Browsing by Author "Hammas, Aghiles"

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    Compatibility of Slag-Blended Cement with Polycarboxylate Ether Superplasticisers: Rheological Properties Study
    (2021) Chalah, Kaci; Abdelbaki, Benaoumeur; M’hamed, Mahdad; Akkouche, Ali; Hammas, Aghiles
    The compatibility of slag blended-cement (SBC) with superplasticisers was investigated using rheological measurements. Accordingly, continuous flow tests and thixotropic behaviors were studied for different ages of hydration. In this work, the slag was used in the range of 0-40% in order to substitute the ordinary Portland cement (OPC). Two polycarboxylates ether superplasticisers (PCEs) were used, the acrylic copolymer (PA) and modified polycarboxylate (PC). The saturation point of each superplasticiser was determined on pastes by rheological tests, it is 2% on amount of cement, and the water/cement report is equal to 0.35. The investigation was carried out using a rotational rheometer AR2000 with coaxial cylinders’ geometry. The results showed that the PC- admixture is more efficient than the PA-admixture in OPC; the consistence was consecutively 4.75 Pa.s and 10.45 Pa.s. In addition, the fluidizing effect of the admixtures on cement pastes is conditioned by the presence of slag. The use of PA-admixture in SBC improved rheological properties. However, the use of PC-admixture in SBC increased greatly the viscosity, which involves an incompatibility, the thixotropy increment was from 46898.9 Pa/s (F4) to 59690.1 Pa/s (F9).
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    Coulage en bande et anisotropie des céramiques multimatériaux
    (Université M'Hamed Bougara Boumerdès, 2021) Hammas, Aghiles; Zibouche, Fatima(Directeur de thèse)
    Ces travaux de thèse visent principalement la synthèse d’un nouveau type de céramiques technique dites composites à base de cordiérite et de mullite. Cependant, une argile kaolinitique de Tamazert (Jijel, Algérie) a été sélectionné comme matière première pour cette étude grâce à sa composition minéralogique spécifique et à sa grande capacité d’utilisation dans l’industrie céramiques. Le procédé de coulage en bande a été utilisé pour la mise en forme des différentes bandes crues avec divers formulations en argile kaolinitique et de magnésite. Ces travaux de thèse consistent, en premier lieu, à étudier l’effet de l’ajout de la magnésite avec des teneurs entre 3 à 12% en masse sur la dispersion des suspensions en argile kaolinique, en utilisant des mesures de potentiel zêta et des caractérisations rhéologiques. D’autres parts, examiner les propriétés des échantillons crus et frittés par des analyses thermiques (thermodilatométrie), diffraction des rayons X, mesure de la conductivité thermique, microscopie électronique à balayage, et des essais de flexion biaxiale. Les différents échantillons crus ont été frittés dans la plage de température de 1 000 à 1 200 °C pendant 30 min, 90 min et 3 h (le palier de frittage varient seulment à la température de 1 200 °C). Les résultats obtenus durant ces travaux de thèse ont montré qu’une meilleure stabilité des suspensions d’argile kaolinitique est obtenue en présence des quantités optimale en hexamétaphosphate de sodium et de silicate de sodium comme dispersants, 0,2 et 1,2% en masse, respectivement. Nous avons constaté aussi qu’une augmentation de la concentration en magnésite au-dessus de 6% en masse inhibe la dispersion des suspensions de l’argile kaolinitique par formation des complexes solubles. D’un autre côté, nous avons conclu que l’augmentation de la température de frittage jusqu’à 1200 °C réduit fortement la porosité totale des échantillons, ce qui implique l’augmentation des valeurs de le contrainte à la rupture. En effet, les échantillons avec 6 et 12% en masse de magnésite, frittés durant 3h présentent des valeurs de contrainte à la rupture les plus élevées, 117 et 115 MPa, respectivement, et une porosité apparente modérée de 27 et 26 %, respectivement. Les céramiques obtenues semblaient prometteuses pour une utilisation ultérieure comme substrat, avec une forte anisotropie dans les propriétés dues à la microstructure texturée
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    Kaolinite-magnesite based ceramics. Part I : surface charge and rheological properties optimization of the suspensions for the processing of cordieritemullite tapes
    (MDPI, 2019) Hammas, Aghiles; Lecomte-Nana, Gisele; Azril, Nadjet; Daou, Imane
    The present study aimed at investigating the influence of the concentration of sodium silicate and sodium hexametaphosphate on the dispersion of an aqueous kaolinitic clay slurry regarding further use for the tape casting process. The zeta potential of the kaolinitic clay slurry matched the requirements for tape casting. The addition of magnesite in the kaolinitic slurries tended to increase the zeta potential towards the required limit values. Despite this, the further addition of surfactants allowed improving the zeta potential in agreement with the tape casting conditions. Accordingly, the rheological behavior, under continuous and oscillatory flow conditions, of various mixtures of magnesite and a kaolinitic clay was studied. Regarding the pH and the zeta potential measurements, the E–F attraction prevailed at low pH value, and F–F or E–E attraction was predominant at high pH value. All slurries exhibited a shear thinning behavior, which was well-correlated by the Herschel–Bulkley model. It appeared that the best stability for the kaolinitic clay slurries was obtained while using 0.4 mass% and 1.2 mass% of sodium hexametaphosphate and sodium silicate, respectively. An increase in the magnesite concentration above 6 mass% led to a complex behavior with low cohesion energy due to the occurrence of soluble complexes
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    Kaolinite-Magnesite or Kaolinite–Talc-Based Ceramics. Part II: Microstructure and the Final Properties Related Sintered Tapes
    (MDPI, 2020) Hammas, Aghiles; Lecomte-Nana, Gisèle; Daou, Imane; Tessier-Doyen, Nicolas; Peyratout, Claire; Zibouche, Fatima
    In recent decades, talc and kaolinite have been widely used as raw materials for the ceramic industry. In this study, the final characteristics of kaolinitic clay mixed with 6 mass% of magnesite obtained in our previous work were compared with those obtained with mixtures of kaolin (kaolin BIP) and talc (as the source of magnesium oxide). However, different amounts of talc in the kaolin powder were studied, namely 10, 30, and 50 mass% of added talc (with respect to kaolin + talc). The tape casting process was used during this work in order to manufacture the green tapes in an aqueous system with 0.2 mass% of dispersant. Subsequently, the green tapes were heated to 1000 and 1100 °C with a dwelling time of 12 min. The green and sintering tapes were characterized using the following techniques: DTA/TG, X-ray diffraction, porosity, and flexural strength analyses. The results obtained from our previous work indicate that the specimen with 6 mass% of MgCO3 sintered at 1200 °C for 3 h exhibited the best performances, with high flexural strength and weak porosity value—117 MPa and 27%—respectively. As results from this study, the optimal mechanical and thermal properties of sintering tapes were obtained for the specimen with 10 mass% of added talc sintered at 1100 °C. Indeed, this specimen exhibited 50 MPa and 43% of stress to rupture and apparent porosity, respectively
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    Sintering and final properties of kaolinite-magnesite tapes for the manufacture of cordierite-mullite ceramics
    (Blackwell Publishing, 2020) Hammas, Aghiles; Lecomte-Nana, G.; Daou, Imane; Zibouche, Fatima
    The present work aims at studying the effect of the sintering temperature and magnesite addition on the structure and final properties of silicate ceramics tapes. A kaolinitic clay from Algeria was selected and mixed with different magnesite contents (≤12 mass%). Tape casting process was used to produce the green tapes in an aqueous system with optimized amount of surfactants. The green tapes were fired from 1000°C to 1200°C using a dwelling time of 30 minutes. The effect of the dwelling time was investigated for a firing temperature of 1200°C namely: 30 minutes, 1 hour 30 minutes and 3 hours for samples with 6 and 12 mass% of magnesite. Regarding firing conditions, crystalline phases, thermal conductivity, porosity, and flexural strength were analyzed. The results showed that increasing the sintering temperature to 1200°C tended to significantly decrease the total porosity of samples, which led to the improvement of the stress to rupture values. Specimens with 6 and 12 mass% sintered during 3 hours exhibited highest stress to rupture values (≈117 MPa) and lowest thermal conductivity (<0.2 W.m−1.K−1) and moderate open porosity (27%). The as-obtained ceramics appeared promising for further utilization in refractory industry, thanks to the presence of both cordierite and mullite phases