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Looking back to less than three centuries of industrialization, responsible for alarming levels of pollution and consumption of non-renewable resources that has led to the exhaustion of the earth's capacity, the humankind only now begins to grasp the overwhelming potential of natural systems. During almost 40 million centuries, Nature has developed materials and processes with optimal performance which are totally biodegradable. Analysis of bioinspired materials requires the knowledge of both biological and engineering principles which are being a part of a large research area termed biotechnology. This hot area is one of the six strategic Key Enabling Technologies that will be funded under the EU Framework Programme Horizon 2020. This paper reviews the current knowledge on the potential of this emerging field, particularly in the development of materials and technologies for the construction industry. It covers the use of bacteria for enhancing concrete durability and for soil stabilization. It also covers bioinspired tough composite materials, bioinspired adhesives and coatings, and self-cleaning materials. Incorporation of biology basics in the civil engineering curriculum would ease the communication between biologists and civil engineers, helping to foster research on biotechnologies and bioinspired materials for the construction industry. [ABSTRACT FROM PUBLISHER]

Abstract: This work describes the attempt to reuse rejected sieved fractions from the lightweight expanded clay aggregates production, as filter bed, used in the removal of some water contaminants, namely nickel, lead and suspended particles, as an alternative to land filling deposition. Expanded clay fractions and materials used for efficiency comparison were first characterised, by means of physical, chemical and mineralogical tests, in such a way that possible factors, on which removal depends, could be determined. Besides the classical purpose of suspended particles’ removal, assay on the removal of heavy metals were also performed through the filtration in fixed beds. Experiments were performed at different contaminant concentrations and by testing several operational conditions. The performance is better for all the studied contaminants using beds made of smaller sieved fractions, 0/0.5mm, showing higher packing density values (straining is favored), and for lower filtration rates which improve contact time between pollutants and filtration material. Pb(II) removal was higher than Ni(II) one. When comparing with the traditional filtration materials, lightweight aggregates rejects demonstrate their good performance, once it was more effective than sand, considering suspended particles’ removal, and for heavy metal removal, efficiencies were similar or higher than those found for granular activated carbon (GAC). [Copyright &y& Elsevier]

Abstract: Mullite and cordierite based refractory ceramic materials were produced from formulations based on an industrial Al-rich sludge derived from the wastewater treatment of the aluminium anodising process. Some common ceramic raw materials, like ball clay, kaolin, diatomite and talc, were also added. Cylindrical samples processed by uniaxial dry pressing were sintered at different temperatures (between 1300 and 1650°C, 1h soak at each temperature) to study the ceramic properties. The fired properties of materials was evaluated (firing shrinkage, water absorption, bending strength, thermal expansion coefficient, refractoriness and SEM microstructure) and demonstrated that optimal properties were obtained at 1650°C for mullite and 1350°C for cordierite. [Copyright &y& Elsevier]

The production of biogas from anaerobic digestion is emerging as an alternative to fossil fuels due to its lower carbon footprint. However problems such as low methane yield and process instability arise when using low pH waste streams, hindering the technology widespread. In this study, porous metakaolin-based and biomass fly ash-based geopolymer spheres were produced using a simple and low cost technology. Afterwards, the pH buffer capacity of the produced spheres was evaluated. Results demonstrate that the geopolymers alkalis leaching can be controlled by the content of fly ash in the geopolymers, higher content promoting greater leaching. The fly ash-based spheres showed superior pH buffer capacity than their metakaolin-based counterparts, with a narrow pH fluctuation (1.6–1.9) over the 30 days measurements. The maximum leaching of hydroxyl ions from the geopolymer spheres (0.0317 mol/dm 3 g) demonstrates the high pH buffer capacity of this innovative material, suggesting their use as pH regulator in anaerobic digestion. [ABSTRACT FROM AUTHOR]

The production of paper pulp by the Kraft method generates considerable amounts of wastes. Namely, lime mud generated in the recovery circuit of chemical reagents, biological sludge from the wastewater treatment of wood digestion process and fly ash collected in the fluidized bed combustor used to generate electricity from biomass burning. The final destination of such wastes is an important concern, since environmental regulations are becoming stricter regarding their landfill. Driven by this fact, industries are looking for more sustainable solutions, such as the recycling in distinct products. This work tested these wastes as secondary raw materials to produce clinker/cement that was then experienced in mortar formulations. The first step involved the residues detailed characterization and a generated amounts survey. Then, specific but simple steps were suggested, aiming to facilitate transport and manipulation. Distinct blends were prepared and fired in order to get belitic and Portland clinkers. The Portland clinkers were processed at lower temperatures than the normally used in the industry due to the presence of mineralizing impurities in some wastes. Belite-based cements were used to produce mortars that developed satisfactory mechanical strength and did not reveal signs of deterioration or durability weaknesses. [ABSTRACT FROM AUTHOR]

The increasing demand for building materials exerts tremendous pressure on the Earth's natural resources, as many raw materials are reaching critical and distressing levels. As a result new materials that can, totally or partially, substitute conventional raw materials have been the focus of intense research and are eagerly pursued. Waste materials emerge as ideal candidates for partial substitution of ceramic raw materials, due to their large scale production. Despite their high annual production rate wood wastes have seldom be used in building materials, so their valorisation in the construction sector would be highly advantageous from an environmental and economic point of view. This work reports the incorporation of wood wastes (sawdust) as a pore forming agent into ceramic tiles for the production of lightweight bi-layered ceramic tiles with tailored thermal conductivity. To the best of our knowledge this is the first investigation concerning the incorporation of wood wastes in this type of material. Optical micrographs of the sintered discs did not reveal the presence of a black core, indicating that sawdust was totally burn out even when industrial fast-firing cycles were applied. Moreover its decomposition does not induce defects in the ceramic bodies. The results demonstrate that sawdust incorporation promotes a threefold decrease in the thermal conductivity of the ceramic tile, and reduces product weight (up to 7.5%), while maintaining suitable mechanical resistance in comparison to commercial stoneware tiles. Sawdust can be successfully incorporated into stoneware ceramic tiles ensuring environmental, technical and economic advantages: waste valorisation by sawdust reuse (environmental advantage); density reduction of the product which decreases the tiles transportation and distribution costs (economic advantage); restrain energy loss (technical advantage). The new and exciting features provided by sawdust incorporation may widen the range of applications of this common product while simultaneously contributing towards sustainable construction. [ABSTRACT FROM AUTHOR]

This work reports the production process of bi-layered ceramics tiles, formed from two layers with different densities – dense and porous – and with adjustable thickness. The novel production method comprises a double pressing action, fast and easy to implement industrially, that ensures the development of a perfect interface bonding between layers. The bi-layered ceramic tile is formed by an upper layer with density similar to a conventional porcelain stoneware tile, and a porous bottom layer, which promotes weight reduction of the product maintaining suitable mechanical strength. The introduction of porosity is achieved by means of the incorporation of pore forming agent – polypropylene (PP) – into the ceramic formulation, which undergoes complete and non-harmful thermal decomposition during firing. For comparison, polymethyl methacrylate (PMMA) was also tested as porogen. The rapid and complete combustion of PP is suitable for fast-firing ceramic products, such as porcelain stoneware. In addition, the polymer decomposition does not induce defects in the ceramic pieces, and is environmentally acceptable. The produced tiles are lighter than conventional porcelain stoneware tiles, thus decreasing their transport and distribution costs. Additionally, the thermal attenuation provided by the porous layer could be valuable in innovative applications, such as ventilated facades. [ABSTRACT FROM AUTHOR]

Red mud (RM) is a solid waste derived from processing bauxite ore to produce alumina and is considered a hazardous waste due to its high pH. This paper describes the use of untreated mud and after calcination at distinct temperatures (450, 650, and 1000 °C) to attempt to improve its reactivity in cement mortars. In the formulations, portland cement was replaced with up to 30 wt% red mud, and the addition of the red mud changed the hydration process, setting time, and workability. The temperature of hydration increased as more RM was added, particularly when calcined in the interval of 450-650 °C. In these conditions, the hydration process was accelerated, and the workability decreased. These findings indicate that the presence of red mud significantly altered important properties of portland cement. [ABSTRACT FROM AUTHOR]

Abstract: Carbonation is a major cause of concrete structures deterioration leading to expensive maintenance and conservation operations. The eco-efficient construction agenda favours the increase of the use of supplementary cementing materials (SCMs) to reduce Portland cement’s consumption and also the use of recycled aggregates concrete (RAC) in order to reduce the consumption of primary aggregates and to avoid landfill disposal of concrete waste. There is a wide range of literature published on the field of concrete carbonation related to the use of SCMs and/or RCA. However, the different conditions used by different authors limit comparison and in some cases contradictory findings are noticed. Besides, since most investigations are based on the use of the phenolphthalein indicator, which provides a poor estimate of the real concrete carbonation depth, there is a high probability that past researches could have underestimate the corrosion potential associated to concrete carbonation. This paper reviews current knowledge on concrete carbonation addressing carbonation depth’s measurement, the use of SCMs and or RAC. [Copyright &y& Elsevier]

Abstract: Pure and doped (zinc and iron) nanocrystalline titania powders were prepared by the sol–gel route. Doping tends to change the existing crystalline phases and their degree of crystallinity, but particle size distribution and morphology of the particles are also affected. In the pure titania system, the main crystalline phase is anatase but rutile is also present. The doped (Zn and Fe) titania crystallizes only as anatase. The undoped titania shows a bimodal distribution of particles size: fine (20–40nm) and coarse (300–500nm) grains. The doped TiO2 powder also exhibits a much more uniform particle size distribution, with all grains under 40nm. The photocatalytic efficiency of suspended powders was tested on the decolouration of Orange II aqueous solutions under visible artificial light irradiation. The maximum decolouration reached by the pure TiO2 was 81% at a rate of 3.6×10−3 min−1. Iron doping decreases the photocatalytic activity; the maximum dye degradation was only 43% at a rate of 1.3×10−3 min−1. On the contrary, the performance of Zn-doped titania was better, having a decolouration rate of 17.7×10−3 min−1. [Copyright &y& Elsevier]

Abstract: The photocatalytic behaviour of several commercial titania powders (in aqueous suspension) was evaluated through the decolouration of Orange II aqueous solutions. The performance was correlated with relevant characteristics of the powders, such as crystalline phases, particle size and morphology. The highest efficiency TiO2 powders were those deposited by jet spray on ceramic tiles, and then fired to stabilise the layers. The obtained products were characterised and tested for the photocatalytic degradation of the Orange II dye, in a batch photoreactor under visible light irradiation. Values were compared with those achieved by TiO2 suspensions. The following experimental variables were tested: (i) the amount of deposited titania; (ii) powder manufacturer/source; (iii) firing temperature of deposited layers; and (iv) operation time. Optimal processed layers showed an interesting decolouration performance, as denoted by an attenuation degree of 96% and decolouration rate, assuming an apparent first order reaction, reaching 5.9×10−3 min−1. Thus, these layered ceramic tiles can be considered as an alternative to photocatalytic suspensions of the oxide, with the advantage of avoiding the need to remove any photocatalyst particles at the end of the process. Besides the good photocatalytic performance, the optimized ceramic tiles have an aesthetically pleasing surface, a good adhesion to the substrate, and are easy to clean, thus fulfilling industrial/commercial requirements. [Copyright &y& Elsevier]

Abstract: Inorganic pigments were prepared from industrial wastes: galvanizing sludges resulting from Cr/Ni plating processes (S, G, and T) and a sludge generated from steel wiredraw process that is Fe-rich (F). These industrial wastes were characterized in order to determine the main compositional variations and discover their influence on the colour characteristics of pigments for glazes and ceramics. The toxic character was also investigated and established. Attempting to form the black spinel structure, several combinations of sludges were prepared and then calcined at 1000°C. XRD and microscopy analysis confirmed the presence of nichromite for compositions with higher Ni amounts, while trevorite was detected in iron-rich formulations. The combination of S and F sludges (SF compositions) generates pigments with higher black colorimetric quality, which is similar to, and sometimes better than, a commercial black pigment. Pigments containing GF and TF sludges develop brown hues on glazes and on porcelain stoneware bodies, being this effect more evident upon industrial firing trials. The addition of minor amounts of cobalt or manganese enhances the black coloration, and might adjust some formulation deviations. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports on the use of red mud (RM) in mortars, applying design of experiments. Portland cement was replaced up to 50wt.% RM, adjusting the relative amount of water (34–38wt.%) in order to get mortars with suitable workability as defined by rheometry and flow table measurements. Temperature of hydration, compressive strength and water absorption were also determined. RM decreases the workability and increases the torque, but causes lower impact than water variation. The effect on initial yield stress depends on water content. Mortars with similar spread on table show different behaviour along the rheology test. Values of spread on table follow a quadratic model and RM exhibited an interactive effect with water. RM did not change the hydration process, but above 20% the maximum temperature decreases. The reduction of compressive strength is not constant and depends on the water added. Its variation also follows a quadratic model. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt doped calcium hexaluminate was firstly synthesized using pure reagents; subsequently, the pure reagents were substituted with industrial wastes, the composition of which had been characterized using X-Ray diffraction and X-Ray fluorescence namely, Al-anodising sludge replaced pure aluminium whilst marble cutting rejects and foundry sand were employed as sources of calcite and silica, respectively. As expected, cobalt doped hibonite was the major phase present in calcined powders and displayed an intense blue coloration due to the incorporation of cobalt in tetrahedral positions, as confirmed by transitions from 4A2(F) to the excited 4T1(F) and 4T1(P) states observed from UV–Vis–NIR absorption spectra. The novel waste-derived hibonite pigment showed strong and stable colouring potential when applied in different ceramic supports. [Copyright &y& Elsevier]

Abstract: Especially in rehabilitation works, the use of lime based mortars have been increasing due to the need of compatibility between the old and the new materials. The mortars fresh state properties are extremely important since determines the material workability and also have a great influence on its hardened state characteristics. In this work, the fresh state properties of aerial lime pastes and aerial lime based mortars were investigated. The torque variation with time and the mortar rheological parameters (relative yield stress and plastic viscosity) were obtained using a rheometer suitable for mortars. The correlation of rheological data with slump and relative density measurements was studied. The mortars workability is affected by several parameters, namely, the binder/aggregate and water/binder ratios, the kneading water content, the admixtures type and amount. The admixtures influence (type and amount) on the fresh state properties of aerial lime based mortars are discussed. The used admixtures were the most common ones for several mortars, such as a water-retaining agent, a plasticizer and an air-entraining agent. [Copyright &y& Elsevier]

Abstract: The synthesis and characterisation of chrome-tin red malayaite Ca(Cr,Sn)SiO5 pigments are reported. The novel approach of using a galvanizing sludge from the Cr/Ni plating process as colouring agent is investigated. The ceramic pigments were prepared using a common, solid state reaction process, with optimisation of milling and firing conditions. Characterisation was undertaken using X-ray powder diffraction, diffuse reflectance spectroscopy and application in standard ceramic glazes. The ceramic pigments were of high purity (≥96% malayaite) and developed a burgundy colour due to the occurrence of Cr4+ and Cr3+ and also Ni2+ in the sludge-bearing samples. The hue of the pigments agreed with standard expectations and optimal formulations showed better performance than some commercial pigments, perhaps due to the contribution of nickel. [Copyright &y& Elsevier]

Highlights • Construction wastes were used to produce high moisture buffering capacity. • Addition of H 2 O 2 dramatically enhanced the mortars' moisture buffer value. • Fly ash-based mortars presented low thermal conductivity. Abstract In this study, lightweight waste-based geopolymeric mortars were evaluated for the first time regarding their potential to passively adjust indoor relative humidity (RH) levels. Geopolymer mortars were prepared using a mixture of fly ash (FA) and metakaolin (MK) as a binder, in a proportion of 75:25 wt% (FA:MK), construction and demolition waste as the fine aggregate and a pore forming agent in varying amounts. The results showed that the addition of a pore-forming agent to the compositions considerably increased the moisture buffer value (MBV) of the mortars, that is, from 0.80 (reference mortar) to 5.61 g/m2 Δ%RH (mortar with highest porosity). The moisture buffering capacity shown by these eco-friendly mortars is higher than values reported for other binder materials and can be classified as excellent (MBV > 2 g/m2 Δ%RH). The porous FA-based mortars also presented low thermal conductivity (as low as 0.19 W/m∙K), which suggests that these innovative binders could be simultaneously used for indoor moisture buffering and as low thermal conductivity materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Glass fibre fabrics off-cuts coming from wind turbine blade production were reused. • This waste was used for the first time to produce fibre reinforced geopolymers. • The fabrics significantly increase geopolymers’ flexural strength (up to 144%). • This study provides a sustainable solution for glass fibre off-cuts. • The fabrics reuse enhances the global sustainability of wind energy production. Abstract In this investigation, an innovative and sustainable solution for glass fibre off-cuts is proposed. For the first time, glass fibre fabrics (non-woven mat) produced during wind turbine blade manufacture were used to produce reinforced inorganic polymer composites. The influence of fabric amount on the composites’ microstructure, water absorption, strength and apparent density was investigated. Results show that the fabrics exhibited an impressive flexural strength gain (up to 144%) at the 28th day, when compared to the non-reinforced geopolymer, while simultaneously increasing the composites’ ductility. This feature may extend the application range of such geopolymers. Moreover, the fabric prevents the complete collapse of the composites upon failure, while the matrix alone fails catastrophically under load. [ABSTRACT FROM AUTHOR]