Flaws linked to lime in pottery of Marrakech (Morocco)

The studied clayey materials come from soil of Marrakech Haouz Plain. We discussed the influence of grain size, mineralogical and chemical composition of these raw materials on the lime behaviour in pottery shards. In this paper we propose some recommendations to inhibit lime blowing and the efflorescences responsible for flaws. The application of such recommendations will improve the quality of produced pottery and the income of potters in the region.Peer reviewe

Land erosion and associated evolution of clay minerals assemblages in Mediterranean region (Southern Turkey): Amik Lake

Under Mediterranean context, continuous human occupation is attested in the Amik Basin (southern Turkey) since 6000-7000 BC. The Basin also is crossed by The Dead Sea Fault (DSF), a major neotectonic structure in the Middle East extending from the Red Sea in the south to the East Anatolian Fault Zone in the north. The study focuses on the mineralogy and clay mineralogy record of the Amik Lake occupying the central part of the Basin. Our objective is to constrain major mineralogical and clay minerals evolution in the area over the last 4000 years and assess changes that would be related to the different land uses during the different Bronze, Roman, Ottoman and Modern civilizations. Sediments were collected at 1 to 2 cm intervals in core sediments up to a depth of 6 meters in the clay deposits. Geochemistry (XRF), mineralogy (XRD) and clay mineralogy are applied to study the sediment records. The age of the record is constrained combining radionuclide and radiocarbon dating. Chemical and mineralogical composition of sediments is quite diversified reflecting the significant geological variation of drainage basins. Abundant mixed-layer and partly disordered minerals characterize the different sedimentary levels recorded in those cores. Levels relatively rich in chlorite, illite and quartz are interpreted as corresponding to relatively dry periods, while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale, such as kaolinite. Smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season. The sedimentary record clearly shows two periods indicating strong soil erosion in the Lake catchment. The most recent erosion phase is modern. The oldest one would have started during the late Bronze period and lasted until the late Roman Period. The first and older period is attributed to a strong aggradation linked to major increase in erosion. Our study shows that this episode has specific characteristics: mixed-layer clay mineral, high percent in Ni, Cr and Mg coupled with significant amount of organic matter of terrestrial origin. Ni and Mg most probably come from the Amanos Mountains an ophiolitic belt indicating an intensive upland cultivation and possible exploitation of its mineral resource. The second period is attributed to the modern period. The signature of the increase in erosion is different, because most of the soil cover has already been eroded. Only a patchy thin and unmature soil cover exists since the Late Roman time. Erosion is associated with a marked increase of smectite-illite interstratified clay, goethite and hematite found in deep soil horizons. Moreover, a marked increase in Cr is showed and is probably related to an enhanced exploitation of its mineral resource and to a renew land exploitation of the Amanos Mountain Range

Paleomagnetic and geochemical record from cores from the Sea of Marmara, Turkey: Age constraints and implications of sapropelic deposition on early diagenesis

We present results of a multi-proxy analysis of two sediment cores from the Marmara Sea. The cores were ana- lyzed using paleomagnetic and geochemical measurements. Two sapropels are documented in the last 11 kyr and are recorded in several locations across the Marmara Sea. These two sapropels have contrasting magnetic prop- erties. The magnetic record is affected by intense early diagenesis; the most recent upper sapropelic layer has low remanence and susceptibility values. A record of paleomagnetic inclinations could still be isolated above the dia- genesis front and is compared with secular variation models. The lower sapropel is identified in the deep part of the oldest studied core (Klg07) and has distinct magnetic properties characterized by high remanence and sus- ceptibility values. Using the magnetic properties it is possible to constrain bottom water ventilation and recon- nection episodes between the Marmara Sea and the Black Sea following the sea level rise during the last glacial to inter-glacial transition.Seismic History of Istanbu

Phosphogypsum and Black Steel Slag as Additives for Ecological Bentonite-Based Materials: Microstructure and Characterization

peer reviewedThe Black Steel slag (Ss) and phosphogypsum (PG) are industrial wastes produced in Morocco. In order to reduce these two wastes and to evaluate their pozzolanic reactivity in the presence of water, they were incorporated into bentonite (B) mixed with lime (L). The studied mixtures (BLW, BL–PG–W and BL–PG–Ss–W) were analyzed by X-ray diffraction, Infrared spectroscopy, Raman spectroscopy and SEM/EDX analysis. Compressive strength tests were performed on hardened specimens. The results obtained show that the hydration kinetics of the B–L–W and B–L–PG–W mixtures are slow. The addition of PG to a bentonite––lime mixture induces the formation of new microstructures such as hydrated calcium silicate (C–S–H) and ettringite, which increases the compressive strength of the cementitious specimens. The addition of the Ss to a mixture composed of 8%PG and 8%L–B accelerates the kinetics of hydration and activates the pozzolanic reaction. The presence of C2S in the slag helps to increase the mechanical strength of the mixture B–L–PG–Ss. The compressive strength of the mixtures BL–W, BL–PG–W and BL–PG–Ss–W increases from 15 to 28 days of setting. After 28 days of setting, 8% of Sc added to the mixture 8% PG–8%L–B is responsible for an increase of the compressive strength to 0.6 MPa

Mineralogy and Geochemistry of the Guenfouda Clay Deposit, Jerada Province, Northeastern Morocco

peer reviewedThe Guenfouda clay deposit is located at about 36km to the southwest of Oujda city and 6km to the south of Guenfouda village. It belongs to the Jerada Province of the northeastern Morocco and hosted within the Upper Visean calc-alkaline dacite lava interbedded within a schisto-volcanic complex. This deposit is mined for more than 15 years and the product being mainly used for refractories and industrial ceramics. This clay deposit is funnel or trough-like in form, narrowing downwards and display a E–W trend, which follows the major dextral strike-slip fault that passes through the south of the deposit. Based on mineral assemblages, four lateral alteration zones were defined from the north to south parts of the deposit: the Illite zone, the Pyrophyllite-illite zone, the Pyrophyllite zone and the Quartz zone. The presence of high-temperature minerals such as pyrophyllite, diaspore, the alteration zonation pattern and the chemical characteristics are diagnostic of hypogene origin. However, the variation diagrams, Zr vs TiO2 and P2O5 vs SO3 as well as the values of the chemical Index of Weathering (CIW) and the Alteration Index (AI) revealed a mixed type. It seems that the genesis of Guenfouda clay deposit was first controlled by the eastwest strike-slip faults, which brought ascending hydrothermal solutions that led to clay formation and finally, the weathering processes have continued and extended the argillization

Physico-mechanical properties of phosphogypsum and black steel slag as aggregate for bentonite-lime based materials

This study aim to valorizing phosphogypsum (PG) and steel slag (Sc) in geotechnical applications by incorporating them in bentonite (B) stabilized by lime (L). Mineralogical (XRD), spectroscopic (IR-FTIR), geotechnical (Atterberg limits) analyzes were carried out on the raw material. Resistance to axial compression (UCS) was performed on cylindrical specimens prepared for mixtures B-L, B-L-PG, B-L-PG-Sc and cured for 3, 7, 15 and 28 days. The results obtained revealed that the mechanical strength increases with the addition of PG, and reaches its maximum value for a water content equal to 46%. Slag improves the strength of the B-L-PG mixture. The pH and the electrical conductivity of the solutions containing in porosity of the various mixtures decrease over time. The observed decrease is greatest for B-L-PG and B-L-PG-Sc mixtures due to pozzolanic reactions

Reduction of phosphogypsum to calcium sulfide (CaS) using metallic iron in a hydrochloric acid medium

peer reviewedOur study aims to decompose phosphogypsum (PG), mainly composed of CaSO4.2H2O, by reduction in an acidic medium. We evaluated the decomposition of PG by various reaction mechanisms. Sulfate ions from the acid digestion of PG are reduced to sulfide by the hydrogen gas produced in the solution by hydrochloric attack of the metal iron. The solid residues obtained have been determined and monitored by X-Ray Diffraction, Fourier-Transform Infrared spectroscopy and Ultraviolet-visible spectroscopy. The microstructure of residues was observed by scanning electron microscope (SEM). The results show that hydrogen gas formed by hydrochloric acid attack of iron reduces the sulfur from S(VI) to S(-II). CaSO4.2H2O, insoluble in water, gives a residue containing CaS, which is only sparingly soluble in water. The residue also contains anhydrite, bassanite and ferrous chloride. The monitoring of the quantities of residue obtained under varying experimental conditions (temperature, attack time, mass of iron and PG and volume of acid on PG) and volume of HCl showed that the amounts of residue obtained are less than 32% of mass. When the volume of the HCl added increases, the obtained mass of the solid residue decreases sharply. The residue stabilizes at 10% of mass when the volume of HCl added is higher than that required to attack metal iron

VALORISATION INDUSTRIELLE ET ARTISANALE DES ARGILES DU MAROC

Dans une perspective de développement local durable, la présente étude est focalisée sur la caractérisation des matériaux argileux du Nord du Maroc en vue de leur valorisation dans le secteur de la céramique. Elle a l’avantage de contribuer à la promotion des matériaux locaux de construction tout en améliorant la qualité des céramiques artisanales produites. Les sédiments utilisés dans cette étude proviennent de la région du nord du Maroc (Tétouan, Tanger et Meknès), ainsi que de sites argileux utilisés à l’échelle nationale dans la fabrication de la céramique traditionnelle, à savoir les sites de Fès, Salé et Safi. Dans le cadre de ce travail, nous avons procédé à une caractérisation minéralogique, granulométrique, texturale, physique, chimique, thermique et technologiques de ces argiles afin d’évaluer leurs potentialités en industrie céramique. Les argiles de Tétouan et Tanger sont caractérisées par des assemblages minéralogiques diversifiés (en particulier une proportion variable d'argile, de quartz et de calcite). En particulier, les argiles de Meknès, Fès, Salé et Safi présentent une forte teneur en argile, en quartz et en calcite. La fraction argileuse des échantillons de Tétouan et Tanger est dominée par l'illite et la kaolinite avec des proportions variables de chlorite. Ces trois types de minéraux argileux sont responsables en grande partie des propriétés céramiques favorables des échantillons d’argiles étudiées. Les matériaux argileux étudiés sont généralement constitués de fines particules d'argiles avec une plasticité moyenne à forte et une faible teneur en matière organique. Ces échantillons sont composés essentiellement de SiO2 (35 - 60 %), Al2O3 (7 - 30 %) et Fe2O3 (10 - 22 %). La quantité de CaO dans les argiles de Tanger et Meknès est très variable (0 - 30 %). Le CaO n’est présent que dans certaines argiles de Tétouan. Le taux de Fe2O3 est variable allant de 0 à 22 %. Les autres oxydes représentent de faibles proportions (< 6 %). La capacité d’échange cationique et la surface spécifique de tous les échantillons sont faibles. La masse volumique apparente, le volume poreux et le nombre de micropores sont peu variables pour toutes les argiles. Les argiles de Tétouan et de Meknès montrent globalement un bon comportement au séchage, à l’exception de quelques échantillons qui montrent des fissures superficielles au séchage due à la présence des argiles gonflantes (smectite et vermiculite). Les argiles de Tétouan et de Meknès constituent des ressources minérales industrielles de bonne qualité pour la fabrication des produits variés dont des carreaux de sol, des briques et les tuiles. Afin d’avoir de bon produit fini, ces argiles doivent êtres cuites à des températures supérieur à 1050 °C. Les argiles de Tanger montrent des propriétés conformes avec les critères de production des briques. Néanmoins, la présence de sulfates en faible quantité dans quelques échantillons carbonatés conduit après cuisson à 1000 °C à la formation de nodules blancs de sulfate de calcium (CaSO4) à la surface de la brique, résultant de la réaction de sulfates avec le CaO. Néanmoins, quelques produits cuits ont présenté un retrait à la cuisson supérieur à 10% pour de températures allant de 1100 à 1150°C et une perte en poids à la cuisson supérieur à 10%. Pour une bonne rentabilité industrielle, ces retraits peuvent être minimisés par l’ajout d’une quantité optimale de dégraissant ou en faisant des mélanges et/ ou des formulations avec d’autres argiles proche géographiquement afin d’obtenir un mélange adéquat

Technological behaviour of Cretaceous and Pliocene clays of northern Morocco used in fired brick manufacturing

Northern Morocco has an important local ceramic industry. Twenty-three Craterous and Pliocene clays from Tangier area (Northern Morocco) were studied to test their suitability as raw material for fired brick production. To assess their behaviour, the chemical composition, specific surface area (SSA), cation exchange capacity (CEC), and apparent density of clays were determined. The chemical composition consisted mainly of SiO2 (32 – 60%), Al2O3 (7 – 30%), and CaO (0.5 – 32%). SSA and CEC values of all the samples were low. The apparent density, pore volume, and micropore values were almost similar. Clay bricks were prepared by forming and shaping, and then fired in the range of 800 – 1100°C. Firing shrinkage, loss on mass and water absorption capacity were done in order to characterize clays after firing. Most of the clay samples have the necessary properties for the manufacturing of brick products. However, some clay samples were above the norm of loss on weight, due mainly to their high amount of carbonates. Furthermore, some kaolinitic samples from Pliocene blue marls and Cretaceous marls are inappropriate for building-related brick fabrication, because of the development of portlandite in brick, when in contact with moisture of the air. However, it will be necessary to mix them with other clays with little or no carbonate to dilute their carbonates content and then enhance their workability