Effect of calcination temperature of tunisian clays on the properties of geopolymers (original) (raw)
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Applied Clay Science, 2014
Two Tunisian clays, kaolinitic from the Tabarka (Clay T) region and illito-kaolinitic rich in hematite from the Medenine (Clay M) region, are tested as potential aluminosilicate sources for the synthesis of geopolymers. The raw clays and clays calcined at 700, 800, 850 and 900°C were characterized using XRD, DTA/TG, and FTIR spectroscopy and 29 Si and 27 Al MAS NMR measurements. It was demonstrated that samples based on Clay M present more reactivity than those based on the Clay T because of the amorphization of clay minerals. The structural evolution on calcination is studied in detail to predict the behavior of the clay during geopolymerization. Despite its lower content in kaolinite than Clay T, Clay M is capable of providing geopolymers.
Physical–chemical characterization of Tunisian clays for the synthesis of geopolymers materials
Journal of African Earth Sciences, 2015
Natural clay materials from Tunisia were examined as an aluminosilicate source for the synthesis of consolidated materials at low temperatures. Three clay samples were collected from the El Kef, Douiret and Gafsa basins and calcined at different temperatures. All of the samples were characterized using chemical and mineralogical analyses, thermogravimetry, dilatometry, and Fourier transform infrared spectroscopy (FTIR) measurements. The chemical (XRF) and mineralogical analyses (XRD and FTIR) indicated that all of the samples contained various amounts of kaolinite and quartz, followed by calcite, mica, palygorskite and gypsum. Curing produced a binder which did not significantly affect the physic-chemical properties of these clays. The obtained materials heterogeneous did not reach the geopolymerization stage, most likely because of their low kaolinite content. The addition of a suitable aluminosilicate to these clays is therefore recommended to produce homogeneous consolidated geopolymers. The synthesized materials obtained after the addition of metakaolin to the formulation to improve reactivity have interesting properties, thereby providing good potential for Tunisian clays in the synthesis of geopolymers.
Properties of Geopolymer Composites from two Different Moroccan Clays
Ceramics in Modern Technologies
The aim of this study is to valorise clays from the Fez region in Morocco as aluminosilicate precursors for geopolymer synthesis. In addition to the clays, the use of calcite and dolomite as mineral additives was also investigated. At first, the Moroccan clays were thermally activated by calcining at 700 °C, and then, a potassium alkaline silicate solution was used for alkali activation. Samples were synthetized by combining clay, metakaolin and mineral additive in several ratios. Consolidated materials were successfully obtained, and geopolymerization reaction was monitored by in situ Fourier transform infrared spectroscopy (FTIR), which revealed several networks. The results demonstrated that composite geopolymers with a mechanical resistance range from 8 to 50 MPa could be obtained from Moroccan clays.
Moroccan clays for potential use as aluminosilicate precursors for geopolymer synthesis
E3S Web of Conferences, 2021
Three Moroccan clays, denoted A1, A3 and A5, were sampled from the Fez region with the aim of potential use as aluminosilicate precursors for geopolymer synthesis. Each clay was subjected to calcination at 700 °C and analyzed using DTA/TG, grain size distribution measurements, XRD, and FTIR spectroscopy before and after heat treatment. The results showed that the three clays contain kaolinite in different proportions in addition to some associated minerals, such as quartz, hematite, calcite and dolomite. Heat treatment successfully activated the clay by the amorphization of kaolinite, which is essential for geopolymerization. Some other changes were observed in the associated minerals, especially carbonates, which partially or totally decomposed depending on the clay, while other minerals remained intact. The SBET and NBO values are in accordance with the degree of polymerization, and the obtention of consolidated materials is possible by alkali activation of the calcined clays.
2017
In the present work we sought to determine the most convenient calcination temperature of Tunisian kaolinitic clay in order to produce a more reactive metakaolin and to determine the most suitable potassium hydroxide (KOH) and sodium hydroxide (NaOH) concentration to produce geopolymer cements with good physical and mechanical performance, less energy consumption and low carbon dioxide emission. This product would play the role of a construction material able to replace Portland cement. The kaolinitic clay fractions collected from Tabarka (Tunisia) were first calcined at different temperatures ranging from 550 °C to 1 100 °C. Calcined fractions were then activated by potassium hydroxide and sodium hydroxide solutions with concentrations of between 5 M to 18 M. The mineral and chemical composition of raw and geopolymer samples was characterized by X-ray diffraction, infrared spectroscopy and thermal analysis, whereas the mechanical and physical properties of hardened samples were cha...
The suitability of thermally activated illite/smectite clay as raw material for geopolymer binders
Applied Clay Science, 2009
So called geopolymers or geopolymeric binders and cements are made by means of an alkaline activation of materials reactive in this respect. Such material has to consist of a certain amount of silicate and aluminate phases which can be dissolved by the alkaline medium. In the consequence stable polymeric networks of alumosilicates will be formed. Metakaolins and alumosiliceous fly ashes, in particular, have by now achieved noteworthy significance. The search for alternative low cost or high available materials may lead among other things to "normal clays". This material is widely available all over the world and may show certain reactivity after a thermal activation process. This investigation focuses on the suitability of illite/smectite clay to form a geopolymer after thermal and alkaline activation. Therefore clay containing mainly illite was thermally activated between 550 and 950°C. The degree of dehydroxylation and the reached reactivity were followed by X-ray diffraction, NMR spectroscopy and dissolution techniques. The performance of the geopolymer binder in terms of strength as well as the phase composition was studied.
Geopolymerization Behaviour of Red and White Clays
Journal of Nepal Chemical Society
Construction is one of the most important activities increasing the demand for Portland cement resulting significant amount of CO2 emission, natural resources degradation, and a high amount of energy consumption. The use of geopolymer has been studied as a potential substitute for Portland cement. Geopolymers are environmentally-friendly binding materials that are produced by the polymerization of alumino-silicates in presence of alkali polysilicates forming Si-O-Al bonds, which are used for several building applications. In this study, red and white clays which contain solid alumino-silicate have shown reactive in presence of an alkaline activator. The addition of lime has shown improvement in the mechanical and physical properties of the geopolymer products. The FTIR analysis and SEM images of the product have shown the formation of aluminosilicate gel in the geopolymeric product. The maximum compressive strength of the geopolymer products RCW and RWL were achieved to be 15.91 and...
Journal of Minerals and Materials Characterization and Engineering, 2022
This work consists of determining the right curing temperature for Mouyondzi clay, with a view to obtaining a very reactive metakaolinic amorphous phase, which will give us a geopolymer with good physical and mechanical performance. The kaolin-dominant Mouyondzi clay was calcined at 600˚C, 700˚C and 800˚C with a heating rate of one degree per minute. In order to achieve the objective of this work, the performance of geopolymer was measured by compressive strength on geopolymer prisms of 28 days of age, by XRD and IRFT of geopolymer powders, calcined clay and raw clay, and by SEM of geopolymer blocks. Analysis of the results shows that the resistance value increases with the curing temperature of the clay and reaches a maximum of 49 MPa at 800˚C. At 600˚C we already have 31 MPa, the equivalent of Portland cement with the addition. The XRD confirms the disappearance of clay species from 600˚C. At 800˚C there is not yet the appearance of a new crystalline phase. Quartz is the only mineral species present. We can therefore confirm that at 800˚C, the geopolymer obtained exhibits higher physical and mechanical performance than the other curing temperatures studied for Mouyondzi clay. This is confirmed by the appearance of a new aluminosilicate phase in the IRFT spectra and in the SEM images appearing as a continuous plate.
Procedia Engineering, 2016
The aim of the presented study was the heat treatment response of the pore structure of the aluminosilicate materials (bentonite, kaolin and zeolite) and the resulted characteristics of the metaproducts, presented as the geopolymer raw materials. The treatment of the studied clays at 650 °C during 4 hours caused a high pore structure response represented by the occurrence of the creation of a new pore area on the pore size distribution histograms beginning over 2000 nm pore radius. Its size was strongly dependent on the clay species. The found relation between compressive strength of the related geopolymers and the histograms area size the assumption entitles to valuate that response of the pore structure of the clays to the heat treatment as a factor significantly conditioning the effectivity of the alkali activation and the process of the geopolymer synthesis.
Physicochemical Characterization of Geopolymer Binders and Foams Made from Tunisian Clay
Illito-kaolinitic clay rich in hematite from south Tunisia was investigated in view of producing geopolymer materials. Geopolymers with two different densities were elaborated: cement and foam. e effects of activator concentrations on compressive strength, water absorption (durability), open porosity, and bulk density of geopolymers cement were examined, in order to assure optimal geopolymerization conditions. Geopolymer cements aged 28 days with optimum performances were achieved for 13 M of alkaline solution concentration. At these conditions, the compressive strength of prepared geopolymer reaches 27.8 MPa. e addition of silica fume to reactant geopolymer mixture induces modification of geopolymer density and decrease in the compressive strength of the final product. Geopolymer materials based on calcined Tunisian clay can be suggested as sustainable and cost-effective cement that may be applied to alternate Portland cement in many construction applications.