Showing papers on "Fly ash published in 1999"
TL;DR: In this paper, the mechanism of activation of fly ash with highly alkaline solutions is described, and the product of the reaction is an amorphous aluminosilicate gel having a structure similar to that of zeolitic precursors.
1,779 citations
TL;DR: In this paper, the morphology, composition, and nanostructure of C-S-H in a range of hardened cements were investigated. But the authors focused on the inner product (Ip) of a slag-based mixture of Portland cement and slag.
827 citations
TL;DR: In this article, the authors analyzed data from long-term field and laboratory studies of concrete exposed to chloride environments using a chloride transport model developed at the University of Toronto and found that the incorporation of fly ash and slag may have little impact on transport properties determined at early ages (e.g., 28 days), but can lead to order of magnitude improvements in the long term.
528 citations
TL;DR: In this paper, a typical low-calcium fly ash was used as additive in mortar, replacing part of the volume either of Portland cement or aggregate, and the development of the strength, heat, porosity, bound water, and calcium hydroxide content was measured.
398 citations
TL;DR: In this article, the authors present an update on the development of commercial catalytic wet air oxidation (CWAO) processes, which started as early as the mid-fifties in the United States.
397 citations
TL;DR: In this paper, the effect of mainly Na+ and K+ on the physical and chemical properties of fly ash-based geopolymeric binders both before and after setting has been investigated.
Abstract: The alkali and alkali earth metal cations present during the formation of most known aluminosilicate structures have a very significant effect on both the physical and chemical properties of the final product. Geopolymers are no exception, although this effect has not been thoroughly quantified and in the case of waste-based geopolymers it has not received any significant attention. The present study investigates the effect of mainly Na+ and K+ on the physical and chemical properties of fly ash-based geopolymeric binders both before and after setting has occurred. A variety of tests were conducted, including rheological measurements, various leaching tests, compressive strength testing, specific surface area determinations, and infrared spectroscopy (IR). It is concluded that the alkali metal cation controls and affects almost all stages of geopolymerization, from the ordering of ions and soluble species during the dissolution process to playing a structure-directing role during gel hardening and eventual...
392 citations
TL;DR: In this article, the authors provided selection criteria for substrates that would enhance phosphate removal from waste water in a constructed wetland system (subsurface horizontal flow) by measuring properties of seven substrates (bauxite, shale, burnt oil shale, limestone, zeolite, light expanded clay aggregates (LECA) and fly ash).
388 citations
TL;DR: In this paper, the physical and chemical properties of geopolymers manufactured from fly ash originating from two different regions were investigated using compressive strength testing, specific surface area determinations, Transmission Electron Microscopy (TEM), Nuclear Magnetic Resonance (NMR) and leaching tests.
346 citations
TL;DR: In this article, the main components of the bottom ash are glass, magnetic metals, minerals, synthetic ceramics, paramagnetic metals and unburned organic matter, and the characterization may be used to evaluate the potential applications of bottom ash and its environmental hazards, and evaluate the possibilities of recycling its main components.
319 citations
TL;DR: In this article, the silicon in fly ash can be used for the synthesis of a maximum of 85 g of pure zeolite per kg of fly ash prior to the residual being converted into Zeolite by the traditional method.
314 citations
TL;DR: The pozzolanic properties of coal combustion bottom ash were investigated in this article, where plain pastes containing equal amounts of calcium hydroxide and bottom ash are prepared and analyzed at different ages for their strength and the calcium hyroxide consumption.
TL;DR: In this paper, the results from laboratory studies on the durability of concrete that contains ternary blends of portland cement, silica fume, and a wide range of fly ashes were reported.
TL;DR: In this article, the processes that control the leaching of Cd, Pb, Zn, Cu, and Mo from 3 categories of bottom ash: (A) unweathered bottom ash (grate siftings and unquenched samples), (B) quenched/non-carbonated bottom ash(freshly quenches and 6-week-old samples), and (C) weathered bottom-ash (1.5-and 12-yearold samples).
TL;DR: In this paper, the compressive strength, degree of pozzolanic reaction, and porosity of zeolite modified cement pastes were compared with those obtained from similar blended pastes prepared with silica fume and fly ash replacements.
Journal Article•
TL;DR: In this paper, the authors discuss the increase use of large volumes of fly ash and other supplementary cementing materials in the construction industry and its role in reducing these emissions, since the manufacture of portland cement contributes significantly to carbon dioxide emissions.
Abstract: Environmental issues will play a leading role in the sustainable development of the cement and concrete industry in the 21st century. The World Earth Summits in Rio de Janeiro, Brazil in 1992, and Kyoto, Japan in 1997, have made it abundantly clear that unchecked increased emission of greenhouse gases to the atmosphere is no longer environmentally and socially acceptable for overall sustainable development. The primary greenhouse gas emissions discussed in the sessions of the above conferences are carbon dioxide emissions. Other greenhouse gases such as nitrous oxide and methane, are of serious concern, but the amount involved is relatively small compared with that of carbon dioxide. Consequently, developed countries are considering regulations and mandatory quotas on the emission of these gases, and the main thrust is to stabilize these emissions to the 1990 level by the year 2010. Since the manufacture of portland cement contributes significantly to carbon dioxide emissions, this article discusses the increase use of large volumes of fly ash and other supplementary cementing materials in the construction industry and its role in reducing these emissions.
TL;DR: In this paper, the effect of various factors including the amount of retarder B, P/M ratio, fineness of M, and addition of fly ash and environment temperature on setting time and mechanical properties of magnesium phosphate cement-based binder (MPB) were investigated.
TL;DR: In this paper, a method of monitoring the spatial distribution of pollution due to airborne solid particles based on measurements of magnetic susceptibility of the soil surface near a brown-coal-burning power plant is presented.
TL;DR: In this paper, the authors investigated concrete with oil palm shells (OPS) as coarse aggregate for its workability, density, and compressive strength development over 56 days under three curing conditions.
TL;DR: In this paper, the authors described the preparation and characterization of an environmentally friendly cement with performance characteristics similar to those of Portland cement, from a lime kiln bag house dust, a low-calcium fly ash, and a scrubber sludge.
TL;DR: In this article, coal fly ash was used as a bulking agent to increase the pH of sludge compost for 100 days and showed no significant degradation of the organic carbon and total organic carbon.
TL;DR: In this article, the influence of fly ash composition on the evolution of pore solution chemistry in Portland cement/fly ash systems was investigated using energy-dispersive X-ray analysis.
TL;DR: The LCL response of PMN in general increased with all washed particles, and results point to the possibility that the insoluble constituents of the particles are related to LCL in PMN.
TL;DR: Rajghat fly ash from Delhi, India, and Baumineral fly ash near Bochum, Germany, were mixed with the locally available soils in different proportions to stabilize the fly ash-soil mixtures.
TL;DR: In this article, glass and glass-ceramics were obtained by mixing up to 50% of Italian or Spanish coal fly ash with other wastes (glass cullet and float dolomite).
TL;DR: The chemical characteristics of fly ash samples from combustion of three fuels: coal, peat and wood chips, have been studied in this paper, where they were collected in the 12MW CFB at Chalmers University of Technology during full load combustion with similar standard combustion parameters.
TL;DR: In this article, the authors present a retrospective and future look on the use of fly ash for concrete production in the United States and make suggestions for future research, including the need to produce a performance-oriented standard rather than a prescriptive one.
TL;DR: In this paper, Zeolites X, Y, Na-P1 (90 °C), analcime and sodalite (150 °C) were synthesized from Class F fly ash using 3 M sodium hydroxide solutions and autogenous pressures, and partially zeolitized fly ashes were dried overnight in air at room temperature and then characterized using X-ray diffraction and SEM.
Abstract: Zeolites X, Y, and Na-P1 (90 °C) and analcime and sodalite (150 °C) were synthesized from Class F fly ash using 3 M sodium hydroxide solutions and autogenous pressures. The partially zeolitized fly ashes were dried overnight in air at room temperature and then characterized using X-ray diffraction and SEM. On occasion, a few samples were dried to constant weight for an additional 8−10 min in a microwave oven to remove bound water as well. The dried samples were evaluated for their ability to adsorb sulfur dioxide (SO2) from a simulated stack gas containing ∼2000 ppm SO2. Determinations were made in real time using a UV/vis spectrophotometer followed by a total sulfur analysis of the “loaded” samples once testing was complete. Breakthrough curves indicate that the zeolites in the samples are able to remove all of the SO2 in the simulated flue gas (zero SO2 emission) for varying periods of time, and that the actual amount of SO2 removed by the zeolite depended on the type and degree of “dryness” of the zeol...
TL;DR: Lightweight aggregate concretes containing fly ash with a compressive strength between 61 to 67 MPa were produced in this article, which resulted in long-term shrinkage that was nearly twice as large as normal-weight concrete of somewhat similar strength.
TL;DR: In this paper, the complexation of copper with dissolved organic carbon (DOC) in leachates from fresh and 1.5-year old municipal solid waste incinerator (MSWI) bottom ash was studied using a competitive ligand-exchange solvent extraction procedure.
Abstract: The complexation of Cu with dissolved organic carbon (DOC) in leachates from fresh and 1.5-year old municipal solid waste incinerator (MSWI) bottom ash was studied using a competitive ligand-exchange solvent extraction procedure. At least two different ligands appear to be involved in the complexation of copper with DOC. The dissolved Cu appears to be 95−100% organically bound in leachates from both the fresh and the weathered bottom ash, and geochemical modeling indicates that the leaching of Cu from these ashes is primarily controlled by the availability of the organic ligands in the bottom ash. The mechanism that binds Cu to the solid phase is likely to be tenorite in the fresh bottom ash, and sorption to amorphous Fe/Al−(hydr)oxides in the weathered bottom ash.