environmental pollution as well as the route that can be carried out to tailor sustainable cements are reported and discussed. [Copyright &y& Elsevier]

Abstract: Blended cements are largely used for concrete: they are usually considered cements with a low environmental impact, as they require less clinker than ordinary Portland cement (OPC). Different constituents can be used as supplementary clinker component usually leading to cement with high resistance to outdoor environment. Polishing residue (PR), coming from porcelain stoneware tiles production, can be successfully used as new constituent for blended cement, however its action for enhancing the durability of cement matrix must be assessed. With this purpose, electrochemical tests (half cell potential, impressed voltage and linear polarization techniques) have been carried out on steel reinforced mortar samples, prepared using a 25% PR based cement and 100% OPC as binder and exposed to a 3.5% NaCl solution. The corrosion resistance results and microstructure analysis highlight better durability performances for PR based cement than those exhibited by OPC, mainly for curing time >28days. [Copyright &y& Elsevier]

Waste generated in ceramic tiles manufacturing is not usually recycled inside the productive plant, but rather disposed to landfill. This paper deals with ceramic residues from polishing and glazing processes, as constituents for innovative blended cements. New binders made up of 75% CEM I 52.5 R and 25% residues were chemically, physically, and mechanically characterized with reference to EN 197-1 requirements and the results compared with ordinary Portland cement. Mechanical strength development and microstructure of the relevant mortar have been investigated up to 90 days of curing, and the behavior of polishing and glazing residues as cement constituents is reported. [ABSTRACT FROM AUTHOR]

Abstract: The alkali–silica-reaction (ASR) expanding behavior of different types of glass, all derived from cullet with different chemical composition, has been investigated. The glass reactivity was determined in different alkaline solutions based on sodium and/or calcium hydroxide to simulate concrete environment. The expansion of mortar containing different amounts of the investigated glass as fine aggregate has been carried out in different conditions: data collected underline a different response of glass towards the alkaline environment. Soda–lime glass shows negligible expansion, lead–silicate glass always generates expanding trends while boro–silicate glass has different behaviors depending on its colour. An attempt to link the behavior to the solubility and chemical reactivity of the glass is proposed. [Copyright &y& Elsevier]

Ceramic tiles are bacteriostatic materials; however, the COVID-19 emergency has pushed tile producers to improve surfaces' antibacterial properties. The aim of this work was to validate a silver-based antibacterial treatment applied to porcelain stoneware tiles based on natural and waste materials, thus correlating surface functionalization to tile composition and relevant physical, microstructural, and textural parameters. The treatment was applied before firing, with and without a polymeric primer. Antibacterial activity tests, stain resistance tests, and contact angle measurements were carried out on fired tiles. Further investigations were made by SEM and optical profilometry in order to study the morphological–structural profile of tile surfaces. Results showed strong antibacterial activities for all the functionalized tiles, which were mainly correlated to the morphological and textural parameters of ceramic surfaces, as well as the presence of the polymeric primer. [ABSTRACT FROM AUTHOR]

Morphology of the crack surface of surgical bone cements has seldom been studied in the past despite the clinical relevance of cement failure. Previous studies on a specific cement type suggest that crack morphology depends on crack propagation rate. The objectives of this work were: (i) to develop a quantitative indicator for describing crack morphology; and (ii) to assess if dependency on crack-propagation rate is affected by cement formulation. Known crack surfaces were obtained from specimens under controlled loading conditions. Crack surface roughness was measured for different crack-propagation rates, and compared against the amount of cleaved pre-cured beads (measured with a semi-automated procedure based on micrographs). Such indicators were extremely robust, operator-independent, highly correlated, and sensitive to the type of fracture. Moreover, it was found that crack surface morphology heavily depends upon cement composition. Thus, crack surface roughness is proposed as a method for quantitatively identifying crack morphology, and finally classifying fracture type. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]