Showing papers on "Fly ash published in 2010"
TL;DR: In this article, the utilization of fly ash in construction, as a low-cost adsorbent for the removal of organic compounds, flue gas and metals, light weight aggregate, mine back fill, road sub-base, and zeolite synthesis is discussed.
2,117 citations
TL;DR: In this article, the compressive strength of C fly ash (CFA) and a mixed alkali activator of sodium hydroxide and sodium silicate solution was investigated, where the modulus of the activator viz., molar ratio of SiO 2 /Na 2 O was 1.5, and proper content of this activator as evaluated by the mass proportion of Na 2 O to CFA was 10%.
Abstract: Geopolymers prepared from a class C fly ash (CFA) and a mixed alkali activator of sodium hydroxide and sodium silicate solution were investigated. A high compressive strength was obtained when the modulus of the activator viz., molar ratio of SiO 2 /Na 2 O was 1.5, and the proper content of this activator as evaluated by the mass proportion of Na 2 O to CFA was 10%. The compressive strength of these samples was 63.4 MPa when they were cured at 75 °C for 8 h followed by curing at 23 °C for 28 d. In FTIR spectroscopy, the main peaks at 1036 and 1400 cm −1 have been attributed to asymmetric stretching of Al–O/Si–O bonds, while those at 747 cm −1 are due to the Si–O–Si/Si–O–Al bending band. The main geopolymeric gel and calcium silicate hydrate (C–S–H) gel co-exist and bond some remaining unreacted CFA spheres as observed in XRD and SEM–EXDA. The presence of gismondine (zeolite) was also observed in the XRD pattern.
621 citations
TL;DR: In this article, the influence of varying amount of ground granulated blast furnace slag (GBFS) on the reaction kinetics has been studied using isothermal conduction calorimetry.
Abstract: Ground granulated blast furnace slag (GBFS) has been used to alter the geopolymerisation behaviour of fly ash. The influence of varying amount of GBFS (5–50%) on the reaction kinetics has been studied using isothermal conduction calorimetry. It was observed that the reaction at 27 °C is dominated by the GBFS activation, whereas the reaction at 60 °C is due to combined interaction of fly ash and GBFS. The reaction product of geopolymerisation has been characterised using X-ray diffraction and scanning electron microscopy–X-ray microanalysis. Alumino–silicate–hydrate (A–S–H) and calcium–silicate–hydrate (C–S–H) gels with varying Si/Al and Ca/Si ratio are found to be the main reaction products. Coexistence of A–S–H and C–S–H gel further indicates the interaction of fly ash and GBFS during geopolymerisation. Attempt has been made to relate the microstructure with the properties of the geopolymers.
558 citations
TL;DR: In this paper, the characteristics of municipal solid waste incineration (MSWI) ashes, with a main focus on the chemical properties of the ashes, are reviewed, and the possible treatment methods for the utilization of ash, namely, separation processes, solidification/stabilization and thermal processes, are also discussed.
Abstract: This study reviews the characteristics of municipal solid waste incineration (MSWI) ashes, with a main focus on the chemical properties of the ashes. Furthermore, the possible treatment methods for the utilization of ash, namely, separation processes, solidification/stabilization and thermal processes, are also discussed. Seven types of MSWI ash utilization are reviewed, namely, cement and concrete production, road pavement, glasses and ceramics, agriculture, stabilizing agent, adsorbents and zeolite production. The practical use of MSWI ash shows a great contribution to waste minimization as well as resources conservation.
420 citations
TL;DR: In this paper, the suitability of fly ash stock piles for geopolymer manufacturing was studied and the results of chemical analyses, X-ray diffraction (XRD) and particle size distribution (PSD) of five sources of coal-fired power generating plants in the US are presented.
410 citations
TL;DR: In this paper, the increase in strength and evolution of crystalline phases in inorganic polymer cement, made by the alkali activation of slag, Class C and Class F fly ashes, was followed using compressive strength test and synchrotron X-ray diffraction in order to increase the crystallinity of the product.
388 citations
TL;DR: In this paper, the authors compared the pozzolanic activity of metakaolin, silica fume, coal fly ash, incinerated sewage sludge ash and sand using the Frattini test, the saturated lime test and the strength activity index test.
Abstract: Assessment of the pozzolanic activity of cement replacement materials is increasingly important because of the need for more sustainable cementitious products. The pozzolanic activity of metakaolin, silica fume, coal fly ash, incinerated sewage sludge ash and sand have been compared using the Frattini test, the saturated lime test and the strength activity index test. There was significant correlation between the strength activity index test and the Frattini test results, but the results from these tests did not correlate with the saturated lime test results. The mass ratio of Ca(OH)2 to test pozzolan is an important parameter. In the Frattini test and strength activity index test the ratio is approximately 1:1, whereas in the saturated lime test the ratio is 0.15:1. This explains why the saturated lime test shows higher removal of Ca(OH)2 and why the results from this test do not correlate with the other test methods.
356 citations
TL;DR: In this paper, the authors measured the mercury emissions and their behavior in six typical coal-fired power plants in China, using the Ontario Hydro Method (OHM) and showed that the flue gas was sampled simultaneously at inlet and outlet of Selective Catalytic Reduction (SCR), electrostatic precipitators (ESP), and fluegas desulfurization (FGD) using the OHP.
Abstract: . Comprehensive field measurements are needed to understand the mercury emissions from Chinese power plants and to improve the accuracy of emission inventories. Characterization of mercury emissions and their behavior were measured in six typical coal-fired power plants in China. During the tests, the flue gas was sampled simultaneously at inlet and outlet of Selective Catalytic Reduction (SCR), electrostatic precipitators (ESP), and flue gas desulfurization (FGD) using the Ontario Hydro Method (OHM). The pulverized coal, bottom ash, fly ash and gypsum were also sampled in the field. Mercury concentrations in coal burned in the measured power plants ranged from 17 to 385 μg/kg. The mercury mass balances for the six power plants varied from 87 to 116% of the input coal mercury for the whole system. The total mercury concentrations in the flue gas from boilers were at the range of 1.92–27.15 μg/m3, which were significantly related to the mercury contents in burned coal. The mercury speciation in flue gas right after the boiler is influenced by the contents of halogen, mercury, and ash in the burned coal. The average mercury removal efficiencies of ESP, ESP plus wet FGD, and ESP plus dry FGD-FF systems were 24%, 73% and 66%, respectively, which were similar to the average removal efficiencies of pollution control device systems in other countries such as US, Japan and South Korea. The SCR system oxidized 16% elemental mercury and reduced about 32% of total mercury. Elemental mercury, accounting for 66–94% of total mercury, was the dominant species emitted to the atmosphere. The mercury emission factor was also calculated for each power plant.
355 citations
TL;DR: In this paper, the authors reviewed different approaches adopted in estimating the deportment of trace elements in coal and discussed control strategies for reducing emissions and future directions, and the typical emissions from typical power stations.
331 citations
TL;DR: In this paper, the normal consistency, setting time, workability and compressive strength results of Portland cement-fly ash-silica fume systems were reported, and the results showed that water requirement for normal consistency was found to increase with increasing SF content while a decrease in initial setting time was found.
324 citations
TL;DR: In this article, the effectiveness of locally quarried zeolite in enhancing mechanical and durability properties of concrete is evaluated and is also compared with other pozzolanic admixtures.
Abstract: Natural zeolite, a type of frame-structured hydrated aluminosilicate mineral, is used abundantly as a type of natural pozzolanic material in some regions of the world. In this work, the effectiveness of a locally quarried zeolite in enhancing mechanical and durability properties of concrete is evaluated and is also compared with other pozzolanic admixtures. The experimental tests included three parts: In the first part, the pozzolanic reactivity of natural zeolite and silica fume were examined by a thermogravimetric method. In this case, the results indicated that natural zeolite was not as reactive as silica fume but it showed a good pozzolanic reactivity. In the second part, zeolite and silica fume were substituted for cement in different proportions in concrete mixtures, and several physical and durability tests of concrete were performed. These experimental tests included slump, compressive strength, water absorption, oxygen permeability, chloride diffusion, and electrical resistivity of concrete. Based on these results, the performance of concretes containing different contents of zeolite improved and even were comparable to or better than that of concretes prepared with silica fume replacements in some cases. Finally, a comparative study on effect of zeolite and fly ash on limiting ASR expansion of mortar was performed according to ASTM C 1260 and ASTM C 1567. Expansion tests on mortar prisms showed that zeolite is as effective as fly ash to prevent deleterious expansion due to ASR.
TL;DR: The geopolymer based on FA with the highest content of fine particles (<43 microm), showed the highest compressive strength in all cases, and high strength was directly related to the high Si/Al ratio.
TL;DR: The experimental findings showed that the removal of four dyes on fly ash was a pH-dependent process with the maximum adsorption capacity at the initial solution pH of 7.5-8.5 for reactive dyes and 5-6 for acid dyes.
TL;DR: In this paper, the physical and mechanical properties of fly ash-based geopolymer paste with varying levels of sand aggregate were studied. But the results showed that increasing sand content without increasing the amount of alkaline activator resulted in a decreasing level of geopolymisation within the binder system.
TL;DR: The fly ash from the Jungar Power Plant, Inner Mongolia, China, is unique because it is highly enriched in alumina (Al2O3>50%). The fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum, quartz, char, calcite, K-feldspar, clay minerals, and Fe-bearing minerals.
15 Feb 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, carbon nanotubes of 0.5 and 1% by weight were added for the first time in a fly ash cement system to produce carbon-nanotubes-fly ash composites in the form of pastes and mortars.
Abstract: In this work, carbon nanotubes of 0.5 and 1% by weight were added for the first time in a fly ash cement system to produce carbon nanotubes–fly ash composites in the form of pastes and mortars. Compressive strengths of the composites were then investigated. It was found that the use of carbon nanotubes resulted in higher strength of fly ash mortars. The highest strength obtained for 20% fly ash cement mortars was found at 1% carbon nanotubes where the compressive strength at 28 days was 51.8 MPa. This benefit can clearly be seen in fly ash cement with fly ash of 20% where the importance of the addition of carbon nanotubes means that the relative strength to that of Portland cement became almost 100% at 28 days. In addition, scanning electron micrographs also showed that good interaction between carbon nanotubes and the fly ash cement matrix is seen with carbon nanotubes acting as a filler resulting in a denser microstructure and higher strength when compared to the reference fly ash mix without CNTs.
TL;DR: In this paper, the compressive strength, modulus of elasticity, and water permeability of IPCs depend on the mix proportions, especially the solution to ash (S/A ) ratio and the paste to aggregate (P/Agg ) ratio.
TL;DR: The transport of HG through the boiler and pollution control systems, the mechanisms of Hg oxidation, and the parameters controlling Hg capture by coal-derived fly ash carbons are discussed.
TL;DR: In this paper, an experimental investigation was carried out to evaluate the mechanical and durability properties of high performance concretes containing supplementary cementitious materials in both binary and ternary systems.
TL;DR: In this paper, the fly ash reaction in two different blended OPC-FA systems was studied using a selective dissolution technique based on EDTA/NaOH, diluted NaOH solution, the portlandite content and by backscattered electron image analysis.
TL;DR: IR spectra showed that higher alkaline activator dosage enhanced the structural disruption of the original aluminosilicate phases and a higher degree of polymerization of the geopolymer networks, which suggests that the soluble silicon content serves to reduce the amount of geopolymers.
01 Jan 2010
TL;DR: A summary of the extensive studies conducted on fly ash-based geopolymer concrete is presented in this paper, where test data are used to identify the effects of salient factors that influence the properties of the geopolymers concrete and to propose a simple method for the design of the concrete mixtures.
Abstract: Geopolymer concrete results from the reaction of a source material that is rich in silica and alumina with alkaline liquid. A summary of the extensive studies conducted on fly ash-based geopolymer concrete is presented. Test data are used to identify the effects of salient factors that influence the properties of the geopolymer concrete and to propose a simple method for the design of geopolymer concrete mixtures. Test data of various short-term and long-term properties of the geopolymer concrete and the results of the tests conducted on large-scale reinforced geopolymer concrete members show that geopolymer concrete is well-suited to manufacture precast concrete products that can be used in infrastructure developments. The paper also includes brief details of some recent applications of geopolymer concrete.
TL;DR: In this article, the authors investigated self-compacting concrete (SCC) with levels of up to 80% cement replacement by fly ash in mixes adjusted to give constant fresh concrete properties.
01 Jan 2010
TL;DR: Rice Husk Ash (RHA) is a byproduct material obtained from the combustion of rice husk which consists of non-crystalline silicon dioxide with high specific surface area and high pozzolanic reactivity as mentioned in this paper.
Abstract: In the last decade, the use of supplementary cementing materials has become an integral part of high strength and high performance concrete mix design. These can be natural materials, by-products or industrial wastes, or the ones requiring less energy and time to produce. Some of the commonly used supplementary cementing materials are fly ash, Silica Fume (SF), Ground Granulated Blast Furnace Slag (GGBFS) and Rice Husk Ash (RHA) etc. RHA is a by-product material obtained from the combustion of rice husk which consists of non-crystalline silicon dioxide with high specific surface area and high pozzolanic reactivity. It is used as pozzolanic material in mortar and concrete, and has demonstrated significant influence in improving the mechanical and durability properties of mortar and concrete. This paper presents an overview of the work carried out on the use of RHA as partial replacement of cement in mortar and concrete. Reported properties in this study are the mechanical, durability and fresh properties of mortar/concrete.
TL;DR: In this paper, an analysis of coal fly ash and lignite coal fly ashes was carried out by means of conduction calorimetry, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy to assess their potential for mortar and concrete production.
TL;DR: In this paper, the authors investigated geopolymeric lightweight concretes based on binders composed of metakaolin with 0% and 25% fly ash, activated with 15.2% of Na2O using sodium silicate of modulus SiO2/Na2O = 1.2.
TL;DR: In this article, a temperature programmed decomposition technique was applied in order to acquire an understanding of the mode of decomposition of mercury species during coal combustion, and a series of mercury model compounds were used for qualitative calibration.
TL;DR: A comprehensive approach to qualitative and quantitative characterization of crystalline and amorphous constituent phases of a largely heterogeneous Class F fly ash is presented in this article, where the Rietveld quantitative phase analysis method is applied to determine the relative proportion of each of these phases.
TL;DR: In this paper, the influence of the concentration of the activating agent (4, 6, or 8 m sodium hydroxide solution), and activator-to-binder ratio (0.40, 0.50, or 0.60) on compressive strength, pore structure features, and microstructure of concretes containing Class F fly ash or ground granulated blast furnace slag (GGBFS) as the sole binder is reported.
Abstract: The influence of the concentration of the activating agent (4, 6, or 8 M sodium hydroxide solution), and activator-to-binder ratio (0.40, 0.50, or 0.60) on the compressive strengths, pore structure features, and microstructure of concretes containing Class F fly ash or ground granulated blast furnace slag (GGBFS) as the sole binder is reported. The starting material contents and the curing parameters (temperature and curing duration) are optimized to provide the highest compressive strengths. Statistical analysis of the compressive strength results show that the activator concentration has a larger influence on the compressive strengths of activated concretes made using fly ash and the activator-to-binder ratio influences the compressive strengths of activated GGBFS concretes to a greater degree. Activated fly ash concretes and pastes are found to be more porous and contains a larger fraction of pores greater than 10 μm in size as compared to activated GGBFS mixtures. The differences in the microstructure and the reaction products between activated fly ash and GGBFS pastes are detailed.
TL;DR: In this article, FactSage has been used to calculate the liquidus temperatures of coal ash samples and the proportions of the various phases present as a function of temperature, and the results show that the AFT of coal Ash samples first decrease with increasing CaO, Fe2O3, and MgO contents, then reach a minimum value, before increasing once more.
Abstract: The ash fusion temperatures (AFTs) of coal mineral matter at high temperature are important parameters for all gasifiers. Experiments have been conducted in which mixtures of selected coal ashes and SiO2, Al2O3, CaO, Fe2O3, and MgO were subjected to the standard test for ash fusibility. The computer software package FactSage has been used to calculate the liquidus temperatures of coal ash samples and the proportions of the various phases present as a function of temperature. The results show that the AFTs of coal ash samples first decrease with increasing CaO, Fe2O3, and MgO contents, then reach a minimum value, before increasing once more. However, for the effect of S/A ratio, its AFTs are always increased with increasing S/A ratios. The measured AFTs all show variations with mixture composition that correlated closely with liquidus temperatures for the appropriate pseudoternary phase diagrams. The liquidus and AFTs generally showed parallel compositional trends but are displaced from each other because ...