Publications Internationales
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Item Synthesis and Characterization of Twin Barrel-Like Tungsten Trioxide Obtained by Hydrothermal Treatment(Pleiades Publishing, 2025) Amokrane, Sonia; Hamidouche, Fahim; Irekti, Amar; Saadi, Souad; Meguellati, Zineb; Bouguerra, Kaouthar; Hammadou, Souad née MesdourVarious methods have been presented lately in literature for the elaboration of tungsten oxide (WO3) materials. Herein, WO3 was prepared under properly controlled conditions by hydrothermal route, using Na2WO4·2H2O as a raw material in the presence of different structure directing agents (SDAs) and by acidifying the medium with nitric acid to pH 1. The influence of the SDAs on the structure and morphology of the obtained tungsten oxide has been investigated by scanning electron microscopy (SEM), micro-Raman spectroscopy and X-ray powder diffraction. The obtained WO3 materials have a barrel-like morphology independently of the SDA used. However the crystalline structure obtained is a pure hexagonal WO3 with CoSO4·7H2O, CuSO4·5H2O, ZnSO4·7H2O and Zn(CH3COO)2·2H2O and a hydrated hexagonal WO3: WO3·1/3H2O with MnCl2·4H2O. The results demonstrate a noteworthy effect of the SDA anion on the crystalline structure of the synthesized tungsten oxide as compared to the minor effect from the cation of the SDA. Furthermore, a formation mechanism of the nanobarrel WO3 is proposedItem Durability Indices of a Sealing Mortar Incorporating Blast Furnace Slag(2025) Ikhaddalene, Soumia; Irekti, Amar; Oualit, MehenaGround granulated blast furnace slag generated from steel manufacturing presents environmental challenges, but it can be valuable when utilized as a supplementary material in concrete, contributing to the development of sustainable materials. In this research, a new sealing mortar was prepared by substituting 10% of the cement with slag (M10). This material can provide performance comparable to M234, a M0 sealer used for sealing and wedging supports and machine bases. The mechanical properties and durability indices of both M10 and M234 were compared to the reference mortar MISO, which is a laboratory-made mortar free of slag. XRD analysis was conducted to determine the crystallinity of the starting cement, and granulometry revealed a median size distribution of 23 μm for the slag after grinding. Capillary absorption and water-accessible porosity were tested for all samples.Item Co-Precipitation Synthesis of NiFe2O4 Using NH4HCO3 as Precipitant: Characterization and Photocatalytic Degradation of Organic Pollutant(Pleiades Publishing, 2024) Saadi S.; Kezzim A.; Irekti, Amar; Nas, Mehmet Salih; Guettaf, M.Structural properties and the photocatalytic activity of the synthesized NiFe2O4 via co-precipitation process using NH4HCO3 as a precipitating agent were studied. The resulting sample was calcined at 550°C and the formation of pure ferrite phase with spinel structure was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy methods. The morphology of this spinel was investigated using a scanning electron microscopy (SEM). The optical absorption spectroscopy obtained the optical band gap (Eg = 1.81 eV). This material was applied as a photocatalyst for the photodegradation under UV light of Congo Red (CR) a persistent and recalcitrant dye. The effect of catalyst dose, initial concentration, and pH on photocatalytic degradation was investigated. Degradation efficiency of 82% was achieved for 3 h with a catalyst dose of 0.5 g/L. Furthermore, the material exhibited better photocatalytic activity in an alkaline medium, and the degradation kinetics followed a pseudo-first-order reaction.Item Mechanical performance of metakaolin-based geopolymer mortar blended with multi-walled carbon nanotubes(Elsevier, 2022) Oualit, Mehena; Irekti, AmarIn recent decades, the cement industry has been viewed as a major environmental problem mainly due to carbon dioxide CO2 emissions during the production of Portland Cement (PC). Among the solutions to this problem is to replace Portland cement-based materials with alkali-activated materials. Metakaolin-based geopolymer mortars are currently considered a serious alternative to ordinary Portland cement mortar due to its various advantages. The present experimental study aims to develop metakaolin-based geopolymer mortars reinforced with multi-walled carbon nanotubes (MWCNTs). The content of MWCNTs incorporated was 0.1; 0.2; 0.3, and 0.4 wt%, respectively, with respect to the mass of metakaolin. A mixture without the addition of carbon nanotubes was also prepared and used as a reference (control sample). The alkaline activation of metakaolin was carried out using aqueous sodium silicate solution having a molar ratio (SiO2/Na2O) equal to 1.77. Mechanical characterization of the hardened samples was performed after curing for 3, 7 and 28 days. The results indicate that the incorporation of multi-walled carbon nanotubes in the geopolymer matrices improves compressive strength. Microscopic analysis has shown that these carbon nanotubes contribute to the densification of the geopolymer matrix and give rise to crack bridging mechanisms. The highest value of the compressive strength was recorded using an alkali silicate content equal to 8 (expressed as a percentage of Na2O) combined with 0.2% of multi-walled carbon nanotubes in the geopolymer mortar. The integral absolute error (IAE) calculated on the compressive strength values at different curing ages are all within an acceptable range (0–10%)Item Synthesis and rheological properties of magnetic chitosan hydrogel(Budapest University of Technology and Economics, 2021) Ikhaddalene, Soumia; Zibouche, Fatima; Ponton, Alain; Irekti, Amar; Carn, FlorentThe aim of the present work is first to synthesis a magnetic chitosan hydrogel (chitosan ferrogel) using the blending method and second to study it rheological behavior. Magnetic components ( maghemite particles γ-Fe 2 O ) were synthesized via a simple chemical co-precipitation route also called Massart's procedure. Before being dispersed in chitosan network, γ-Fe 3 2 O particles were covered with a cationic polyelectrolyte (Polydiallyldimethylammonium chloride; PDADMAC) and the exact quantity required to cover the entire surface of maghemite particles was determined by Electrophoretic mobility. The successful functionalization of maghemite particles was confirmed by zeta potential measurement. The prepared ferrogel was gelified using glyoxal as crosslinking agent. The effect of continuous magnetic field on rheological properties of the elaborated ferrogel was studied, under controlled temperature before and after the gelation process, using a rotating rheometer fitted with a new magneto-rheological cell. Moreover the influence of iron oxide content on the gelation time of magnetic hydrogel was studied by comparing two ferrogels with different maghemite particles content. Flow and viscoelastic measurements showed that applying magnetic field facilitates the formation of a new structure (columnlike arrangements), which was confirmed by in situ optical microscopic observation. Kinetic study was investigated by mechanical spectroscopy and demonstrates that the gelation time depends on both iron oxides content and magnetic fieldItem Strength and setting times of Metakaolin-Cement-Based geopolymer pastes(2017) Oualit, Mehena; Irekti, Amar; Jauberthie, RaoulThe objective of this research is, in a first time, to synthesize geopolymer materials from two types of activator concentrated solutions prepared respectively with two different bases (NaOH and KOH). These solutions have been mixed thereafter with a kaolin previously heated under 550°C in order to obtain geopolymers samples, while optimizing the Si/Al ratio. Secondly, the influence of the partial substitution of metakaolin by a Portland cement has been studied in order to reduce the curing time of geo-polymer pastes. Thereafter, mechanical properties of the specimens at hardened state, notably the compressive strengths and the resistances on traction are investigated. The results showed that the use of the activator solution containing KOH during the preparation of the activator solution increases the solubility between KOH and silica gel. However, the solution based on sodium hydroxide (NaOH) promotes obtaining better mechanical resistances in the geopolymer materials. Otherwise, the partial substitution of metakaolin by Portland cement (PC) reduces the setting time of pastes and improves the mechanical resistances of hardened specimens but to a certain percentage before inverse effect appears. Finally, recommendations and perspectives are proposed in relation with the used raw materials and the mechanical performances of the geo-polymers materials foundItem Performance of recycled asphalt mixtures formulated with modified bitumen(Gheorghe Asachi Technical University of Iasi, Romania, 2019) Oualit, Mehena; Irekti, Amar; Hami, BrahimThe maintenance of flexible roads or roads at end of life service generates high quantities of reclaimed asphalt pavement every year. The reuse of these materials, considered for a long time as waste, allows a substantial saving in transport, energy, and maintains dwindling natural resources. Recycling of asphalt also helps to reduce inert waste storage volumes, and conserve valuable landfill space. The applicability of recycled asphalt was tested in laboratory, and asphalt mixtures containing 20%, 40% and 50% of reclaimed asphalt pavement (RAP) were designed. Marshall and Duriez tests have been performed on various formulations using paving grade bitumen and modified bitumen as binders, the latter contains a quantity of Styrene /Butadiene / Styrene (SBS) polymer. This investigation led to the conclusion that the performance of recycled asphalt mixture containing 20% of RAP is significantly closer to those obtained with virgin asphalt mixture without recycled materials. In addition, the use of SBS polymer improves the properties of recycled asphalt mixtures even with high amounts of reclaimed asphalt pavement.Item Effect of Black Liquor from Date Palm on the Workability and Compressive Strength of Portland Cement and Concrete(De Gruyter Open Sp. z o.o., 2019) Irekti, Amar; Oualit, M.; Siahmed, H.; Buncianu, D.; Zibouche, FatimaLignin is the second most abundant natural polymer. Due to the high content of carbon and hydrogen (C-H, C-C, C=O), it can be used as a potential dispersant for cement matrix. The objective of this study is to extract lignin from date palm and study its effect in the form of black liquor (BL) on the rheological and physic-mechanical properties of the cements and concrete. The lignin in black liquor form represents approximately 30 wt% dry weight of date palm. It is a heteropolymer composed primarily of methoxylated phenylpropylene alcohol monomeric units interconnected by a variety of stable carbon-carbon and carbon-oxygen-carbon (ether and esters) linkages. The results found show the positive effect on the workability of cement and concrete and confirms its dispersion effect by improving compressive strength of concrete during the early and the later ages of hydration.Item Etude expérimentale du comportement diélectrique et thermique des nano composites hybrides à matrice époxyde chargée(2014) Irekti, Amar; Bezzazi, Boudjema; Aribi, Chouaib; Zibouche, FatimaItem Saturation point of superplasticizers determined by rheological tests for self compacting concrete(Budapest University of Technology and Economics, 2017) Oualit, Mehena; Irekti, Amar; Melinge, YannickThe dosage of superplasticizer is first determined in mortar mixtures and it is after adjusted in concrete mix trials. Other self compacting concrete (SCC) mix proportioning methods rely on the definition of the superplasticizer saturation dosage in pastes. These approaches to mix design have advantages over the ones based exclusively on concrete batching because it is less expensive and material demanding to perform tests in mortar and paste than in concrete. This paper presents the results of an experimental research carried out to investigate the use of tests performed in paste to define the optimum dosage of superplasticizer for self-compacting concrete. The materials employed were Portland cement, pozzolana and three types of superplasticizers: poly naphthalene sulfonate (PNS), poly melamine sulfonate (PMS) and a polycarboxylate. The saturation point of each superplasticizer was determined in pastes by rheological tests using a coaxial cylinder rheometer AR2000. Self-compacting concretes were prepared using the superplasticizer contents found. The results obtained led to the conclusion that in SCC mixture proportioning methods, the determination of the superplasticizer content in the paste phase is paramount. Nevertheless, final adjustment of w/c+f ratio was always needed in order to produce SCC