Articoli di riviste: "Ash reaction"

1

Liu, Zhiyong, Dong Xu e Yunsheng Zhang. "Experimental Investigation and Quantitative Calculation of the Degree of Hydration and Products in Fly Ash-Cement Mixtures". Advances in Materials Science and Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/2437270.

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To explore the hydration process of fly ash-cement blended mixtures, the degrees of the fly ash and cement reactions as well as the content of nonevaporated water were determined at various water to binder ratios, curing ages, and fly ash incorporation amounts. An equation describing the relationship between the degree of hydration and the effective water to binder ratio was established based on the experimental results. In addition, a simplified scheme describing a model of the degree of reaction in fly ash-cement mixtures is proposed. Finally, using reaction stoichiometry, quantitative equations for the hydration products of fly ash-cement blended pastes are proposed by considering the hydration reactions of fly ash and cement as well as their interactions. The predicted results of the enhanced degree of cement hydration, content of calcium hydroxide (CH), and porosity are consistent with the experimental data.

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Lu, G. Q. "Ash effect on reaction rates during high-ash char activation". Carbon 31, n. 8 (1993): 1359. http://dx.doi.org/10.1016/0008-6223(93)90100-o.

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Gulyaev, Vitaly, Vadim Barsky e Natalya Gurevina. "Effect of Total Ash Content and Coals Ash Composition on Coke Reactivity". Chemistry & Chemical Technology 3, n. 3 (15 settembre 2009): 231–36. http://dx.doi.org/10.23939/chcht03.03.231.

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The article deals with the hypothesis of the influence of coals mineral components on coke reactivity. It has been shown that the reaction between carbon and carbon dioxide proceeds in kinetic area and its rate depends upon total ash content of coked coal. The data showing catalyst effect of coal mineral components upon their organic mass pyrolysis and consequently upon coke reactivity have been presented.

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Ťažký, Martin, e Rudolf Hela. "Synergistic Effect of High Temperature Fly Ash with Fluidized Bed Combustion Fly Ash in Cement Composites". Key Engineering Materials 722 (dicembre 2016): 113–18. http://dx.doi.org/10.4028/www.scientific.net/kem.722.113.

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Using high temperature fly ash for his pozzolan properties to cement composite production is known a few years ago. New ways combustion of fossil fuels also creates a new type of fly ash, named fluidized bed combustion fly ash. However, this fly ash has same pozzolan properties as has high temperature fly ash, this type is not using for production of cement composites. Fluidized bed combustion fly ash has highly variable chemical composition but usually it has a higher amount of free CaO together with sulphates. This higher amounts of free CaO after mixing of fluidized bed combustion fly ash with water to some extent becomes an activator for the beginning of the pozzolanic reaction, during which is consumed the extinguished CaO. If there is also present high temperature fly ash in cement composite, it could be accelerated his pozzolanic reaction in the same manner using a fluidized bed combustion fly ash. In this experiment was tested a synergy effect in the use of fluidized bed combustion fly ash with high temperature fly ash as an additive. The experiment was carried out on cement pastes that have been studied in particular the progress of hydration processes, pointing to a possible acceleration of pozzolanic reactions of both types of fly ash.

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Zhu, Xun Guo, e Kai Cao. "The Inhibition Studying of Many-Doped Mineral Admixture for Concrete Alkali Silicate Reaction". Advanced Materials Research 690-693 (maggio 2013): 771–75. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.771.

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In the theoretical basic of only mixing the pulverized fuel ash, the slag or the silicon ash experiments, carrying on concrete alkali-aggregate reaction experiment separately that double-doped the pulverized fuel ash and the silicon ash, double-doped the pulverized fuel ash and the slag, double-doped the slag and the silicon ash, three-mixed the pulverized fuel ash, the slag and the silicon ash. The result indicated the effect of mixing pulverized fuel ash and the silicon ash is better than the mixing silicon ash and slag or pulverized fuel ash and slag. Besides three-mixed the pulverized fuel ash, the slag and the silicon ash can effectively suppress the reaction of concrete alkali-silica acid response（ASR）

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Wang, Yong Zai, Le Wang, Hong Ming Xu e Shao Hui Luo. "Fabrication of Nano Zeolite P from Coal Fly Ash by Combining Alkaline — Fusion and Hydrothermal Reactions". Key Engineering Materials 591 (novembre 2013): 126–29. http://dx.doi.org/10.4028/www.scientific.net/kem.591.126.

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Well-crystallised nanozeolite P has been synthesized from coal fly ash by combined method of alkaline-fusion and hydrothermal reactions. The influence of preparation parameters, such as the proportion of fly ash/NaOH, the hydrothermal reaction temperature and time on the reaction products were investigated by XRD and FESEM. Results indicated that, the optimum conditions for fabrication of a single phase of zeolite P were the mass ratio of fly ash/ NaOH =1/1, fusion temperature at 550°C and hydrothermal temperature at 100°C for 48h .The average crystallite sizes of the zeolite samples are 29.4nm. The obtained products show crystal morphology heterogeneity comprised by various euhedral forms.

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Bumrongjaroen, Walairat, Richard A. Livingston, Dan A. Neumann e Andrew J. Allen. "Characterization of fly ash reactivity in hydrating cement by neutron scattering". Journal of Materials Research 24, n. 7 (luglio 2009): 2435–48. http://dx.doi.org/10.1557/jmr.2009.0267.

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Partial replacement of hydrating Portland cement by fly ash produces competing effects: it contributes calcium hydrate silicate (C-S-H) gel through the pozzolanic and alkali-activated reactions but dilutes the contribution of the main Portland cement reaction. To investigate this, two neutron-scattering methods were applied to density-fractionated lignite-type and bituminous-type fly ash/Portland cement pastes (20% by mass replacement). Small-angle neutron scattering (SANS) measured the effect of the fly ash on the fractal C-S-H microstructure, whereas inelastic neutron scattering (INS) measured the pozzolanic reaction in terms of calcium hydroxide (CH) consumption. The CH consumption increased with the effective density fraction, and the fractal microstructure evolved more slowly for all fly ash mixes compared with the pure cement control. However, gel volume measured by SANS showed no correlation with the CH consumption measured by INS. The implications of these results are discussed.

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8

Li, Si Qiong, e Jie Chen. "Thermodynamic Analysis in Sintering Reaction of Coal Fly Ash with Alkali". Materials Science Forum 809-810 (dicembre 2014): 895–900. http://dx.doi.org/10.4028/www.scientific.net/msf.809-810.895.

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With sodium carbonate and calcium oxide as sintering additives, through the thermodynamic analysis and sintering experiment, study the thermodynamic behavior of fly ash with both in the sintering process; the sintering products were analyzed by XRD. The research results show that sodium carbonate as sintering additive fly ash thermal decomposition of the main phase of nepheline (NaAlSiO4), calcium oxide as sintering additives, and fly ash sintered products mainly 12CaO·7Al2O3、2CaO·Al2O3·SiO2 and 2CaO·SiO2 etc., And the temperature of the above substances generated is very favorable, fly ash and calcium oxide sintered at high temperature. Through sintering can effectively decompose the fly ash of quartz and mullite, soluble in acid or alkali salts, lay the foundation for the extraction of aluminum and silicon material from fly ash.

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9

Luo, Biwei, Pengfei Li, Yan Li, Jun Ji, Dongsheng He, Qifeng Tian e Yichang Chen. "Feasibility of fly ash as fluxing agent in mid- and low-grade phosphate rock carbothermal reduction and its reaction kinetics". Green Processing and Synthesis 10, n. 1 (1 gennaio 2021): 157–68. http://dx.doi.org/10.1515/gps-2021-0008.

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Abstract The feasibility of industrial waste fly ash as an alternative fluxing agent for silica in carbothermal reduction of medium-low-grade phosphate ore was studied in this paper. With a series of single-factor experiments, the reduction rate of phosphate rock under different reaction temperature, reaction time, particle size, carbon excess coefficient, and silicon–calcium molar ratio was investigated with silica and fly ash as fluxing agents. Higher reduction rates were obtained with fly ash fluxing instead of silica. The optimal conditions were derived as: reaction temperature 1,300°C, reaction time 75 min, particle size 48–75 µm, carbon excess coefficient 1.2, and silicon–calcium molar ratio 1.2. The optimized process condition was verified with other two different phosphate rocks and it was proved universally. The apparent kinetics analyses demonstrated that the activation energy of fly ash fluxing is reduced by 31.57 kJ/mol as compared with that of silica. The mechanism of better fluxing effect by fly ash may be ascribed to the fact that the products formed within fly ash increase the amount of liquid phase in the reaction system and promote reduction reaction. Preliminary feasibility about the recycling of industrial waste fly ash in thermal phosphoric acid industry was elucidated in the paper.

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10

Gong, Yanbing, Junmin Sun, Shu-Ying Sun, Guozhi Lu e Ting-An Zhang. "Enhanced Desilication of High Alumina Fly Ash by Combining Physical and Chemical Activation". Metals 9, n. 4 (4 aprile 2019): 411. http://dx.doi.org/10.3390/met9040411.

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In this work, a physical–chemical activation desilication process was proposed to extract silica from high alumina fly ash (HAFA). The effects of fly ash size, hydrochloric acid concentration, acid activation time, and reaction temperature on the desilication efficiency were investigated comprehensively. The phase and morphology of the original fly ash and desilicated fly ash were analyzed by X-ray diffraction (XRD) and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS). Compared with the traditional desilication process, the physical–chemical activation desilication efficiency is further increased from 38.4% to 53.2% under the optimal conditions. Additionally, the kinetic rules and equations were confirmed by the experimental data fitting with shrinking core model of liquid–solid multiphase reaction. Kinetic studies show that the enhanced desilication process is divided into two processes, and both steps of the two-step reaction is controlled by chemical reaction, and the earlier stage activation energy is 52.05 kJ/mol and the later stage activation energy is 58.45 kJ/mol. The results of mechanism analysis show that physical activation breaks the link between the crystalline phase and the amorphous phase, and then a small amount of alkali-soluble alumina in the amorphous phase is removed by acid activation, thereby suppressing the generation of side reactions of the zeolite phase.

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Narmluk, Mongkhon, e Toyoharu Nawa. "Effect of Curing Temperature on Pozzolanic Reaction of Fly Ash in Blended Cement Paste". International Journal of Chemical Engineering and Applications 5, n. 1 (2014): 31–35. http://dx.doi.org/10.7763/ijcea.2014.v5.346.

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12

Luo, Zhong Tao, Bao Guo Ma, Jiu Jun Yang e Xiang Guo Li. "Hydration Process and Mechanism of Fly Ash in the Cement Mortars". Materials Science Forum 675-677 (febbraio 2011): 551–54. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.551.

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In the environments of saturated limewater at 20±2°C and fly ash in cement mortars at 20±2°C, the hydration mechanism of fly ash is studied. The results indicate: under this test condition, the reaction speed of fly ash presents the degressive tendency basically within 90 days, and its chemical activation is an accumulation change process. The hydrated course of fly ash in the two environments is resembled, and only the age effectiveness is inconsistent. The test methods of Ka value and reaction degree can be used to analyze chemical activation of fly ash effectively. Rapid evaluation can be used on early activation of fly ash by Ka value and the later period one can be estimated by reaction degree.

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13

Derkowski, Arkadiusz, e Marek Michalik. "Statistical Approach to the Transformation of Fly Ash into Zeolites". Mineralogia 38, n. 1 (1 gennaio 2007): 47–69. http://dx.doi.org/10.2478/v10002-007-0018-5.

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Statistical Approach to the Transformation of Fly Ash into ZeolitesThe experimental conversion of F-class fly ash into zeolites is described. The ash, composed mainly of aluminosilicate glass, mullite and quartz, was collected in the Cracow power plant (southern Poland). The experiments involved the heating of fly ash samples in PTFE vessels. Time, temperature and solution composition were the reaction parameters considered in the experiments and in the subsequent modeling. A series of reactions with 0.5, 3 and 5M NaOH solutions (and some with additional 3M NaCl) were carried out at 70°, 100° and 150°C for 12-48 hours under autogenic pressure (not measured) and at a constant ash-to-solution ratio of 33.3 g/l. The following zeolite phases were synthesized: sodalite (SOD structure), hydroxysodalite (SOD), CAN type phases, Na-X (FAU), and NaP1 (GIS). Statistically calculated relationships based on the mineral- and chemical compositions of the reaction products support the conclusion that the type of zeolite phase that crystallizes depends on the concentration of OH- and Cl- in solution and on the temperature of the reaction. The duration of reaction, if on the order of tens of hours, is of less significance. The nature of the zeolite phase that crystalises is controlled by the intensity and selectivity of the substrate dissolution. That dissolution can favour, in sequence, one or other of the components in the substrate, resulting in Si/Al variation in the reaction solutions. Mullite dissolution (decreasing solution Si/Al) characterizes the most advanced reaction stages. The sequence of crystallization of the zeolite phases mirrors the sequential dissolution of substrate components, and the composition of the crystallizing zeolite crystals reflects the changes in the solution Si/Al.

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14

Luo, Zhong Tao, Bao Guo Ma, Jiu Jun Yang e Jun Xia Liu. "Effects of Fineness on Activity Character of Fly Ash". Advanced Materials Research 266 (giugno 2011): 114–17. http://dx.doi.org/10.4028/www.scientific.net/amr.266.114.

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The hydrated character of cement paste with fly ash was studied, through the methods of compressive strength, non-evaporable water content, reaction degree of fly ash and micro-analysis. The results indicated that the chemical activity of fly ash was an accumulative change process under this test condition. The starting point of chemical reaction of fly ash was nearby 28 days. In front of 28 days, the chemical activation of fly ash was not wakened, and the compressive strength of cement pastes with fly ash at this age was mainly from multiplex effects of cement hydration and the micro-aggregate effect, granule morphology effect and pozzolanic effect of fly ash.

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Doddi, Adinarayana, Michael Weinhart, Alexander Hinz, Dirk Bockfeld, Jose M. Goicoechea, Manfred Scheer e Matthias Tamm. "N-Heterocyclic carbene-stabilised arsinidene (AsH)". Chemical Communications 53, n. 45 (2017): 6069–72. http://dx.doi.org/10.1039/c7cc02628e.

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N-Heterocyclic carbene adducts of the parent arsinidene (AsH) were prepared by two different synthetic routes, either by reaction of As(SiMe₃)₃ with 2,2-difluoroimidazolines followed by desilylation or by reaction of [Na(dioxane)_3.31][AsCO] with imidazolium chlorides.

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16

Qi, Wen Bin, Chun Yan Tian e Xiao Xin Feng. "Alkali-Silica Reaction in Concrete Engineering Suppression Measures of Inquiry". Applied Mechanics and Materials 529 (giugno 2014): 26–31. http://dx.doi.org/10.4028/www.scientific.net/amm.529.26.

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Local materials was used as raw materials in the test. Test methods are standard test methods. It compared the use of fly ash alone or lithium hydroxide used alone inhibited the effect of alkali-silica reaction, and to a certain percentage of fly ash and lithium hydroxide complex joint effect of inhibiting alkali-silica reaction in the test. The results showed that compound admixtures overcome the shortcomings of the use of fly ash alone or lithium hydroxide inhibition of alkali-silica reaction. It can achieve the goal of complementary advantages.

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Li, Bei Xing, Jian Feng Zhang e Da Ke. "Effectiveness and Mechanism of Fly Ash in Inhibiting Alkali-Silica Reaction of Sandstone". Advanced Materials Research 250-253 (maggio 2011): 40–45. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.40.

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The effectiveness of fly ash in suppressing expansion due to alkali-silica reaction (ASR) of sandstone are studied respectively based on accelerated mortar bar test and concrete prism test. The mechanism of fly ash in inhibiting the ASR of sandstone is examined by scanning electron microscope (SEM) and energy dispersive analysis of x-ray (EDAX). Moreover, the reliability of fly ash in inhibiting ASR of sandstone was discussed through concrete strength and frost resistance tests. Results indicate that the replacement amount of fly ash is 20%, the expansion due to ASR can be decreased to the critical value of a non-reactive aggregate. The reason why fly ash can inhibit the alkali reactivity for the sandstone is that the strong reaction between alkali and fly ash dissipates the alkali, and the products of alkali-silica-aluminate gels are non-expansible. For the concrete specimens suffered from accelerated ASR tests, their strength and frost resistance are decreased with the increment of fly ash replacement.

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Djobo, Jean Noël Yankwa, e Dietmar Stephan. "Control of the setting reaction and strength development of slag-blended volcanic ash-based phosphate geopolymer with the addition of boric acid". Journal of the Australian Ceramic Society 57, n. 4 (27 maggio 2021): 1145–54. http://dx.doi.org/10.1007/s41779-021-00610-4.

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AbstractThis work aimed to evaluate the role of the addition of blast furnace slag for the formation of reaction products and the strength development of volcanic ash-based phosphate geopolymer. Volcanic ash was replaced by 4 and 6 wt% of ground granulated blast furnace slag to accelerate the reaction kinetics. Then, the influence of boric acid for controlling the setting and kinetics reactions was also evaluated. The results demonstrated that the competition between the dissolution of boric acid and volcanic ash-slag particles is the main process controlling the setting and kinetics reaction. The addition of slag has significantly accelerated the initial and final setting times, whereas the addition of boric acid was beneficial for delaying the setting times. Consequently, it also enhanced the flowability of the paste. The compressive strength increased significantly with the addition of slag, and the optimum replaced rate was 4 wt% which resulted in 28 d strength of 27 MPa. Beyond that percentage, the strength was reduced because of the flash setting of the binder which does not allow a subsequent dissolution of the particles and their precipitation. The binders formed with the addition of slag and/or boric acid are beneficial for the improvement of the water stability of the volcanic ash-based phosphate geopolymer.

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NAGANUMA, Hiroshi, Nobuya IKEDA, Tadashi ITO, Fumio SATO, Kazuaki URASHIMA, Tsuyoshi TAKUWA, Ryo YOSHIIE e Ichiro NARUSE. "Elucidation of Ash Deposition Mechanisms with Interfacial Reaction". Journal of the Japan Institute of Energy 88, n. 9 (2009): 816–22. http://dx.doi.org/10.3775/jie.88.816.

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Zeng, Qiang, e Kefei Li. "Reaction and microstructure of cement–fly-ash system". Materials and Structures 48, n. 6 (16 febbraio 2014): 1703–16. http://dx.doi.org/10.1617/s11527-014-0266-y.

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21

García-Lodeiro, I., A. Palomo e A. Fernández-Jiménez. "Alkali–aggregate reaction in activated fly ash systems". Cement and Concrete Research 37, n. 2 (febbraio 2007): 175–83. http://dx.doi.org/10.1016/j.cemconres.2006.11.002.

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Prasetia, Irfan, e M. Fahmi Rizani. "Analysis of fly ash from PLTU Asam-Asam as a construction material in terms of its physical and mechanical properties". MATEC Web of Conferences 280 (2019): 04013. http://dx.doi.org/10.1051/matecconf/201928004013.

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Nowadays, PLTU Asam-Asam produced enormous amounts of combustion waste in the form of coal ash. On the contrary, only a little effort has been made to utilize coal ash from PLTU Asam-Asam, especially from the research side. In fact, due to its siliceous material, when reacting with CH in concrete, will form CSH hence improves concrete strength. In this study, in order to analyze the physical and mechanical properties of concrete using fly ash from PLTU Asam-Asam, 54 concrete samples were prepared according to SNI-03-2834-2000. The examination of concrete samples workability was conducted based on the slump test according to SNI 1972:2008. Moreover, the compressive tests were carried out in accordance with SNI 1974:2011. The slump test results show that the pozzolanic reaction of fly ash contributes to the improvement of concrete workability. Furthermore, the variation in w/b ratio was also affecting the results of the slump test. As for the compressive strength, in general speaking, the replacement ratio of 30% of cement with fly ash in concrete could produce concrete strength up to 30 Mpa. It is also important to note that due to the pozzolanic reactions tends to delayed, it is expected that at later ages (above 28 days) concrete with fly ash will gain much more strength compared to ordinary concrete.

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Fernández, J., e M. J. Renedo. "HYDROTHERMAL REACTION OF FLY ASH/HYDRATED LIME: CHARACTERIZATION OF THE REACTION PRODUCTS". Chemical Engineering Communications 193, n. 10 (ottobre 2006): 1253–62. http://dx.doi.org/10.1080/00986440500440199.

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Zhou, Hong Yi, Fu Hai Li, Si Yin Chen, Xiao Gang Zhao e Gu Hua Li. "Study on Experiments of Matekaolin in Relation to Alkali-Silica Reaction". Key Engineering Materials 629-630 (ottobre 2014): 528–33. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.528.

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The influence of the content of matekaolin powder and fly ash in cement on controlling ASR was evaluated using Accelerated Mortar Bar Test (AMBT). Replacing cement with matekaolin powder to the extent of 5%,10%,15%,20%,25%,and with fly ash to the extent of 10%,20%,30%,35%,40%, 45% respectively. The result show that matekaolin powder and fly ash both can control Alkali-aggregate activity but to different degrees. Small amount of metakaolin powder exerts significant influence, whereas only when the proportion of fly ash is up to 35%, can it control ASR effectively. The effect and mechanism of the control of the extension of glass aggregate activity was studied by means of SEM analysis.

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Rahman, Norbaizurah, Andri Kusbiantoro, Khairunisa Muthusamy e Mohd Mustafa Al Bakri Abdullah. "Degree of Reaction and Alkali-Leaching of Geopolymer Containing Ca-Rich Source Material and Dipotassium Hydrogen Phosphate". Key Engineering Materials 765 (marzo 2018): 275–79. http://dx.doi.org/10.4028/www.scientific.net/kem.765.275.

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Disparity of anion and cation in geopolymer framework may result in the formation of efflorescence on the surface of hardened geopolymer specimen. The existence of efflorescence would be intensified with the use of dipotassium hydrogen phosphate (K2HPO4) as a chemical retarder for geopolymer mixture. In this study, paper mill sludge ash (PMSA) was used as a Ca-rich aluminosilicate source to reduce the development of efflorescence crystals. PMSA was utilized to partially replace fly ash at 5% and 10% (by weight of fly ash). Meanwhile, K2HPO4 was used as the external agent with various proportions, which were 0.1%, 0.3%, and 0.5% (by weight of fly ash). The external agent in this study was purposed to extend the setting time and enhance the mechanical properties of geopolymer. Fly ash and PMSA (if any) were activated by reacting them with 6M sodium hydroxide and sodium silicate solution. Freshly cast specimens were cured for 24 hours in electronic oven with the temperature setting of 30°C and 90°C. They were demoulded after 24 h and kept at room temperature (28±2 °C) until the testing day. Evaluation on the setting time characteristic of fresh geopolymer mortar was conducted with Vicat test while degree of reaction was performed on the hardened specimens to measure the reaction of fly ash during geopolymerization. Based on the experimental result, the inclusion of 5% PMSA shows the greatest effect in reducing the development of efflorescence crystal and increase the degree of reaction of geopolymer system. It is presumed that PMSA has altered the geopolymerization process by activating calcium oxide precursors to form three tetrahedral structures in the framework.

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Han, Hong Jing, Yan Guang Chen, Jia Lu, Dan Dan Yuan, Jun Song e Ying Chen. "Investigation on the Extraction of Aluminum and Iron from Fly Ash by Sodium Carbonate Fusion Method". Advanced Materials Research 807-809 (settembre 2013): 1262–65. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.1262.

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In recent years, utilization of fly ash has gained much attention in public and industry, which will help reduce the environmental burden and enhance economic benefit. In the utilizations of fly ash, the most high value-added applications is extraction of metal elements from fly ash. In this paper, the aluminum and iron extraction was investigated by orthogonal experiments. The results show that the optimum extraction condition was reaction temperature 800 °C, reaction time 3 h, the mass ratio of fly ash to Na2CO3 was 1:1.5.

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Bai, Guang Hui, Lin Lv, Tong Song Wang, Peng Cheng Li e Cai Ling He. "Study on the Method of Lime Cream to Remove Sodium from Fly Ash Red Mud by Soda-Lime Sintering Process". Advanced Materials Research 726-731 (agosto 2013): 2790–94. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.2790.

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It is the first time to remove sodium from the fly ash red mud by soda-lime sintering process to determine whether the fly ash red mud can be used in cement production. This paper studies the effects of the reaction time, the reaction temperature, the ratio of liquid to solid, and the amount of sodium removal agent on the removal of milk of lime method of fly ash red mud in sodium. The optimal reaction conditions are that: the reaction time is 120min, the reaction temperature is 90°C, the ratio of liquid to solid ratio is 6:1, and the ratio of sodium removal agent Ca (OH) 2 to the red mud of Na2O use ratio is 9:1. Under this condition, the sodium removal rate (Na2O, the same below) to 57.2%, the total sodium content in fly ash red mud decreases from 4.7% to 1.8% after sodium removal, achieving the expected goal.

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Yan, Han Dong. "Studies on the Carbonation Restraint Capability of Dam Concrete with High Fly Ash Content". Advanced Materials Research 374-377 (ottobre 2011): 781–86. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.781.

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A quantificational relationship between carbonization depth and fly ash content as well as carbonation age to the mortars corresponding to five typical concrete mixture ratio of dam interior，exterior and foundation was educed by means of accelerating carbonation test and plurality regression means. The experimental results demonstrated that the carbonation restraint capability of the concrete was degreased with the increase of the fly ash content. The studies on the Ca(OH)2 content of the fly ash-cement paste attested that the replacement of fly ash to cement should be low to 40% in dam exterior concrete according to the results of theoretics calculation, glycerine-ethanol and XRD measurement. The extent of the Pozzloan reaction of the fly ash was reduced with the increase of the fly ash content according to the Ca(OH)2 quantity expended by the Pozzolan reaction resulted from the TG-DTA measurement. The Pozzloan reaction of the fly ash occurred mainly before 90d of the curing age, and it would not be high form 90d till to one year. The fly ash content of the dam interior and foundation concrete may be enhanced to 55% because the dam interior and foundation concrete were not contacted with the atmosphere and the carbonation extent may be very low.

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Tennakoon, Chandani, Kwesi Sagoe-Crentsil, Jay G. Sanjayan e Ahmad Shayan. "Early Age Properties of Alkali Activated Brown Coal Fly Ash Binders". Advanced Materials Research 931-932 (maggio 2014): 457–62. http://dx.doi.org/10.4028/www.scientific.net/amr.931-932.457.

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The present study evaluates potential re-use options for two different types of brown coal fly ash (class C) sourced from Australia as feedstock for geopolymer binder systems. The study covers analysis of fundamental material and mix-design requirements for geopolymer binders as a basis to achieve durable brown coal ash geopolymer matrices. The study established that reference unblended 100% brown coal ash geopolymer mortar samples yielded low strength, typically below 5MPa and poor durability. However, appropriate blends of brown coal ash with selected black coal fly ash (class F) and blast furnace slag to achieve target Si/Al ratios significantly enhanced both setting characteristics, as well as early age compressive strength development (25-35MPa) while improving overall durability performance compared to reference mixes. Moreover, lagoon fly ash blended geopolymer shows better durability while dry precipitator fails to perform well. The discussion also focuses on key source material parameters and reaction processes that influence compressive strength and durability behaviour of marginal brown coal ash sources during geopolymerisation reactions.

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Rahman, Norbaizurah, Andri Kusbiantoro, Nabilah Mamat, Khairunisa Muthusamy e Mohd Mustafa Al Bakri Abdullah. "Roles of Calcium in Geopolymer Containing Paper Mill Sludge Ash". Materials Science Forum 917 (marzo 2018): 311–15. http://dx.doi.org/10.4028/www.scientific.net/msf.917.311.

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High amount of calcium oxide (CaO) in source material is known to positively influence the mechanical strength of fly ash based geopolymer. This study was conducted to investigate the suitability of paper mill sludge ash (PMSA) to partially replace fly ash in geopolymer mortar based on its degree of reaction. Fly ash was activated by a combination of sodium silicate solution and 6 M sodium hydroxide solution. The mixtures were designed to replace fly ash content with PMSA at 5%, 10% and 15% (by weight of fly ash). To observe its effect on the mechanical strength, the specimens were cured in three different temperatures, which are 30°C, 60°C and 90°C for 24 hours. After 24 hours, the hardened specimens were demoulded and placed at room temperature until the testing days. Measurement on fresh geopolymer properties was conducted with setting time and flowability tests, while degree of reaction tests was conducted on the hardened specimen. Based on the results, 5% PMSA demonstrated superior degree of reaction than other mixtures, particularly at higher curing temperature.

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31

Kath, Aline Hernandez, Gláucia Oliveira Islabão, Ledemar Carlos Vahl e Juliana Brito da Silva Teixeira. "Reaction rate and residual effect of rice husk ash in soil acidity parameters". Revista Ceres 65, n. 3 (giugno 2018): 278–85. http://dx.doi.org/10.1590/0034-737x201865030008.

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ABSTRACT The rice husk ash has been applied in agricultural land, with potential of replace limestone and, supply phosphorus and potassium. However, its residual effect in soil is still unknown. This investigation aimed to evaluate the reaction rate and residual effect of rice husk ash in soils acidity parameters. A field experiment was conducted with five treatments: four rice husk ash dosages 0, 30, 60 and 120 t ha-1 and one treatment with recommended soil lime and fertilizer (dolomitic limestone to reach pH 6, 150 kg ha-1 P2O5 as single superphosphate and 80 kg ha-1 K2O as potassium chloride) where five soil samples. Soil samples were collected in the layers 0.00 - 0.10 m and 0.10 - 0.20 m at 15, 211, 400, 517 and 804 days after ash incorporation. Chemical attributes were determined: soil pH (pH), soil base, exchangeable cation values (Ca, Mg, K and Na) and cation exchange capacity (CEC) at pH 7. Results showed that reaction rate of rice husk ash is faster when compared to liming. As greater was rice husk ash dosage applied in soil, higher is the residual effect in pH. As corrective of soil acidity, the residual effect of rice husk ash is just the required time to occur the natural process of reacidification and leaching of basic cations, about 33 months for soils and weather conditions similar to this work.

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32

Zhou, Kun, Wei Fu, Hongxi Xie, Jihu Bao, Yayun Li, Lei Lu e Yunlang Cheng. "Study on reaction kinetics of single slime". E3S Web of Conferences 236 (2021): 02012. http://dx.doi.org/10.1051/e3sconf/202123602012.

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The study of the combustion characteristics of single slime fuels is the basis for achieving clean combustion of solid fuels. This paper uses a combination of experimental and theoretical analysis, combined with the Coats-Redfen integration method, to study the influence of ash content and heating rate on the kinetic parameters of coal slime, and solve the combustion kinetic parameters. The results show that under the same heating rate, the activation energy gradually increases. As the ash content of coal slime increases, the activity of the coal slime sample decreases, and the reaction activation energy gradually increases.

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33

Feng, Jingjing, Jianwei Sun e Peiyu Yan. "The Influence of Ground Fly Ash on Cement Hydration and Mechanical Property of Mortar". Advances in Civil Engineering 2018 (2018): 1–7. http://dx.doi.org/10.1155/2018/4023178.

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In this study, the ground fly ash is made of ordinary grade I fly ash by grinding. Compared with grade I fly ash, the influence of ground fly ash on cement hydration and mechanical property of mortar was investigated. The results show that ground fly ash can improve the hydration of cement at all the ages compared with grade I fly ash, and not only does its pozzolanic reaction start earlier, but the reaction degree is higher and the speed is quicker. Before 3 days, the contribution of ground fly ash to the strength is mainly due to physical filling and microaggregate effect. After that, the contribution of pozzolanic effect to the strength becomes obvious and can significantly increase the compressive strength after 60 days and the flexural strength after 28 days. The ground fly ash is better than grade I fly ash to optimize the pore structure of hardened pastes. It can significantly reduce the number of harmful pores (>20 nm) and increase the number of harmless pores (<20 nm), which refines the pore structure and makes the structure denser.

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34

Simatupang, Minson, Lukas Kano Mangalla, Romy Suryaningrat Edwin, Adris Ade Putra, Muhammad Thahir Azikin, Nini H. Aswad e Wayan Mustika. "The Mechanical Properties of Fly-Ash-Stabilized Sands". Geosciences 10, n. 4 (8 aprile 2020): 132. http://dx.doi.org/10.3390/geosciences10040132.

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Abstract (sommario):

The stabilization of soil through the addition of fly ash has been shown to be an effective alternative for improving the strength and stiffness of soil through the resulting chemical reactions. The chemical reaction that occurs dissociates the lime (CaO) in the fly ash, and the establishment of cementitious and pozzolanic gels (consisting of calcium silicate hydrate (CSH) gel and calcium aluminate hydrate (CAH) gel) binds the soil particles and increases the strength and stiffness of the soil. Investigations into the mechanical properties of sands stabilized with fly ash (fly-ash-stabilized sands) were conducted through a series of unconfined compressive strength (UCS) and direct shear strength tests for various fly ash percentages, curing times, grain sizes, degrees of saturation during sample preparation, and content of fines. It was found that the mechanical properties—UCS and direct shear strength (DSS)—of fly-ash-stabilized sands increased with both increasing fly ash content in the specimen and curing time, but decreased with increasing grain size, degree of saturation during sample preparation, and content of fines. The results indicated that fly-ash-stabilized sands required more than a month to attain their optimum performance with regard to binding sand particles.

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35

Ren, Xin, Wei Li, Zhongyang Mao e Min Deng. "Inhibition of the Alkali-Carbonate Reaction Using Fly Ash and the Underlying Mechanism". Crystals 10, n. 6 (5 giugno 2020): 484. http://dx.doi.org/10.3390/cryst10060484.

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In this paper, fly ash is used to inhibit the alkali-carbonate reaction (ACR). The experimental results suggest that when the alkali equivalent (equivalent Na2Oeq) of the cement is 1.0%, the adding of 30% fly ash can significantly inhibit the expansion in low-reactivity aggregates. For moderately reactive aggregates, the expansion rate can also be reduced by adding 30% of fly ash. According to a polarizing microscope analysis, the cracks are expansion cracks mainly due to the ACR. The main mechanisms of fly ash inhibiting the ACR are that it refines the pore structure of the cement paste, and that the alkali migration rate in the curing solution to the interior of the concrete microbars is reduced. As the content of fly ash increases, the concentrations of K+ and Na+ and the pH value in the pore solution gradually decrease. This makes the ACR in the rocks slower, such that the cracks are reduced, and the expansion due to the ACR is inhibited.

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36

Menéndez, Esperanza, Cristina Argiz e Miguel Ángel Sanjuán. "Reactivity of Ground Coal Bottom Ash to Be Used in Portland Cement". J 4, n. 3 (23 giugno 2021): 223–32. http://dx.doi.org/10.3390/j4030018.

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Ground coal bottom ash is considered a novel material when used in common cement production as a blended cement. This new application must be evaluated by means of the study of its pozzolanic properties. Coal bottom ash, in some countries, is being used as a replacement for natural sand, but in some others, it is disposed of in a landfill, leading thus to environmental problems. The pozzolanic properties of ground coal bottom ash and coal fly ash cements were investigated in order to assess their pozzolanic performance. Proportions of coal fly ash and ground coal bottom ash in the mixes were 100:0, 90:10, 80:20, 50:50, 0:100. Next, multicomponent cements were formulated using 10%, 25% or 35% of ashes. In general, the pozzolanic performance of the ground coal bottom ash is quite similar to that of the coal fly ash. As expected, the pozzolanic reaction of both of them proceeds slowly at early ages, but the reaction rate increases over time. Ground coal bottom ash is a promising novel material with pozzolanic properties which are comparable to that of coal fly ashes. Then, coal bottom ash subjected to an adequate mechanical grinding is suitable to be used to produce common coal-ash cements.

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37

Li, Han Xu, Xiang Cao e Yong Xin Tang. "Study of Effect of Ternary-Component Blended Coal on Coal Gasification Reaction at High Temperature". Applied Mechanics and Materials 295-298 (febbraio 2013): 3104–9. http://dx.doi.org/10.4028/www.scientific.net/amm.295-298.3104.

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Three typical Chinese individual coals which existed remarkable difference on coal ash chemical composition and ash fusion temperature were selected to carry out coal blending experiments to study the coal gasification reaction at high temperature by means of using ternary-component blended coal technique and TGA-DTA method. According to ternary-component blended coal with a certain proportion, ash chemical composition and coal-char/CO2 gasification reactivity were analyzed by X-ray fluorescence (XRF) and thermogravimetric analysis-derivative thermogravimetric analysis (TGA-DTG), respectively. The results show that the ash chemical components change because ternary-component blended coals change the mineral composition, and hence, the gasification reactivity can be affected as well. Moreover, in accordance with reactivity index R, it indicates that the order of gasification reactivity of three individual coals and four blended coal options is coal x > option B > option A > option D > option C > coal z >coal y. Meanwhile, a new mathematical model called per unit ash alkali index B* was established by using the ash chemical component dates, which has a good corresponding relationship with R for four blending coal options. Utilizing ternary-component blended coal technique could improve the high-temperature coal ash gasification reaction.

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38

Han, Hong Jing, Yan Guang Chen, Jia Lu, Ting Ting Xu, Yong Hui Jiang e Jia Li Bai. "Investigation of Removing Iron from Fly Ash". Advanced Materials Research 807-809 (settembre 2013): 1194–97. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.1194.

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Abstract (sommario):

Fly ash, as an environmental pollutant, is generated in the process of coal combustion for energy conversion. It has been widely used in so many applications, such as, preparation of zeolite, extracting alumina, and so on. Iron composition has some side-effect on the purity and whiteness of the products prepared form fly ash. In this paper, removal of unburned carbon and iron composition was investigated. The results show that the carbon can be removed completely from fly ash after calcination under 800°C for 2h. Acid leaching was used to remove iron from the fly ash after decarburization. The optimum processing parameter is, hydrochloric acid concentration 5mol·L-1, reaction temperature 80°C and reaction time 2h.

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39

Yao, Zhidong, Chikashi Tamura, Motohide Matsuda e Michihiro Miyake. "Resource recovery of waste incineration fly ash: Synthesis of tobermorite as ion exchanger". Journal of Materials Research 14, n. 11 (novembre 1999): 4437–42. http://dx.doi.org/10.1557/jmr.1999.0601.

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Tobermorite was synthesized successfully from waste incineration fly ash by hydrothermal treatment in the presence of sodium hydroxide solution. The tobermorite synthesis was examined as a function of reaction temperature, time, and NaOH concentration. The formation of tobermorite was identified in all of the fly ash treated with NaOH at 180 °C, followed by the minor generations of sodalite and cancrinite phases with increasing NaOH concentration and extending reaction time. The NaOH-treated fly ash revealed the uptake behaviors for Cs+ and NH4+, whereas the fly ash untreated with NaOH solution did not show that. The uptake amounts of resulting products were also determined: 0.40 mmol/g for Cs+ and 0.35 mmol/g for NH4+ in the fly ash treated with 2.0 M NaOH at 180 °C for 20 h.

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40

Becelic-Tomin, Milena, Bozo Dalmacija, Dragana Tomasevic, Jelena Molnar e Ljiljana Rajic. "Application of the pyrite ash in the microwave Fenton process of decolorization of the synthetic color solution". Chemical Industry 67, n. 3 (2013): 399–409. http://dx.doi.org/10.2298/hemind120428088b.

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The aim of this study is to investigate the possibility of fly ash and pyrite ash applications as a Fenton catalysts in the advancement of the microwave/hydrogen peroxide (MW/H2O2) treatment in the Rhodamine B decolorization process. At the same time, a comparison of the influence of these heterogenous catalysts with the homogenous Fenton catalyst on the decolorization process was conducted. The influence of the catalyst was tracked in previously optimized conditions MW/H2O2: [Rhodamine B] = 0.2 mM; pH 3.2; temperature 85?C; [H2O2] = 80 mM; power = 300 W. Under such conditions, the efficiency of 99.5% was achieved after 30 minutes of reaction time. The same efficiency was achieved through the application of MW/Fe2+/H2O2 and MW/pyrite ash/H2O2 after only 10 minutes of reaction time. The order of the tested integrated processes according to the initial reaction rate is as follows: MW/Fe2+/H2O2>MW/fly ash/H2O2>MW/H2O2. The results of this study present a basis for further research and optimization of water solution decolorization process through pyrite ash with MW and hydrogen peroxide application.

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41

MURAYAMA, Norihiro, Kazuo OGAWA, Yasuyoshi NISHIKAWA, Hideki YAMAMOTO e Junji SHIBATA. "Reaction Mechanism of Zeolite Synthesis from Coal Fly Ash." Shigen-to-Sozai 116, n. 6 (2000): 509–14. http://dx.doi.org/10.2473/shigentosozai.116.509.

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42

Ordóñez, L. M., J. Payá, A. M. Coats e F. P. Glasser. "Reaction of rice husk ash with OPC and portlandite". Advances in Cement Research 14, n. 3 (luglio 2002): 113–19. http://dx.doi.org/10.1680/adcr.2002.14.3.113.

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43

Takeya, Hirotoshi, Toshiyuki Nago e Masahiro Sasaki. "Development of Hydrothermal Reaction Solidification of Paper Sludge Ash". JAPAN TAPPI JOURNAL 62, n. 4 (2008): 427–32. http://dx.doi.org/10.2524/jtappij.62.427.

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44

Glosser, Deborah, Prannoy Suraneni, O. Burkan Isgor e W. Jason Weiss. "Estimating reaction kinetics of cementitious pastes containing fly ash". Cement and Concrete Composites 112 (settembre 2020): 103655. http://dx.doi.org/10.1016/j.cemconcomp.2020.103655.

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45

Haha, M. Ben, K. De Weerdt e B. Lothenbach. "Quantification of the degree of reaction of fly ash". Cement and Concrete Research 40, n. 11 (novembre 2010): 1620–29. http://dx.doi.org/10.1016/j.cemconres.2010.07.004.

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46

Bloise, Andrea, Chiara Benedetta Cannata e Rosanna De Rosa. "Hydrothermal Alteration of Etna Ash and Implications for Mars". Minerals 10, n. 5 (17 maggio 2020): 450. http://dx.doi.org/10.3390/min10050450.

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Abstract (sommario):

Volcanic activity represents one of the main factors controlling the geological evolution of Mars, whose morphology has remarkable counterparts on Earth. Studies on the Martian surface revealed the widespread occurrences of newly formed minerals originated by the hydrothermal alteration of volcanic rocks. In this work, we carried out a series of experiments to test the reactions occurring during the hydrothermal alteration of basaltic ash from Etna (Italy) as a possible similar reaction fully grown on the Martian rock. The volcanic ash used for the hydrothermal alteration experiments was collected during the eruption of Etna in 2001, and its composition shares similarities with Martian bedrocks. Ash was altered under hydrothermal conditions at initial pH 5 at two temperatures (150 and 200 °C) and reaction times of 5, 10, and 31 days. After a number of runs, we attained analcime NaAlSi2O6·H2O. Our findings are in line with the hypothesis that zeolite on Mars probably originated from a low-temperature hydrothermal environment. The conclusions accord with the assumption that the analcime crystals recognized on Mars formed under the same conditions as those of our experimental setups.

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47

He, Xiao Fang, Chang Wen Miao, Yong Hao Wu, Xin Xin Cao e Dan Liu. "Thermal Reaction Kinetics of Fly Ash Cement Paste at the Age of 28 Days". Applied Mechanics and Materials 668-669 (ottobre 2014): 91–94. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.91.

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The thermal reaction kinetics of fly ash cement pastes were studied by Differential Scanning Calorimetry (DSC) and Thermal Gravity Analysis-Differential Thermal Gravity (TG-DTG) method, the kinetics parameters such as apparent activation energy was calculated by the Kissinger method, and the physical parameters were obtained. The result show that the fly ash cement pastes performance three endothermic reaction stages at different heating rates, peak temperatures of each stage at the range of 91.85~121.08°C, 453.93~496.48°C, and 680.21~751.62°C. TG-DTG show there were three thermal decomposition stages, thermal dehydration reaction apparent activation energy of fly ash cement pastes in each stage were 47.23kJ/mol, 128.84kJ/mol, and 134.07kJ/mol.

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48

Xu, Li Wei. "Method to Determine Reaction Degrees of Portland Cement and Fly Ash in Complex Pastes". Advanced Materials Research 374-377 (ottobre 2011): 1657–60. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.1657.

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To determine the reaction degrees of Portland cement and fly ash in complex pastes, an experiment of hydration degree for composite pastes, hydrochloric acid dissolution method for fly ash and solution heat method for cement is applied. It is shown from the test that a rather precise result has been obtained by the combined method. The hydration degrees of cement and fly ash in composite pastes agree well with those from theoretical analysis.

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49

Liu, Kai Wei, Min Deng e Li Wu Mo. "Effect of Fly Ash on Resistance to Sulfate Attack of Cement-Based Materials". Key Engineering Materials 539 (gennaio 2013): 124–29. http://dx.doi.org/10.4028/www.scientific.net/kem.539.124.

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The resistance to sulfate attack of mortars containing 0%, 20%, and 40% of fly ash cured in 5 wt. % sodium sulfate solution at 20°C was investigated in this paper. Visual appearance, cracking analysis, velocity of ultrasonic wave and length change were applied to evaluate the sulfate resistance of mortars. The phases and microstructure of the reaction products due to sulfate attack were examined by XRD and SEM, and the pore structure of the mortars was analyzed by MIP. The effects of fly ash on the sulfate attack of mortars were analyzed. Results indicated that the addition of fly ash improved the resistance of sulfate attack significantly, this probably contributed to the pozzonlanic reaction of fly ash.

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Li, Hui, Shi Shi, De Long Xu, Li Jun Zhuge e Le Le Zhang. "Research on the Dissolving Character of Active Si/Al in Fly Ash Activated by Alkali". Advanced Materials Research 150-151 (ottobre 2010): 1790–95. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.1790.

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This paper investigated the influence of activator concentration, reaction time and fineness of fly ash on the dissolving character of the active Si/Al in fly ash activated by alkali. The results indicated that with the increase of the NaOH solution concentration, the dissolving percentage of active Si/Al in the fly ash went up. The finer the fly ash particles were, the higher dissolving percentage of active Si/Al was obtained. Under strong basic (2M NaOH solution) and boiling condition, the reaction time of active Si/Al dissolving was short and less than 10 minutes. The content of vitreous phase contributed to the content of active components. Active Si existed in the state of Q0 unit which presented an isolated silicon-oxide tetrahedron in fly ash, and active Al exhibited as Al[OSi]3 and Al[OSi]4 units in 4 coordinate. As the fly ash was activated by alkali, smooth shell of fly ash was gradually corroded by NaOH solution, glass phase was dissolved and crystal phase was exposed to the outside.

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