Showing papers on "Fly ash published in 2004"
TL;DR: In this article, fly ash-based geopolymer concrete was developed to reduce greenhouse gas emissions, and the test results showed the effects of various parameters on the properties of the concrete.
Abstract: To reduce greenhouse gas emissions, efforts are needed to develop environmentally friendly construction materials. This paper presents the development of fly ash-based geopolymer concrete. In geopolymer concrete, a by-product material rich in silicon and aluminum, such as low-calcium (ASTM C 618 Class F) fly ash, is chemically activated by a high-alkaline solution to form a paste that binds the loose coarse and fine aggregates, and other unreacted materials in the mixture. The test results presented in this paper show the effects of various parameters on the properties of geopolymer concrete. The application of geopolymer concrete and future research needs are also identified.
797 citations
TL;DR: An inexpensive and effective adsorbent was developed from bagasse fly ash, obtained from a sugar industry, for the dynamic uptake of lead and chromium, and found to be exothermic in nature.
675 citations
TL;DR: In this article, the properties of high-volume fly ash high-strength concrete incorporating nano-SiO2 (SHFAC) were compared with those of control Portland cement concrete (PCC) and of high volume fly-ash high strength concrete (HFAC) based on short and long-term performance.
606 citations
TL;DR: In this paper, the results of an experimental investigation dealing with concrete incorporating high volumes of Class F fly ash Portland cement was replaced with three percentages (40, 45, and 50%) of Class-F fly ash Tests were performed for fresh concrete properties: slump, air content, unit weight, and temperature Compressive, splitting tensile, and flexural strengths, modulus of elasticity, and abrasion resistance were determined up to 365 days of testing.
478 citations
TL;DR: In this article, the influence of fineness of fly ash on water demand and some of the properties of hardened mortar are examined and it is suggested that the fine fly ash is more reactive and its use resulted in a denser cement matrix and better mechanical properties of mortar.
393 citations
TL;DR: The conclusions were that whilst Fe-oxides may be used as effective in situ amendments to attenuate As in soils, their effects on other trace elements, such as Pb and Cd, require careful consideration.
380 citations
TL;DR: In this paper, the effect of fly ash content on the free swell index, swell potential, swelling pressure, plasticity, compaction, strength, and hydraulic conductivity characteristics of expansive soil was evaluated.
Abstract: This note presents a study of the efficacy of fly ash as an additive in improving the engineering characteristics of expansive soils. An experimental program has evaluated the effect of the fly ash content on the free swell index, swell potential, swelling pressure, plasticity, compaction, strength, and hydraulic conductivity characteristics of expansive soil. The plasticity, hydraulic conductivity and swelling properties of the blends decreased and the dry unit weight and strength increased with an increase in fly ash content. The resistance to penetration of the blends increased significantly with an increase in fly ash content for a given water content. Excellent correlation was obtained between the measured and predicted undrained shear strengths.
348 citations
15 Jun 2004
TL;DR: FTIR study shows that a chemisorption process occurs between CR and fly ash, probably indicating dye/fly ash complexing, and obeyed the pseudo-second-order kinetic model.
Abstract: The adsorption of Congo red from solution was carried out using calcium-rich fly ash with different contact times, concentrations, temperatures, and pHs. While the amount of dye adsorbed per unit weight of fly ash increases with increasing concentration and temperature, it decreases slightly with increasing pH. The adsorption was between 93 and 98% under the conditions studied. Kinetic studies showed that the adsorption process obeyed the pseudo-second-order kinetic model. It was also determined that the adsorption isotherm followed Freundlich and Dubinin–Radushkevich models. From thermodynamic studies, it was seen that the adsorption was spontaneous and endothermic. Desorption studies suggested that desorption was 29.18% in the presence of 0.1 N HCl and was 47.21% in the presence of CH 3 COOH (50% v/v). This indicated that most of the dye was held by fly ash via chemisorption as well as ion exchange. Furthermore, FTIR study also shows that a chemisorption process occurs between CR and fly ash, probably indicating dye/fly ash complexing.
325 citations
01 Jan 2004
TL;DR: In this paper, the authors present a brief review of the theory and construction practice with concrete mixtures that contain more than 50% fly ash by mass of the cementitious material, and the mechanisms by which the incorporation of high volume of the ash in concrete reduces the water demand, improves the workability, minimizes cracking due to thermal and drying shrinkage, and enhances durability to reinforcement corrosion, sulfate attack, and alkalile-silica expansion.
Abstract: This paper presents a brief review of the theory and construction practice with concrete mixtures that contain more than 50% fly ash by mass of the cementitious material. The mechanisms by which the incorporation of high volume of the ash in concrete reduces the water demand, improves the workability, minimizes cracking due to thermal and drying shrinkage, and enhances durability to reinforcement corrosion, sulfate attack, and alkalile-silica expansion are discussed. This technology can play a huge role in meeting the large demand for infrastructure in a sustainable manner for countries like China and India.
325 citations
TL;DR: In this paper, coal fly ash was used to synthesize X-type zeolite by alkali fusion followed by hydrothermal treatment and the maximum surface area of the product was found to be 383 m2/g with high purity.
Abstract: Coal fly ash was used to synthesize X-type zeolite by alkali fusion followed by hydrothermal treatment. The synthesized zeolite was characterized using various techniques such as X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, BET method for surface area measurement etc. The synthesis conditions were optimized to obtain highly crystalline zeolite with maximum BET surface area. The maximum surface area of the product was found to be 383 m2/g with high purity. The crystallinity of the prepared zeolite was found to change with fusion temperature and a maximum value was obtained at 823 K. The cost of synthesized zeolite was estimated to be almost one-fifth of that of commercial 13X zeolite available in the market.
293 citations
TL;DR: In this paper, the effect of replacing part of portland cement with fly ash and bottom ash, both from municipal solid waste incinerators (MSWIs), was investigated. And the results showed that MSWI bottom ash is potentially attractive as mineral addition for the production of concrete, provided that the risk of entrapment of hydrogen bubbles produced by corrosion of aluminium metallic particles in the fresh concrete is prevented.
TL;DR: In this paper, two methods have been evaluated for the synthesis of zeolites using a UK fly ash as raw material, one consisting of a conventional hydrothermal technique in which fly ash is mixed with NaOH solution, and the other comprises a combination of alkaline fusion of fly ash with Naoh prior to a Hydrothermal treatment, where the fusion product was mixed with water.
TL;DR: In this article, a factorial design was carried out to mathematically model the influence of five key parameters on filling and passing abilities, segregation and compressive strength, which are important for the successful development of medium strength self-compacting concrete incorporating PFA.
TL;DR: In this article, three different types of soil have been considered using different percentage of fly ash ranging from 9 to 46% by weight of soil and the main objectives of the present investigation is to assess the usefulness of fly-ash as a soil admixture, and focused to improve the engineering properties of soil to make it capable of taking more load from the foundation structures.
TL;DR: In this article, the effect of different supplementary cementitious materials (silica fume, fly ash, slag, and their combinations) on strength and durability of concrete cured for a short period of time was studied.
TL;DR: In this article, the influence of coal properties on fly ash properties in this isolated case was discussed. But coal properties are not representative of the reality of coal purchasing and coal combustion in the eastern US, attempts to follow a single coal through the process can be instructive for the purposes of understanding the origin and fate of trace elements in combustion.
TL;DR: In this paper, improved palm oil fuel ash (POFA) was used as a pozzolanic material in producing high-strength concrete and the POFA was ground by ball mill until the median particle size was reduced to about 10μm.
Abstract: This paper presents use of improved palm oil fuel ash (POFA) as a pozzolanic material in producing high-strength concrete. The POFA was ground by ball mill until the median particle size was reduced to about 10μm. It was used to replace portland cement, ASTM Type I, by 10, 20, and 30% by weight of cementitious materials to make high-strength concrete. It was found that high-strength concrete can be achieved by using ground POFA to replace portland cement Type I up to 30%. At the age of 28days, concretes containing 10, 20, and 30% of ground POFA gave compressive strengths of 81.3, 85.9, and 79.8MPa, respectively. Concrete with 20% replacement of ground POFA had the highest strength. It is slightly higher than that of concrete containing 5% condensed silica fume and about 92–94% that of 10% condensed silica fume concrete. The ground POFA content up to 30% had slightly effect on lowering the modulus of elasticity of concrete. In addition, the use of ground POFA reduced the peak temperature rise of concrete u...
Journal Article•
TL;DR: In this paper, the fundamentals of high-performance high-volume fly ash (HVFA) concrete, gives its properties and durability characteristics, and makes a case for applicability use in the construction of highways in developing countries such as China and India.
Abstract: This article outlines the fundamentals of high-performance high-volume fly ash (HVFA) concrete, gives its properties and durability characteristics, and makes a case for applicability use in the construction of highways in developing countries such as China and India. Sections on use of HVFA blended cement, curing of HVFA concrete, and rigid vs. flexible pavements are also included.
TL;DR: In this paper, the effects of zeolite, coal bottom ash and fly ash as Portland cement replacement materials on the properties of cement are investigated through three different combinations of tests, and physical properties such as setting time, volume expansion, compressive strength and water consistency of the mortar are determined.
TL;DR: In this paper, fly ash treatment can effectively reduce the swell potential of highly plastic clays and prevent the swell beneath the smaller foundation pressures. Fly ash is used in the combustion of subbituminous coals and exhibits self-cementing characteristics.
TL;DR: Shredded bulky waste in input waste increased the concentration of some metals, such as Cd and Pb, and the effect was confirmed by analysis of shredded bulky waste.
TL;DR: In this article, the initial fly ash carbon sorbents were generated by the chemical treatment of carbon-enriched fly ash concentrates with a 3-chloropropylamine-hydrochloride (CPAHCL) solution at 25 C.
TL;DR: In this article, the authors investigated co-combustion of sewage sludge together with coal or wood in two circulating fluidized bed (CFB) plants, a laboratory scale plant and a pilot scale 12MWth CFB boiler, in both of which the gas residence times are comparable to those in commercial plant.
TL;DR: Ash amendment significantly reduced the availability of heavy metals by chemical modification of their chemical speciation into less available forms by increasing fly ash amendment rate and decreasing DTPA-extractable Cu, Zn, Ni and Cd concentrations.
TL;DR: In this paper, the compressive strength of fly ash-based geopolymer concrete has been analyzed and the effects of several factors on the properties, such as the age of concrete, curing time, curing temperature, quantity of superplasticizer, rest period prior to curing, and the water content of the mix.
Abstract: This paper describes the effects of several factors on the properties of fly ash based geopolymer concrete, especially the compressive strength. The test variables included were the age of concrete, curing time, curing temperature, quantity of superplasticizer, the rest period prior to curing, and the water content of the mix.
The test results show that the compressive strength of geopolymer concrete does not vary with age, and curing the concrete specimens at higher temperature and longer curing period will result in higher compressive strength. Furthermore, the commercially available Naphthalene-based superplasticizer improves the workability of fresh geopolymer concrete. The start of curing of geopolymer concrete at elevated temperatures can be delayed at least up to 60 minutes without significant effect on the compressive strength. The test data also show that the water content in the concrete mix plays an important role.
TL;DR: In this article, a scanning electron microscope (SEM) point-counting technique was employed to study the hydration of plain portland and blended cement pastes containing fly ash or slag.
TL;DR: The results of batch equilibrium studies showed that the solution pH was the key factor affecting the adsorption characteristics of Zn(II) onto fly ash, a waste produced from a coal-burning power plant as mentioned in this paper.
TL;DR: In this article, a set of nine coal fly ashes, obtained from various US utilities, were fractionated by standard dry-sieving techniques, and the carbon contents of the different size fractions were measured and the nature of the carbon particles was examined.
Journal Article•
TL;DR: In this article, the authors present a review of fly ash characterization with reference to geotechnical applications and show that fly ash is a freely draining material with angle of internal friction of more than 30 degrees.
Abstract: Thermal power stations use pulverized coal as fuel. They produce enormous quantities of coal ash as a by-product of combustion. This calls for the development of strategies to encourage and establish technological concepts which will ensure consumption of fly ash in bulk. Among the various uses of fly ash, its bulk utilization is possible only in geotechnical engineering applications. This necessitates characterization of the fly ash with reference to geotechnical applications. This paper presents a review of such studies carried out. The results show that fly ash is a freely draining material with angle of internal friction of more than 30 degrees. The specific gravity is lower leading to lower unit weights resulting in lower earth pressures. It can be summarized that fly ash (with some modifications/additives, if required) can be effectively utilized in geotechnical applications.
TL;DR: In this paper, a byproduct fly ash from oil shale processing was converted into zeolite by alkali hydrothermal activation using sodium hydroxide, which was used as an ion exchanger for the treatment of wastewater for metal ions.