Showing papers on "Fly ash published in 2000"
TL;DR: The activation of fly ash/slag pastes with NaOH solutions has been studied in this paper, where the authors established the equations of the models describing the mechanical behaviour of these pastes as a function of the factors and levels considered.
745 citations
TL;DR: In this paper, the possibility of using finely ground waste glass as partial cement replacement in concrete was examined through three sets of tests: the lime-glass tests to assess the pozzolanic activity of ground glass, the compressive strength tests of concrete having 30% cement replaced by ground glass to monitor the strength development, and the mortar bar tests to study the potential expansion.
591 citations
TL;DR: In this article, the degree of hydration of the cement in Portland cement (PC) paste was obtained by determining the non-evaporable water (Wn) content of the fly ash.
540 citations
TL;DR: In this paper, the durability of Portland cement systems incorporating supplementary cementing materials (SCM; silica fume, low and high-calcium fly ash) is investigated.
534 citations
TL;DR: In this article, the authors presented the results of a laboratory study on high strength concrete prepared with large volumes of low calcium fly ash, and the results demonstrated the dual effects of fly ash in concrete: (i) act as a microaggregate and (ii) being a pozzolana.
369 citations
TL;DR: In this paper, the authors investigated coal combustion flue gas with fly ash and found that adding 50 and 100 ppmv of HCl(g) and ≈12.6 wt.% of CaO(s) to the subbituminous coal combustion environment inhibited Hg(p) formation, primarily via a change in ash surface chemistry and a decrease in particle surface area.
352 citations
01 Jan 2000
TL;DR: In this paper, the authors present a concrete incorporating large volumes of fly ash that has all the attributes of high-performance concrete i.e. excellent mechanical properties, low permeability, superior durability, and that is environmentally friendly.
Abstract: The challenge for the civil engineering community in the near future will be to realize projects in harmony with the concept of sustainable development, and this involves the use ol high-performance materials produced at reasonable cost with the lowest possible environmental impact. Portland cement concrete is a major construction material worldwide. Unfortunately, the production of portland cement releases large amounts of CO 2 into the atmosphere, and because this gas is a major contributor to the greenhouse effect and the global warming of the planet, the developed countries are considering very severe regulations and limitations on the CO 2 emissions. In view of the global sustainable development, it is imperative that supplementary cementing materials be used to replace large proportions of cement in the concrete industry, and the most available supplementary cementing material worldwide is fly ash, a by-product of thermal power stations. In order to increase considerably the utilization of fly ash that otherwise is being wasted, and to have a significant impact on the production of cement, it is necessary to advocate the use of concrete that will incorporate large amounts of fly ash as replacement for cement. However, such concrete will have to demonstrate performance comparable to that of conventional portland cement concrete, and must be cost effective. In 1985, CANMET developed a concrete incorporating large volumes of fly ash that has all the attributes of high-performance concrete i.e. excellent mechanical properties, low permeability, superior durability, and that is environmentally friendly. This paper gives an overview of the properties of this type of concrete that is believed to be a very promising alternative for the industry seeking to meet the sustainable development objectives.
348 citations
TL;DR: In this article, Bagasse fly ash, a waste produced in sugar industries, has been converted into an inexpensive and effective adsorbent, which has been used for the removal of copper and zinc from wastewater.
297 citations
TL;DR: In this article, the results from expansion tests on concrete prisms and mortar bars containing reactive aggregate and different types and levels of fly ash were tested, and the results show that the bulk chemical composition of the fly ash provides a reasonable indication of its performance in physical expansion tests but cannot be used to accurately predict the degree of expansion or the minimum safe level of fly ashes required to suppress expansion to an acceptable limit.
278 citations
TL;DR: In this article, the authors present a concrete incorporating large volumes of fly ash that has all the attributes of high-performance concrete: one that has excellent mechanical properties, low permeability, superior durability, and that is environmentally friendly.
Abstract: Portland cement concrete is a major construction material worldwide. Unfortunately, the production of portland cement releases large amounts of carbon dioxide (CO2) into the atmosphere, and because this gas is a major contributor to the greenhouse effect and the global warming of the planet, developed countries are considering very severe regulations and limitations on CO2 emissions. In view of global sustainable development, it is imperative that supplementary cementing materials be used to replace large proportions of cement in the concrete industry. The most available supplementary cementing material worldwide is fly ash, a by-product of thermal power stations. To considerably increase the utilization of fly ash that otherwise is being wasted, and to have a significant impact on the production of cement, it is necessary to advocate the use of concrete that will incorporate large amounts of fly ash as a replacement for cement. Such concrete, however, must demonstrate performance comparable to that of conventional portland cement concrete and must be cost effective. In 1985, CANMET developed a concrete incorporating large volumes of fly ash that has all the attributes of high-performance concrete: one that has excellent mechanical properties, low permeability, superior durability, and that is environmentally friendly. This paper gives an overview of the properties of this type of concrete that is believed to be a promising alternative for the industry seeking to meet sustainable development objectives.
268 citations
TL;DR: The melting process was developed in the 1980's and has been in practical operation at around 24 municipal solid waste (MSW) incineration facilities including scheduled ones as mentioned in this paper, where PCDDs/PCDFs in residues are decomposed at a temperature of approximately 1400°C in the furnace and volatile heavy metals are concentrated in the fly ash of the melting process.
TL;DR: In this article, the influence of the pozzolanic activity of metakaolin (MK) on the hydration heat has been studied in comparison to the behaviour of other traditional materials such as fly ash and silica fume.
TL;DR: In this article, the authors used the Nernst-Einstein equation to calculate the diffusion coefficient of chloride ions of high-performance concrete (HPC), analyzing and discussing the property of resistance to chloride ion of HPC with fly ash or blast furnace slag.
TL;DR: In this paper, deposits collected on air-cooled probes and directly at the existing heat transfer surfaces of a straw-fired boiler have been examined, and it is argued that the K2SO4 layer present adjacent to the metal surface may lead to reduced corrosion rates at this boiler.
TL;DR: In this paper, the engineering performance of moist cured fly ash pellets including the effect of lime and cement additions both for geotechnical application and concrete production purposes were investigated and the results obtained are quite satisfactory for the related design requirements.
Abstract: Although pelletization process is a world wide known technique in the production of artificial aggregates, it has not been widely used in construction sector. The 1985 figures show that overall pellet production for use as metallurgical product was 435 million tons and with respect to statistical figures that belong to 1989 the agglomerated product use in construction sector as lightweight aggregate was only 1.2 million tons. The reasons of low utilization of coal combustion by-products as lightweight aggregates in the construction sector are: — the availability of natural resource products and relatively higher costs of agglomeration process due to initial investments and — energy requiring curing procedures to obtain adequate strength for construction applications (e.g. steam curing and sintering). However, depending on the agglomerated materials’ properties and process efficiency, artificial aggregates with adequate engineering performance may be produced by moisture treatment under atmospheric conditions. In this study, the engineering performance of moist cured fly ash pellets including the effect of lime and cement additions both for geotechnical application and concrete production purposes were investigated and the results obtained are quite satisfactory for the related design requirements.
TL;DR: In this article, the authors proposed a flow sheet for the hydrometallurgical treatment of fly ash by means of alkaline leaching followed by dilute acid washing is a potentially feasible method.
TL;DR: In this paper, the hydration processes of high-volume fly ash cement paste were investigated by examining the non-evaporable water content, the CH content, pH of pore solution and the fraction of reacted fly ash, curing at either 20°c or elevated temperatures after an initial curing at 20°C.
Abstract: The hydration processes of high-volume fly ash cement paste were investigated by examining the non-evaporable water content, the CH content, the pH of pore solution and the fraction of reacted fly ash, curing at either 20°C or elevated temperatures after an initial curing at 20°C. The replacement percentage levels of fly ash were 40%, 50% and 60% by weight, respectively. The results revealed that the non-evaporable water content in high-volume fly ash cement pastes does not develop as plain cement pastes does, so it may be improper to apply the non-evaporable water content to evaluate the hydration process in high-volume fly ash cement matrix. The reduction in CH content increases with the progressing of hydration process and varies linearly with the logarithm of curing age. The addition of 3.0% of Na2SO4 could accelerate the pozzolanic reaction of fly ash at early ages. At 20°C, the pH of pore solution of high-volume fly ash cement paste was reduced to a great extent at early ages and it continued to decline at later ages due to the inclusion of large amount of fly ashes. At elevated temperatures, however, this trend was not found. The fraction of reacted fly ash directly reflects the pozzolanic reactivity of fly ash both at normal and elevated temperatures. There is some inherent correlation between the reduction in CH content, the pH of pore solution and the fraction of reacted fly ash. For specified matrix, the consumption of CH and the pH of pore solutions change linearly with the increase of the fraction of reacted fly ash.
TL;DR: In this article, the behaviour of different ashes was predicted by the combination of extended fuel analysis with advanced global thermodynamic equilibrium calculations, which is a fractionation method that consists of sequential leaching of a solid fuel with water, ammonium acetate and hydrochloric acid.
TL;DR: It is reasoned that 5-15% precipitator fly ash, and less than 30% lagoon fly ash could be added to coarse sands to produce an infiltration bed, which would result in a better quality effluent than can be obtained with untreated sand alone.
TL;DR: Experimental results on the mass and compositions of particles between 0.03 and >20 μm in aerodynamic diameter show that PM from the combustion of these fuels produces distinctive bimodal and trimodal PSDs, with a fine mode dominated by vaporization, nucleation, and growth processes.
Abstract: U.S. Environmental Protection Agency (EPA) research examining the characteristics of primary PM generated by the combustion of fossil fuels is being conducted in efforts to help determine mechanisms controlling associated adverse health effects. Transition metals are of particular interest, due to the results of studies that have shown cardiopulmonary damage associated with exposure to these elements and their presence in coal and residual fuel oils. Further, elemental speciation may influence this toxicity, as some species are significantly more water-soluble, and potentially more bio-available, than others. This paper presents results of experimental efforts in which three coals and a residual fuel oil were combusted in three different systems simulating process and utility boilers. Particle size distributions (PSDs) were determined using atmospheric and low-pressure impaction as well as electrical mobility, time-of-flight, and light-scattering techniques. Size-classified PM samples from this study are also being utilized by colleagues for animal instillation experiments. Experimental results on the mass and compositions of particles between 0.03 and > 20 microns in aerodynamic diameter show that PM from the combustion of these fuels produces distinctive bimodal and trimodal PSDs, with a fine mode dominated by vaporization, nucleation, and growth processes. Depending on the fuel and combustion equipment, the coarse mode is composed primarily of unburned carbon char and associated inherent trace elements (fuel oil) and fragments of inorganic (largely calcium-alumino-silicate) fly ash including trace elements (coal). The three coals also produced a central mode between 0.8- and 2.0-micron aerodynamic diameter. However, the origins of these particles are less clear because vapor-to-particle growth processes are unlikely to produce particles this large. Possible mechanisms include the liberation of micron-scale mineral inclusions during char fragmentation and burnout and indicates that refractory transition metals can contribute to PM < 2.5 microns without passing through a vapor phase. When burned most efficiently, the residual fuel oil produces a PSD composed almost exclusively of an ultrafine mode (approximately 0.1 micron). The transition metals associated with these emissions are composed of water-soluble metal sulfates. In contrast, the transition metals associated with coal combustion are not significantly enriched in PM < 2.5 microns and are significantly less soluble, likely because of their association with the mineral constituents. These results may have implications regarding health effects associated with exposure to these particles.
TL;DR: In this paper, various combinations of salt mixtures were employed for the zeolitization of fly ash, using NaOH, KOH, or NH 4 F as mineralizer, and NaNO 3, KNO 3, orNH 4 NO 3 as stabilizer.
TL;DR: In this article, the unburned carbon that remains in coal fly ash could be used as an inexpensive and effective replacement for activated carbon, and two types of data were obtained: equilibrium and breakthrough data suitable for obtaining adsorption kinetics.
Abstract: The injection of large quantities of pulverized activated carbon is one method used to remove elemental mercury (Hg0) from flue gas streams. The purpose of this project was to determine whether the unburned carbon that remains in coal fly ash could be used as an inexpensive and effective replacement for activated carbon. Bench-scale tests were conducted at conditions representative of those found in the flue gas trains of coal-fired power plants and municipal waste incinerators. The temperatures and concentrations ranged from 121 to 177 °C and from 0.019 to 11.7 mg of Hg/m3. Two types of data were obtained: equilibrium data suitable for obtaining adsorption isotherms and breakthrough data suitable for obtaining adsorption kinetics. Adsorbed-phase concentrations were as high as 600 ppm. Forward adsorption rate constants were ≈0.06−2.3 m3/g/s for particle sizes and carbon contents ranging from 59 to 206 μm and from 2% to 36%. Mathematical models were developed to simulate the capture of Hg0 in flue gas duc...
TL;DR: A modified fusion process was studied to synthesize zeolites A and X from fly ash as mentioned in this paper, and it was found that the addition of aluminum hydroxide to the fused fly ash solution followed by hydrothermal treatm...
Abstract: A modified fusion process was studied to synthesize zeolites A and X from fly ash. It was found that the addition of aluminum hydroxide to the fused fly ash solution followed by hydrothermal treatm...
TL;DR: In this article, the corrosion process of steel embedded in concrete with various amounts of fly ash (up to 50% of the total binder) was tested under complete and partial immersion, in sodium chloride solution.
Abstract: The corrosion process of steel embedded in concrete with various amounts of fly ash (up to 50% of the total binder) was tested under complete and partial immersion, in sodium chloride solution. The corrosion process was followed by monitoring of open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). Fly ash addition has led to a raise of concrete resistivity and of the time for corrosion initiation and to a decrease of corrosion rate.
TL;DR: In this paper, bottom ash and glass cullet coming from the municipal solid waste incineration and a community glass recycling program, respectively, are particularly suitable to be subjected to a vitrification/devitrification process, leading to the production of alkaline and alkaline-earth silicate differently colored glasses with good chemical properties, capable to be transformed into surface nucleated basaltic glass-ceramics.
Abstract: Municipal (bottom ash and glass cullet coming from the municipal solid waste incineration and a community glass recycling program, respectively) and industrial (steel fly ash) wastes are particularly suitable to be subjected to a vitrification/devitrification process, leading to the production of alkaline and alkaline-earth silicate differently colored glasses with good chemical properties, capable to be transformed into surface nucleated basaltic glass-ceramics. These materials were investigated by means of differential thermal analysis, durability and release tests, X-ray diffraction and scanning electron microscopy.
TL;DR: In this paper, a bench-scale test rig was designed and built to simulate flue gas conditions, which consisted of O2, CO2, H2O, and N2.
TL;DR: In this paper, Fourier transform infrared (FTIR), X-ray diffraction, and compressive strength analyses were used to characterize the matrixes of fly ash-based geopolymers.
Abstract: Little attempt has been made to understand the chemical and physical consequences of incorporating non-aluminosilicate materials into geopolymers. In the present work zirconia was chosen as an inert reference to examine the effects of a non-aluminosilicate source on the chemical and physical properties of a geopolymer matrix. Fourier transform infrared (FTIR), X-ray diffraction, and compressive strength analyses were used to characterize the matrixes. Inclusion of only a small quantity of zirconia was shown to impart a substantial increase in compressive strength for fly ash-based geopolymers. The basis of this increase in strength has been hypothesized to be due to the formation of specific zirconia-associated, three-dimensional polysialate species, which reduce the mobility of sodium while maintaining the charge balance and structural stability of the matrix. Through a simplified study based on zirconium polysialate solubility and FTIR measurements, an attempt was made to rationalize and correlate the o...
TL;DR: In this paper, a Mercury intrusion porosimetry study was carried out on samples of ordinary Portland cement mortars made with mineral additives such as fly ash, granulated blast furnace slags, phosphorous furnace slag, limestone, and lime sludge.
TL;DR: In this article, carbon was separated from the fly ash from a Kentucky power plant using density gradient centrifugation and a lithium heterolpolytungstate high-density media.
Abstract: Carbon was separated from the fly ash from a Kentucky power plant using density gradient centrifugation and a lithium heterolpolytungstate high-density media. Relative concentrations of inertinite (up to 77% vol), isotropic carbon (up to 77% vol), and anisotropic carbon (up to 76% vol) were isolated from the original fly ash. Mercury concentration was lowest in the parent fly ash (which contains non-carbon components); followed by inertinite, isotropic coke, mixed isotropic−anisotropic coke fraction, and, with the highest concentration, the anisotropic coke concentrate. The latter order corresponds to the increase in BET surface area of the fly ash carbons. Previous studies have demonstrated the capture of mercury by fly ash carbon. This study confirms prior work demonstrating the varying role of carbon types in the capture, implying that variability in the carbon forms influences the amount of mercury retained on the fly ash.
TL;DR: Natural weathering of MSWI bottom ash for a period of about 90 days reduced the leaching of heavy metals, stabilising the bottom ash pH to minimise the solubility of metal hydroxides, and enabled the residue to be used as secondary building material.