Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (leaves 62-63).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

Coal powered power plants account for more than 40 percent of the electricity production of the United States. The combustion of coal results in a large number of solid waste materials, or coal combustion byproducts (CCBs). These waste materials are stored in landfill or ponds. The construction industry is heavily reliant on concrete which is used to make the building blocks for any type of structures, bricks. Concrete is a composite material made of a binder and coarse and fine aggregate. The most widely used binder in concrete production is Ordinary Portland Cement (OPC). Since cement manufacture is costly and environmentally damaging, research has increased in recent years to find a more readily available binder. This study aims at investigating the properties of Illinois fly ash as a binder in the production of geopolymer concrete. Geopolymer concrete is an innovative material made by using Alumina and Silica rich materials of geological origins as a binder as well as an alkali activated solution. Sodium Silicate and Sodium Hydroxide were used to make the activator solution of two different ratios. Geopolymer Concrete with a ratio of 1:1 of Sodium Silicate to Sodium Hydroxide reached a compressive strength above 6000 psi while samples made with a ratio of 1:2 reached a compressive strength above 4000 psi. This environmentally-friendly, green concrete was also found to have a cost comparable to conventional concrete.

Since a substantial amount of coal combustion byproducts (CCB) are produced each year, generating value-added product from fly ash, which is a major constituent of these CCBs, has been an important area of research for several decades. Natural magnetite (NM), which is used to maintain dense medium slurry pulp density in coal preparation plants, has a current market value of more than $200 per ton. The use of fly ash derived magnetite (FAM) as an alternative to natural magnetite has potential benefits for dense medium processes, such as lower cost, greater stability at low medium density, more efficient delivery systems. This study developed a suitable processing scheme to extract high-grade (> 96%) magnetite from fly ash generated from burning high sulfur coal, and investigated the suitability of the FAM product for dense medium application in coal preparation plants. A classifying cyclone was utilized in the process flow sheet for the pre-concentration of FAM in its underflow stream, which was enriched to high grade FAM by a single stage wet magnetic separator of low intensity (~1000 gauss). A statistically designed experimental program was utilized to maximize the magnetite grade and recovery achieved from the above mentioned flow sheet. The FAM product particles had a slightly coarser particle size distribution than the NM particles. In addition, the FAM particles were found to have a spherical shape; but about one unit lower specific gravity in comparison to the NM particles. However, the F5 Stability Index of the resulting FAM product was found to be in the desired range of 30 to 40 for its suitable application as a dense medium. The coal cleaning performance obtained from a 0.15 m diameter dense medium cyclone using dense medium prepared from both of FAM and NM, were quite similar. However, the effective separation density (SG50) obtained from the FAM-based dense medium was significantly different from the medium density; this may need further investigation in future. A preliminary economic analysis, conducted for a hypothetical mini-plant having a fly ash handling capacity of 100 ton/hour, indicated the cost of FAM extraction to be nearly $5/ton. The cost assumes that the FAM extraction plant is located at the fly ash producing utility site and does not include the cost of thermal drying that may be required to reduce the moisture content of the FAM filter cake produced at the FAM plant. A preliminary civil engineering study conducted to investigate the effect of FAM extraction on the compressive strength property of the non-magnetic flyash (left behind after FAM extraction) failed to produce a conclusive finding. The specimens prepared using 10% and 30% fly ash replacements indicated that the compressive strength does not change due to FAM extraction. However, the specimens using 20% fly ash replacement indicated that compressive strength does change due to FAM extraction. Hence, a more detailed study is recommended to investigate this discrepancy.

Fly ash is a waste product from thermal power plants where pulverised coal is used for the generation of electricity. Fly ash is being utilised in the blended cements, additive for concrete and manufacturing of concrete blocks and bricks. Fly ash-lime-gypsum bricks are being manufactured and marketed throughout the country. The literature review on fly ash-lime-gypsum (FALG) mixtures as intended to manufacture bricks or blocks for masonry applications indicates several gaps in understanding the various aspects of the technology. The present thesis is an attempt to understand the behaviour of compacted stabilised fly ash mixtures for the manufacture of fly ash bricks and characteristics of masonry using such bricks. A brief introduction to the technology of compacted stabilised fly ash bricks for structural masonry is provided. Review of the literature on fly ash-lime and fly ash-lime-gypsum mixtures, and fly ash bricks is provided in chapter 1. Chapter 2 gives details of the experimental programme, properties of raw materials used in the experimental investigations, methods of preparing different types of specimens and their testing procedures. Chapter 3 deals with the strength and absorption characteristics of compacted stabilised fly ash mixtures in greater detail. The main focus of the investigations is on arriving at the optimum stabilizer-fly ash mixtures considering density, stabilizer-fly ash ratio, curing conditions, etc. as the variables. Therefore the parameters/variables considered in the investigation include: (a) density of the compacted fly ash mixture, (b) stabilizer-fly ash ratio, (c) curing duration (normal curing and steam curing) and (d) dosage of additives like gypsum. Some of the major conclusions of the investigations are (a) compressive strength of compacted stabilised fly ash mixtures is sensitive to dry density of the specimens and the strength increases with increase in density irrespective of stabiliser content and type of curing, (b) Optimum limefly ash ratio yielding maximum strength is 0.75, (c) addition of gypsum accelerates rate of strength gain for compacted fly ash-lime mixtures (d) for 28 days wet burlap curing optimum gypsum content yielding maximum strength is 2% and maximum compressive strength is achieved for lime contents in the range of 10 – 17%, (e) steam curing (at 80 °C for 24 hours) gives highest compressive strength for compacted fly ash-lime mixtures. Characteristics of compacted fly ash-lime, fly ash-lime-gypsum and fly ash-cement bricks and their masonry are presented in chapter 4. Compressive strength, elastic modulus, water absorption, initial rate of absorption, dimensional stability and durability of the bricks were examined. Compressive strength, flexure bond strength and stress strain relationship for the fly ash brick masonry using cement-lime mortar were evaluated. The investigations clearly show the possibility of producing bricks of good quality using compacted fly ash-lime gypsum mixtures. Wet compressive strengths of 8- 10 MPa was obtained for compacted fly ash-lime-gypsum bricks at the age of 28 days. Wet strength to dry strength ratio for these bricks is in the range of 0.55 – 0.67. Initial tangent modulus for the fly ash-lime-gypsum bricks in saturated condition is in the range of 8000 – 12000 MPa. There is a large scope for selecting optimum mix ratios of fly ash, sand, lime and other additives to obtain a specific designed strength for the brick. The thesis ends with Chapter 5 highlighting major conclusions of the investigations.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016. / This study has explored the CVD synthesis of carbon nanofibres (CNFs) using Eskom’s waste coal fly ash as a catalyst with acetylene and hydrogen as the carbon source and carrier gas, respectively. In the process, a possible growth mechanism for these carbon nanofibres was sought. CNFs were successfully synthesised from fly ash and were found to have an average diameter of 22±7 nm. The growth mechanism of these CNFs was studied using EDS, TEM and laser Raman spectroscopy. It was observed that CNFs grew via root growth on spherical particles of fly ash and by tip growth on irregular-shaped metal oxide agglomerates. Both of these were found, through EDS analysis, to be Fe-rich. CNFs were functionalised between 2-12 h under reflux at 110 °C using a 3:1 (v/v) combination of HNO3 and H2SO4 in order to introduce functional groups onto their surfaces to act as anchors for hydrophilic reactants. The functionalisation of these CNFs was studied using TEM, laser Raman spectroscopy, ATR-FTIR spectroscopy, PXRD, BET, XRF and TGA. ATR-FTIR spectroscopy showed that some carbonyl functional groups were present on the surfaces of these CNFs after functionalisation. The functionalised CNFs (fCNFs) were then treated using a simple hydrothermal method to deposit 10% (m/m) of TiO2 nanoparticles onto their surface. This hydrothermal method employed the drop-wise addition of TiCl4 to a cold water-fCNFs mixture, which was then refluxed at 115 °C for 2-12 h. Laser Raman spectroscopy confirmed the presence of both TiO2 (phase pure anatase) and CNFs. ATR-FTIR spectroscopy provisionally revealed the presence of covalent Ti-O-C bonds. Studies where the duration of exposure to TiCl4 and the functionalisation time of CNFs were examined showed that the particle size and agglomeration of the TiO2 nanoparticles did not affect the surface area of the CNF-TiO2 hybrids significantly. However, CNF-TiO2 hybrids which were shown by TGA to have high fly ash content were observed to have low surface areas. fCNFs functionalised at 2 h had the highest surface area, at all fixed durations of exposure to TiCl4 by comparison with fCNFs which had been functionalised for longer periods. / GR2016

Thesis. 1976. Sc.D.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 321-328. / by Ashok S. Padia. / Sc.D.

On-going research at Texas A&M University indicated that soil stabilization using calcium chloride filter cake along with Class F fly ash generates high strength. Previous studies were conducted with samples containing calcium chloride filter cake and both Class C fly ash and Class F fly ash. Mix design was fixed at 1.3% and 1.7% calcium chloride and 5% and 10% fly ash with crushed limestone base material. Throughout previous studies, recommended mix design was 1.7% calcium chloride filter cake with 10% Class F fly ash in crushed limestone base because Class F fly ash generates early high and durable strength. This research paper focused on the strength increase initiated by greater than 1.7% pure calcium chloride used with Class F fly ash in soil to verify the effectiveness and optimum ratio of calcium chloride and Class F fly ash in soil stabilization. Mix design was programmed at pure calcium chloride concentrations at 0% to 6% and Class F fly ash at 10 to 15%. Laboratory tests showed samples containing any calcium chloride concentration from 2% to 6% and Class F fly ash content from 10% to 15% obtained high early strength however, optimum moisture content, different mix design, and mineralogy deposit analysis are recommended to evaluate the role and the effectiveness of calcium chloride in soil stabilization because of the strength decreasing tendency of the samples containing calcium chloride after 56 days.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 152 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 87-91).

Pulverized samples of Utah bituminous, Beulah (North Dakota) low Na lignite, Beulah high Na lignite and Texas (San Miguel) lignite coals were burned at a rate of 2.5 kg/hr in a laboratory furnace under various (overall fuel lean) combustion conditions. Particle size distributions (PSD) and size segregated particle filter samples were taken at various positions within the convection section. Temperature and gas concentrations were measured throughout. The evolution of the submicron PSD within the convection section for the four coals was similar, although the location of the initial particle mode at the convection section inlet varied with coal type. While staged (.8/1.2) combustion of the Utah bituminous coal had a variable effect on the volume of submicron aerosol produced, staged combustion of two of the three lignites (Beulah low Na and Texas) caused a definite increase in the submicron aerosol volume. Vapor enhancement due to a localized reducing atmosphere, which would effect coals of higher ash volatility or higher inherent ash content, is thought to explain this behavior. Depressed combustion temperatures associated with the high moisture content of the Beulah high Na lignite are thought to offset the effects of staging. Increased combustion temperatures (through oxygen enrichment) caused staged volume increases for the Beulah high Na lignite. Combustion temperatures are a controlling factor even at more extreme staging conditions. Chemical analysis of the size segregated particle samples show the trace elements, As, Pb, Zn and the major elements, Na and K to be enriched in the submicron aerosol. Auger depth profiles show these small particles to be comprised of a core enriched in Fe, Si, Ca and Mg and surface layers enriched in Na and K. These results point to a mechanism of homogeneous nucleation of low vapor pressure species followed by successive layering of progressively more volatile species. Volatile species are enriched in the submicron aerosol due to the large surface areas provided. Modeling efforts show that while coagulation may be the dominant mechanism to describe the aerosol evolving within the convection section, it cannot be used solely to predict the PSD. Another mechanism, presumably surface area dependent growth (condensation) must be included.