Geopolymerization Ability of Natural and Secondary Raw Materials by Solubility Test in Alkaline Media (original) (raw)
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The role of active silica and alumina in geopolymerization
Vietnam Journal of Science, Technology and Engineering
In this study, the alkaline solutions (NaOH) with concentrations from 1M to 18M, red mud (RM) and silica fume (SF) were used as reactors in geopolymer reactions. RM contains 7.40% SiO 2 and 13.65% Al 2 o 3 and SF has 94.50% SiO 2 , but only the active oxides can participate in the geopolymer reactions. The activity of the oxides was investigated by determining the compressive strength of the samples under different curing conditions. The characteristics of the geopolymer samples were determined by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA)/differential thermal analysis (DTA) and nuclear magnetic resonance analysis (NMR). The experimental results indicate that active silica mainly exists in SF. In the structure of geopolymers, the silicon can bond directly with each other (Si-Si) or be linked through 'bridging' oxygen (Si-O-Si) to form independent polymer chains, while aluminium atoms can only replace the silicon atoms in Si-O-Si polymer chains to form Si-O-Al instead.
Results in Physics, 2016
This paper is based on the characterization of synthesized geopolymer binders based on either powder or solution silicate, and the amount of water contained in synthesized binders is determined to evaluate their possibility to coat a brick. The structural evolution of the formed geopolymers was investigated using FTIR spectroscopy. The mechanical properties were evaluated using compression tests. The structural evolution ensured that the solutions prepared from silicate powder or liquid had different degrees of polymerization, which modified the polycondensation reaction of the mixture. Nevertheless, the use of aluminosilicate solutions based on powder or liquid display similar behavior in a polycondensation reaction. The obtained materials show good mechanical properties, and it is possible to deposit this binder on the brick depending on the water content.
Geopolymerization: A Review on Physico-chemical Factors Influence to the Reaction Process
Journal of Polymer & Composites, 2020
A geopolymer is one of materials belonging to an inorganic polymer group based on aluminosilicate structural networks. The material is a product of reactions among the activated alumino-silicate resources and solutions of alkaline activators in various conditions. There have been many investigations conducted to produce geopolymer using different raw materials and methods. The chemical factors have a decisive role in the reaction process and the formation of the geopolymeric structural networks. The physical factors significantly influenceon engineering properties, microstructural characteristicsas well as the effectiveness of the reactions. This study is a review on evaluation of relationships among physico-chemical factors in the reaction process. In which, the chemical factors were considered both the alumino-silicate raw materials and alkaline activators. The physical factors were evaluated on the various conditions known as mixing time, curing time and curing temperature.
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 Sol-Gel Science and Technology, 2014
Precursors are critical parameters in geopolymerization mechanisms because they govern the reaction kinetics as well as the working properties of the final materials. This study focuses on the effect of alkaline solutions on geopolymer formation. Toward this end, several geopolymer samples were synthesized from the same metakaolin and various alkaline solutions. First, the solutions were characterized by thermogravimetric analysis as well as DTA-TGA, infrared spectroscopy, and MAS-NMR spectrometry. The structural evolution of the formed geopolymers was investigated using infrared spectroscopy. The measurement of mechanical strength was tested by compression. The results provide evidence of relationships between the chemical composition, the extent of depolymerization of the alkaline solutions, the kinetics of Si-O-Si bond substitution by Si-O-Al and the compressive strength. For a given aluminosilicate source, the nature and the quantity of siliceous species in the activation solution appear to lead to variation in the reactivity and, consequently, to the formation of various networks that control the kinetics of formation of geopolymers and their mechanical properties. Keywords Si/K ratio Á Alkaline solution Á Depolymerization Á Siliceous species Á 29 Si MAS-NMR Á TEM
Ceramics International, 2017
The alkali activation of metakaolinite permits the preparation of new amorphous cementitious materials denoted as «geopolymers». The formation of these aluminosilicates depends on the thermal activation of kaolinites and the amount of silica in the activating solutions. In this work, the influence of Si:Al ratios on the geopolymer's formation is investigated for short reaction times. Structural and morphological transformations were followed with the XRD, SEM, IR and MAS-NMR (29 Si, 27 Al, 23 Na and 1 H) techniques. For kaolinites (Si:Al =1) heated at 550ºC, geopolymers with tectosilicate networks easily formed; however, in kaolinites heated at 800ºC, the formation of geopolymers was delayed as a consequence of silica segregation. The addition of silica (Si:Al= 3) favoured the formation of geopolymers particles surrounded by sodium-silicates with tubular morphology. In this association, kinetic and thermodynamic parameters play an important role. For prolonged alkaline activations, zeolites formed from the geopolymers. The quantitative analysis of the NMR spectra made possible the study of the formation of zeolites from amorphous geopolymers.
Molecules, 2021
In this study, the role of two reactive fillers, specifically a sand from a clay washing process as an alternative to waste glass powder and a commercial metakaolin (MK), into the geopolymerization process of waste clay-based materials was assessed. Three kinds of clayey wastes from mining operations—halloysitic, kaolinitic and smectitic clays—were tested as potential precursor of geopolymeric materials in view of a potential valorisation of these by-products. A mix-design based on the addition of low percentages (20%) of these fillers or MK to improve the mechanical and chemico-physical properties of geopolymeric formulations was evaluated. All the clays were thermally treated at a temperature of 650 °C, while the geopolymeric pastes were cured at room temperature. In particular, the chemical stability in water (pH and ionic conductivity of leachate water, weight loss), the variations in the microstructure (XRD, SEM), and in the mechanical performance (compressive strength) were an...
Thermally treated clay sediments as geopolymer source material
Applied Clay Science, 2015
The management of reservoirs for water supply is a great environmental problem, since regular de-silting operations produce huge quantities of sediments. Among the recycling possibilities, the use of clay sediments for the manufacture of geopolymer-based materials seems to be an interesting alternative to disposal, due to their low cost and easy availability. In particular, two sediments, coming from reservoirs located in Southern Italy, were firstly characterized by X-ray diffraction, differential thermogravimetry, Fourier transformed infrared (FTIR) spectroscopy and 27 Al and 29 Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy. The reactivity of raw and thermally treated clay sediments in alkaline media was also investigated. Finally, geopolymeric samples were produced and chemically, physically and mechanically characterized. The results showed that the calcined clay sediments can be suitable source materials in polycondensation reactions and that the increase of the calcination temperature from 400 to 750°C resulted in an increased reactivity. Moreover, good mechanical properties were obtained by all the geopolymers prepared with heat-treated sediments.
Utilization of Complex Clay Deposits for Geopolymer Production
Gongcheng Kexue Yu Jishu/Advanced Engineering Science, 2023
The current work investigates the potential use of complex clay deposits for geopolymer production. The used deposits, as well as the final product, were both characterized. The results indicated a higher plasticity limit, bulk density, and silica content for the studied clay deposit than the pure deposits due to multiple clay minerals. The maximum given compressive strength was 8.69 MPa at a 1.5 ratio of Na2SiO3/NaOH, with water absorption of about 7%. The mineralogical and microstructural analysis of the product reveals the formation of the hydroxysodalite phase and gel phase, with high amounts of unreacted components. As a result, it is strongly advised to utilize complex clay deposits to reduce the amount of aluminosilicate materials needed in geopolymer production.
Effect of calcination temperature of tunisian clays on the properties of geopolymers
Ceramics Silikaty
Geopolymers are amorphous three dimensional aluminosilicate materials that may be synthesized at room or slightly higher temperature by alkaline activation of aluminosilicates obtained from industrial wastes, calcined clays and natural minerals. Among the different family of geopolymers, two Tunisian clays (a kaolinite clay from Tabarka and illito/kaolinitic clay from Medenine) are tested for their feasibility of geopolymers at low temperature. The unfired and calcined clays were dissolved in strongly alkaline solution in order to produce consolidated materials whose pastes were characterized by their compressive strength. Hardened geopolymer samples were also submitted to X-Ray diffraction, FTIR spectroscopy and scanning electron microscopy analyses. The geopolymer strength is related to the structure and reactivity of the clay generated by thermal treatment and to the role of associated minerals in clays. The amorphous character of obtained geopolymers and the displacement of the ...