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

Call number: LD2668 .T4 1965 V145 / Master of Science

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.

Thesis (MScAgric (Conservation Ecology and Entomology))--Stellenbosch University, 2011 / ENGLISH ABSTRACT: Climate change will alter both temperature and moisture availability in the future and therefore will likely affect vector borne disease prevalence. Organisms faced with changes in weather can respond in a variety of ways and this complicates any predictions and inferences for these organisms with climate change. Cause-and-effect links between climate change, insect vector responses, and changes in risk of disease transmission are poorly established for most vector borne diseases. Tsetse (Diptera, Glossinidae) are important vectors of trypanosome parasites posing a major threat to human health and socio-economic welfare in Africa. Water balance plays an important role in determining activity patterns, energy budgets, survival and population dynamics and, hence, geographic distribution and abundance of insects. Glossina species occupy a wide range of habitats in Africa and are notable for their desiccation resistance in xeric environments. Yet, whether or not the different species, subgroups or ecotype groups differ in susceptibility to changes in weather remain undetermined. The first main focus of my thesis was to test the effects of climate change on water balance traits (water loss rate, body water content and body lipid content) of adult tsetse flies. Four species from xeric and mesic habitats were exposed to a range of temperature (20 – 30 °C) and relative humidity (0 – 99 %) combinations. Water loss rates were significantly affected by measurement treatments, while body water content, body lipid content and mass were less affected and less variable across treatment combinations. The results provide support for mass-independent inter- and intra-specific variation in water loss rate and survival times. Therefore, water balance responses to variation in temperature and relative humidity are complex in Glossina, and this response varies within and among species, sub-groups and ecotypes in terms of magnitude and the direction of effect change. Secondly, I apply a mechanistic distribution model for G. pallidipes to predict potential population responses to climate change. I validate the mechanistic model (NicheMapperTM) results spatially and temporally using two methods. Both tests of the model showed that NicheMapper‟s predicted resting metabolic rate has great potential to capture various aspects of population dynamics and biogeography in G. pallidipes. Furthermore, I simulate the effect of phenotypic plasticity under different climate change scenarios and solve for the basic reproductive number of the trypanosomiasis disease (R0) under a future climate scenario. This integrated thesis provides strong evidence for a general decrease in optimal habitat for G. pallidipes under future climate change scenarios. However, it also provides strong support for a 1.85 fold increase in R0 based on changes in biting frequency as a result of higher predicted metabolic rates in the future. This might suggest that the reduction in optimal habitat could be outweighed by the increase in R0. The results demonstrate that an understanding of the physiological mechanism(s) influencing vectors of disease with climate change can provide insight into forecasting variation in vector abundance and disease risk. / AFRIKAANSE OPSOMMING: Die invloed van klimaatsverandering op die temperatuur en vog beskikbaarheid mag moontlik insek-oordraagbare siektes in the toekoms beïnvloed. Organismes wat verandering in klimaat ervaar kan op verskillende maniere reageer en daarom is voorspelling en afleidings van die reaksies op klimaatsverandering nie eenvoudig nie. Boonop is die verband tussen klimaatsverandering, insek reaksies en veranderinge in die oordragsrisiko van siektes onbekend vir die meeste insekoordraagbare siektes. Tsetse (Diptera: Glossinidae) is belangrike draers van trypanosoom parasiete wat 'n bedreiging inhou vir mensegesondheid en sosio-ekonomiese welsyn in Afrika. Waterbalans speel 'n belangrike rol in die energiebondel samestelling, aktiwiteitspatrone, oorlewing en populasie dinamika van insekte en, dus, die geografiese voorkoms en verspreiding van insekte. Glossina spesies kom in 'n verskeidenheid habitatte in Afrika voor en is bekend daarvoor dat hulle weerstand bied teen uitdroging in droё habitatte. Maar, die mate waartoe die verskillende subgroepe, ekotiepegroepe en spesies kwesbaar is vir klimaatsverandering, is steeds onbekend. Die eerste hooffokus van my tesis was om die uitwerking van klimaatsverandering op waterbalansrelevante uitkomste (tempo van waterverlies, waterinhoud en vetinhoud) van volwasse tsetse vlieё te bestudeer. Vier spesies van droë en klam habitatte is aan verskillende kombinasies van temperatuur (20 – 30 °C) en relatiewe humiditeit (0 – 99 %) blootgestel. Die tempo van waterverlies is betekenisvol deur die verskillende toetskombinasies beïnvloed, terwyl die waterinhoud, vetinhoud en liggaamsmassa tot 'n minder mate beïnvloed is en minder gevarieer het tussen die toetskombinasies. Die resultate toon bewyse vir gewigs-onafhanklike inter- en intraspesie variasie in waterverlies tempo‟s en oorlewingstyd. Die waterbalans uitkomste op variasie in temperatuur en relatiewe humiditeit is dus ingewikkeld in Glossina, en dit varieer binne en tussen spesies, subgroepe en ekotiepe in terme van die graad en rigting van effek verandering. Tweedens pas ek 'n meganistiese verspreidingsmodel toe vir G. pallidipes om die moontlike populasiereaksies met klimaatsverandering te voorspel. Ek toets die antwoorde van die model (NicheMapperTM) oor tyd en skaal op twee verskillende maniere. Beide toetse het aangedui dat die NicheMapper voorspelde rustende metaboliese tempo die verskillende aspekte van G. pallidipes populasie dinamika en biogeografie goed beskryf. Ek simuleer die uitkomste van die fenotipiese veranderbaarheid van G. pallidipes onder „n verskeidenheid klimaatsverandering-uitkomste, en los „n model van die basiese ommekeer van trypanosomiasis (R0) op onder 'n klimatsverandering situasie in die toekoms. Hierdie geïntegreerde tesis toon sterk bewyse dat die optimale habitat van G. pallidipes verminder met klimaatsverandering. Dit toon egter ook bewyse vir 'n 1.85 keer toename in R0 gebasseer op 'n verhoging in die frekwensie van bytgeleenthede weens die hoër voorspelde metaboliese tempo van die vlieë in die toekoms. Laasgenoemde stel voor dat die afname in optimale habitat moontlik deur 'n toename in R0 oorheers sal word. Die resultate demonstreer dat beter begrip van die fisiologiese meganisme(s) wat parasiet-draers beïnvloed verdere insig kan voorsien in die toekomstige voorspelling van draer teenwoordigheid en siekte waarskynlikheid.

Bacterial endosymbionts of eukaryotes are generally studied in terms of their benefit or detriment to their hosts. The constraints that the host's life history imposes on its endosymbionts are rarely considered, although bacterial genome content and size are influenced by both the biotic and abiotic factors in the environment. The host organism is the primary habitat of the endosymbiont. Thus, desecribing the environment a host provides its endosymbiont is essential for understanding the evolution of endosymbiotic bacteria. I propose a system to classify the endosymbiotic environment by three characteristics: 1) host life cycle 2) host metabolism, and 3) endosymbiont location relative to host tissues. Insect-bacterial mutualisms have been classified in terms of endosymbiont environment. The majority of insect-bacterial mutualisms currently studied involve monophagous, hemimetabolous hosts that provide a relatively constant endosymbiotic enviroment. A relatively constant environment may explain the extremely reduced genomes of their endosymbionts. In contrast, polyphagous, holometabolous hosts provide the most variable endosymbiotic environment. In this work, I examined the interactions between the polyphagous, holometabolous insect, Bactrocera oleae (Rossi), and the enteric gammaproteobacterium, Candidatus Erwinia dacicola, throughout host development. Candidatus Erwinia dacicola was found in the digestive system of all life stages of wild olive flies. PCR and microscopy demonstrated that Ca. Erwinia dacicola resided intracellularly in the gastric caeca of the larval midgut, but extracellularly in the lumen of the foregut and ovipositor diverticulum of adult flies. I document the widespread distribution and high frequency of Ca. Er. dacicola in ten populations of wild olive flies sampled in four countries (3 Old World and 1 New World). The relative abundance of the bacterium was highest in adults and less prevalent in the egg and pupal stages. Among adult flies, the bacterium was most common in ovipositing females. These results suggest that Ca. Er. dacicola is a persistent, autochthonous endosymbiont of the olive fly. Finally, mating initiation was examined to study the influence of Ca. Er. dacicola on mating between a laboratory and a wild population of olive flies from Israel. Behavioral differences between the two populations, not presence of the endosymbiont, explained mating initiation.

No description available.

No description available.