Synthesis and characterization of belite calcium sulfoaluminate cements produced by oxyfuel combustion residues

In this work, the possibility of reusing ashes issued by an oxyfuel combustion process (OC) as a source of material in the production of belite calcium sulfoaluminate BCSA cements has been investigated. OF process is one of the most promising combustion technologies for CO2 reduction from power plants. Combustion tests were carried out in an oxyfuel bubbling fluidized bed pilot plant. Four BCSA clinker-generating raw mixes were heated in a laboratory electric oven in the temperatures range 1150°-1350°C: one included only natural materials (limestone, clay, bauxite and gypsum), the others contained OC ashes as total substitute for clay. X-ray diffraction (XRD) analysis on the burning products showed high conversion of reactants toward the main BCSA clinker components (C2S and C4A3$), especially at 1200° or 1250°C. Moreover, physical-mechanical tests associated with XRD and differential thermal-thermogravimetric analyses accomplished on all the cements (obtained by adding natural gypsum to the clinkers produced at the best synthesis temperatures) generally displayed a similar hydration behaviour

Li+ distribution into V2O5 films resulting from electrochemical intercalation reactions

We studied interface effects of thin film V2O5 electrodes on top of indium tin oxide (ITO) glass for Li intercalation by means of a combination of methods: depth-profiling by secondary ion mass spectroscopy (SIMS), electrochemical insertion-extraction of lithium ions by slow-scan cyclic voltammetry (SSCV) and by potentiostatic intermittent titration technique (PITT). We show that the Li+ distribution inside the oxide film is always far from homogeneous, and that different diffusion paths (parallel to interfaces as well as perpendicular to them) have to be considered in experiments with electrodes having areas of few cm². The exposed edge formed when cutting out coupons from the coated glass plate supporting the V2O5 electrode plays a significant role in the process, because it exposes the V2O5-ITO interface to the electrolyte.Estudamos os efeitos de interface de filmes finos de eletrodos de V2O5 sobre vidros com óxido de índio-estanho (ITO) para intercalação de Li utilizando combinações de métodos: perfil de profundidade por espectrometria de massas de íons secundários (SIMS), inserção-extração eletroquímica de íons lítio por voltametria cíclica de varredura lenta (SSCV) e por técnica de titulação potenciostática intermitente (PITT). Nós demonstramos que a distribuição de Li+ no interior do filme de óxido é sempre distante de ser considerada homogênea e que diferentes etapas de difusão (paralelas às interfaces e bem como perpendiculares a elas) são consideradas por conter áreas de alguns cm² em experimentos com eletrodos. A margem exposta pelo corte da placa de vidro revestida com ITO e recoberta com V2O5 desempenha um papel importante no processo, pelo fato de expor a interface V2O5-ITO ao eletrólito.66767

Use of Potabilized Water Sludge in the Production of Low-Energy Blended Calcium Sulfoaluminate Cements

Ordinary Portland cement (OPC) manufacture determines about 8% of the global anthropogenic CO2 emissions. This has led to both the cement producers and the scientific community to develop new cementitious materials with a reduced carbon footprint. Calcium sulfoaluminate (CSA) cements are special hydraulic binders from non-Portland clinkers; they represent an important alternative to OPC due to their peculiar composition and significantly lower impact on the environment. CSA cements contain less limestone and require lower synthesis temperatures, which means a reduced kiln thermal energy demand and lower CO2 emissions. CSA cements can also be mixed with supplementary cementitious materials (SCMs) which further reduce the carbon footprint. This article was aimed at evaluating the possibility of using different amounts (20 and 35% by mass) of water potabilization sludges (WPSs) as SCM in CSA-blended cements. WPSs were treated thermally (TT) at 700° in order to obtain an industrial pozzolanic material. The hydration properties and the technical behavior of two different CSA-blended cements were investigated using differential thermal–thermogravimetric and X-ray diffraction analyses, mercury intrusion porosimetry, shrinkage/expansion and compressive strength measurements. The results showed that CSA binders containing 20% by mass of TTWPSs exhibited technological properties similar to those relating to plain CSA cement and were characterized by more pronounced ecofriendly features