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Said Jalali - One of the best experts on this subject based on the ideXlab platform.
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tungsten Mine Waste geopolymeric binder preliminary hydration products investigations
Construction and Building Materials, 2009Co-Authors: F Pachecotorgal, Joao Castrogomes, Said JalaliAbstract:Abstract Geopolymeric Mine Waste mud (GMWM) binders are obtained from dehydroxylated Waste powder mixed with minor quantities of calcium hydroxide, activated with NaOH and waterglass solutions. In this work recent investigations of GMWM binders hydration products have been carried out. The hydration products have been investigated by means of X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). Results indicate that mechanical strength as a function of the concentration of the alkaline activator is closely related to the Mineralogy of the hardened geopolymeric binder. Results show that a new crystalline phase, phlogopite a trioctahedral layered structure, was formed as a result of the geopolymerization process. SEM and EDS analysis indicates that the hydration products were alkali aluminosilicate gel and calcium silicate hydrates.
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Investigations of tungsten Mine Waste geopolymeric binder: Strength and microstructure
Construction and Building Materials, 2008Co-Authors: Fernando Pacheco-torgal, João Castro-gomes, Said JalaliAbstract:Abstract This paper reports some results of a research project related to the development of a new binder using Mineral Waste mud from the Portuguese Mine. Some aspects related to the effect of aggregates in the microstructure and mechanical behaviour of tungsten Mine Waste geopolymeric binder are reported in the present study. Test results showed that the aggregate type influences strength development.
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investigations on mix design of tungsten Mine Waste geopolymeric binder
Construction and Building Materials, 2008Co-Authors: F Pachecotorgal, Joao Castrogomes, Said JalaliAbstract:Abstract Strength data show that the parameters, which lead to optimum strength for 7 days curing, remain the same for long curing ages. However, when calcium hydroxide percentages above 10% are used, strength decrease after 14th curing day is noticed. In order to explain this behaviour several hypotheses are discussed. The use of an activator with a sodium hydroxide concentration of 24 M leads to a compressive strength of almost 70 MPa. The strength performance is typical of a very reactive binder, being suggested that it is due to the calcium hydroxide and also to the nucleation centers provided by the iron oxide of the Mine Waste mud. Results allow foreseeing that even higher strength performance could be achieved if lower water/sodium molar ratios were used.
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Properties of tungsten Mine Waste geopolymeric binder
Construction and Building Materials, 2008Co-Authors: Fernando Pacheco-torgal, João Castro-gomes, Said JalaliAbstract:Abstract Tungsten Mine Waste mud (TMWM) geopolymeric binder is a new cementitious material with a very high early age strength. It is obtained from dehydroxylated Mine Waste powder mix with minor quantities of calcium hydroxide and activated with NaOH and waterglass solutions. Tests on properties of TMWM binders such as workability, setting time, unrestrained shrinkage, water absorption and static modulus of elasticity were carried out and the results are reported in this paper. This is followed by comparisons with literature related data and a discussion about it. The results showed that current devices use to assess OPC fresh properties are not recommended to evaluate TMWM binders. It has also been found that traditional procedures used to evaluate unrestrained shrinkage may be responsible for misleading results when using those new binders. Water absorption data shows that TMWM has a very compacted structure. Results concerning the static modulus of elasticity are similar to the ones obtained by other authors. However the hypothesis related to modulus of elasticity decrease due to the use of high Al/Si alkali activated mixtures was not confirmed.
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investigations about the effect of aggregates on strength and microstructure of geopolymeric Mine Waste mud binders
Cement and Concrete Research, 2007Co-Authors: F Pachecotorgal, Joao Castrogomes, Said JalaliAbstract:Geopolymeric binders appear to be an alternative to traditional Portland cement, due to high mechanical performances and environmental advantages. Some aspects related to the effect of aggregates in the microstructure and mechanical behaviour of geopolymeric Mine Waste mud (GMWM) binders are reported in the present study. Compressive and tensile strength of Mine Waste mud binders were analyzed. The factors investigated were the aggregate/binder ratio, the aggregate dimension and aggregate type, schist, granite and limestone. Test results showed that GMWM binders have a very high strength at early ages and also possess a very high tensile strength. It's suggested that behaviour may be due to the dissolution of quartz and alumina in the presence of alkalis enhancing bonding between paste and aggregates. The aggregate dimension showed only significant effect on tensile strength. Limestone aggregates showed a chemical bond to the alkaliactivated paste but presented higher shrinkage. It was also found that no traditional porous ITZ was detected in GMWM binders. © 2007 Elsevier Ltd. All rights reserved.
Fernando Pacheco-torgal - One of the best experts on this subject based on the ideXlab platform.
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Investigations of tungsten Mine Waste geopolymeric binder: Strength and microstructure
Construction and Building Materials, 2008Co-Authors: Fernando Pacheco-torgal, João Castro-gomes, Said JalaliAbstract:Abstract This paper reports some results of a research project related to the development of a new binder using Mineral Waste mud from the Portuguese Mine. Some aspects related to the effect of aggregates in the microstructure and mechanical behaviour of tungsten Mine Waste geopolymeric binder are reported in the present study. Test results showed that the aggregate type influences strength development.
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Properties of tungsten Mine Waste geopolymeric binder
Construction and Building Materials, 2008Co-Authors: Fernando Pacheco-torgal, João Castro-gomes, Said JalaliAbstract:Abstract Tungsten Mine Waste mud (TMWM) geopolymeric binder is a new cementitious material with a very high early age strength. It is obtained from dehydroxylated Mine Waste powder mix with minor quantities of calcium hydroxide and activated with NaOH and waterglass solutions. Tests on properties of TMWM binders such as workability, setting time, unrestrained shrinkage, water absorption and static modulus of elasticity were carried out and the results are reported in this paper. This is followed by comparisons with literature related data and a discussion about it. The results showed that current devices use to assess OPC fresh properties are not recommended to evaluate TMWM binders. It has also been found that traditional procedures used to evaluate unrestrained shrinkage may be responsible for misleading results when using those new binders. Water absorption data shows that TMWM has a very compacted structure. Results concerning the static modulus of elasticity are similar to the ones obtained by other authors. However the hypothesis related to modulus of elasticity decrease due to the use of high Al/Si alkali activated mixtures was not confirmed.
F Pachecotorgal - One of the best experts on this subject based on the ideXlab platform.
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tungsten Mine Waste geopolymeric binder preliminary hydration products investigations
Construction and Building Materials, 2009Co-Authors: F Pachecotorgal, Joao Castrogomes, Said JalaliAbstract:Abstract Geopolymeric Mine Waste mud (GMWM) binders are obtained from dehydroxylated Waste powder mixed with minor quantities of calcium hydroxide, activated with NaOH and waterglass solutions. In this work recent investigations of GMWM binders hydration products have been carried out. The hydration products have been investigated by means of X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). Results indicate that mechanical strength as a function of the concentration of the alkaline activator is closely related to the Mineralogy of the hardened geopolymeric binder. Results show that a new crystalline phase, phlogopite a trioctahedral layered structure, was formed as a result of the geopolymerization process. SEM and EDS analysis indicates that the hydration products were alkali aluminosilicate gel and calcium silicate hydrates.
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investigations on mix design of tungsten Mine Waste geopolymeric binder
Construction and Building Materials, 2008Co-Authors: F Pachecotorgal, Joao Castrogomes, Said JalaliAbstract:Abstract Strength data show that the parameters, which lead to optimum strength for 7 days curing, remain the same for long curing ages. However, when calcium hydroxide percentages above 10% are used, strength decrease after 14th curing day is noticed. In order to explain this behaviour several hypotheses are discussed. The use of an activator with a sodium hydroxide concentration of 24 M leads to a compressive strength of almost 70 MPa. The strength performance is typical of a very reactive binder, being suggested that it is due to the calcium hydroxide and also to the nucleation centers provided by the iron oxide of the Mine Waste mud. Results allow foreseeing that even higher strength performance could be achieved if lower water/sodium molar ratios were used.
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investigations about the effect of aggregates on strength and microstructure of geopolymeric Mine Waste mud binders
Cement and Concrete Research, 2007Co-Authors: F Pachecotorgal, Joao Castrogomes, Said JalaliAbstract:Geopolymeric binders appear to be an alternative to traditional Portland cement, due to high mechanical performances and environmental advantages. Some aspects related to the effect of aggregates in the microstructure and mechanical behaviour of geopolymeric Mine Waste mud (GMWM) binders are reported in the present study. Compressive and tensile strength of Mine Waste mud binders were analyzed. The factors investigated were the aggregate/binder ratio, the aggregate dimension and aggregate type, schist, granite and limestone. Test results showed that GMWM binders have a very high strength at early ages and also possess a very high tensile strength. It's suggested that behaviour may be due to the dissolution of quartz and alumina in the presence of alkalis enhancing bonding between paste and aggregates. The aggregate dimension showed only significant effect on tensile strength. Limestone aggregates showed a chemical bond to the alkaliactivated paste but presented higher shrinkage. It was also found that no traditional porous ITZ was detected in GMWM binders. © 2007 Elsevier Ltd. All rights reserved.
Michael Hitch - One of the best experts on this subject based on the ideXlab platform.
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structural and chemical changes in Mine Waste mechanically activated in various milling environments
Powder Technology, 2017Co-Authors: Jia-jie Li, Michael HitchAbstract:Abstract This paper evaluates the mechanical activation of Mine Waste (e.g. partially serpentinized olivine) using different milling machines, with a special focus on changes in microstructure and chemical transformation. The mechanical activation experiments were carried out using lab-scale high-energy planetary and vibratory mills, as well as a pilot-scale stirred mill, and laser diffraction, nitrogen adsorption, X-ray diffraction, and infrared spectroscopy were employed to identify mechanically-induced changes in the Mine Waste. Direct aqueous carbonation was used to identify the best type of mechanical activation for carbon storage in the Mine Waste. The experimental results demonstrate that agglomeration of the particles takes place during extended milling in dry conditions, and that there is an effective mechanical activation limit for crystallite size reduction during dry grinding; the higher the milling intensity, the smaller the forsterite's crystallite size will be at the mechanical activation limit. Additionally, stirred milling in wet conditions produces the largest specific surface area, and vibratory milling in dry conditions generates the most disordered materials. The serpentine content was slightly dehydrated during dry milling and was not activated at all during wet milling. The stirred mill proved to be the most efficient form of mechanical activation vis-a-vis the direct aqueous carbonation process, followed by the planetary mill and the vibratory mill, respectively.
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ultra fine grinding and mechanical activation of Mine Waste rock using a planetary mill for Mineral carbonation
International Journal of Mineral Processing, 2017Co-Authors: Michael HitchAbstract:Abstract In order to mitigate the effects of climate change, a worldwide effort is being launched to use ultramafic Mine Waste as feedstock for CO2 sequestration by Mineral carbonation. To enhance the rate of Mineral carbonation at any specific Mine site, it is important to develop individualized methods for use at that specific Mine site, and with respect to its particular Waste Mineralogy. This study exaMines mechanical activation as the pre-treatment method for ultramafic Mine Waste containing forsterite and serpentine. Particle size distribution, specific surface area, microstructure and direct aqueous Mineral carbonation were measured to test the effects of mechanical activation. The Rietveld method was used to analyze the microstructure of untreated and mechanically-activated material. It was found that, as a result of the grinding energy input on olivine, particle size was decreased, surface area was increased, crystallite size was reduced and micro-strain was accumulated. During the dry mechanical activation of Mine Waste, serpentine content was partially dehydrated and converted to olivine. The concurrent grinding of serpentine with olivine promoted the formation of new surface area, but it hindered the disordering of the crystal structure of forsterite. Forsterite makes up the majority of the content and contributes to CO2 sequestration under selected carbonation conditions. The CO2 sequestration conversion of mechanically-activated olivine and Mine Waste are 22.5% and 31.5%, respectively, with 3600 kWh/t specific milling energy input after one hour direct aqueous carbonation. For the purposes of Mineral carbonation, the mechanical activation of Mine Waste is preferable to simply grinding pure olivine.
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mechanical activation of ultramafic Mine Waste rock in dry condition for enhanced Mineral carbonation
Minerals Engineering, 2016Co-Authors: Michael HitchAbstract:Abstract This study exaMines mechanical activation as the pre-treatment method for ultramafic Mine Waste containing olivine and serpentine. Specific surface area, microstructure and carbonation conversion in a direct aqueous carbonation process were measured to test the effects of mechanical activation. It was found that, as a result of the grinding energy input on materials, surface area was increased, crystallite size was reduced and microstrain was accumulated, carbonation conversion was enhanced. With the presence of serpentine content, the formation of new surface area was promoted and the disordering of forsterite structure was prevented. Forsterite makes up the majority of the content and contributes to CO2 sequestration under selected carbonation conditions. For the purposes of Mineral carbonation, the mechanical activation of Mine Waste is preferable to simply grinding pure olivine.
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Ultra-fine grinding and mechanical activation of Mine Waste rock using a high-speed stirred mill for Mineral carbonation
International Journal of Minerals Metallurgy and Materials, 2015Co-Authors: Jia-jie Li, Michael HitchAbstract:CO_2 sequestration by Mineral carbonation can permanently store CO_2 and mitigate climate change. However, the cost and reaction rate of Mineral carbonation must be balanced to be viable for industrial applications. In this study, it was attempted to reduce the carbonation costs by using Mine Waste rock as a feed stock and to enhance the reaction rate using wet mechanical activation as a pre-treatment method. Slurry rheological properties, particle size distribution, specific surface area, crystallinity, and CO_2 sequestration reaction efficiency of the initial and mechanically activated Mine Waste rock and olivine were characterized. The results show that serpentine acts as a catalyst, increasing the slurry yield stress, assisting new surface formation, and hindering the size reduction and structure amorphization. Mechanically activated Mine Waste rock exhibits a higher carbonation conversion than olivine with equal specific milling energy input. The use of a high-speed stirred mill may render the Mineral carbonation suitable for mining industrial practice.
João Castro-gomes - One of the best experts on this subject based on the ideXlab platform.
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Investigations of tungsten Mine Waste geopolymeric binder: Strength and microstructure
Construction and Building Materials, 2008Co-Authors: Fernando Pacheco-torgal, João Castro-gomes, Said JalaliAbstract:Abstract This paper reports some results of a research project related to the development of a new binder using Mineral Waste mud from the Portuguese Mine. Some aspects related to the effect of aggregates in the microstructure and mechanical behaviour of tungsten Mine Waste geopolymeric binder are reported in the present study. Test results showed that the aggregate type influences strength development.
-
Properties of tungsten Mine Waste geopolymeric binder
Construction and Building Materials, 2008Co-Authors: Fernando Pacheco-torgal, João Castro-gomes, Said JalaliAbstract:Abstract Tungsten Mine Waste mud (TMWM) geopolymeric binder is a new cementitious material with a very high early age strength. It is obtained from dehydroxylated Mine Waste powder mix with minor quantities of calcium hydroxide and activated with NaOH and waterglass solutions. Tests on properties of TMWM binders such as workability, setting time, unrestrained shrinkage, water absorption and static modulus of elasticity were carried out and the results are reported in this paper. This is followed by comparisons with literature related data and a discussion about it. The results showed that current devices use to assess OPC fresh properties are not recommended to evaluate TMWM binders. It has also been found that traditional procedures used to evaluate unrestrained shrinkage may be responsible for misleading results when using those new binders. Water absorption data shows that TMWM has a very compacted structure. Results concerning the static modulus of elasticity are similar to the ones obtained by other authors. However the hypothesis related to modulus of elasticity decrease due to the use of high Al/Si alkali activated mixtures was not confirmed.
