COMPORTEMENT A LA CORROSION DES REVETEMENTS A BASE DE NICKEL ET DE CHROME SUR DES SUBSTRATS DE CUIVRE

Le besoin d'améliorer les revêtements pour une meilleure résistance à la corrosion a permis le développement des dépôts électrolytiques composites par l’incorporation de Cr2(SO4)3 ; 6H2O dans la structure du nickel.L’objet de notre travail est l’élaboration et la caractérisation des dépôts composites nickel-chrome sur un substrat en cuivre afin d’étudier leurs comportement à la corrosion. Ces dépôts sont obtenus à partir de bains de watts d’électrodéposition.La caractérisation est faite par des méthodes conventionnelles telles que la diffraction des RX, la microscopie électronique à balayage MEB et l’EDS.Les tests de corrosion ont été faits dans une solution de 3,5% NaCl. Les techniques utilisées sont celles de la polarisation et de l’impédance. Les résultats obtenus ont révélé une résistance à la corrosion élevée des dépôts composites

Influence du type d’addition minérale sur les propriétés de transfert des Bétons AutoPlaçants Influence of the type of mineral admixtures on the transport properties of self compacting concrete

La formulation des bétons autoplaçants (BAP) présente certaines spécificités dont un volume élevé de pâte et une quantité importante d’ajouts minéraux. Ces deux paramètres influencent sensiblement les propriétés de transfert de ces bétons. Dans ce travail, nous avons étudié l’influence de la nature et du pourcentage de plusieurs additions minérales sur certaines propriétés de transfert (la diffusion des ions chlore et la perméabilité au gaz) des BAP. Trois différentes additions minérales ont été testées : des fillers calcaires, de la pouzzolane naturelle et des cendres volantes. Ensuite, nous avons cherché une probable relation analytique entre ces propriétés et la résistance à la compression de ces bétons. Au total, douze formulations ont été étudiées, elles couvrent trois différentes classes de résistances (30 MPa, 50 MPa et 70 MPa) et quatre types de bétons: un béton ordinaire vibré, un BAP à base de pouzzolanes naturelles, un BAP à base de fillers calcaires et un BAP à base de cendres volantes. Les résultats montrent que la nature de l’addition minérale dans les BAP influe considérablement sur les propriétés de transferts de ces bétons. Après 28, 90 et 360 jours de cure, les BAP contenant de la pouzzolane naturelle représentent des performances très comparables à celles obtenues sur des BAP à base de cendres volantes et bien meilleures que celles obtenues sur des BAP formulés avec du filler calcaire. Indépendamment du type d’addition minérale, les résultats confirment l’existence d’une forte corrélation entre le développement de la résistance à la compression et les propriétés de transferts des BAP. Formulation of self compacting concrete (SCC) has some specific characteristics including a high volume of paste and a large amount of mineral admixtures. These two parameters influence significantly the transport properties of SCC. In this work, we studied the influence of nature and the percentage of several mineral admixtures on some transport properties (the ions diffusion and chloride gas permeability) of the SCC. Three different mineral additives were tested: the limestone fillers, the natural pozzolan and the fly ash. Then we looked for the analytical relationship between these properties and the compressive strength of concrete. A total of twelve formulations were studied, they cover three different compressive strength classes (30 MPa, 50 MPa and 70 MPa) and four types of concrete: ordinary vibrated concrete, a SCC containing natural pozzolan, a SCC based with limestone fillers and SCC containing fly ash. The results show that the nature of the mineral admixtures in SCC influence on the transport properties of these concretes. After 28, 90 and 360 days of curing, the SCC containing natural pozzolan represent very similar performance to those obtained on SCC containing fly ash and much better than those obtained on SCC formulated with limestone filler. Regardless of the type of mineral admixtures, the results confirm the existence of a strong correlation between development of compressive strength and transport properties of SCC

Influence du type d’addition minérale sur les propriétés de transfert des Bétons AutoPlaçants

La formulation des bétons autoplaçants (BAP) présente certaines spécificités dont un volume élevé de pâte et une quantité importante d’ajouts minéraux. Ces deux paramètres influencent sensiblement les propriétés de transfert de ces bétons. Dans ce travail, nous avons étudié l’influence de la nature et du pourcentage de plusieurs additions minérales sur certaines propriétés de transfert (la diffusion des ions chlore et la perméabilité au gaz) des BAP. Trois différentes additions minérales ont été testées : des fillers calcaires, de la pouzzolane naturelle et des cendres volantes. Ensuite, nous avons cherché une probable relation analytique entre ces propriétés et la résistance à la compression de ces bétons. Au total, douze formulations ont été étudiées, elles couvrent trois différentes classes de résistances (30 MPa, 50 MPa et 70 MPa) et quatre types de bétons: un béton ordinaire vibré, un BAP à base de pouzzolanes naturelles, un BAP à base de fillers calcaires et un BAP à base de cendres volantes. Les résultats montrent que la nature de l’addition minérale dans les BAP influe considérablement sur les propriétés de transferts de ces bétons. Après 28, 90 et 360 jours de cure, les BAP contenant de la pouzzolane naturelle représentent des performances très comparables à celles obtenues sur des BAP à base de cendres volantes et bien meilleures que celles obtenues sur des BAP formulés avec du filler calcaire. Indépendamment du type d’addition minérale, les résultats confirment l’existence d’une forte corrélation entre le développement de la résistance à la compression et les propriétés de transferts des BAP

Characterisation and standardisation of different-origin end-of-life building materials toward assessment of circularity

YesConstruction and demolition waste (CDW) management and recycling practices are crucial for transitioning to a circular economy. This study focuses on the detailed characterization of CDWs, including hollow brick (HB), red clay brick (RCB), roof tile (RT), concrete (C), and glass (G), collected from seven different sites. The CDWs were characterized based on particle size distribution, chemical composition, and crystalline nature. Pozzolanic activity was evaluated through compressive strength measurements of cement mortars with 20% cement replacement by CDWs at 7, 28, and 90 days. The results showed that clayey CDWs exhibited similar physical/chemical properties and crystalline structures. Compositions of Cs varied significantly based on their original materials. CDWs satisfied the minimum strength activity index for supplementary cementitious materials, with pozzolanic activity influenced by fineness and SiO2+Al2O3 contents. The average strength activity indexes for HB, RCB, RT, C, and G were 84.5%, 86.3%, 83.4%, 80.7%, and 75.8%, respectively. Clayey CDWs contributed to mechanical strength development, while Cs' contribution was related to hydration of unreacted cementitious particles. G exhibited the weakest pozzolanic activity due to its coarser particle size. Overall, CDWs demonstrated suitable properties for use as supplementary cementitious materials in PC-based systems

Influence of Mineral Admixtures on the Permeation Properties of Self-Compacting Concrete at Different Ages

International audienceDue to its specific properties, the study of self-compacting concrete (SCC) represents an area of research that has strong potential for development. However, in spite of the interest of researchers in this new material, SCC has not yet gained universal acceptance as a construction material, and its application remains limited. The development of an economical SCC with interesting properties in the fresh and hardened state is important for the acceptance of such a concrete. Algerian natural source Pozzolan is rarely used in SCC due to the absence of any thorough study of its properties. This study investigates the permeation properties of SCC mixtures made with this Algerian natural Pozzolan, compared with conventional vibrated concrete and other SCC mixtures containing fly ash or limestone filler. Additionally, the correlations between chloride diffusion and sorptivity, and between apparent gas permeability and chloride diffusion, were investigated. Results indicate that, despite its economic benefits, SCC incorporating natural Pozzolan presents very low permeation properties (for example: lower migration coefficients compared to the SCC mixtures with limestone filler or ordinary vibrated concrete (difference > 50 % for results of the 30 MPa strength class). The relation between chloride diffusion and sorptivity, and between apparent gas permeability and chloride diffusion, is also confirmed

Effect of mineral admixture on resistance to sulphuric and hydrochloric acid attacks in selfcompacting concrete

International audienceThis paper presents a detailed experimental investigation of the acid resistance of economical self-compacting concrete (SCC) prepared with natural pozzolan, immersed for up to 12 weeks in sulphuric acid (H2SO4) and hydrochloric acid (HCl) solutions. The results are compared with those from a control concrete and other SCCs prepared with fly ash and limestone filler. The different factors considered in this study were the effect of mineral admixture type and the strength classes (30, 50, and 70 MPa) of the concrete specimens. In total, 12 formulations were tested. Mass and compressive strength losses are the main properties investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were used to better understand the kinetics of deterioration of each type of concrete. The results show the positive influence of natural pozzolan on the behaviour of SCC under both sulphuric and hydrochloric acid mediums

Influence du type d'addition minérale sur les propriétés de transfert des Bétons AutoPlaçants

International audienceLa formulation des bétons autoplaçants (BAP) présen te certaines spécificités dont un volume élevé de pâte et une quantité importante d'ajouts m inéraux. Ces deux paramètres influencent sensiblement les propriétés de transfert de ces bét ons. Dans ce travail, nous avons étudié l'influence de l a nature et du pourcentage de plusieurs additions minérales sur certaines propriétés de tra nsfert (la diffusion des ions chlore et la perméabilité au gaz) des BAP. Trois différentes add itions minérales ont été testées : des fillers calcaires, de la pouzzolane naturelle et des cendre s volantes. Ensuite, nous avons cherché une probable relation analytique entre ces propriétés e t la résistance à la compression de ces bétons. Au total, douze formulations ont été étudiées, elle s couvrent trois différentes classes de résistances (30 MPa, 50 MPa et 70 MPa) et quatre ty pes de bétons: un béton ordinaire vibré, un BAP à base de pouzzolanes naturelles, un BAP à base de fillers calcaires et un BAP à base de cendres volantes. Les résultats montrent que la nature de l'addition minérale dans les BAP influe considérablement sur les propriétés de transferts de ces bétons. Apr ès 28, 90 et 360 jours de cure, les BAP contenant de la pouzzolane naturelle représentent d es performances très comparables à celles obtenues sur des BAP à base de cendres volantes et bien meilleures que celles obtenues sur des BAP formulés avec du filler calcaire. Indépendammen t du type d'addition minérale, les résultats confirment l'existence d'une forte corrélation entr e le développement de la résistance à la compression et les propriétés de transferts des BAP

Influence Of Natural Pozzolan On The Behavior Of Self-Compacting Concrete Under Sulphuric And Hydrochloric Acid Attacks, Comparative Study

International audienceAcidic attack is a topic of increasing significance, owing to the spread of damage to concrete structures in both urban and industrial areas. Mineral addition type is an important factor affecting performance of Self-Compacting Concrete (SCC) in an aggressive environment. Pozzolan from natural sources in Algeria is rarely used in SCC due to the absence of a thorough study of its properties. The goal of this study was to compare the hydrochloric and sulphuric acid behaviors of a SCC-containing Algerian natural pozzolan with SCC-containing fly ash and limestone filler additions. For this purpose, twelve formulations were prepared with three different strength classes (30, 50, and 70 MPa). After 28 days of curing, the samples were immersed in hydrochloric sulfuric acid solutions for a period of 12 weeks. The changes in mass loss and compressive strength loss for each acid solution within the test period were recorded. The Scanning Electron Microscope (SEM) and XRD analysis were used to better understand the mechanism of deterioration of each type of concrete. In spite of their economical properties, the results confirm that the use of Algerian natural pozzolan contributes to the improvement of resistance of SCC under sulphuric and hydrochloric acid attack

Influence of pumice and zeolite on compressive strength, transport properties and resistance to chloride penetration of high strength self-compacting concretes

International audienceThis paper investigates the effect of two different natural pozzolan (pumice and zeolite) on compressive strength (fc), transport properties and resistance to chloride penetration both in immersion and tidal conditions when used in high strength self-compacting concrete (HSSCC). First, the chemical and mineralogical composition as well as the microstructure and the pozzolanic activity of the natural pozzolan are studied. Then, two percentages, 10% and 15%, of pumice and zeolite instead of Portland cement in HSSCC are investigated. Five concrete mixtures with a control mixture without any pozzolan are prepared and tested in both fresh and hardened states. The results show that the studied zeolite is a clinoptilolite that presents higher pozzolan activity compared to pumice. However, the compressive strength of mixtures containing zeolite remains low compared to control mixture. On the contrary, mixtures with pumice present compressive strength values close or higher than the ones of the control mix at both early and long term ages with a remarkable increase at long term. For durability purposes, the transport properties of the different mixtures are studied through capillary absorption, water absorption, water penetration, electrical resistivity, chloride migration and diffusion tests. The results show that, both pumice and zeolite pozzolan are found to have a significant effect on the increase of the resistance to chloride penetration in both immersion and tidal conditions. However, zeolite mixtures exhibit better resistance. This research shows that, the substitution of Portland cement by 15% of pumice or 10% of zeolite in HSSCC is affordable in all aspects. © 2017 Elsevier Lt

Characterization of the degradation of self-compacting concretes in sodium sulfate environment: Influence of different mineral admixtures

International audienceThe effects of the type of mineral addition on the behavior of SCCs in sodium sulfate environments were studied. Three strength classes (30 MPa, 50 MPa and 70 MPa) and three different mineral additions were investigated: limestone filler, fly ash and natural pozzolan. The results were compared to those of vibrated concretes. Compressive strength, mass and dimensional changes dues to sodium sulfate attack were determined. The microstructure was studied using SEM-EDS and XRD analysis. For 720 days of immersion in 5% Na2SO 4 solution, the penetration depth of sulfate in different samples was quantified using SEM-EDS. The results were consistent with those of XRD analysis. This study shows the benefic effect of the incorporation of a natural pozzolan as a mineral admixture in SCC on the resistance of these concretes in sodium sulfate medium. SCCs with natural pozzolan present characteristics very comparable with those of SCC mixtures with fly ash. It appears that the use of vibrated concretes or SCC with limestone filler, especially with low compressive strength, in a rich sodium sulfate environment is not recommended