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Mirja Illikainen - One of the best experts on this subject based on the ideXlab platform.
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towards designing reactive glasses for Alkali Activation understanding the origins of Alkaline reactivity of na mg aluminosilicate glasses
PLOS ONE, 2020Co-Authors: Harisankar Sreenivasan, Mirja Illikainen, John L Provis, Wei Cao, Qunfeng Xiao, Mohsen Shakouri, Marko Huttula, Paivo KinnunenAbstract:Alkali-activated materials (AAMs), sometimes called geopolymers, are eco-friendly cementitious materials with reduced carbon emissions when compared to ordinary Portland cement. However, the availability of most precursors used for AAM production may decline in the future because of changes in industrial sectors. Thus, new precursors must be developed. Recently there has been increased interest in synthetic glass precursors. One major concern with using synthetic glasses is ensuring that they react sufficiently under Alkaline conditions. Reactivity is a necessary, although not sufficient, requirement for a suitable precursor for AAMs. This work involves the synthesis, characterization, and estimation of Alkaline reactivity of Na-Mg aluminosilicate glasses. Structural characterization showed that replacing Na with Mg led to more depolymerization. Alkaline reactivity studies indicated that, as Mg replaced Na, reactivity of glasses increased at first, reached an optimal value, and then declined. This trend in reactivity could not be explained by the conventional parameters used for estimating glass reactivity: the non-bridging oxygen fraction (which predicts similar reactivity for all glasses) and optical basicity (which predicts a decrease in reactivity with an increase in Mg replacement). The reactivity of the studied glasses was found to depend on two main factors: depolymerization (as indicated by structural characterization) and optical basicity. Depolymerization dominated initially, which led to an increase in reactivity, while the effect of optical basicity dominated later, leading to a decrease in reactivity. Hence, while designing reactive synthetic glasses for Alkali Activation, structural study of glasses should be given due consideration in addition to the conventional factors.
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Mine tailings as a raw material in Alkali Activation: A review
International Journal of Minerals Metallurgy and Materials, 2020Co-Authors: Jenni Kiventerä, Juho Yliniemi, Priyadharshini Perumal, Mirja IllikainenAbstract:The mining industry produces billions of tons of mine tailings annually. However, because of their lack of economic value, most of the tailings are discarded near the mining sites, typically under water. The primary environmental concerns of mine tailings are related to their heavy metal and sulfidic mineral content. Oxidation of sulfidic minerals can produce acid mine drainage that leaches heavy metals into the surrounding water. The management of tailing dams requires expensive construction and careful control, and there is the need for stable, sustainable, and economically viable management technologies. Alkali Activation as a solidification/stabilization technology offers an attractive way to deal with mine tailings. Alkali activated materials are hardened, concrete-like structures that can be formed from raw materials that are rich in aluminum and silicon, which fortunately, are the main elements in mining residues. Furthermore, Alkali Activation can immobilize harmful heavy metals within the structure. This review describes the research on Alkali activated mine tailings. The reactivity and chemistry of different minerals are discussed. Since many mine tailings are poorly reactive under Alkaline conditions, different pretreatment methods and their effects on the mineralogy are reviewed. Possible applications for these materials are also discussed.
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structural collapse in phlogopite mica rich mine tailings induced by mechanochemical treatment and implications to Alkali Activation potential
Minerals Engineering, 2020Co-Authors: He Niu, Paivo Kinnunen, Elijah Adesanya, Harisankar Sreenivasan, Mirja IllikainenAbstract:Abstract The Alkali Activation of mine tailings is of interest to diminish the impoundment storage of large waste stream from mining industry. However, most of the mine tailings, like phosphate mine tailings generated in Finland, are rather inert and need pre-treatment to induce the reactivity for Alkali Activation. In this work, mechanochemical treatment was conducted to improve the reactivity of phosphate mine tailings. The ground specimens were subjected to the crystal structural analysis of X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermal analyses by Thermogravimetry/Differential Thermal Analysis (TG/DTA), showing the increment of amorphous content and structural degradation as a function of grinding time. The subsequent Alkaline reactivity test illustrated incremental Alkaline dissolution of Si, Al and K and a schematic diagram of altered phlogopite structure (sources of aluminosilicates in tailings) was also proposed. Additionally, the mineralogical composition of individual particles was carried out by mineral liberation analysis (MLA), thereby evaluating the influence of pre-treatment on the mineralogy of tailings. The results indicate profound micromorphological changes and structural cleavage of the precursor due to grinding, which strongly increase Alkaline reactivity.
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Influence of activator type on reaction kinetics, setting time, and compressive strength of Alkali-activated mineral wools
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: Juho Yliniemi, B. Walkley, J. L. Provis, P. Kinnunen, Mirja IllikainenAbstract:Alkali Activation is a promising utilisation route for mineral wool wastes, due to suitable chemical composition, high reactivity, and surface area. One key factor in the development of Alkali-activated binders is the selection of the suitable Alkali activator. Here, the effect of sodium hydroxide, sodium silicate, sodium aluminate, and sodium carbonate solution on the Alkali-Activation kinetics of two main types of mineral wools, stone wool and glass wool, is investigated. Setting time and compressive strength development results are presented, which are explained and discussed in the context of isothermal calorimeter data obtained at temperature of 40 °C. Sodium hydroxide and sodium silicate solutions provided fast reaction with both mineral wools, evidenced by high heat release, high early strength, and fast setting. The reaction with sodium aluminate solution took several days to initiate, but it produced high compressive strength after 28 days of curing with both mineral wools. Glass wool reacted and hardened rapidly with sodium carbonate solution, but stone wool reacted slowly with sodium carbonate and exhibited a low extent of reaction, likely due to lower extent of reaction of stone wool under less Alkaline conditions. These results show that mineral wool Alkali Activation kinetics and binder gel formation are controlled by the activator type and highlight the importance of choosing the most appropriate activator for each desired application.
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Alkali Activation as new option for gold mine tailings inertization
Journal of Cleaner Production, 2018Co-Authors: Jenni Kiventerä, Francesco Dal Poggetto, Cristina Leonelli, Michelina Catauro, Isabella Lancellotti, Mirja IllikainenAbstract:Abstract The mining industry produces a huge quantity of sulphidic mine tailings, which cause several short- and long-term environmental problems when disposed by landfilling in impounding lakes. The possibility of immobilizing several heavy metals from gold mine tailings by reactive geopolymerization technique has been investigated in the present study. The chemical stability of geopolymers synthetized by the Alkali Activation of metakaolin and blast furnace slag and the addition of 40–50 wt% gold mine tailings is demonstrated. The geopolymers were cured at room temperature, and the effects of different Si/Al and Na/Al molar ratios and curing times were investigated. The inertization effectiveness was evaluated by means of leaching tests carried out according to standard EN 12457 after 7 and 28 days and after 18 months. The samples were immersed into the water for 1 day, and the leachable metals in the test solution were determined by ICP-OES. The results show that various elements (Cr, Cu, Ni, Zn and Mn) from gold mine tailings are able to immobilize almost completely by Alkali Activation with proper co-binder material. The immobilization efficiency were highly improved with longer curing period also for the problematic elements As, V, Sb and B.
Xiaohui Wang - One of the best experts on this subject based on the ideXlab platform.
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mullite based ceramic tiles produced solely from high alumina fly ash preparation and sintering mechanism
Journal of Alloys and Compounds, 2018Co-Authors: Yang Luo, Chunli Liu, Shili Zheng, Dajie Han, Xiaohui WangAbstract:Mullite-based ceramic tiles were successfully prepared using only high-alumina fly ash (HAFA) at relatively low sintering temperatures (1100-1400 degrees C). The effects of Alkali Activation on the chemical composition, mineral phase, and morphology of the HAFA were respectively characterised by ICP-OES, XRD, and SEM methods. The Alkali-Activation pretreatment not only modifies the chemical composition of HAFA to match that of mullite, but also can introduce Na-rich compounds to promote sintering. The macroscopic and microscopic characteristics of the fully ash-based ceramic tiles formed at different sintering temperatures were examined. The ceramic samples sintered at 1300 degrees C exhibited optimal post-sintering properties (relative density: 90.85%, water absorption: 0.10%, rupture modulus: 109.67 MPa, linear shrinkage: 15.70%, and apparent porosity: 0.68%) and a well-developed cubic puncheon-shaped mullite morphology. Finally, through the isothermal sintering method, the melt viscosities and the sintering kinetics were calculated theoretically, and the results show that the Alkali Activation could dramatically reduce the melt viscosity and the apparent Activation energy. This research may provide a new method in utilising the vast amounts of HAFA waste to produce mullite-based ceramic tiles at low costs. (C) 2017 Elsevier B.V. All rights reserved.
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effect of particle size and Alkali Activation on coal fly ash and their role in sintered ceramic tiles
Journal of The European Ceramic Society, 2017Co-Authors: Yang Luo, Chunli Liu, Zhenqing Zhao, Shili Zheng, Xiaohui WangAbstract:Abstract We focus on fly ashes of different sizes and their Alkali-Activation on ceramic products. Backscattered electron imaging-energy dispersive X-ray spectroscopy was used to classify coal fly ash particles according to particle size and to study the pre-Activation of particles with different sizes. Secondary electron imaging-energy dispersive X-ray spectroscopy was used to study the role of coal fly ash particles of different sizes in ceramic bodies before and after Alkali-Activation. Ash particles can be divided into three classes based on size: clay-, quartz- and feldspar-like particles, which act as clay, quartz and feldspar, respectively, in ceramic bodies. The pre-Activation process contributes to the plasticity of ash particles, the crystal skeleton role of clay-like particles and the fluxing agent role of feldspar-like particles, so preprocessing can improve the performance of ash-based ceramic tiles significantly. This research provides a new pretreatment method for coal fly ash in ceramic fields.
Angel Palomo - One of the best experts on this subject based on the ideXlab platform.
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reuse of waste sandstone sludge via Alkali Activation in matrices of fly ash and metakaolin
Construction and Building Materials, 2018Co-Authors: Marina Clausi, Angel Palomo, Ana Fernandezjimenez, Serena C Tarantino, Michele ZemaAbstract:Abstract This work aims at investigating the possibility of reusing sludge from sandstone sawing in Alkaline cements. In particular, the behaviour towards Alkali Activation process of Pietra Serena sludge (sPS), either alone or in binary mixtures with class F fly ashes and metakaolin, was evaluated. The binders were synthesised with 8 M and 12 M NaOH solutions and cured at 85 °C for 5 or 20 h. Mechanical strength was determined after one day and the reaction products were characterized by XPRD, FTIR and SEM/EDX. Also colorimetry tests were performed. The Alkali Activation of sPS gives a material with limited amount of amorphous gel, in which unreacted particles can be still recognized, and showing a compressive strength of 3.6(2) MPa. The use of fly ashes and metakaolin in different proportions enhances mechanical strength up to 36(2) MPa. In these blends, the sludge acts basically like a filler. However, calcium carbonates present on the sludge partially dissolve and react in the Alkaline mixture favouring the formation of some local high-calcium, high Si/Al ratio (C-A-S-H-type gel) areas co-existing with N-A-S-H-type gel.
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Alkali Activation of fly ash part iii effect of curing conditions on reaction and its graphical description
Fuel, 2010Co-Authors: Maria Criado, Ana Fernandezjimenez, Angel PalomoAbstract:The micro- and nano-structural characteristics of the reaction products of fly ash Alkali Activation depend, among others, on the curing conditions used: temperature, time and relative humidity. The present study focuses primarily on relative humidity. When the material is cured in air-tight containers, the silicon content of the initial aluminium-rich material gradually increases. This end product is dense and compact. When samples are in direct contact with the atmosphere, however, early age carbonation takes place, resulting in water loss and persistence of a high-aluminium content. This resulting material is granular and develops lower mechanical strength than the paste cured under high RH conditions. The main nano- and micro-structural differences observed in the materials as a result of different curing conditions have been shown through a graphical description of the reactions.
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Effect of the SiO2/Na2O ratio on the Alkali Activation of fly ash. Part II: 29Si MAS-NMR Survey
Microporous and Mesoporous Materials, 2008Co-Authors: Maria Criado, Ana Fernández-jiménez, Isabel Sobrados, Angel Palomo, Jesús SanzAbstract:Abstract 29 Si MAS-NMR spectroscopy was used to characterize the reaction products resulting from the Alkali Activation of a type F fly ash. Specifically, analyses focused on the degree of polymerization of the activating solution (SiO 2 /Na 2 O ratio = 0.0, 0.19, 0.69 and 1.17) and thermal curing time (from 8 h to 180 days at 85 °C). The results obtained showed that the degree of polymerization of the predominant silica species in the Activation solutions plays an important role in the kinetics, structure and composition of the gel initially formed. The Alkaline aluminosilicate gel formed exhibits short-range order, with the silicon appearing in a wide variety of Q 4 ( n Al) ( n = 0, 1, 2, 3 and 4) environments. In the absence of soluble silica (SiO 2 /Na 2 O ratio = 0.0, 0.19), the Al-rich gels initially generated evolved rapidly into zeolites. At higher levels of anion polymerization (SiO 2 /Na 2 O ratio ⩾0.5), zeolite crystallization was retarded.
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effect of the sio2 na2o ratio on the Alkali Activation of fly ash part ii 29si mas nmr survey
Microporous and Mesoporous Materials, 2008Co-Authors: Maria Criado, Isabel Sobrados, Angel Palomo, Ana Fernandezjimenez, Jesús SanzAbstract:Abstract 29 Si MAS-NMR spectroscopy was used to characterize the reaction products resulting from the Alkali Activation of a type F fly ash. Specifically, analyses focused on the degree of polymerization of the activating solution (SiO 2 /Na 2 O ratio = 0.0, 0.19, 0.69 and 1.17) and thermal curing time (from 8 h to 180 days at 85 °C). The results obtained showed that the degree of polymerization of the predominant silica species in the Activation solutions plays an important role in the kinetics, structure and composition of the gel initially formed. The Alkaline aluminosilicate gel formed exhibits short-range order, with the silicon appearing in a wide variety of Q 4 ( n Al) ( n = 0, 1, 2, 3 and 4) environments. In the absence of soluble silica (SiO 2 /Na 2 O ratio = 0.0, 0.19), the Al-rich gels initially generated evolved rapidly into zeolites. At higher levels of anion polymerization (SiO 2 /Na 2 O ratio ⩾0.5), zeolite crystallization was retarded.
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an xrd study of the effect of the sio2 na2o ratio on the Alkali Activation of fly ash
Cement and Concrete Research, 2007Co-Authors: M Criado, Ana Fernandezjimenez, A G De La Torre, Miguel A G Aranda, Angel PalomoAbstract:Soluble silica has a very significant effect on the microstructural and mechanical development of the cementitious materials produced as a result of the Alkali Activation of fly ash. In this study, four different Alkaline solutions with different soluble silica contents were used to activate fly ash. The primary reaction product was a sodium aluminosilicate gel, while different types of zeolites appeared as minority phases. The percentage and composition of these reaction products were found to depend on both the soluble silica content present in the activating solutions and the thermal curing time. In addition, the amount of gel was observed to have a decisive effect on the mechanical strength developing in the material.
Enrico Bernardo - One of the best experts on this subject based on the ideXlab platform.
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glass ceramic foams from weak Alkali Activation and gel casting of waste glass fly ash mixtures
Materials, 2019Co-Authors: Acacio Rincon Romero, N Toniolo, Aldo R Boccaccini, Enrico BernardoAbstract:A ‘weak Alkali Activation’ was applied to aqueous suspensions based on soda lime glass and coal fly ash. Unlike in actual geopolymers, an extensive formation of zeolite-like gels was not expected, due to the low molarity of the Alkali activator (NaOH) used. In any case, the suspension underwent gelation and presented a marked pseudoplastic behavior. A significant foaming could be achieved by air incorporation, in turn resulting from intensive mechanical stirring (with the help of a surfactant), before complete hardening. Dried foams were later subjected to heat treatment at 700–900 °C. The interactions between glass and fly ash, upon firing, determined the formation of new crystal phases, particularly nepheline (sodium alumino–silicate), with remarkable crushing strength (~6 MPa, with a porosity of about 70%). The fired materials, finally, demonstrated a successful stabilization of pollutants from fly ash and a low thermal conductivity that could be exploited for building applications.
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novel inorganic gel casting process for the manufacturing of glass foams
Journal of The European Ceramic Society, 2017Co-Authors: Acacio Rincon, Giovanni Giacomello, Marco Pasetto, Enrico BernardoAbstract:Abstract A new technique for the production of glass foams was developed, based on Alkali Activation and gel casting. The Alkali Activation of soda-lime waste glass powders allowed for the obtainment of well-dispersed concentrated suspensions, undergoing gelification by treatment at low temperature (75 °C). An extensive direct foaming was achieved by mechanical stirring of partially gelified suspensions, comprising also a surfactant. The suspensions were carefully studied in terms of rheological behavior, so that the final microstructure (total amount of porosity, cell size) can be directly correlated with the degree of gelification. A sintering treatment, at 700–800 °C, was finally applied to stabilize the foams, in terms of leaching of Alkaline ions. Considering the high overall porosity (88–93%), the newly obtained foams exhibited a remarkable compressive strength, in the range of 1.7–4.8 MPa.
Yang Luo - One of the best experts on this subject based on the ideXlab platform.
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mullite based ceramic tiles produced solely from high alumina fly ash preparation and sintering mechanism
Journal of Alloys and Compounds, 2018Co-Authors: Yang Luo, Chunli Liu, Shili Zheng, Dajie Han, Xiaohui WangAbstract:Mullite-based ceramic tiles were successfully prepared using only high-alumina fly ash (HAFA) at relatively low sintering temperatures (1100-1400 degrees C). The effects of Alkali Activation on the chemical composition, mineral phase, and morphology of the HAFA were respectively characterised by ICP-OES, XRD, and SEM methods. The Alkali-Activation pretreatment not only modifies the chemical composition of HAFA to match that of mullite, but also can introduce Na-rich compounds to promote sintering. The macroscopic and microscopic characteristics of the fully ash-based ceramic tiles formed at different sintering temperatures were examined. The ceramic samples sintered at 1300 degrees C exhibited optimal post-sintering properties (relative density: 90.85%, water absorption: 0.10%, rupture modulus: 109.67 MPa, linear shrinkage: 15.70%, and apparent porosity: 0.68%) and a well-developed cubic puncheon-shaped mullite morphology. Finally, through the isothermal sintering method, the melt viscosities and the sintering kinetics were calculated theoretically, and the results show that the Alkali Activation could dramatically reduce the melt viscosity and the apparent Activation energy. This research may provide a new method in utilising the vast amounts of HAFA waste to produce mullite-based ceramic tiles at low costs. (C) 2017 Elsevier B.V. All rights reserved.
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effect of particle size and Alkali Activation on coal fly ash and their role in sintered ceramic tiles
Journal of The European Ceramic Society, 2017Co-Authors: Yang Luo, Chunli Liu, Zhenqing Zhao, Shili Zheng, Xiaohui WangAbstract:Abstract We focus on fly ashes of different sizes and their Alkali-Activation on ceramic products. Backscattered electron imaging-energy dispersive X-ray spectroscopy was used to classify coal fly ash particles according to particle size and to study the pre-Activation of particles with different sizes. Secondary electron imaging-energy dispersive X-ray spectroscopy was used to study the role of coal fly ash particles of different sizes in ceramic bodies before and after Alkali-Activation. Ash particles can be divided into three classes based on size: clay-, quartz- and feldspar-like particles, which act as clay, quartz and feldspar, respectively, in ceramic bodies. The pre-Activation process contributes to the plasticity of ash particles, the crystal skeleton role of clay-like particles and the fluxing agent role of feldspar-like particles, so preprocessing can improve the performance of ash-based ceramic tiles significantly. This research provides a new pretreatment method for coal fly ash in ceramic fields.