Showing papers on "Fly ash published in 1994"
KEMA1
TL;DR: In this article, the authors investigated the relationship between the elements in different process streams and established the collection efficiency of the new generation of high-efficiency cold-side electrostatic precipitators in relation to their collection both of total particulate matter and of each individual element.
370 citations
TL;DR: In this paper, the size-segregated speciation of trace metals in pulverized coal-fired power plant effluents has been investigated and new theoretical results interpreting existing data are presented.
224 citations
TL;DR: In this article, the long-term exposure test data showed that the replacement of portland cement by fly ash and silica fume effectively improved the resistance of the mortar to the sulfuric acid and sulfate solution attack.
189 citations
TL;DR: In this article, the authors provide an overview of recent research efforts to characterize the combustion process in large, utility-scale boilers as it affects the release, transformation and partitioning of coal's trace inorganic components in both the combustion zone and the heat transfer sections of the boiler.
154 citations
TL;DR: In this article, the results of investigations to determine the various durability aspects of high-volume fly ash concrete using eight fly ashes and two portland cements from United States (U.S.) sources were presented.
Abstract: This paper presents the results of investigations to determine the various durability aspects of high-volume fly ash concrete using eight fly ashes and two portland cements from United States (U.S.) sources. Briefly, in high-volume fly ash concrete, the water and cement content are kept low at about 115 and 155 kg/m of concrete, respectively, and the proportion of fly ash in the total cementitious materials content ranges from 55 to 60 percent. The durability aspects investigated included resistance to the repeated cycles of freezing and thawing, the deicing salt-scaling resistance, the resistance to the chloride-ion penetration, and the determination of water permeability coefficient. Based upon the test results, it is concluded that regardless of the type of fly ash and the cements used, the air-entrained high-volume fly ash concrete exhibited excellent durability characteristics in the tests investigated. The only exception was the deicing salt-scaling test in which the performance of the concretes investigated was less than satisfactory.
143 citations
TL;DR: In this paper, a process for the treatment of industrial wastewater containing heavy metals, using fly ash adsorption and cement fixation of the metal-laden adsorbent, was investigated.
Abstract: A process for the treatment of industrial wastewater containing heavy metals, using fly ash adsorption and cement fixation of the metal-laden adsorbent, was investigated. Results show that the fly ash can be an effective metal adsorbent, at least for Zn(II) and Cd(II) in dilute industrial wastewaters. Fly ash adsorption capacities for Zn(II) and Cd(II) were 0.27 mg/g and 0.05 mg/g, respectively. A mortar specimen prepared with 10% metal-laden fly ash showed a 56-day strength, about the same or even greater than that of cement alone. Leachates from the fixed metal-laden fly ash, obtained by using both the ASTM and U.S. Environmental Protection Agency-extraction procedure (USEPA-EP) leaching tests, exhibit metal concentrations lower than the drinking water standards. Compressive strength and leaching tests results suggest that metal-laden fly ash can be considered for use in secondary construction materials.
130 citations
TL;DR: In this paper, the mobility of Cd, Co, Cu, Ni, Pb, Sb, and Zn from six different coal-fired power plant fly ashes that show a wide compositional range was examined using a sequential extraction procedure in order to assess their mobility when these wastes are ponded or landfilled.
Abstract: The mobility of Cd, Co, Cu, Ni, Pb, Sb, and Zn from six different coal-fired power plant fly ashes that show a wide compositional range was examined using a sequential extraction procedure in order to assess their mobility when these wastes are ponded or landfilled. The extraction sequence was as follows: (1) water extractable, (2) cation exchangeable (CH3COONH4 at pH 7), (3) surface oxide-bound cations (CH3COONH4 at pH 5), (4) Fe oxide-bound cations (HONH3Cl), and (5) residual (HF, HCl, HNO3, 2∶1∶1). The heavy metal contents in the extraction solutions were determined by anodic (Cd, Cu, Pb, Sb, and Zn) and cathodic (Ni and Co) stripping voltammetry. The results reveal differences in the total contents of the selected trace elements among the fly ash samples, which must be related to differences in coal composition and combustion technology. The extractable fraction under natural conditions ranges from 1.5 to 36.4 percent of the total element content. Cadmium, Co, Cu, and Zn show the highest extractable fraction (10.8–18.9 percent on average). Cadmium is the most easily water-extractable element, while Co, Cu, and Zn increase their mobility as the severity of the extraction increases. Cobalt, Ni, Pb, and Zn are mainly associated with the surface oxide-bound and Fe oxide-bound fractions. Nickel, Pb, and Sb have low mobility potentials (5.3–6.6 percent as extractable fraction), but Sb presents a relatively high water-extractable fraction.
124 citations
TL;DR: In this article, the influence of fly ash on concrete permeability was evaluated by using the Figg method and the results showed that the addition of a Class C fly ash caused a decrease in chloride permeability of concrete up to 50% cement replacement.
108 citations
Patent•
14 Nov 1994TL;DR: In this paper, concrete compositions are provided which contain particulate rubber, preferably recycled rubber from such sources as automobile tires, in amounts between about 0.05 and about 20 percent by weight of the concrete composition.
Abstract: Concrete compositions are provided which contain particulate rubber, preferably recycled rubber from such sources as automobile tires, in amounts between about 0.05 and about 20 percent by weight of the concrete composition. The concrete compositions further contain portland cement, water, and an aggregate material. Additional materials such as superplasticizers and fly ash can also be admixed with the concrete compositions.
107 citations
TL;DR: In this paper, the use of sorbents to control trace metal emissions from combustion processes was investigated, and the underlying mechanisms governing the interactions between trace metals and sarsbents, were explored.
TL;DR: In this article, the authors compared the influence of different amounts of four combustion byproducts (fly ash and bed ash from a fluidized bed combustion furnace, lime-injected multistage burner residue, and spray dryer residue) and CaCO3 on soil pH and enzyme activities.
Abstract: There is considerable interest in the use of coal combustion byproducts as soil liming materials in agricultural production, but there is concern that such use may be detrimental to the quality of agricultural soils. To evaluate these byproducts as liming materials and address issues related to soil quality, we compared the influence of different amounts of four combustion byproducts [fly ash and bed ash from a fluidized bed combustion furnace, lime-injected multistage burner residue, and spray dryer residue] and CaCO3 on soil pH and activities of urease, phosphatase, arylsulfatase, and dehydrogenase in an acidic soil. Studies comparing the influence of the combustion byproducts and CaCO3 on soil pH showed that on a weight basis of application, substantial differences were observed in the ability of these materials to influence soil pH but that such differences decreased markedly after the data were transformed to a CaCO3 equivalent basis of application. Analysis of covariance for these transformed data indicated that whereas the liming abilities of fly ash and CaCO3 were not significantly different when compared on the CaCO3 equivalent basis, those of bed ash, multistage burner residue, and spray dryer residue were less than that of CaCO3. Studies comparing the influence of the byproducts and CaCO3 on soil enzyme activities showed that the effect of these liming materials on the enzyme activities studied was largely due to their influence on soil pH. The relationships obtained between soil pH and enzyme activities in soil amended with the liming materials generally demonstrated the marked similarities in the influence of the combustion byproducts and CaCO3 on these activities when observed within the domain of soil pH. These studies showed that the combustion byproducts tested functioned as soil liming materials in a manner similar to that of CaCO3 and seemed to have little adverse effect on soil quality.
TL;DR: In this article, the authors compared the leaching of As and Se from fly ash with the sorption of arsenate and selenite on hematite, portlandite and mullite.
TL;DR: In this article, the authors describe the development of cast aluminum-fly ash particle composites (ash alloy), which are a waste byproduct of coal-based power generation, reducing the cost of aluminum castings by acting as a filler; decreases their density, and increases their hardness, abrasion resistance, and stiffness.
Abstract: In recent years there has been considerable activity in the development of metal-matrix composites, especially for aerospace, ground transportation, and the leisure industry. Short-fiber-reinforced pistons and cylinder blocks have been marketed by Japanese companies for several years. It is likely that in the near future cast particulate composites like aluminum-graphite, aluminum-silicon carbide, and aluminum-alumina will find widespread applications as brake rotors, drive shafts, cylinder liners, connecting rods, and wrist pins. The cost of metal-matrix composites has been one of the major barriers toward their widespread application. This paper describes the development of cast aluminum-fly ash particle composites (ash alloy). Incorporation of fly-ash particles, which are a waste by-product of coal-based power generation, reduces the cost of aluminum castings by acting as a filler; decreases their density, and increases their hardness, abrasion resistance, and stiffness. Several prototype castings have been made from aluminum-fly ash composites to demonstrate their castability. With sustained research and the support of manufacturing organizations, these alloys can find widespread applications as low-cost aluminum composite components.
TL;DR: In this paper, the authors investigated the use of fly ash from a municipal sludge incinerator, cement kiln dust, and bagasse for dewatering primary sludge from a wastewater treatment plant that processes a mixture of industrial and municipal effluents.
TL;DR: In this paper, the hydration behavior of blended cements containing fly ash, silica fume, and granulated blast furnace slag over the temperature range of 10 to 55°C was studied by isothermal calorimetry.
Abstract: The hydration behavior of blended cements containing fly ash, silica fume, and granulated blast furnace slag over the temperature range of 10 to 55°C was studied by isothermal calorimetry. The rates of heat evolution during the first 24 h of hydration were examined. The results were analyzed to determine the kinetics of hydration of portland and blended cements. Relationships between the reactivities of these blended cements and the curing temperature were established. The results show that the rates of hydration reactions increased with an increase in temperature in all instances. Comparison among the blends containing fly ash, silica fume, and slag was made to establish activation energies for the hydration reactions. Arrhenius activation energy Ea values obtained were 39.0, 26.7, 30.4, and 49.3 KJ/mol for portland cement, fly ash, silica fume, and slag blended cements, respectively. The relatively constant Ea values for the blended cements may be related to diffusionally controlled hydration of the mineral admixtures.
TL;DR: In this article, a 0.5 MW test combustor burning pulverized coal, with burner or in-furnace air-staging, was investigated with an unburnt carbon content of ~10 wt%, acceptable for small test facilities.
TL;DR: In this article, a model based on siloxane and silaloxane hydrolysis, alkali ion exchange, and precipitation of calcium silicates, aluminates, and aluminosilicates is proposed to explain the observed processes.
Abstract: This paper presents a summary of work in progress on an examination of the hydration chemistry and microstructure of a paste prepared incorporating 58 percent of a typical American Society for Testing and Materials (ASTM) Class F fly ash and a portland cement from United States sources and a paste with the portland cement only. Thermal analysis, x-ray diffraction, pore fluid extraction, and scanning electron microscope have been employed to study cement and cement-fly ash pastes cured up to 180 days. High levels of nonevaporable water and removal of alkali ions from pore solutions in pastes cured for 7 to 14 days were found. Etching of fly ash particles and extensive deposition of reaction products at ash/matrix boundaries were evident in scanning electromicrographs. Together, these observations clearly demonstrate extensive participation by the fly ash in hydration and cementation reactions. However, despite the extensive reactivity, up to 180 days, many fly ash particles remain as intact pseudomorphs embedded in the hydrate mass. A model based on siloxane and silaloxane hydrolysis, alkali ion exchange, and precipitation of calcium silicates, aluminates, and aluminosilicates, is proposed to explain the observed processes.
TL;DR: In this paper, the authors measured the portlandite content of concrete pastes made with two condensed silica fumes, three pulverized fly ashes and one ground granulated blast furnace slag during a 1 year time period.
Patent•
06 Oct 1994
TL;DR: In this article, the authors propose a mixture of 10-30 parts of cementitious material, 50-80 parts fly ash weight, and 1.5-8 parts of hydroxycarboxylic acid.
Abstract: A cementitious composition comprising (A) 10-30 parts cementitious material; (B) 50-80 parts fly ash weight; and (C) 1.5-8 parts hydroxycarboxylic acid and/or salt thereof.
TL;DR: In this paper, the Lagergren equation and the intraparticle diffusion rate equation were derived from which adsorption rate constants, diffusion rate constants and diffusion coefficients were determined.
Abstract: The factors affecting the rate processes involved in the removal of phenolic compounds, eg initial phenol concentration, particle size, impregnation of fly ash (IFA), pH and temperature have been studied The removal rate of phenols varied in the order p-nitrophenol > m-nitrophenol > o-nitrophenol > p-cresol > phenol > m-cresol > o-cresol The process followed first order rate kinetics The sorption data generally fit the Lagergren equation and the intraparticle diffusion rate equation from which adsorption rate constants, diffusion rate constants and diffusion coefficients were determined Intraparticle diffusion was found to be the rate-limiting step These kinetic parameters were compared for various phenols under different conditions using fly ash (FA) and impregnated fly ash (IFA)
TL;DR: In this paper, a laboratory study was conducted to evaluate the performance of APCCC under control conditions, including stability, indirect tensile strength, compressive strength, resilient modulus, water sensitivity, freezing and thawing, and chloride intrusion resistance.
Abstract: The lack of strain characteristics of rigid pavements and bridge deck overlays and the susceptibility of flexible pavements and hot‐mix asphalt overlays to abrasion wear, fuel spillage, and stripping suggests the search for a material that possesses the unique properties of both Portland cement concrete and hot‐mix asphalt such as asphalt‐Portland cement concrete composite (APCCC). APCCC is a hot‐mix asphalt with a high air void content (25–30%) filled with resin‐modified cement grout. The grout consists of Portland cement, fly ash, sand, water, and Prosalvia admixture. The resulting concrete has the properties of both flexible and rigid concrete. A laboratory study was conducted to evaluate the performance of APCCC under control conditions. The program included the following tests: stability, indirect tensile strength, compressive strength, resilient modulus, water sensitivity, freezing and thawing, and chloride intrusion resistance. The tests were performed at three levels of moist curing: no moist curi...
Patent•
19 Dec 1994
TL;DR: An improved lightweight cementitious product made up of an aqueous cementitious mixture that can incorporate fly ash, portland cement, sand, lime, and the weight saving component, which is micronized polystyrene particles having particle sizes in the range of 50 to 2000 microns.
Abstract: An improved lightweight cementitious product made up of an aqueous cementitious mixture that can incorporate fly ash, portland cement, sand, lime, and the weight saving component, which is micronized polystyrene particles having particle sizes in the range of 50 to 2000 microns. The final mix can be poured into molded products such as foundation walls, roof tiles, bricks and the like. The product can also be used as a mason's mortar, a plaster, a stucco or a texture.
TL;DR: In this article, a reference plain portland cement concrete was proportioned to obtain 28-day strength of 41 MPa using the rotating cutter method as per ASTM C-944.
TL;DR: In this article, the microstructural development in a high-volume flyash (HVFA) cement system containing 60% fly ash by weight of binder is presented, and the authors present the results of research findings on the micro structural development in the HVFA system.
Abstract: The writers present the results of research findings on the microstructural development in a highvolume flyash (HVFA) cement system containing 60% fly ash by weight of binder. Although the oneday s...
Patent•
20 May 1994TL;DR: In this paper, the compressive strength of concrete and other hardenable mixtures, such as concrete, mortar, and fly ash, is predicted for use in building and highway construction.
Abstract: The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention includes a method for predicting the compressive strength of such a hardenable mixture, which is very important for planning a project. The invention also relates to hardenable mixtures comprising cement and fly ash which can achieve greater compressive strength than hardenable mixtures containing only concrete over the time period relevant for construction. In a specific embodiment, a formula is provided that accurately predicts compressive strength of concrete containing fly ash out to 180 days. In other specific examples, concrete and mortar containing about 15% to 25% fly ash as a replacement for cement, which are capable of meeting design specifications required for building and highway construction, are provided. Such materials can thus significantly reduce construction costs.
TL;DR: Sulphoaluminate belite cements containing the phases C[sub 2]S, S, A[sub 4]A[sub 3][bar S], S, AF, C[bar S] were synthesized from limestone, fly ash and gypsum at 1,200 C as discussed by the authors.
TL;DR: In this paper, the effect of fly ash blending on pore solution composition and physical characteristics of hardened concrete have been evaluated, showing that partial cement replacement by fly ash caused significant pore refinement, reduced permeability to water and chloride ions, and increased electrical resistivity.
Abstract: Accelerated corrosion tests were carried out on reinforced concrete specimens made with plain and fly ash blended cements. The fly ash blended cements were formulated by replacing 30 percent by fly ash on weight basis. Corrosion initiation time and corrosion rate of steel reinforcement in the post-corrosion initiation period were measured for plain and fly ash blended cements. To explain the corrosion resistance performance of steel in fly ash blended cement concrete, the effect of fly ash blending on pore solution composition and physical characteristics of hardened concrete have been evaluated. Results show that partial cement replacement by fly ash caused significant pore refinement, reduced permeability to water and chloride ions, and increased electrical resistivity. The observed superior corrosion resistance performance of fly ash blended cement concrete compared to plain cement concrete in terms of corrosion initiation time and corrosion rate is attributable to the improved physical structure of the cement matrix due to fly ash blending.
TL;DR: In this paper, a polypropylene fiber reinforced, high-volume fly ash concrete for shotcreting rock outcrops has been developed, which has satisfactory workability and strength characteristics.
Abstract: Investigations at CANMET have led to the development of polypropylene fiber reinforced, high-volume fly ash concrete for shotcreting rock outcrops. This type of concrete has a very low water-to-cementitious material ratio, fly ash content greater than 50 percent of the cementitious material, and contents of fibers up to 5 kg/m of concrete. The workability of the concrete is maintained by the use of high dosages of superplasticizers. This paper presents the results of CANMET investigations dealing with the development of this type of concrete. The test results show that polypropylene fiber reinforced, high-volume fly ash concrete has satisfactory workability and strength characteristics. It also has very low permeability, low drying shrinkage, adequate ductility, and toughness characteristics.
TL;DR: In this article, the authors examined fly ash by X-ray diffractometer (XRD), thermogravimetric analyzer (TGA), Fourier transformed infrared spectrophotometer (FTIR) and scanning force microscopy (SFM).