The future of construction materials research and the seventh UN Millennium. Development Goa l: a few insights

Although the unsustainability of the human civilization has been recognized long ago, little has ever been done to change it. During the last century, materials use increased 8-fold and as a result Humanity currently uses almost 60 billion tons (Gt) of materials per year. The construction industry alone consumes more raw materials than any other economic activity. However, research on construction materials still is excessively focused on their mechanical properties with minor concerns regarding environmental considerations. In September of 2000 189 UN member states signed the Millennium Development Goals (MDGs), in which the seventh goal is related to environmental sustainability. This is a cornerstone event of paramount significance. However, research in the field of the built environment especially on the field of construction materials still seems unable to recognize its importance. This paper provides some insights on future construction materials research priorities in the context of the seventh MDG. It reviews publication patterns on the field of construction materials highlighting investigations gaps and misdirected research lines. It addresses the importance of nano and biotech hot areas and briefly analyzes the gap between research and market use

Biotech cementitious materials : some aspects of an innovative approach for concrete with enhanced durability

The deterioration of reinforced concrete structures is a very common problem due to the fact that this material has a high permeability which allows water and other aggressive media to enter, thus leading to corrosion problems. The use of sealers is a common way of contributing to concrete durability. However, the most common ones are based on organic polymers which have some degree of toxicity. The Regulation (EU) 305/2011 related to the Construction Products Regulation emphasizes the need to reduce hazardous substances. Therefore, new low toxicity forms to increase concrete durability are needed. Recent investigations in the field of biotechnology show the potential of bioinspired materials in the development of low toxic solutions. This paper reviews current knowledge on the use of bacteria for concrete with enhanced durability. It covers the use of bacteria in concrete mix and also biomineralization in concrete surface treatments. Investigation gaps are described. Results from practical applications in which there is exposure to environmental conditions are still needed in order to confirm the importance of this new approach

Valorisation of Phosphorus Extracted from Dairy Cattle Slurry and Municipal Solid Wastes Digestates as a Fertilizer

Phosphorus is a vital cell component and an essential and irreplaceable element. Yet at the current rate of exploitation, the phosphate’s reserves will be fast depleted. Dairy cattle slurry and digestates from anaerobic digestion of municipal solid wastes (MSW) are organic wastes containing phosphorus which can potentially be used as a secondary source of this nutrient. The present study investigated the effect of pH in phosphorus release from these wastes using acid and base extraction followed by phosphorus recovery via precipitation, targeting the production of a fertilizer. Results showed that when using HNO3, 100 % of P content was extracted from dairy cattle slurry (2.0\pH\3.3) and 90 % from MSW digestates (1.2\pH\1.5). The maximum extraction was obtained after 2.5 h for dairy cattle slurry and 48 h for MSW digestates. The extraction efficiencies using NaOH were only 22 % for dairy cattle slurry (12.9\pH\13.4) and 9 % for MWS digestates (13.0\pH\13.4). Phosphorus precipitation from extracted solutions was carried out at a molar ratio of 1:1:1 for Mg:N:P and at pH around 8.0. Analysis of the harvested precipitates by XRD and SEM–EDS ruled out the formation of struvite, but validated the formation of amorphous calcium phosphates, a potential fertilizer that can help to close the cycle of this nutrient. During the process, heavy metals might become enriched in the precipitates. In the perspective of producing a fertilizer this is an undesirable process, and one that should be taken into account when considering phosphorus recovery from wastes.info:eu-repo/semantics/publishedVersio

Are geopolymers more suitable than Portland cement to produce high volume recycled aggregates HPC?

The 70% minimum construction and demolition wastes-C&DW recycling rate set by the Revised Waste framework Directive No. 2008/98/EC to be enforced beyond 2020, will increase the need of effective recycling methods in a dramatic manner. So far, recycled aggregates (which constitute the majority of C&DW) are reused in low volume percentages for average compressive strength concretes and mostly as road sub-base and back-fill material which, in turn, constitutes a down-cycling option. Most investigations related to concrete made with recycled aggregates use aggregates produced in laboratory context which are not contaminated at all. It is then no surprise to find out that some investigations shows the potential to reuse as much as 100%, however, industrially produced recycled aggregates contain a certain level of impurities that can be deleterious for Portland cement concrete, thus making very difficult for the concrete industry to use such investigations unless uncontaminated recycled aggregates are used. This paper reviews current knowledge on concrete made with recycled aggregates, with a special focus on the crucial importance of impurities presence and how those aggregates are not suitable for the production of HPC. Also, the potential of geopolymers to produce HPC based on high volume recycled aggregates is discussed

Role of the mixing conditions and composition of galvanic sludges on the inertization process in clay-based ceramics

Hydroxide-metal sludges from electroplating industry are a potential source of environmental contamination due to their high content of heavy metals. The incorporation of these residues in a ceramic matrix can be a promising way to suppress the harmful effect of metals normally present in those sludges. This work reports the role of the mixing time between the waste and ceramic materials and of the calcination step on the fixing level of several metal-containing species (Al, Zn, Ni, Fe, Ca, Cu, Cr) after sequential leaching in different media (aqueous, acetate and citrate). A strong and/or long mixing process will promote the deagglomeration of the coarser agglomerates and then will increase the reactivity of remaining grains towards the ceramic material during the calcination. As a consequence, inertization is improved for fired samples. With non-calcined samples leaching increases as a result of increasing dispersability/availability of species

Solvent extraction aplied to the recovery of heavy metals from galvanic sludges

In this study, a hydrometallurgical treatment involving the solvent extraction and recovery of some heavy metals from a sulphuric acid leach solution of galvanic sludge, using di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and bis-(2,4,4- trimethylpentyl)-phosphinic acid (Cyanex 272), both diluted in kerosene, has been investigated. The preliminary tests revealed the necessity to remove other metal species than zinc and nickel, contained in the leach solution, and therefore, processes to cement copper and precipitate chromium were then applied to finally obtain a Zn and Ni pregnant solution prior to solvent extraction. For the experimental conditions studied, Cyanex 272 showed a good recovery of Zn after the stripping stage using H2SO4, but D2EHPA effectively promoted a higher Zn extraction than Cyanex 272 did. The dependence of the solvent extraction method on variables such as pH, contact time and concentration of extractant, as well as the effect of different concentrations of sulphuric acid on stripping, are discussed. The discussion also includes the previous conditions developed to separate the main interfering metallic species from the leach solution in order to improve the extraction and recovery of zinc by solvent extraction. The final objective has been to achieve a solution as pure as possible to recover nickel sulphate.Estudou-se o desenvolvimento de um processo metalúrgico para a extracção de metais a partir de lamas galvânicas, passando por fases e extracção com solventes orgânico

An overview on concrete carbonation in the context of eco-efficient

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

Effect of experimental variables on the inertization of galvanic sluges in clay-based ceramics

The incorporation of several industrial wastes in ceramic matrixes had been attempted as an effective low expense technique for the fixation of metallic species in usable products or simply to reduce the residue volume for further disposal. However, the dominant mechanism of the inertization process and the relevant influent parameters are still unknown, mostly due to the complexity of the systems. This work reports the effect of several processing parameters such as the mixing time, the calcination temperature and duration, the relative amount of sludge, and the physical aspect of the sample (powdered or pressed pellets) on the fixing level of relevant species (SiO2, SO4 2−, Zn, Ni, Ca, Cu, Cr) by leaching in different media (aqueous, acetate, and citrate). Statistical tools were used to define the relevance of each experimental variable on the inertization process of the used galvanic sludge. The relative amount of sludge in the mixture, the calcination temperature and the agglomeration state of the sample were found to be the most influent parameters of the inertization process. The incipient reaction between sludge and ceramic matrix components points out for the dominance of a macro- encapsulation mechanism

Effect of waste glass (TV/PC cathodic tube and screen) on technological properties and sintering behaviour of porcelain stoneware tiles

In the present work, the effects of TV and PC cathodic tube and screen glasses additions (5 and 10 wt.%) to a porcelain stoneware body, in replacement of feldspar, were evaluated simulating the tilemaking process. The presence of glass allows to preserve good technological and mechanical properties, complying with the latest requirements of the industrial practice. The sintering pattern of the glass-added bodies, evaluated by hot stage microscopy, is modified according to the different glass amount and typology; in particular, cathodic tube glass when present at 5 wt.% brings about a lowering of the maximum densification temperature and of the activation energy

Physical and chemical characterisation of metal finishing industrial wastes

In EU countries approximately 150,000 ons/year of galvanic sludges are generated by 4000 industrial units from the orresponding wastewater treatment plants. These sludges are generally classified as hazardous (European Waste Catalogue as adopted in Council Decision 2000/532/CE and as amended by Decisions 2001/118/EC, 2001/119/EC and 2001/573/CE), basically due to the presence of heavy metals. This work attempts to better understand the physical and chemical characteristics of these sludges, by studying 39 samples collected in different Portuguese industries that should represent all kinds of similar wastes independent of their place of generation. Chemical composition and leaching characteristics are given, together with density, grain size distribution, and specific surface area values. Statistical analysis was used for grouping the wastes according to chemical parameters, which might be useful to predict potential reuse as raw materials for different applications