Utilization of air granulated basic oxygen furnace slag as a binder in belite calcium sulfoaluminate cement: A sustainable alternative

Basic oxygen furnace (BOF) slag negatively impacts ordinary Portland cement performance when replacement levels exceed 5%. This necessitates the exploration of alternative applications for the slag. Simultaneously, a high-volume slag utilization is desired to benefit slag recycling as supplementary cementitious materials. Therefore, this study aims to optimize the air granulated BOF slag substitution potential in belite calcium sulfoaluminate cement by investigating the hydration products in standard mortar. The reactivity of the novel binder is correlated with workability, and mechanical performance by thermal, mineralogical, and microstructure analysis. Consequently, the 10–30% replacement delays the final setting time by inhibiting the ettringite formation leading to a decrease in mechanical performance till 28 days. At later ages (28–180 days), the 30–50% substitution exhibited the synergy in mechanical performance, which is attributed to the hydrogarnet, calcium silicate hydrate, and strätlingite formation. Moreover, all the mortar samples exhibited heavy metals’ leaching and drying shrinkage below the permissible limit.</p

Evaluation et contrôle non destructif de combustible nucléaire par ultrasons laser

Le travail de thèse s inscrit dans le cadre d une collaboration entre l industriel AREVA NP et le laboratoire PEC de l université du Maine et a été financée par une convention CIFRE. Ce travail vise à développer des techniques pour le contrôle et l évaluation non destructive de combustible nucléaire, qui sont essentielles à la sûreté des centrales. Le combustible étudié se présente sous la forme de particules sensiblement sphériques d environ 1 mm de diamètre adaptées à une nouvelle génération de réacteurs nucléaires dite High Temperature Reactor (HTR). De plus, il a été effectué des essais de contrôle sur des gaines de Zircaloy conditionnant le combustible actuellement utilisé dans les réacteurs classiques à eau pressurisée. Ces gaines se présentent sous forme de tubes d environ 10 mm de diamètre et 0,5 mm d épaisseur. La technique des ultrasons laser présente l avantage de ne pas nécessiter de contact mécanique. La source laser crée à la surface du matériau un échauffement qui engendre dans celui-ci un champ de contraintes qui se traduit par la propagation d ondes de volume et de surface. En utilisant cette technique, le spectre des vibrations des particules HTR a été mesuré. La modélisation du comportement vibratoire de la particule a été effectuée d une part, en utilisant un calcul par éléments finis et d autre part, en effectuant un calcul analytique des fréquences propres. Plusieurs caractéristiques de la particule HTR peuvent être déterminées par la résolution du problème inverse consistant à recaler les fréquences propres calculées et mesurées. Une approche originale permettant de bien poser le problème inverse, basée sur la méthodologie des plans d expériences est utilisée. La technique des ultrasons laser permet de détecter des défauts sur la couche de céramique qui est essentielle au confinement des produits de fission. Les expériences ont mis en évidence une altération significative du comportement vibratoire en présence d une fissure dans la couche de confinement. La simulation par éléments finis d une particule fissurée, en particulier l observation des déformées modales, permet d interpréter les modifications du spectre vibratoire obtenu expérimentalement. Dans la perspective d une industrialisation du procédé de contrôle, il a été développé un support pour la particule HTR qui permet de manipuler aisément les particules et de ne pas altérer de manière importante leur comportement vibratoire. La technique des ultrasons laser a également été utilisée pour détecter des entailles (1,5mm x 0,1mm x 50 m) situées sur la surface externe et interne d un tube de Zircaloy. Pour cela, il a été employé des ondes guidées se propageant soit selon une génératrice soit dans une direction circonférentielle. Des indicateurs de présence d une fissure ont été dégagés.This research, financed by a CIFRE grant, was carried out in the Laboratoire de Physique de l Etat Condensé (Université du Maine, France) as a response to a request of the AREVA NP company for developing non destructive testing and evaluation (NDT&E) with contactless techniques which would be applied to nuclear fuel to improve nuclear power plants safety. The fuel that is to be controlled is conditioned in the form of ultilayered spherical particles of approximately 1 mm in diameter. This nuclear fuel has been designed for a new generation of nuclear power reactor known as High Temperature Reactor (HTR). In a parallel direction, the laser ultrasonic technique was applied to test Zircaloy pipes (about 9.5 mm in diameter and 0.5 mm in thickness) that are currently used to contain the fuel in the conventional pressurized water reactors. Laser ultrasonics has the advantage to be a contactless technique. The laser source heats up the material s surface and generates an elastic perturbation, that results in the propagation of bulk and surface ultrasonic waves. Using this technique, we have measured the vibrational spectrum of HTR particles. In order to understand the vibrational behaviour and calculate the resonance frequencies of a HTR particle, we have performed simulations using finite elements analysis as well as analytical calculations. By fitting the calculated with the measured vibration frequencies, we have proved that the elastic properties of some layers can be determined. For solving more efficiently the inverse problem, we have used an original approach based on an experimental design methodology. In addition, the laser ultrasonic technique has been applied for non destructive testing of the ceramic layer, the role of which is to contain fission products. The vibrational spectrum of a particle is significantly changed when a micro-crack (damage) is present in the ceramic rigid layer. The finite element analysis simulations of a micro-cracked particle show that changes in some modal structure would explain the appearance of new vibrational frequencies. In order to permit an easy handling of the HTR particles, we have designed a special particle holder, which would be employed for industrial control. While maintaining the particle fixed during de measurement, this holder induces a negligible perturbation in the vibration spectrum. Finally, we have used the laser ultrasonic technique for crack detection (1.5 mm x 0.1 mm x 50 m) located on the external and internal surfaces of Zircaloy tubes. We have generated acoustic waves that can propagate along the circumference or the generatrix of the cylinder. Some indicators of the presence of the crack have been isolated.LE MANS-BU Sciences (721812109) / SudocSudocFranceF

Development and analytical validation of a method for the determination of lead, cadmium, mercury and their isotopes in milk, honey, meat, fish and eggs by icp-ms

recent decades, industrial and urban development has been accompanied by real health problems linked to environmental pollution and the contamination of foodstuffs of animal origin by heavy metals such as lead, cadmium and mercury which are toxic to the immune, hematological, renal and neurological system with a risk of developing cancer in the consumer of contaminated food. The aim of this study was to develop and validate an analytical method to determine the metals Cadmium (111Cd, 114Cd), Lead (208Pb) and Mercury (202Hg) in milk, honey, meat, fish and eggs using inductively coupled plasma mass spectrometry (ICP-MS). For sample preparation, microwave oven digestion with nitric acid and hydrogen peroxide is adopted. The method showed linearity, accuracy and limits of quantification and detection acceptable for LABGTA45 protocol validation of analytical methods in the area of food analysis. Therefore, the method using ICP-MS was developed and validated to determine metals concentrations in food matrixes and the proposed method could be applied in routine analytical laboratory

Laser ultrasonics detection of an embedded crack in a composite spherical particle

International audienc

Trends and opportunities of using local sustainable building materials in the Middle East and North Africa region

International audienceIn recent decades, most of construction activities have been taking place in developing countries such as the Middle East and North Africa region. The expansion in infrastructure has great impact in the technological, social, economic and environmental transformation of this region. Construction sector contribution to Gross Domestic Product (GDP) varies throughout the region and ranges between 2-10%. Currently, sustainable construction requires integrated and comprehensive sustainable design including careful choice of materials and methods. Materials that are locally available and require less energy to produce and transport would pave the way to more sustainable practices. Many countries in the region have realised the benefits of using local building materials on the economy, society and environment. This paper outlines the key trends and opportunities of using sustainable and affordable local building materials in the region to respond to the global climate change crisis and to promote more sustainable and environmentally friendly practices. The current practice of using various building materials such as bio-based materials, treated municipal solid waste incineration bottom ash (MSWI-BA), construction and demolition waste, gypsum-containing by-products (phosphorgypsum, FGD gypsum, borogypsum and others) and rammed earth will be reviewed. It is concluded that the use of these local building materials in construction activities would foster the development of the society. However, some of these materials are already developed and reached the implementation stage while most of them are still at R&D stage. Therefore, there is an urgent need for a comprehensive local and regional strategies to enhance the utilization of these materials

Virgibacillus ainsalahensis sp. nov., a Moderately Halophilic Bacterium Isolated from Sediment of a Saline Lake in South of Algeria

International audienc

Field validation of models for predicting lateral form pressure exerted by SCC

International audienceOne obstacle to increased use of self-consolidating concrete (SCC) in cast-in-place applications is a fear of high, lateral formwork pressure. The literature has repeatedly shown that pressures far lower than hydrostatic can be obtained, but still a widespread concern of high pressure exists. Several models for predicting the lateral pressure when casting SCC have been developed. A number of experts representing these models gathered in Stockholm, Sweden to carry out a field evaluation. Eight instrumented wall elements with various geometries were cast with SCC using different mix designs as well as various casting rates. Pressure transducers were used to determine the lateral pressure. All necessary parameters for the respective models were characterized simultaneously by the participants using samples taken from the same batch. Results show a wide range of form pressures, and the evaluation of the ten included models reveals that all of them predict the lateral form pressure satisfactorily