References of "El Ouahabi, Meriam"
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See detailPhysico-mechanical properties of phosphogypsum and black steel slag as aggregate for bentonite-lime based materials
Harrou, Achraf; Gharibi, Elkhadir; Nasri, Hicham et al

in Materials Today: Proceedings (2020)

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 ... [more ▼]

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. [less ▲]

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See detailNon-destructive portable X-ray Fluorescence (pXRF) method for the characterization of Islamic architectural ceramic: Example of Saadian tombs and El Badi palace ceramics (Marrakech, Morocco)
El Halim, Mouhssin ULiege; Daoudi, Lahcen; EL Alaoui, El Fels et al

in Journal of Archaeological Science: Reports (2020), 32

Archeological decorated ceramics from the Saadian tombs and El Badi palace sites (Marrakech, Morocco) have reached an advanced deterioration phase; the glazes have been increasingly weakened due to human ... [more ▼]

Archeological decorated ceramics from the Saadian tombs and El Badi palace sites (Marrakech, Morocco) have reached an advanced deterioration phase; the glazes have been increasingly weakened due to human and environmental impacts over time. Portable X-ray Fluorescence (pXRF) was performed in situ and on samples selected from these two monuments, in order to define the chemical agents responsible for the color of the studied glazed ceramics and to determine their evolution over time to help find answers and link between degradations and chemical compositions of different type of glazes. The results show that all samples are lead-silica type glazes with 25–59 wt% of PbO and 51 wt% of SiO2. The coloring agents used for the original glaze are conventional, copper (Cu2+) for the green color, iron (Fe3+) and manganese (Mn2+) for the yellow and black glaze. Phosphorus (P2O5), comes from carbonate mineral phases, is responsible for the blue opalescence of glazes. The study reveals that the ceramic industry has evolved recently in Morocco; elements such as calcium and potassium are currently used in small quantities while lead is increasingly used as flux in the glaze mixture. Iron and copper are still used for black, yellow and green colors, while the use of phosphorus has been replaced by other elements such as cobalt and copper. [less ▲]

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See detailThermodynamics and kinetics of the removal of methylene blue from aqueous solution by raw kaolin
Harrou, Achraf; Gharibi, Elkhadir; Nasri, Hicham et al

in SN Applied Sciences (2020), 2(277),

Remediation of contaminated water with organic dyes originated from variety of industrial processes deserves increased attention. Raw clay is an effective low-cost and eco-environmentally friendly ... [more ▼]

Remediation of contaminated water with organic dyes originated from variety of industrial processes deserves increased attention. Raw clay is an effective low-cost and eco-environmentally friendly adsorbent for the removal of methylene blue (MB) from solution. This study aims to determine kinetics and thermodynamics of MB adsorption onto raw kaolin clays (halloysite and kaolinite/illite) from northeast of Morocco. The apportion capacity of the two kaolin clays to adsorb the MB dye by varying temperature and pH conditions was studied. The thermodynamic parameters show that the sorption of MB is spontaneous and endothermic for halloysite-rich clay, whereas adsorption onto kaolinite/illite is inhibited by electrostatic exothermic effects and the sorption is thermodynamically unfavorable. The kinetic study showed that the adsorption capacity of MB on halloysite is greater than on kaolinite. The intraparticle diffusion process controls the adsorption reaction, and the kinetic is more important for halloysite. [less ▲]

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See detailPhosphogypsum waste as additives to lime stabilization of bentonite
Oumnih, Safae ULiege; Bekkouch, Nadia ULiege; Gharibi, El Khadir et al

in Sustainable Environment Research (2019)

Waste recycling with increasing the lifecycle of resource is a novel approach for enhancing circular economy. Within this context, this study aims to give a second life cycle to phosphogypsum (PG) waste ... [more ▼]

Waste recycling with increasing the lifecycle of resource is a novel approach for enhancing circular economy. Within this context, this study aims to give a second life cycle to phosphogypsum (PG) waste, which is a by-product from phosphoric acid manufacture, as useful resources. This study evaluates the sustainability of this harmful waste, which is accumulated in large stockpiles and becomes hazardous during storage, and to stabilize bentonite-based concrete intended for road construction. The effect of raw bentonite (Ca-Na montmorillonite), PG, and lime on the properties of cementitious materials has been investigated through various tests. The properties examined include chemistry (X-ray Fluorescence Spectrometry), mineralogy (X-ray Powder Diffraction and Fourier-Transform Infrared Spectroscopy), calorimetry (Differential Thermal Analysis/Thermogravimetry) and microstructure (Scanning Electron Microscopy) of the mortar based on different mixtures of bentonite, PG and lime. The result show that lime and PG addition involves in the formation of new nanocrystalline phases and the disappearance of certain minerals as portlandite. Calcium silicate hydrate gel appeared in the mixture with 8% of lime, whereas strätlingite was neoformed in the mixture with 8% of lime and 8% of PG. These nanocrystalline phases are responsible for enhancing mechanical strength through the pozzoloanic reaction. [less ▲]

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See detailUnderstanding exchange networks in the basin of the Garigliano during mid-Republican period: evidences from Artena and Alba Fucens
Dienst, Simon ULiege; Mainet, Grégory ULiege; El Ouahabi, Meriam ULiege

Conference (2019, November 13)

Our knowledge of economic trade in Central Italy during the mid-Republican era is fairly limited. Pottery and terracotta, however, offer some opportunities to further our understanding of these exchanges ... [more ▼]

Our knowledge of economic trade in Central Italy during the mid-Republican era is fairly limited. Pottery and terracotta, however, offer some opportunities to further our understanding of these exchanges, but, so far, scholars have focused to a great extent on chronological aspects, such as the chronology of black-glazed ware, or on oversea trade through the study of amphorae. Nevertheless, few studies have considered common ware, whereas it is very helpful to grasp regional exchanges, as the preliminary results of our enquiries on two mid-Republican deposits in Artena (Province of Rome) and Alba Fucens (Province of L’Aquila) suggest. These cities, located in Central Italy, are 60 kilometres away from each other and offer pottery in contexts which can be traced back to the 4th – 3rd century BC. On one hand, the “Piano della Civita” in Artena, a town dated between the 4th and the 2nd century BC, is situated at the beginning of the Sacco river valley, near Rome. On the other hand, Alba Fucens is a Latin colony founded at the end of the 4th century BC near lake Fucino, immediately north of the spring of the Liri river and abandoned during Late Antiquity. The contexts of both these cities are currently under study. Our observations result from a multiproxy approach combining typological study, fabric observations with binocular loupe and pXRF (PIXE/PIGE, XRD and thin sections analysis forthcoming). The obtained information is then compared to other pertinent data from and vicinity to the Garigliano Basin. In a nutshell, this paper will begin with a short overview of the current assertions about Republican ware in Central Italy, centred on black-glazed production with a long-distance circulation. Then the results of our study on these unpublished contexts, focused on common ware, will discussed. The pertinence of considerate the hydrographical network of the Garigliano basin as a vector of medium-scale trade will be examined in detail, considering the different approaches carried out. The conclusion will open the problematic on other networks that could have existed during the mid-Republican era and the connectivity between these areas on a larger scale. [less ▲]

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See detailMineralogy and Geochemistry of the Guenfouda Clay Deposit, Jerada Province, Northeastern Morocco
Dahmani, Hafida; Jadid, Mohamed; El Hammouti, Kamal et al

in European Journal of Scientific Research (2019), 154(361 -384),

The 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 ... [more ▼]

The 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. [less ▲]

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See detailHAND MADE POTTERY FROM BAELO CLAUDIA: ARCHAEOMETRIC RESULTS
El Ouahabi, Meriam ULiege; Deru, Xavier ULiege; Gomes, Manuel

Poster (2019, October 15)

The late pottery (5th-6th century) from the south-eastern sector of the Baelo Claudia forum has already been presented at the RCRF congress in Lisbon (Deru et al. 2018). Among it, hand made pottery is in ... [more ▼]

The late pottery (5th-6th century) from the south-eastern sector of the Baelo Claudia forum has already been presented at the RCRF congress in Lisbon (Deru et al. 2018). Among it, hand made pottery is in the minority, less than 5%. Observation with a binocular magnifying glass had already made it possible to distinguish several fabrics. Archaeometry improves our first characterization by chemical (XRF), mineralogical (XRD) and thin sections analysis. Results are then compared to other pertinent data from the Mio-Pliocene sedimentary sandstone, clay and marl vicinity to the Tarifa region. This brings new data on crafts and trade in the Western Mediterranean during the Roman period. [less ▲]

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See detailLate Roman Ware at Artena, Latium (3rd-7th c.): Archaeological Evidence and Archaeometric Data
Dienst, Simon ULiege; El Ouahabi, Meriam ULiege; Chene, Grégoire ULiege et al

Conference (2019, October 15)

This contribution aims to present the particularities of the assemblages from the Piano della Civita at Artena, near Rome, during Late Antiquity. Excavated since 1978 by a Belgian then Franco-American ... [more ▼]

This contribution aims to present the particularities of the assemblages from the Piano della Civita at Artena, near Rome, during Late Antiquity. Excavated since 1978 by a Belgian then Franco-American team under the supervision of Roger Lambrechts, then Cécile Brouillard and Jan Gadeyne, the artificial terrace of this Middle Republican settlement was later occupied by a complex succession of buildings. The Late Antique occupation, consisting mainly of farming and storage edifices, was followed by an early medieval structure with four golden solidi dated to 654-659 CE in the foundation. The study of the pottery from the Late Antique layers gives us valuable information about the economy and culture of this region. Very few assemblages from this time period around Artena have been published and the material culture seems clearly different from Rome. Our paper will present the characteristics of the pottery from Artena, using both typology, quantifications and archaeometry (XRF, PIXE/PIGE, CPAA). These data will then be compared to other assemblages from this period around Artena and at Rome. Lastly, they will be discussed in the light of regional connectivity, changes in the food practices and esthetical choices. Special attention will be paid to the question of the changes in the choice and the preparation of the clays for certain uses (cooking, tableware), as well as to the provenance of a great amount of cooking ware that in their forms and fabric is very different from the Roman ware as well as from the local ware of the valle del Sacco. [less ▲]

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See detailMechanical properties and durability of lime mortar using aggregate made from phosphogypsum and steel mill slag
Harrou, Achraf; Oumnih, Safae ULiege; Gharibi, Elkhadir et al

Poster (2019, April)

The present investigation deals with the utilization of phosphogypsum and steel mill slag combined with lime and raw bentonite as a cementitious material used for road construction and durability of ... [more ▼]

The present investigation deals with the utilization of phosphogypsum and steel mill slag combined with lime and raw bentonite as a cementitious material used for road construction and durability of mortar. The result reveals that the stabilization of bentonite by lime enhances mechanical strength of the material, mainly due to the alkaline environment promoting the formation of aluminates and silicates found in Portland cement. Additionally, the addition of phosphogypsum increases the compressive strength by 7 times, with an increase of 20% compared to lime-bentonite aggregate. This is partially due to stratlingite formation, obtained by reaction of CAH10 with C-S-H. The steel mill slag further increases this compressive strength by 10 times, because the occurrence of dicalcium silicate and metal flakes. [less ▲]

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See detailMoroccan clay deposits: Physico-chemical properties in view of provenance studies on ancient ceramics
El Ouahabi, Meriam ULiege; El Boudour El Idrissi, Hicham ULiege; Daoudi, Lahcen et al

in Applied Clay Science (2019), 172(65-74),

Features of clayey raw materials from most important traditional pottery centers in the vicinity of the main medieval sites in Morocco, and their fired products were investigated. Besides clay from the ... [more ▼]

Features of clayey raw materials from most important traditional pottery centers in the vicinity of the main medieval sites in Morocco, and their fired products were investigated. Besides clay from the North of Morocco, the used raw material was illitic clays (10–100%) and smectite-rich clays (0–67%) with variable amount of kaolinite, quartz and feldspars. Chlorite was also present in a small amount. The main major oxides were Si2O, Al2O3 and CaO. The fired tests (800–1100 °C) displayed a decrease in open porosity of the sintered clay by raising the temperature, mainly from 1000 °C due to the inception of melting. This change was coupled with the change in mineralogical composition. New crystalline phases as Ca silicates (diopside and gehlenite), hematite, spinel and mullite occurred during firing process, attesting to the inception of melting and were responsible for porosity reduction. Reference clays for pottery were established based on the clay mineralogy and chemical composition. The present study would help to answer some archeological questions concerning possible sourcing areas for archeological ceramics, to determine techniques for the production of artefacts, and then to interpret cultural influences. Furthermore, the obtained results will support the inception of development of a compositional database for Moroccan pottery. [less ▲]

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See detailCHARACTERIZATION OF NEOGENE MARLS FROM THE KERT BASIN (N.E. MOROCCO): SUITABILITY FOR THE CERAMIC INDUSTRY
Nasri, Hicham; Azdimousa, Ali; EL Hamouti, Kamal et al

in Clay Minerals (2019)

The North-Eastern region of Morocco is filled with marine marls of Neogene age. The Neogene marls from the lower-Kert area were characterized to evaluate their suitability in the ceramic industry. To meet ... [more ▼]

The North-Eastern region of Morocco is filled with marine marls of Neogene age. The Neogene marls from the lower-Kert area were characterized to evaluate their suitability in the ceramic industry. To meet this objective, two cross-sections involving all the Neogene facies were performed on the both banks of the Kert River. Grey and green marls occurring between sandstone and tuffs were characterized by mineralogical (XRD) and physico-chemical analyses (grain-size, Atterberg limits, XRF, and specific surface area). The studied Neogene clays are mainly calcareous silty marls with CaCO3 content ranging from 13 to 20 wt.%. The mineralogical composition showed the occurrence of quartz, calcite, feldspars, dolomite, illite, kaolinite, chlorite, and mixed-layers (10-14 Å). Cristobalite occurred only in the uppermost level of the green marls supplied from volcanic ash during the Messinian. Siderite and rhodochrosite occurred as traces pointing out to reducing or locally oxidizing conditions during sedimentation or shortly thereafter. There, marls have medium to high plasticity that is optimum for extrusion. Raw Neogene marls are suitable for structural clay products manufacturing. More specific uses were supported by geochemical results and grain-size distribution as hollow products, roofing tiles, and masonry bricks. [less ▲]

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See detailElaboration of a high mechanical performance refractory from halloysite and recycled alumina
El Haddara, Abdelilah; Manni, Ahmed; Azdimousa, Ali et al

in Boletin de la Sociedad Espanola de Ceramica y Vidrio (2019)

The present study is a contribution to the valorization of halloysite clay from North Eastern Rif (Nador, Morocco) in the field of Silica-alumina refractory. For this purpose, six mixtures (M1–M6) were ... [more ▼]

The present study is a contribution to the valorization of halloysite clay from North Eastern Rif (Nador, Morocco) in the field of Silica-alumina refractory. For this purpose, six mixtures (M1–M6) were tested using marl, diatomite and silica sand aggregates in order to enhance halloysite performances, and to develop high temperature ceramic up to 1300 °C (silico-aluminous refractory “S-Al-R”). Among all the mixtures tested, the mixture M6 provides good technical quality: Porosity (P) = 21.75%; density (d) = 1.94 g/cm3; thermal shrinkage (R) = 2.7% and flexural strength (Rf) = 29.05 MPa. Addition to the mixture (M6) of 25% of the recycled alumina “Rec-Al”, obtained from silico-aluminous refractory bricks waste, has substantially strengthened the mechanical performance of the silico-aluminous refractory (Rf = 45.08 MPa). [less ▲]

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See detailWeathering pattern of Messinian lithothamnium limestones: implication about paleoclimatic conditions
Moulana, Meriem Lina ULiege; El Ouahabi, Meriam ULiege; Boulvain, Frédéric ULiege et al

in Geologica Belgica (2019)

Limestones are prevalent in Algeria. These formations since their deposition have been affected by a range of weathering, dissolution and recrystallization processes dependant of the paleoclimatic ... [more ▼]

Limestones are prevalent in Algeria. These formations since their deposition have been affected by a range of weathering, dissolution and recrystallization processes dependant of the paleoclimatic conditions they sustained. These transformations also affect the potential hazard that these karstic terrains represent. We focus here on the Boukadir Region situated at the foot of the Ouarsenis Mountain (Fig. 1). The region comprises the Ouarsenis northern piedmont composed of ~15o north dipping lithothamnium limestones of the Messinian period that rest unconformably upon blue marls of the upper Miocene, and to the south the E-W striking lower Chlef Basin filled by Plio-Quaternary sediments and flooded by the Chlef River. The lithothamnium carbonates rocks form a major deep aquifer in the Basin. The Basin is crossed along its southern edge by the Relizane strike-slip fault. In June 1988, there was a large collapse sinkhole of 60 m in diameter and 35 m of deep that occurred along the national road RN4 near the southern edge of the basin (LCTP, 1989). Drilling shows that sinkhole can be associated to lithothamnium limestones that were covered by more than 61 m of sediments at that location. No other sinkhole formed since this accident. In this study we investigate the weathering pattern of the lithothamnium limestones to unravel the likelihood of formation of large sinkholes in this formation. Boreholes and quarries show that the Messinian Calcareous limestones of the Boukadir region are deeply weathered and partly recrystallized calcareous rocks; the weathering affects its entire thickness reaching a maximum of 200 m. This weathering pattern is not visible a few kilometres more to the east, in limestones having a similar origin. To unravel the specific paleoclimatic conditions that these limestones sustained, we combine field work and on selected samples, petrographic thin section and mineralogical (XRD) analysis and SEM observations. Field work in quarries and in the wadi shows that the lithothamnium limestones are composed of altering sandstone rich beds with a calcareous cement and bioconstructions rich beds. .. [less ▲]

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See detailPosphogypsum waste valorization by acid attack with the presence of metallic iron
Oumnih, Safae ULiege; Bekkouch, Nadia ULiege; El Ouahabi, Meriam ULiege et al

Poster (2018, November 21)

During the classical production of phosphoric acid using phosphate rock, a high quantity of phosphogypsum “PG” waste is produced. Storage and management of this quantity present a serious problem, because ... [more ▼]

During the classical production of phosphoric acid using phosphate rock, a high quantity of phosphogypsum “PG” waste is produced. Storage and management of this quantity present a serious problem, because the elevated levels of impurities which originate primarily from the source phosphate rock. The consumption or the re-use of this waste generates several environmental risks due to its composition. Several valorization processes of the PG, economic and environmental, are in phase of development and study. Among the valorization processes, we can find desulphurization, bacteriological or thermal methods, allowing to produce sulphur dioxide SO2 used in the synthesis of the sulphuric acid. The main objective of the present study is to develop an alternative technique to valorize the PG and produce sulphur dioxide “SO2”, using an alternative procedure based on a strong acid attack with the presence of a metal catalyst. The results indicate that the leaching of the PG with acid alone does not allow reduction of the sulfates ions dissolved in SO2. However, when the leaching occurs with the presence of the metal elements, the release of SO2 is observed. The values of the calculated ΔGr and ΔHr permit to discuss the possibility of the reactions involved and to argument the experimental results found. [less ▲]

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See detailStabilization of bentonite by treatment of lime and phosphogypsum
Bekkouch, Nadia ULiege; Oumnih, Safae ULiege; Fagel, Nathalie ULiege et al

Conference (2018, November)

Morocco produces 15 million tons of phosphogypsum residues coming mainly from the phosphate processing industry. Those acid wastes are rich in heavy metals. The release of heavy metals into the ... [more ▼]

Morocco produces 15 million tons of phosphogypsum residues coming mainly from the phosphate processing industry. Those acid wastes are rich in heavy metals. The release of heavy metals into the environment, and especially in seawater, results in a number of environmental problems. The present study aims at valorizing the phosphogypsum residues for geotechnical applications (e.g, roadbase, subbase, embankment material). In order to stabilize bentonite, we mixed it with different proportions of lime and phosphogypsum . The bentonites was sampled from a TRIBIA’s deposit located 15 km west of the city Nador in Northeast of Morocco,. For that purpose chemical (XRF), mineralogical (XRD), thermal (TAG), geotechnical (Atterberg limits) and mechanical (Proctor and compressive strength) analyzes were performed on the different mixtures of bentonite, phosphogypsum and lime. We observe that lime and phosphogypsum significantly enhance the behavior of bentonite through different reactions. First, a decrease in the plasticity index (PI) and density of the proctor optimum associated with an increase in the optimum water content can be observed. The texture of mixture evolves from a plastic state to a solid, friable, non-tacky state with a partial loss of sensitivity to water. Long-term modifications also occur. Indeed the lime raises the pH of the bentonite and causes an hydrolysis, It forms then crystalline aluminates and hydrated calcium silicates, acting as a binder between the grains thus causing an increase in the compressive strength. In contrast, the phosphogypsum decreases the time of setting [less ▲]

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See detailAnalytical study of ancient ceramics from the archaeological site of Aghmat, southern Morocco
El Halim, Mouhssin ULiege; Daoudi, Lahcen; El Ouahabi, Meriam ULiege et al

in Materiocedia: Proceedings Series on Materials (2018), 1(1), 47-58

This paper explores Aghmat archaeological materials (VII centuries) using two types of ceramics, come from a recent archaeological excavation in Aghmat (Morocco) in order to enhance documentation ... [more ▼]

This paper explores Aghmat archaeological materials (VII centuries) using two types of ceramics, come from a recent archaeological excavation in Aghmat (Morocco) in order to enhance documentation, conservation and restoration issues, then putting into value the architectural heritage. Fortuitously discovered in 2005, Aghmat village has allowed the reformulation of several hypotheses about Aghmat population skills in construction and handicrafts. Even though the areal extent of this archaeological site exceeds 20 Km2, no traces of furnaces have been found yet, only ruins of buildings and streets. Bricks and pottery samples were the most abundant types of ceramics founded. Mineralogical and chemical analyses of this materials provided information about the origin of raw materials and manufacturing process. The chemical compositions indicated that SiO2, Al2O3 and Fe2O3 are major elements while K2O and MgO are less abundant. The ceramics were produced using at least two raw materials, non calcareous clay of permo-triassic age for bricks, and carbonate quaternary clays for pottery samples, as the calcium oxide content is generally more than 10%. [less ▲]

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See detailGeotechnical and chemical properties of stabilized bentonite with lime-phosphogypsum
Oumnih, Safae ULiege; Bekkouch, Nadia ULiege; El Ouahabi, Meriam ULiege et al

Scientific conference (2018, September)

Phosphogypsum (PG), produced from phosphoric acid production, is accumulated in large stockpiles and occupies vast areas of land. The phosphate industry in Morocco produces 15 million tons of ... [more ▼]

Phosphogypsum (PG), produced from phosphoric acid production, is accumulated in large stockpiles and occupies vast areas of land. The phosphate industry in Morocco produces 15 million tons of phosphogypsum waste by year (Hakkou, 2016). Those wastes contain toxic elements which may cause environmental damage during storage, especially by contact with aquatic environments (Gaudry, 2007). The aim of this study was to propose a sustainable management of those harmful wastes. We test different mixings to trap the toxic elements. We mix some phosphogypsum waste with raw bentonite (B). Bentonite is abundant clay material in Morocco and is successfully used for decades as an adsorbent for removing toxic heavy metals from aqueous solutions (Chiban, 2012). The raw bentonite was sampled from the Tribia deposit located in Northeast of Morocco. We also test several mixings with both bentonite and lime (L). Chemical (XRF), mineralogical (XRD), thermal (ATG), geotechnical (Atterberg limits) and mechanical (Proctor and compressive strength) analyzes analysis were performed on the different mixtures. The results display that lime and phosphogypsum significantly enhance the behavior of bentonite by increasing the compressive strength through different reactions. The optimal results are reached when 8% of PG is added to the bentonite, highlighted by an increase of 20% compared to the mixture made only by bentonite and lime at 28 days (Fig. 1). Over time, long-term modifications occur. In particular, lime as a strong base raises the pH of the clay and causes silica and alumina mobilization. Phosphogypsum decreases the time of setting. It forms then aluminates and hydrated calcium silicates which, by crystallizing, act as a binder between the grains thus causing an increase in the compressive strength. In addition, immediate changes in geotechnical properties of bentonite were observed. Those changes are expressed by a decrease in the density of the Proctor optimum values and increase in the optimum water content with the addition of 5%, 8%, 10% and 15% of lime (Fig. 3). We suggest that the additional water is retained in the agglomerates resulting during the reaction of the lime with bentonite. The mixture evolves almost instantaneously from a plastic state to a solid, friable, non-tacky state and partially loses its sensitivity to water. The increase in unconfined compressive strength was the highest with 8% lime and 8% phosphogypsum (Fig. 2). Furthermore, the addition of phosphogypsum increases the liquid limit compared to the bentonite and lime mixture. [less ▲]

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