Supplementary cementitious materials (SCMs), are beneficial when used as partial replacement of cement in concrete mixtures for coastal concrete structures, blended with Portland cement (binary or ternary mixes), i.e., high-performance concrete provides improved properties when exposed to marine harsh environment. In order to characterize selected durability properties of different concrete mixtures, a testing program was established. The intent of this study consists of testing 10cm diameter x 20cm long concrete specimens prepared with a range of different mix designs. 1) to evaluate the rate of water absorption due to capillary suction, referred to as sorptivity, 2) to evaluate the concrete surface resistivity, 3) to evaluate and compare the total porosity of specimens with different mixes, and 4) to obtain correlations between resistivity and sorptivity. All of these experimental tests were carried out according to ASTM International Standards (Sorptivity, Porosity) and Florida Method of Test (Resistivity). The tests were performed on concrete samples at various ages. Moreover, The results provided a fast and reasonable approximation of the concrete durability over time. Ordinary portland cement was partially replaced with supplementary cementitious materials including: fly ash (20%), silica fume (8%) and blast furnace slag (50%). These SCMs are highly effective in creating more durable concrete design mixtures. The water-to-cementitious (w/cm) ratios of 0.41 and 0.35 were investigated. The concrete that contains pozzolanic materials has demonstrated progress in extending the time for initiation of corrosion. The test results obtained indicate that the concurrent inclusion of fly ash and silica fume greatly reduced water penetration. The mixes containing slag also showed lower porosity and water absorption result, when compared to specimens containing fly ash only. Ternary concrete mixtures specimens showed much higher surface resistivity values than binary mixture specimens. These results suggest that reducing w/cm ratio, adding SCMs to concrete mixtures improved the concrete durability. The possibilities for the risks of corrosion initiation would be minimized (delayed) by prescriptive and then performance-based concrete blends with SCM materials optimized for service exposure in aggressive environments. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

In this dissertation the effects of different types of Pulverized Fuel Ash (PF A)-types on the workability of cementitious pastes containing relative large amounts of PF A were investigated. The different types of PF A were produced at the same source thus they were chemically similar but differed in terms of average particle size and size distribution (grading). By using a two-point measurement technique based on flow through a J-shaped tube it was possible to detect relative small differences in workability between pastes. It was found and concluded that the different types of PFA had a significant effect on the workability of pastes containing cement and PFA as well as PF A alone. The physical differences between the PF A-types were quantified and their effects on workability investigated. It was concluded that PF A with a broader particle size distribution range produced pastes with higher workability at constant water content. It was found that compressive strength as measured after 28 days were solely a function of the water/cementitious ratio for the curing regime employed. It was concluded that for curing conditions used the type of PF A used could have a significant effect on compressive strength when constant workability is required. / Dissertation (MSc (Transportation))--University of Pretoria, 2006. / Civil Engineering / unrestricted

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>Magister Scientiae - MSc / Coal is seen as a reliable and secure energy source in many countries around the world despite the development of a number of alternative sources of energy. A rise in global energy demand has led to an increase in coal consumption. Consequently, global coal fly ash (CFA) production has increased creating a pressing need for recycling and utilisation of coal fly ash. South Africa produces 50 million tons of ash per year from coal combustion with only about 10 % being utilised. There has been a rise in demand for REEs over the past decades due to their use in optics, automotive, electronics, energy, defence industries etc. These precious elements are known to be contained in CFA, making it a potential source.

>Magister Scientiae - MSc / There has been increasing interest in finding alternative sources for Rare Earth Elements (REEs) due to their application in green energy and Coal Fly Ash (CFA) has been found to be a viable potential source. Thus investigations on the feasibility of recovering REEs from CFA and the possibility of optimizing the current recovery techniques have become popular. The main focus in the investigations has been to use equipment and products that are environmentally sustainable and economically efficient. In addition, studies have shown that there is a relationship between the particle size of CFA and the REE concentration, which can potentially increase the recovery of REEs. However, there have been inconsistencies in the findings of this relationship.

With a growing human population, food insecurity is becoming a worldwide problem. As the search for sustainable sources of protein continues, black soldier fly larvae come to the forefront as a partial solution. Full of proteins and fats, the larvae will consume most organic matter and rapidly develop into a usable form. Supplementing black soldier fly larvae with oleaginous microbes Arthrobacter AK19 and Rhodococcus rhodochrous increases their body size by 25%, potentially accelerates their development by one day, and increases their conversion efficiency. Supplementing with Bifidobacterium breve decreased body size, slowed development, and decreased conversion efficiency, underscoring the importance of selecting supplemental microbes and testing first on a small-scale. Promising results on the small-scale led to an industrial study, where similar results were also seen, resulting in greater optimization of this system.

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Among terrestrial orchids, and particularly among the subtribe Orchidinae, flies are underrepresented as pollinators. The European Neotinea ustulata, which developed specialized pollination by tachinid flies, is known to produce high relative concentrations of the floral cuticular alkenes (Z)-11-tricosene and (Z)-11-pentacosene (referred to as (Z)-11-C23/C25enes), which seem to be uncommon among orchid flowers. If the evolution of tachinid pollination is related to that of (Z)-11-C23/C25enes, we can expect that closely related species have a different floral chemical pattern and significantly small or no production of (Z)-11-C23/C25enes, independently of their pollinator guild identity (e.g., bees, flies, moths). We chemically compared the floral cuticular composition among Neotinea species, performed electrophysiological analyses, reconstructed the phylogenetic Orchidinae tree, and identified the evolutionary history of pollinator guild and (Z)-11-C23/C25enes production within the Orchidinae. Neotinea ustulata has evolved a markedly different floral cuticular composition compared to other Neotinea and produces both compounds ((Z)-11-C23/C25enes) in high relative quantities (i.e., above 8% in combination), which are detectable by tachinid antennae. Moreover, most Orchidinae taxa have minimal or no production of these alkenes, independently of the identity of their pollinator guild. Our ancestral reconstruction suggested that (Z)-11-C23/C25enes production was an evolutionary exaptation in Neotinea, whereas tachinid pollination was a unique evolutionary innovation for N. ustulata. Floral cuticular composition and, in particular, the combined production of (Z)-11-C23/C25enes at relatively high concentrations is intimately linked to the evolution of tachinid pollination within the Orchidinae.

<p> Social learning, defined as learning from other individuals has been well studied in vertebrates and social insect species. I used fruit fly egg laying site selecting as a paradigm to test for social learning in a non-social insect. Focal females that experienced novel food together with mated females (models), who had laid eggs on that food, subsequently exhibited a stronger preference for laying eggs on that food over another novel food than focal females that experienced the same food alone. This socially influenced learning was also observed when focal females experienced both foods, one with mated models and their eggs and one alone. In contrast to the strong effect of a food with mated models and their eggs, neither a food with virgin models nor the aggregation pheromone (cVA) alone generated socially influenced learning. These results provide the first evidence for social learning about egg laying substrate in fruit flies. Further research utilizing fruit flies as a model system may help us gain a better understanding of the evolution and neurogenetics of social learning.</p> / Thesis / Master of Science (MSc)

Yes / Bond between substrate and overlay concretes is a key factor for the success of the repair method and significantly influences the structural performance of the repaired element. This study investigated the effect of fly ash and the surface preparation method on the bond strength of repaired concrete after exposure to high temperatures, that has not been comprehensively studied in the literature. For this purpose, overlay concretes containing 0, 5, 10, 15, and 20% fly ash as a replacement by weight of cement were cast on the original concrete surface prepared by four methods namely, as-cast, wire brushed, grooved and grooved-wire brushed. The bond strength of the interface between concrete substrate and overlay concrete was evaluated after exposure to 23, 200, 400, and 600oC temperatures for 1 hour. The results showed that partial replacement of cement by fly ash in the overlay concrete increased the bond strength of repaired concrete by up to 71%, depending on the amount of fly ash used, surface preparation method, and the temperature to which the sample was exposed. The maximum increase of bond strength was recorded for concrete containing 20% fly ash when the wire brushed preparation method was adopted at temperature of 200oC. However, surface preparation was the most influential parameter, achieving a bond strength gradual increase in order from as-cast, wire brushed, grooved to grooved-wire brushed methods. The results also showed that for most of the samples having similar surface preparation and the same percentage of fly ash, bond strength decreased with the increase of exposure to temperature; for example, for overlay concretes without fly ash, in as-cast and wire brushed surface preparation methods at temperatures of 400 and 600 oC, the bond strength has reached zero. On the other hand, for grooved and grooved-wire brushed surface preparation methods, the bond strength reduction was about 63%, when temperature increased from 23 to 600oC. / The full-text of this article will be released for public view at the end of the publisher embargo, 12 month from first publication.