The Experts below are selected from a list of 2535 Experts worldwide ranked by ideXlab platform
Pen-chi Chiang - One of the best experts on this subject based on the ideXlab platform.
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deployment of Accelerated Carbonation using alkaline solid wastes for carbon mineralization and utilization toward a circular economy
ACS Sustainable Chemistry & Engineering, 2017Co-Authors: Kinjal J Shah, Yi Hung Chen, Minghuang Wang, Pen-chi ChiangAbstract:This study suggests that the waste-to-resource supply chain can offer an approach to address simultaneously the issues of waste management and CO2 emissions toward a circular economy. Alkaline solid wastes can be used to mineralize CO2 through an Accelerated Carbonation reaction, especially if the wastes are generated near the point source of CO2, to achieve environmental and economic benefits. To enhance the performance of Accelerated Carbonation, a high-gravity Carbonation process using a rotating packed bed reactor was developed and deployed. Due to additional energy consumption in high-gravity Carbonation, the environmental benefits and economic costs should be critically assessed from a life-cycle perspective. In this study, the resource potential of alkaline solid wastes in Taiwan was first determined for CO2 mineralization and utilization using the high-gravity Carbonation process. Then, the performances of the process from engineering, environmental, and economic perspectives were evaluated and ex...
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Principles of Accelerated Carbonation Reaction
Carbon Dioxide Mineralization and Utilization, 2017Co-Authors: Pen-chi ChiangAbstract:Industrial alkaline solid wastes are ideal Accelerated Carbonation materials due to their availability and low cost. These materials are generally rich in calcium content and often associated with CO2 point source emissions so no mining is needed and the consumption of raw materials is avoidable. This chapter provides the principles and definitions of Accelerated Carbonation reaction using alkaline solid wastes. Two types of Carbonation processes, i.e., direct and indirect Carbonation, are briefly discussed from the theoretical considerations, including process chemistry and key performance indicators. The performance and application of both direct and indirect Carbonation processes can be found in detail in Chap. 8.
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integrated and innovative steel slag utilization for iron reclamation green material production and co2 fixation via Accelerated Carbonation
Journal of Cleaner Production, 2016Co-Authors: Rahul Adhikari, Pen-chi Chiang, Yi Hung Chen, Ping LiAbstract:Abstract Huge amounts of iron and steel slags are generated annually worldwide from integrated manufacturing processes and/or the electric arc furnace. However, conventional uses of untreated iron and steel slags in civil engineering have encountered several technological barriers, such as fatal volume expansion, heavy metal leaching and low cementitious property of slag. In this study, the physico-chemical properties of four different types of slag, blast furnace slag, basic oxygen furnace slag, electric arc furnace slag and ladle refining furnace slag, are illustrated. The challenges and barriers in direct use of steel slags in civil engineering are comprehensively summarized. To overcome the barriers of slag utilization, an Accelerated Carbonation process is proposed and reviewed in terms of theoretical perspectives and practical considerations. Since diluted CO2 in flue gas can be directly introduced for Carbonation, additional environmental and economic benefits such as CO2 emission reduction are obtained. In addition, the performance of various new carbonated slags or products is systematically reviewed, in terms of changes in the physico-chemical properties of carbonated slag. To facilitate the industrialization of Accelerated Carbonation, several suggestions are made regarding future research directions.
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co2 capture by Accelerated Carbonation of alkaline wastes a review on its principles and applications
Aerosol and Air Quality Research, 2012Co-Authors: E E Chang, Pen-chi ChiangAbstract:ABSTRACTCO2 capture, utilization, and storage (CCUS) is a promising technology wherein CO2 is captured and stored in solid form for further utilization instead of being released into the atmosphere in high concentrations. Under this framework, a new process called Accelerated Carbonation has been widely researched and developed. In this process, alkaline materials are reacted with high-purity CO2 in the presence of moisture to accelerate the reaction to a timescale of a few minutes or hours. The feedstock for Accelerated Carbonation includes natural silicate-minerals (e.g., wollastonite, serpentine, and olivine) and industrial residues (e.g., steelmaking slag, municipal solid waste incinerator (MSWI) ash, and air pollution control (APC) residues). This research article focuses on Carbonation technologies that use industrial alkaline wastes, such as steelmaking slags and metalworking wastewater. The Carbonation of alkaline solid waste has been shown to be an effective way to capture CO2 and to eliminate the contents of Ca(OH)2 in solid residues, thus improving the durability of concrete blended with the carbonated residues. However, the operating conditions must be further studied for both the economic viability of the technology and the optimal conditions for CO2 reaction.
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Accelerated Carbonation of steelmaking slags in a high gravity rotating packed bed
Journal of Hazardous Materials, 2012Co-Authors: E E Chang, Yi Hung Chen, Pen-chi ChiangAbstract:Abstract Carbon dioxide (CO 2 ) sequestration using the Accelerated Carbonation of basic oxygen furnace (BOF) slag in a high-gravity rotating packed bed (RPB) under various operational conditions was investigated. The effects of reaction time, reaction temperature, rotation speed and slurry flow rate on the CO 2 sequestration process were evaluated. The samples of reacted slurry were analyzed quantitatively using thermogravimetric analysis (TGA) and atomic absorption spectrometry (AAS) and qualitatively using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and transmission electron microscopy (TEM). The sequestration experiments were performed at a liquid-to-solid ratio of 20:1 with a flow rate of 2.5 L min −1 of a pure CO 2 stream under atmospheric temperature and pressure. The results show that a maximum conversion of BOF slag was 93.5% at a reaction time of 30 min and a rotation speed of 750 rpm at 65 °C. The experimental data were utilized to determine the rate-limiting mechanism based on the shrinking core model (SCM), which was validated by the observations of SEM and TEM. Accelerated Carbonation in a RPB was confirmed to be a viable method due to its higher mass-transfer rate.
Paula Carey - One of the best experts on this subject based on the ideXlab platform.
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Accelerated Carbonation treatment of industrial wastes
Waste Management, 2010Co-Authors: Peter John Gunning, Colin Hills, Paula CareyAbstract:The disposal of industrial waste presents major logistical, financial and environmental issues. Technologies that can reduce the hazardous properties of wastes are urgently required. In the present work, a number of industrial wastes arising from the cement, metallurgical, paper, waste disposal and energy industries were treated with Accelerated Carbonation. In this process Carbonation was effected by exposing the waste to pure carbon dioxide gas. The paper and cement wastes chemically combined with up to 25% by weight of gas. The reactivity of the wastes to carbon dioxide was controlled by their constituent minerals, and not by their elemental composition, as previously postulated. Similarly, microstructural alteration upon Carbonation was primarily influenced by mineralogy. Many of the thermal wastes tested were classified as hazardous, based upon regulated metal content and pH. Treatment by Accelerated Carbonation reduced the leaching of certain metals, aiding the disposal of many as stable non-reactive wastes. Significant volumes of carbon dioxide were sequestrated into the Accelerated carbonated treated wastes.
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Accelerated Carbonation for the treatment of landfilled cement kiln dust
2008Co-Authors: Aurora Antemir, Colin Hills, Peter Gunning, Paula CareyAbstract:Accelerated Carbonation Technology (ACT) can be used to treat a wide range of alkaline wastes and metal-contaminated soils by exposing them to a carbon dioxide rich atmosphere in a way that promotes the massive precipitation of calcium carbonate. The material obtained has improved physical and chemical characteristics. This work presents the characterisation of historically deposited cement kiln dust (CKD) and its potential reactivity with carbon dioxide gas. The CKD investigated originated from a landfill, up to one hundred years old. The bulk chemical composition was determined by X-ray Fluorescence (XRF), the mineralogy of the untreated and carbonated CKD by X-ray Diffractometry (XRD) and the change in microstructure upon Carbonation was examined by Scanning Electron Microscopy (SEM/EDS). Key characteristics of treated and untreated CKD such as carbon dioxide uptake, pH, and moisture content are presented and discussed.
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Accelerated Carbonation of municipal solid waste incineration fly ashes
Waste Management, 2007Co-Authors: Xiaomin Li, Colin Hills, Paula Carey, Marta Fernandez Bertos, Stef SimonAbstract:As a result of the EU Landfill Directive, the disposal of municipal solid waste incineration (MSWI) fly ash is restricted to only a few landfill sites in the UK. Alternative options for the management of fly ash, such as sintering, vitrification or stabilization/solidification, are either costly or not fully developed. In this paper an Accelerated Carbonation step is investigated for use with fly ash. The Carbonation reaction involving fly ash was found to be optimum at a water/solid ratio of 0.3 under ambient temperature conditions. The study of ash mineralogy showed the disappearance of lime/portlandite/calcium chloride hydroxide and the formation of calcite as Carbonation proceeded. The leaching properties of carbonated ash were examined. Release of soluble salts, such as SO4, Cl, was reduced after Carbonation, but is still higher than the landfill acceptance limits for hazardous waste. It was also found that Carbonation had a significant influence on lead leachability. The lead release from carbonated ash, with the exception of one of the fly ashes studied, was reduced by 2–3 orders of magnitude.
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investigation of Accelerated Carbonation for the stabilisation of msw incinerator ashes and the sequestration of co2
Green Chemistry, 2004Co-Authors: Fernandez M Bertos, Colin Hills, X Li, S J R Simons, Paula CareyAbstract:Accelerated Carbonation has been used for the treatment of contaminated soils and hazardous wastes, giving reaction products that can cause rapid hardening and the production of granulated or monolithic materials. This technology provides a route to sustainable waste management and it generates a viable remedy to the problems of a decreasing number of landfill sites in the UK, global warming (due to greenhouse gas emissions) and the depletion of natural aggregate resources, such as sand and gravel. The application of Accelerated Carbonation (termed Accelerated Carbonation Technology or ACT) to sequester CO2 in fresh ashes from municipal solid waste (MSW) incinerator/combined heat and power plants is presented. The purpose of this paper is to evaluate the influence of fundamental parameters affecting the diffusivity and reactivity of CO2 (i.e. particle size, the reaction time and the water content) on the extent and quality of Carbonation. In addition, the major physical and chemical changes in air pollution control (APC) residues and bottom ashes (BA) after Carbonation are evaluated, as are the optimum reaction conditions, and the physical and chemical changes induced by Accelerated Carbonation are presented and discussed.
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a review of Accelerated Carbonation technology in the treatment of cement based materials and sequestration of co2
Journal of Hazardous Materials, 2004Co-Authors: Fernandez M Bertos, Colin Hills, S J R Simons, Paula CareyAbstract:Moist calcium silicate minerals are known to readily react with carbon dioxide (CO2). The reaction products can cause rapid hardening and result in the production of monolithic materials. Today, Accelerated Carbonation is a developing technology, which may have potential for the treatment of wastes and contaminated soils and for the sequestration of CO2, an important greenhouse gas. This paper reviews recent developments in this emerging technology and provides information on the parameters that control the process. The effects of the Accelerated Carbonation reaction on the solid phase are discussed and future potential applications of this technology are also considered.
Colin Hills - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of Accelerated Carbonation of alkaline waste residues by ultrasound.
Waste Management, 2016Co-Authors: Paris Araizi, Colin Hills, Alan Maries, Peter Gunning, David WrayAbstract:Abstract The continuous growth of anthropogenic CO2 emissions into the atmosphere and the disposal of hazardous wastes into landfills present serious economic and environmental issues. Reaction of CO2 with alkaline residues or cementitius materials, known as Accelerated Carbonation, occurs rapidly under ambient temperature and pressure and is a proven and effective process of sequestering the gas. Moreover, further improvement of the reaction efficiency would increase the amount of CO2 that could be permanently sequestered into solid products. This paper examines the potential of enhancing the Accelerated Carbonation of air pollution control residues, cement bypass dust and ladle slag by applying ultrasound at various water-to-solid (w/s) ratios. Experimental results showed that application of ultrasound increased the CO2 uptake by up to four times at high w/s ratios, whereas the reactivity at low water content showed little change compared with controls. Upon sonication, the particle size of the waste residues decreased and the amount of calcite precipitates increased. Finally, the sonicated particles exhibited a rounded morphology when observed by scanning electron microscopy.
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Ultra-rapid hardening of cement by Accelerated Carbonation – Past, present and future
2015Co-Authors: Alan Maries, Colin HillsAbstract:The ancient Greeks and Egyptians may have unwittingly employed Accelerated Carbonation with the polishing technique that they used to achieve seamless crack-free linings in lime-based pipe and stucco work. However, it was not until the advent of Portland cement in the mid-19th century that Carbonation with gaseous CO2at atmospheric pressure was proposed as a means of accelerating the setting and hardening of mortar and concrete. In the 1970s the first attempts were made to achieve a more thorough scientific understanding of the process, most notably in the USA by Berger and colleagues, but also by researchers in the USSR, Israel and Sweden. The authors’ own development of a Carbonation process to accelerate the hardening of precast concrete dates from over 30 years ago, when lowering atmospheric emissions of CO2 by sequestration was not yet an issue. But today, with global cement production increasing relentlessly at around 8% per annum to a current total of 4 Gtonnes and releasing a similar mass of CO2, emission reduction is now a pressing concern in the cement and concrete sector. This paper will report on current commercial operations involving Accelerated Carbonation of concrete and will look forward to challenges and opportunities in a low-carbon future.
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Carbon negative: First commercial application of Accelerated Carbonation technology
2014Co-Authors: Peter Guning, Colin HillsAbstract:Carbon dioxide gas can be used as a resource to rapidly harden cementitious materials and manage the risks associated with hazardous waste and contaminated soil. The process is known as Accelerated Carbonation Technology or ACT. Carbon dioxide primarily combines with calcium and/or magnesium minerals present in many industrial thermal residues to form carbonates; this reaction can also be promoted by the addition of, for example, Portland cement. Carbon8 Systems Ltd. was formed in 2006 as spinout-company of the University of Greenwich to commercialise ACT. Carbon8 has applied ACT to hazardous wastes in the production of non-hazardous construction products.By using the Carbon8 process, industrial thermal residues are solidified and stabilised in a hardened pellet form. The pelleted product is a direct substitute for natural aggregate, and can be used in the production of concrete construction blocks. From 2009 to 2012, a series of pilot and full-scale demonstrations of the technology were carried out. The aggregates produced were rigorously tested and given ‘end-of-waste’ designation by the Environment Agency. In early 2012, a bespoke commercial plant was commissioned at Brandon in Suffolk, UK, operated by Carbon8 Aggregates Ltd. This plant, the first of its kind anywhere in the world, produced 24,000 tonnes of aggregate from municipal solid waste incineration (MSWI) air pollution control residues (APCr) in its first year. In 2014, a second production line was added to the Brandon facility, increasing its capacity to 50,000 tonnes per year. The aggregate is supplied to Lignacite, the UK’s largest independent concrete block manufacturer, and other companies. The ACT-produced aggregate is carbon negative as it contains more imbibed carbon than is generated by its production. Consequently, the concrete construction blocks produced by Lignacite are also carbon negative, and are marketed under the name: ‘Carbon Buster’. Plans are at an advanced stage for the construction of a second and third production facility in the UK. These are scheduled to be operational by mid-2015 and will increase aggregate production to 200,000 tonnes per year. The present work discusses the development of the Carbon8 process and describes the commercial application of Accelerated Carbonation technology for the production of sustainable carbon-negative construction materials.
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Homogeneous catalysis of the Accelerated Carbonation of Portland cement
2013Co-Authors: Alan Maries, Colin HillsAbstract:A mechanism proposed for the Accelerated Carbonation of Portland cement has shown how the reaction proceeds through gaseous, liquid and solid phases in 9 distinct sequential steps. The overall speed of reaction is thus determined by the slowest step, and we have found that solvation and hydration of CO2 in water is commonly the rate-limiting step in the Carbonation process. The literature suggests that the speed of this step might possibly be increased by three different classes of chemical 'enhancers' of CO2 hydration: (1) inorganic oxy-anions such as hypochlorite (ClO– ) or sulphite (SO32–) which act as Lewis bases to CO2; (2) organic solutes which form anions at alkaline pH, such as sugars and polyhydric alcohols; or (3) amines and alkanolamines, which may exert catalytic action by producing carbamates with CO2 by either zwitterion formation or charge-transfer. This paper explores these options in detail, supporting theoretical predictions with precise measurement of the rate of CO2 uptake in a 'eudiometer', to determine whether such rates might be beneficially enhanced in the Carbonation of hydraulic binders and wastes, or in CO2 capture by mineral sequestration.
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Monitoring of carbon dioxide uptake in Accelerated Carbonation processes applied to air pollution control residues
2012Co-Authors: Felice Alfieri, Peter Gunning, Michela Gallo, Adriana Del Borghi, Colin HillsAbstract:The application of Accelerated Carbonation Technology (ACT) has potential for the sequestration of carbon in waste and geological materials. ACT also has potential to be supported by carbon credit mechanisms based upon the amount of carbon sequestered from industrial emissions. For this to happen, the routine monitoring of CO2 sequestered into the solid phase is required for the planning and operation of any Accelerated Carbonation plant. The present paper reports the preliminary results from an assessment of existing methods for measuring CO2 imbibed into a solid by an Accelerated Carbonation processes. Laboratory-scale experiments were carried out to evaluate the accuracy of methodologies for measuring mineralised carbon including: loss on ignition, acid digestion and total carbon analysis. The CO2 reactivity of several wastes from municipal incineration known as Air Pollution Control residues (APCr) were also included in the study. A detailed characterisation of the materials being carbonated, using X-ray diffraction (XRD), X-ray fluorescence (XRF), thermogravimetric analysis (TGA) and ion chromatography was carried out. The results of this study showed that monitoring CO2 during Accelerated Carbonation is made difficult by the complex mineralogy of materials such as APCrs. As such, the presence of calcium bearing species and polymorphs of calcium carbonate formed varied between the materials investigated. The use of an acid digestion technique was not subject to interference from the chemistry or mineralogy of an ash. Among the investigated methods, acid digestion gives the most promising results as it provided robust data on the amount of carbon imbibed during processing.
Jun Chang - One of the best experts on this subject based on the ideXlab platform.
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foaming characteristics and microstructure of aerated steel slag block prepared by Accelerated Carbonation
Construction and Building Materials, 2019Co-Authors: Jun Chang, Cang Xiong, Yangyang Zhang, Dan WangAbstract:Abstract The present paper discusses investigated the foaming behaviors and microstructure of three aerated steel slag block (ASSB) samples prepared with three different foaming agents (namely animal protein, hydrogen peroxide, aluminum powder) and by Accelerated Carbonation. The composition and microstructure of the ASSB samples before and after Accelerated Carbonation were characterized using X-ray diffraction (XRD), Rietveld method, thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FE-SEM). It is an advisable method for foamed steel slag products to use the aluminum powder and Accelerated Carbonation technology. The aluminum powder favored a good foaming behavior for steel slag owing to (i) a high porosity and low dry density, (ii) a high hydration degree of minerals in steel slag, including brownmillerite, larnite, and lime, which was confirmed by the analysis of mineral compositions using Rietveld method, and (iii) the interlaced lamellas of monocarboaluminate and calcium silicate hydrate (C-S-H) gel strengthen the bubbles wall, which was confirmed by morphology analysis using FE-SEM. After Accelerated Carbonation, the monocarboaluminate shifted to aragonite, vaterite, calcite and amorphous aluminum hydroxide (Al(OH)3), which was confirmed by XRD, TGA and FT-IR. The network skeleton formed by aragonite crystals improved the compressive strength of ASSB prepared by aluminum powder. In addition, the reactions of the formation and Carbonation of monocarboaluminate phase were proved to be thermodynamically possible in this work.
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rapid hardening β c2s mineral and microstructure changes activated by Accelerated Carbonation curing
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Yanfeng Fang, Jun ChangAbstract:This paper presents a study on rapid hardening behaviors of β-C2S by Accelerated Carbonation curing. β-C2S cubes compacted at various molding pressures were subjected to different CO2 concentration for Accelerated Carbonation curing. The CO2 uptake and microstructure changes were analyzed by thermogravimetric analysis (TG), QXRD, FT-IR and MAS-NMR. The results indicated that CO2 uptake was affected by molding pressure and CO2 concentration seriously. TG analysis indicated that the Carbonation reaction was rapid in the first hour. The Carbonation degree reached 21.6% and giving a compressive strength of 85.7 MPa after 6 h Carbonation in 99.9% CO2 concentration. And it showed a much less Carbonation degree in 20.0% CO2. Calcite, vaterite and amorphous silica-rich phase formed in the Carbonation progress. The FT-IR and NMR analysis indicated β-C2S was decalcified to C–S–H gel and further decalcified to formation of an amorphous silica gel composed of Q 3 and Q 4 silicate tetrahedral. The chain length of C–S–H gel increased from to 2.67 to 6.36 with prolonged Carbonation time, showing a lower C/S ratio and higher polymerization and also resulting in a lower C–S–H content.
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microstructure changes of waste hydrated cement paste induced by Accelerated Carbonation
Construction and Building Materials, 2015Co-Authors: Yanfeng Fang, Jun ChangAbstract:Abstract From the perspective of effective utilization of resources and environmental preservation, Accelerated Carbonation of waste cement paste is a promising and environmentally beneficial application. Greenhouse gas CO 2 can be captured, waste hydrated cement can be reused, and building materials with excellent performance can be produced. In this study, samples were exposed to high CO 2 concentration (99.9 wt%, 0.2 MPa) for Accelerated Carbonation. The compacts with water/solid ratio of 0.15 absorbed 19.8 wt% CO 2 after carbonated for 2 h, and the compressive strength was 28.6 MPa. The total pore volume decreased from 0.41 cm 3 /g to 0.26 cm 3 /g due to the precipitation of calcium carbonate and silica gel. Rietveld refinement quantitative phase analysis and TG analysis showed calcium carbonate are mainly from Ca(OH) 2 and C–S–H, accounting for about 70–80% of the total calcium carbonate. Ca(OH) 2 has superiority in the early Carbonation period, and the carbonated compacts has a relative higher “compressive strength-to-CO 2 uptake” value, corresponding. When the Carbonation degree of C–S–H and other Carbonation phase exceed Ca(OH) 2 in the later stage, the compressive strength has a slower gain tendency.
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quantitative analysis of Accelerated Carbonation products of the synthetic calcium silicate hydrate c s h by qxrd and tg ms
Journal of Thermal Analysis and Calorimetry, 2015Co-Authors: Jun Chang, Yanfeng FangAbstract:In this study, calcium silicate hydrate(C–S–H) with CaO/SiO2 ratio of 1.5 target mixture is synthesized and C1.27SH0.76 with 93.4 % purity is obtained. The dried C–S–H was compacted at 8 MPa to 20 mm × 20 mm × 20 mm for Accelerated Carbonation. The Carbonation products and Carbonation degree of synthetic calcium silicate hydrate are characterized and quantitatively evaluated by QXRD (Rietveld refinement), mass gain method, and TG/MS analysis. After Accelerated Carbonation at 0.2 MPa CO2 pressure for 2 h, the Carbonation degree from mass gain method is 71.5 %, and from TG/MS analysis is 78.0 %. Calcite, aragonite, vaterite, and amorphous phase exist simultaneously in the Accelerated carbonated samples, accounting for 33.98, 17.13, 18.74, and 30.15 %, respectively. Two mass-loss stages were observed for calcium carbonate decomposition. The first mass-loss stage (300–660 °C range) was mainly caused by the decomposition of aragonite and vaterite, and calcite formed in the Accelerated Carbonation process has a relatively high decomposition temperature which is mainly centered in the 660–800 °C range.
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Quantitative analysis of Accelerated Carbonation products of the synthetic calcium silicate hydrate(C–S–H) by QXRD and TG/MS
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Jun Chang, Yanfeng FangAbstract:In this study, calcium silicate hydrate(C–S–H) with CaO/SiO2 ratio of 1.5 target mixture is synthesized and C1.27SH0.76 with 93.4 % purity is obtained. The dried C–S–H was compacted at 8 MPa to 20 mm × 20 mm × 20 mm for Accelerated Carbonation. The Carbonation products and Carbonation degree of synthetic calcium silicate hydrate are characterized and quantitatively evaluated by QXRD (Rietveld refinement), mass gain method, and TG/MS analysis. After Accelerated Carbonation at 0.2 MPa CO2 pressure for 2 h, the Carbonation degree from mass gain method is 71.5 %, and from TG/MS analysis is 78.0 %. Calcite, aragonite, vaterite, and amorphous phase exist simultaneously in the Accelerated carbonated samples, accounting for 33.98, 17.13, 18.74, and 30.15 %, respectively. Two mass-loss stages were observed for calcium carbonate decomposition. The first mass-loss stage (300–660 °C range) was mainly caused by the decomposition of aragonite and vaterite, and calcite formed in the Accelerated Carbonation process has a relatively high decomposition temperature which is mainly centered in the 660–800 °C range.
Yanfeng Fang - One of the best experts on this subject based on the ideXlab platform.
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rapid hardening β c2s mineral and microstructure changes activated by Accelerated Carbonation curing
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Yanfeng Fang, Jun ChangAbstract:This paper presents a study on rapid hardening behaviors of β-C2S by Accelerated Carbonation curing. β-C2S cubes compacted at various molding pressures were subjected to different CO2 concentration for Accelerated Carbonation curing. The CO2 uptake and microstructure changes were analyzed by thermogravimetric analysis (TG), QXRD, FT-IR and MAS-NMR. The results indicated that CO2 uptake was affected by molding pressure and CO2 concentration seriously. TG analysis indicated that the Carbonation reaction was rapid in the first hour. The Carbonation degree reached 21.6% and giving a compressive strength of 85.7 MPa after 6 h Carbonation in 99.9% CO2 concentration. And it showed a much less Carbonation degree in 20.0% CO2. Calcite, vaterite and amorphous silica-rich phase formed in the Carbonation progress. The FT-IR and NMR analysis indicated β-C2S was decalcified to C–S–H gel and further decalcified to formation of an amorphous silica gel composed of Q 3 and Q 4 silicate tetrahedral. The chain length of C–S–H gel increased from to 2.67 to 6.36 with prolonged Carbonation time, showing a lower C/S ratio and higher polymerization and also resulting in a lower C–S–H content.
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microstructure changes of waste hydrated cement paste induced by Accelerated Carbonation
Construction and Building Materials, 2015Co-Authors: Yanfeng Fang, Jun ChangAbstract:Abstract From the perspective of effective utilization of resources and environmental preservation, Accelerated Carbonation of waste cement paste is a promising and environmentally beneficial application. Greenhouse gas CO 2 can be captured, waste hydrated cement can be reused, and building materials with excellent performance can be produced. In this study, samples were exposed to high CO 2 concentration (99.9 wt%, 0.2 MPa) for Accelerated Carbonation. The compacts with water/solid ratio of 0.15 absorbed 19.8 wt% CO 2 after carbonated for 2 h, and the compressive strength was 28.6 MPa. The total pore volume decreased from 0.41 cm 3 /g to 0.26 cm 3 /g due to the precipitation of calcium carbonate and silica gel. Rietveld refinement quantitative phase analysis and TG analysis showed calcium carbonate are mainly from Ca(OH) 2 and C–S–H, accounting for about 70–80% of the total calcium carbonate. Ca(OH) 2 has superiority in the early Carbonation period, and the carbonated compacts has a relative higher “compressive strength-to-CO 2 uptake” value, corresponding. When the Carbonation degree of C–S–H and other Carbonation phase exceed Ca(OH) 2 in the later stage, the compressive strength has a slower gain tendency.
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quantitative analysis of Accelerated Carbonation products of the synthetic calcium silicate hydrate c s h by qxrd and tg ms
Journal of Thermal Analysis and Calorimetry, 2015Co-Authors: Jun Chang, Yanfeng FangAbstract:In this study, calcium silicate hydrate(C–S–H) with CaO/SiO2 ratio of 1.5 target mixture is synthesized and C1.27SH0.76 with 93.4 % purity is obtained. The dried C–S–H was compacted at 8 MPa to 20 mm × 20 mm × 20 mm for Accelerated Carbonation. The Carbonation products and Carbonation degree of synthetic calcium silicate hydrate are characterized and quantitatively evaluated by QXRD (Rietveld refinement), mass gain method, and TG/MS analysis. After Accelerated Carbonation at 0.2 MPa CO2 pressure for 2 h, the Carbonation degree from mass gain method is 71.5 %, and from TG/MS analysis is 78.0 %. Calcite, aragonite, vaterite, and amorphous phase exist simultaneously in the Accelerated carbonated samples, accounting for 33.98, 17.13, 18.74, and 30.15 %, respectively. Two mass-loss stages were observed for calcium carbonate decomposition. The first mass-loss stage (300–660 °C range) was mainly caused by the decomposition of aragonite and vaterite, and calcite formed in the Accelerated Carbonation process has a relatively high decomposition temperature which is mainly centered in the 660–800 °C range.
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Quantitative analysis of Accelerated Carbonation products of the synthetic calcium silicate hydrate(C–S–H) by QXRD and TG/MS
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Jun Chang, Yanfeng FangAbstract:In this study, calcium silicate hydrate(C–S–H) with CaO/SiO2 ratio of 1.5 target mixture is synthesized and C1.27SH0.76 with 93.4 % purity is obtained. The dried C–S–H was compacted at 8 MPa to 20 mm × 20 mm × 20 mm for Accelerated Carbonation. The Carbonation products and Carbonation degree of synthetic calcium silicate hydrate are characterized and quantitatively evaluated by QXRD (Rietveld refinement), mass gain method, and TG/MS analysis. After Accelerated Carbonation at 0.2 MPa CO2 pressure for 2 h, the Carbonation degree from mass gain method is 71.5 %, and from TG/MS analysis is 78.0 %. Calcite, aragonite, vaterite, and amorphous phase exist simultaneously in the Accelerated carbonated samples, accounting for 33.98, 17.13, 18.74, and 30.15 %, respectively. Two mass-loss stages were observed for calcium carbonate decomposition. The first mass-loss stage (300–660 °C range) was mainly caused by the decomposition of aragonite and vaterite, and calcite formed in the Accelerated Carbonation process has a relatively high decomposition temperature which is mainly centered in the 660–800 °C range.
