Showing papers on "Fly ash published in 2001"
TL;DR: In this paper, the initial results of an experimental program aimed at producing and evaluating self-compacting concrete (SCC) made with high-volumes of fly ash are presented and discussed.
449 citations
TL;DR: In this paper, the strength and durability performance of normal and high-strength pozzolanic concretes incorporating silica fume, fly ash, and blast furnace slag was compared at elevated temperatures up to 800°C.
384 citations
TL;DR: In this paper, the hydration progress in metakaolin-blended high-performance cement pastes with age was assessed from the measurements of compressive strength, porosity, and pore size distribution, the degree of pozzolanic reaction, and the Ca(OH)2(CH) content of the MK-blending pastes at a water-to-binder ratio of 0.3.
366 citations
TL;DR: In this paper, the use of fly ash as a value-added product beyond incorporation in construction materials is reviewed with the aim of looking at new areas that will expand the positive reuse of Fly Ash, thereby helping to reduce the environmental and economic impacts of disposal.
Abstract: The disposal of fly ash from coal-fired power stations causes significant economic and environmental problems. A relatively small percentage of the material finds application as an ingredient in cement and other construction products, but the vast majority of material generated each year is held in ash dams or similar dumps. This unproductive use of land and the associated long-term financial burden of maintenance has led to realization that alternative uses for fly ash as a value-added product beyond incorporation in construction materials are needed. Utilization of fly ash in such areas as novel materials, waste management, recovery of metals and agriculture is reviewed in this article with the aim of looking at new areas that will expand the positive reuse of fly ash, thereby helping to reduce the environmental and economic impacts of disposal.
347 citations
TL;DR: The leaching of heavy metals in the S/S materials can be considered as a pH dependent and corresponding metal hydroxide solubility controlled process.
341 citations
TL;DR: In this article, the compressive strength of concretes cured under sealed conditions was investigated and it was shown that up to 67% of the concrete could be replaced without any significant reductions in strength.
314 citations
TL;DR: In this paper, an experimental program was undertaken to study the individual and combined effects of randomly oriented fiber inclusions and cement stabilization on the geotechnical characteristics of fly ash-soil mixtures.
Abstract: An experimental program was undertaken to study the individual and combined effects of randomly oriented fiber inclusions and cement stabilization on the geotechnical characteristics of fly ash-soil mixtures. An Indian fly ash was mixed with silt and sand in different proportions. The geotechnical characteristics of the raw fly ash-soil specimens and fly ash-soil specimens containing 1% randomly oriented polyester fiber inclusions were investigated. Unconfined compression tests were carried out on fly ash-soil specimens prepared with 3% cement content alone and also with 3% cement and 1% fiber contents, after different periods of curing. The study shows that cement stabilization increases the strength of the raw fly ash-soil specimens. The fiber inclusions increase the strength of the raw fly ash-soil specimens as well as that of the cement-stabilized specimens and change their brittle behavior to ductile behavior. Depending on the type of fly ash-soil mixture and curing period, the increase in strength caused by the combined action of cement and fibers is either more than or nearly equal to the sum of the increase caused by them individually.
284 citations
Patent•
05 Oct 2001TL;DR: In this paper, the authors proposed methods of cementing underground zones using cement compositions comprising calcium aluminate, fly ash, sodium polyphosphate and water for underground underground areas.
Abstract: The present invention provides methods of cementing subterranean zones using cement compositions comprising calcium aluminate, fly ash, sodium polyphosphate and water.
279 citations
TL;DR: In this article, the authors investigated the effects of replacing large volumes of cement with both classified and unclassified fly ash on the properties of foamed concrete and found that water vapour permeability increased with increasing porosity and ash content.
274 citations
TL;DR: The bagasse fly ash system has been used for the removal of DDD and DDE from the wastewater and the developed system is very useful, economic, and reproducible.
238 citations
TL;DR: In this paper, the effects of aggressive chemical environments were evaluated on the mortars prepared with ordinary portland cement (OPC) and silica fume (SF)/metakaolin (MK)/low-calcium fly ash at various replacement levels.
TL;DR: In this article, the compressive strengths of fly ash-cement mortars were determined and compared with the control mortar, showing that the degree of pozzolanic reaction, as determined using compressive strength, of coarse fly ash increased when its fineness was increased by grinding.
Abstract: The aim of this study is to evaluate the properties of ground coarse fly ashes, from five sources in Thailand, the shapes, sizes, and chemical compositions of which are completely different. Coarse fly ash was fractionated by an air classifier and ground into three different finenesses ranging from median particle sizes of 1.9–17.2 μm. Physical and chemical properties of the Portland cement and the fly ashes were investigated. Mortar cubes of 5 cm were cast with 20% replacement by weight of Portland cement with ground coarse fly ash. The compressive strengths of the fly ash–cement mortars were determined and compared with the control mortar. The results revealed that the degree of pozzolanic reaction, as determined using compressive strength, of coarse fly ash increased when its fineness was increased by grinding. The strength activity indices of the original fly ash–cement mortars at the curing ages of 7 and 28 days were in the range of 69–82% and 76–90%, respectively. When the particle size smaller than 9 μm of ground coarse fly ash was used, the strength activity index achieved was over 100% of that of the control within 28 days. The results also showed that the fineness of fly ash, not the chemical composition, was the major factor affecting the strength activity index of ground coarse fly ash–cement mortar.
TL;DR: Decontamination tests of three acid mine waters from southwestern Spain were carried out using the zeolites derived from fly ash and commercial synthetic zeolite, demonstrating that the zeolitic material could be employed for heavy metal uptake in the water purification process.
Abstract: Two pilot plant products containing 65 and 45% NaP1 zeolite were obtained from two Spanish coal fly ashes (Narcea and Teruel Power Station, respectively). The zeolitic product obtained showed a cation exchange capacity (CEC) of 2.7 and 2.0 mequiv/g, respectively. Decontamination tests of three acid mine waters from southwestern Spain were carried out using the zeolite derived from fly ash and commercial synthetic zeolite. The results demonstrate that the zeolitic material could be employed for heavy metal uptake in the water purification process. Doses of 5-30 g of zeolite/L have been applied according on the zeolite species and the heavy metal levels. Moreover, the application of zeolites increases the pH. This causes metal-bearing solid phases to precipitate and enhances the efficiency of the decontamination process.
TL;DR: In this paper, the effects of initial and pozzolanic reactions were investigated to evaluate the stress-strain behavior of a sandy soil improved through the addition of carbide lime and fly ash.
Abstract: Unconfined compression tests, Brazilian tensile tests, and saturated drained triaxial compression tests with local strain measurement were carried out to evaluate the stress-strain behavior of a sandy soil improved through the addition of carbide lime and fly ash. The effects of initial and pozzolanic reactions were investigated. The addition of carbide lime to the soil-fly ash mixture caused short-term changes due to initial reactions, inducing increases in the friction angle, in the cohesive intercept, and in the average modulus. Such improvement might be of fundamental importance to allow site workability and speeding construction purposes. In addition, under the effect of initial reactions, the maximum triaxial stiffness occurred for specimens molded on the dry side of the optimum moisture content, while the maximum strength occurred at the optimum moisture content. After 28 days, pozzolanic reactions magnified brittleness and further increased triaxial peak strength and stiffness; the maximum triaxial strength and stiffness occurred on the dry side of the optimum moisture content.
TL;DR: In this paper, a study on the mechanical properties and durability of concrete made with a high-volume fly ash (HVFA) blended cement using a coarse fly ash that does not meet the fineness requirement of ASTM C 618 was presented.
TL;DR: In this article, the results from X-ray diffraction data obtained from electronic low-temperature (oxygen-plasma) ash residues, from ashes produced by heating the coals in air at 370°C, and also from the raw coals themselves, were evaluated using an interactive data processing system ( siroquant ™) based on Rietveld interpretation methods.
TL;DR: The hardening mechanism of a paste composed of a low calcium fly ash and alkali was investigated in this article, where it was found that a fraction of fly ash reacted with water-glass and formed amorphous or low-ordered crystalline compounds of the type of Na2O−Al2O3−SiO2, after the paste was cured at 60°C for 24 h.
TL;DR: In this paper, the effects of mix proportion and curing temperature on the pozzolanic reaction of fly ash in cement paste were investigated by examining the productions of calcium hydroxide and the reaction ratio of fly-ash.
TL;DR: In this paper, the effect of lime and fly ash on the compressibility and hydraulic characteristics of an expansive soil in Cyprus was evaluated. But the results were limited to a series of laboratory tests.
Abstract: The paper presents a series of laboratory tests and evaluates the effect of lime and fly ash on the compressibility and hydraulic characteristics of an expansive soil in Cyprus The tests were perf
TL;DR: In this article, Atterberg limits tests of molded ash-clay mixtures indicated that both plastic index and dry shrinkage decrease with an increasing amount of ash in the mixture.
Abstract: Brick manufactured from incinerated sewage sludge ash and clay is investigated. The results of Atterberg limits tests of molded ash-clay mixtures indicated that both plastic index and dry shrinkage decrease with an increasing amount of ash in the mixture. Results of tests indicated that the ash proportion and firing temperature were the two key factors determining the quality of brick. Increasing the firing temperature and decreasing the amount of ash in the brick resulted in a decrease of water absorption. The appropriate percentage of ash content for producing quality bricks was in the range of 20 to 40% by weight with a 13 to 15% optimum moisture content prepared in the molded mixture and firing at 1,000°C for 6 h. With 10% ash content, the ash-clay bricks exhibited higher compressive strength than normal clay bricks. This study showed that the pulverized sludge ash could be used as brick material. The bonding strength can be further enhanced by controlling operating conditions.
TL;DR: The sintering process of untreated MSW fly ashes proved to be ineffective for manufacturing sintered products for reuse as a construction material, because of the adverse chemical characteristics of these fly ashes in terms of sulfate, chloride, and vitrifying oxide contents.
TL;DR: In this paper, an exploratory study on the effectiveness of anhydrite in activating fly ash cement systems was presented. But, the authors did not consider the effect of the other ingredients, such as gypsum and sodium sulfate, on the early strength of the fly ash mortars.
TL;DR: In this paper, coal fly ash was converted into two types of porous materials, MCM-41 and SBA-15, using the supernatant of the fly ash.
Abstract: Coal fly ash was converted into two types of porous materials, MCM-41 and SBA-15 (both of hexagonal structure), using the supernatant of the fly ash. It was found that most of the Si and Al components in the fly ash could be effectively transformed into mesoporous materials, depending on the hydrothermal conditions, and that fusion is essential. Investigation by 29Si and 27Al MAS NMR demonstrated that fusion plays an important role in enhancing the hydrothermal conditions for synthesis of these materials. A high concentration of Na ions in the supernatant of the fused fly ash was not found to be critical in the formation of Al-MCM-41 when prepared under controlled pH conditions. Pyridine adsorption experiments on Al-MCM-41 prepared from coal fly ash revealed the presence of Bronsted and Lewis acid sites. It was also found that the catalytic activity in the cumene cracking reaction is linked only to the accessible aluminium, and not to the
total incorporated aluminium present in the Al-MCM-41.
TL;DR: In this paper, a small percentage of coal ash particles, present in the pulverized coal ash, consists of thin-walled hollow spheres or cenospheres, which float on the ash slurry when it is impounded in the ash ponds or lagoons.
TL;DR: Ash treatment did not significantly influence water infiltration rate, bulk density, or temperature of the soil, but substantially improved water-holding capacity (WHC) and plant-available water (PAW).
Abstract: A field study (1993-96) assessed the benefits of applying unusually high rates of coal fly ash as a soil amendment to enhance water retention of soils without adversely affecting growth and marketability of the turf species, centipedegrass [Eremochloa ophiuroides (Munro) Hack] A Latin Square plot design was employed that included 0 (control, no ash applied), 280, 560, and 1120 Mg ha-1 application rates of unweathered precipitator fly ash The fly ash was spread evenly over each plot area, rototilled, and allowed to weather under natural conditions for 8 mo before seeding High levels of soluble salts, indicated by the electrical conductivity (EC) of soil extracts, in tandem with an apparent phytotoxic effect from boron (B), apparently inhibited initial plant establishment as shown by substantially lower germination counts in treated soil However, plant height and rooting depth were not adversely affected, as were the dry matter (DM) yields throughout the study period Ash treatment did not significantly influence water infiltration rate, bulk density, or temperature of the soil, but substantially improved water-holding capacity (WHC) and plant-available water (PAW) Enhanced water retention capacity improved the cohesion and handling property of harvested sod
TL;DR: In this paper, the authors investigated the activation of reactivity of fly ash in different blended cements such as lime, fly ash, lime-fly ash slag and Portland fly ash cements.
TL;DR: In this paper, the authors reported a technology for producing cement from incineration ash of municipal solid waste, including sludge and other wastes such as aluminium dross and copper slag, and verified that proper treatment (formation of calcium-chloroaluminate) is capable of fixing the chlorine.
Abstract: Incineration ash of municipal solid waste accounts for a great portion of the matter in landfills, and minimization of resource consumption and recycling of waste are important factors for ensuring the future welfare of humankind. The study presented in this paper reports a technology for producing cement from incineration ash of municipal solid waste, incineration ash of sewage sludge and other wastes such as aluminium dross and copper slag. As incineration ash of municipal solid waste contains chlorine, special attention should be paid to fixing the chlorine within the cement. It was verified that proper treatment (formation of calcium-chloroaluminate) is capable of fixing the chlorine. In order to confirm the efficacy of this technology before it is used on an industrial scale, a pilot-scale test (50 tons/day) was conducted. The quality of the resulting cement is sufficient to enable the cement to be put to practical use. Furthermore, the tested process does not cause secondary pollution. Consequently, 50% of raw materials for cement production can be obtained from incineration ash of municipal solid waste.
TL;DR: In this paper, the mobility of water-soluble major and trace elements in six Spanish fly ashes using room temperature open and closed and heated closed leaching systems in an attempt to reduce the content of undesirable species in coal combustion byproducts to increase their potential applications.
TL;DR: Operating conditions which would conciliate a high removal of the five metallic cations and a low desorption of these metal ions from the contaminated sorbents are defined and the formation of calcium silicate hydrate, resulting from the pozzolanic activity of fly ash, is assumed to be partially responsible for these mechanisms.
Patent•
29 Jan 2001
TL;DR: In this article, hydraulic cements are disclosed that include reactive magnesium oxide prepared by low temperature calcination, which can be formulated to suit a large number of applications with various setting times, strength and levels of sustainability either by adding iron salts such as ferrous sulphate or blending with other compatible faster setting cements such as Portland cement.
Abstract: Novel hydraulic cements are disclosed that include reactive magnesium oxide prepared by low temperature calcination. The cements can be formulated to suit a large number of applications with various setting times, strength and levels of sustainability either by adding iron salts such as ferrous sulphate or blending with other compatible faster setting cements such as Portland cement or by using both methods. The compositions are able to incorporate relatively large amounts of low cost pozzolans such as fly ash to advantage as well as wastes. Many excellent properties are exhibited and in particular good comprehensive strength and resistance to sulphates is able to be achieved.