>Magister Scientiae - MSc / Coal is the main source of electricity in South Africa, the combustion of which produces a large amount of waste (coal fly ash) annually. The large-scale generation of coal fly ash places major strain on landfills and the material is toxic in nature. The high silicon and aluminium content in fly ash makes it a suitable starting material for zeolite synthesis. Utilisation of fly ash as a starting material for zeolite synthesis alleviates an environmental burden by converting a waste product to an industrially applicable material. In this study, hierarchical zeolite X was synthesised from coal fly ash via the fusion method. The clear fused fly ash (FFA) extract (with molar composition 0.12 Al·14.6 Na·1.00 Si·163 H₂O) served as the synthesis solution for hydrothermal treatment. The influence of synthesis parameters (such as Si/Al ratio, aluminium source, hydrothermal temperature and stirring) on hierarchical zeolite X formation was studied to determine the cause behind the formation of this material. Synthesised zeolites and starting materials (Arnot coal fly ash and fused fly ash) were characterised by various analytical techniques such as XRD and SEM-EDS to determine the phase purity, morphology and elemental composition (framework Si/Al ratio) of these materials. The synthesis of hierarchical zeolite X under hydrothermal conditions was found to be highly sensitive to the aluminium content of the synthesis solution. The hierarchical morphology of zeolite X was formed preferentially in relatively aluminium-deficient (i.e. high Si/Al ratio) synthesis environments under stirred hydrothermal conditions of 90 °C for 16 hours. In the case of sodium aluminate addition, octahedral shaped zeolite X crystals were formed in relatively low Si/Al ratio synthesis environments, which was attributed to the presence of excess sodium cation content in the synthesis solution. Selected hierarchical zeolites (D2 and E2) were characterised further to gain more insight into the properties of this material. HR-TEM and FTIR revealed that hierarchical zeolite D2 and E2 exhibited the typical structural features of zeolite X. Zeolite D2 and E2 contained both micropores and mesopores and had a high BET surface area of 338-362 m²/g. These zeolites also exhibited appreciable solid acidity (0.81-1.12 mmol H/g zeolite). These properties make hierarchical zeolite X a favourable material for application in catalysis or adsorption. Overall, the formation of zeolite X with hierarchical morphology was proposed to be linked to the presence of zeolite P1 structural units in the framework of the zeolite. / National Research Foundation

Pozzolanic reactions play a key role in improving the compressive strengths of compacted fly ash-lime specimens. Based on studies performed with cement amended fly ash (FA), activation of fly ash-lime pozzolanic reactions should accelerate the rate of strength development and mobilize larger compressive strengths facilitating improved engineering performance of fly ash amended materials. Further, use of phosphogypsum (PG) is a cause of environmental concern as the material is acidic (pH < 3.0) and contains considerable amounts of fluoride (0.86%). The main research objectives of the thesis are to activate lime-fly ash reactions by thermal and chemical activation process and examine the efficacy of fly ash pozzolanic reactions in controlling fluoride release by phosphogypsum. A comprehensive laboratory experimental program was performed to examine the influence of curing temperature (thermal activation) and calcined PG addition (chemical activation) on lime-fly ash reactions. The kinetics of fly ash-lime reactions are examined by monitoring the reacted lime content as function of curing period and temperature. The influence of variations in fly ash/lime content and dry density on the compressive strength developed by specimens is evaluated. The thermodynamic parameters for the fly ash-lime (FA-L) reactions have been delineated. Fly ash-lime-phosphogypsum (FA-L-G) mixes in slurry and compacted states were monitored for fluoride released as function of curing period The influence of curing temperature in activating fly ash-lime reactions is first examined. Specimens were cured at 25°C (termed RTC or room temperature cured) and at 80° (termed SC or steam cured) to understand thermal activation of fly ash-lime reactions. The rate of lime consumption by SC specimens classified as 2 stage process. The robust increase during stage 2 of steam curing suggested that the lime-solidification reactions did not reach equilibrium even after 4 days of curing at the elevated temperature. While only 3.1 to 3.3 % of added lime was consumed after 28 days of curing at room temperature, much larger amounts of lime ( 8.6-9.3%) were consumed after 4 days of steam-curing. Further, the lime-fly ash reactions were accelerated by 6 to 7 folds on curing the specimens at elevated temperature. The results indicated that activation of lime-fly ash reactions by curing at elevated temperature besides accelerating the rate of strength development also facilitated development of larger strength. Analysis of the free energy change values (ΔG°) indicated that the lime solidification reaction alters from dis-favored (less spontaneous) to favoured (spontaneous) state on curing at 80oC. The positive ΔH° (enthalpy change) values for the fly ash-lime reactions indicated that the reactions are endothermic in nature and are facilitated by increase in curing temperature. Gypsum activation was achieved by addition of 2.5 to 5% calcined phosphogypsum to fly ash lime mixes and curing the compacted specimens at room temperature (FA-L-G specimens). The rate of lime consumption by FA-L-G specimens appeared to be three stage process. The mass of lime consumed by FA-L-G specimens was about 1.5 to 3 folds higher than values of the RTC and SC specimens. Additional lime is consumed by FA-L-G specimens in ettringite formation. A similarity existed between rate of lime consumed and rate of strength developed by the FA-L-G specimens. It is proposed that besides lime solidification reactions, densification of the matrix by filling up of voids by fine gypsum particles and compaction of matrix by the growth of ettringite crystals also contribute to compressive strength of FA-L-G specimens; this additional mechanism of strength development accounts for their higher compressive strength in comparison to the SC and RTC specimens despite similar initial lime addition values. The trend of results suggests that activation of FA-L reactions by calcined PG addition is more effective than steam curing. Comparison of ΔG° values of RTC, SC and FA-L-G specimens revealed that the spontaneity of the lime solidification reactions is least for RTC specimens and improves with addition of phosphogypsum and further improves on curing at elevated temperature. Fly ash-lime pozzolanic reactions substantially reduced the fluoride released from the FA-L-G specimens. The marked reduction in fluoride released by PG amended with fly ash and lime is ascribed to entrapment of PG particles in the cemented matrix formed by fly ash-lime pozzolanic reactions together with consumption of fluoride in formation of insoluble fluoride bearing compounds. The thesis brings out that activation of fly ash-lime reactions leading to quicker and larger compressive strength development is achieved by curing the compacted fly ash-lime specimens at 80°C for 24 hr or by addition of 2.5 to 5% of calcined PG to fly ash-lime mix and curing the compacted specimens at room-temperature. As larger strengths are developed by PG addition than by curing at 80oC, it is recommended that FA-L-G technique be adopted for manufacture of building materials in the civil engineering industry. This technique is also sustainable as it does not require energy for heating which is needed in the steam-curing technique.

No description available.

Research estimated toxicity of refuse-derived fuel fly ash (RDF-FA) on two earthworms species, Lumbricus terrestris and Eisenia foetida. Specific objectives were to: (1) Compare their 14-day LC50s under light and dark conditions; (2) separate toxicity due to osmotic, pH and physical factors from that of heavy metal contaminants; (3) compare relative differences of artificial soil and commercial soil as exposure media for evaluating toxicity to earthworms. The 14-d LC50s for L. terrestris in dark and light were 57.0 and 48.34 % RDF-FA, and 59.25 and 41.00 % RDF-FA for E. foetida using artificial soil. All of the toxicity resulted from heavy metals within the RDF-FA. Using L. terrestris, the LC50s for artificial soil and commercial soil were 52.30 and 64.34%.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Master of Science / Department of Civil Engineering / Kyle Riding / Fly ash is a by-product of coal-fired power plants. This material can be used as a partial cement substitute in portland cement concrete. Use of fly ash can improve concrete durability as well as utilize an industrial by-product that would otherwise be discarded in landfills. However, research on fly ash concrete has shown that in some cases, concrete with high volumes of fly ash can have deicer salt scaling problems. Salt-scaling is the flaking of a concrete surface that when severe enough may result in lower skid resistance and service life of the concrete. In this study, concrete mixtures with six different fly ashes were tested in a laboratory using the ASTM C 672 standard. Curing compound, a wax-based coating sprayed on the fresh concrete surface to reduce evaporation, was used to compare the effects of curing on salt scaling of concrete containing high volumes of fly ash. Different variables measured were the type of fly ash, curing conditions, and total paste volume included in the mix. Results showed that curing compounds will improve the salt-scaling resistance of concrete containing a fly ash that only marginally exhibits salt scaling. However, the salt-scaling performance of concrete that contains fly ash from a source that performs poorly in ASTM C 672 is not markedly improved by using a curing compound. Additionally, results showed that salt-scaling resistance of concrete containing fly ash performs better when the total paste volume is not increased by the addition of fly ash to the mixture. The Kansas Outdoor Concrete Exposure Site (KOCE) at the Kansas State University Civil Infrastructure Systems Laboratory (CISL) was constructed to compare laboratory results to actual field conditions in the future. The site was developed based on experiences from the University of Texas-Austin outdoor exposure site and the CANMET exposure site in Ottawa, Canada. Alika silica reaction blocks were made to develop the procedure for future concrete durability testing at KOCE.

This work includes two different areas of research. Both areas are related to the combustion of the binder-enhanced densified refuse derived fuel (bdRDF) with high sulfur coal and examining trace elements. The first area of this work involved studying the trace metals in the combustion gas of bdRDF/coal blend and the effect of the binder, CA(OH)2, on reducing the trace elements emissions. The second area of work involved studying the trace elements in the fly ash and the effect of the dRDF and the binder of trace metals.

Master of Science / Department of Civil Engineering / Kyle Riding / The relationship between in-place concrete strength and permeability with concrete cylinder strength and permeability with time is of interest - especially when supplementary cementitious materials (SCMs) are used. A joint research project between The University of Kansas was undergone to quantify these relationships. The permeability of concrete is directly tied to its ability to mitigate certain failure mechanisms such as corrosion and sulfate attack. The three concrete mixtures being tested by Kansas State University (KSU) vary in cementitious content as follows: (1) 100% ordinary portland cement (OPC), (2) 25% Class F fly ash (F-ash) and 75% OPC, (3) 25% Class C fly ash (C-Ash) and 75% OPC. The mixtures were also placed in three different seasons to present differing curing environmental effects. The summer slabs were cast during July and August. The fall slabs were cast in October and November. The final set of slabs were cast in March and April. Three sets of concrete specimens (lab cured, field cured and in-situ core specimens) were tested at 28, 56, 90, 180, and 360 days for strength and permeability properties. The permeability performance tests being utilized are ASTM C1202 and ASTM C642. The results have shown very desirable permeability and strength data for the mixes using blended fly ash cements. The F-ash exhibited the best high early strength and low permeability data for the summer placement season and slower strength and permeability performance at cold weather. The C-ash performed the best overall for all seasons and had the least environmental effects. The OPC performed the worst in regards to permeability and did not reach as high long term strength.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering (Metallurgy and Materials Engineering), May 2016 / The solvent extraction of iron and titanium from solution generated by the two-step sulphuric acid leaching of coal fly ash by Primene JMT was investigated. The influence of hydrogen ion concentration, Primene JMT concentration, aqueous to organic volume phase ratio and temperature on the extraction of iron and titanium was determined by the use of Design of Experiments. Hydrogen ion concentration and the interaction between the aqueous to organic volume phase ratio with Primene JMT concentration had a significant effect on the extraction of iron while temperature did not. Hydrogen ion concentration and temperature did not have a significant effect on the extraction of titanium, while the interaction between Primene JMT concentration and aqueous to organic volume phase ratio had a significant effect. Extraction improvement tests showed that at a hydrogen ion concentration of 0.28M, 88% iron and 99% extraction of titanium from coal-fly ash leach solution could be achieved. Construction of a McCabe-Thiele diagram showed that a four-stage solvent extraction system with Primene JMT could reduce the iron and titanium concentration in the coal fly ash leach solutions to below 0.05g/L / GS2016

Geopolymer concrete (GC) is a sustainable construction material and a great alternative to regular concrete. GC is a zero-cement material made from a combination of aluminate, silicate and an activator to produce a binder-like substance. This investigation focused on the effects of wet and dry cycles on the strength and durability of fly ash-based recycled aggregate geopolymer concrete (RAGC). The wet-dry cycles were performed approximately according to ASTM D559 standards. RAGC specimens with nearly 70% recycled materials (recycled aggregate and fly ash) achieved a compressive strength of approximately 3600 psi, after 7 days of heat curing at 60ºC. Although the recycled aggregate is prone to high water absorption, the compressive strength decreased by only 4% after exposure to 21 wet-dry cycles, compared to control specimens that were not exposed to the same conditions. Accordingly, the RAGC material developed in this study can be considered as a promising environmentally friendly alternative to cement-based regular concrete. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection