In this study, the freeze-thaw performance and other engineering properties of different cementitious mixtures containing Type I/II portland cement, Type IL (10) portland Limestone cement (PLC) and Coarse Ground cement (CG-P) with or without partial replacement of fly ash (Class F) were examined. The goal was to develop a concrete mixture with better or similar freeze-thaw durability without adversely affecting other engineering properties of concrete. Crucial engineering properties reviewed include compressive strength, splitting tensile strength, workability, the degree of hydration, setting time, shrinkage and resistivity. The study was divided into two parts, one consisting of mechanical testing of engineering properties including the freeze-thaw test. The second part consisted of microstructure study which involved detection and quantification of micro-cracks/defects using μ-CT and fluorescence microscopy. The results showed that the portland limestone cement in combination with fly ash demonstrated better or similar durability in comparison to the conventional portland cement concrete mixtures.

>Magister Scientiae - MSc / The thesis aims to determine the depositional environments, rock types and petrophysical characteristics of the reservoirs in Wells E-S3, E-S5 and F-AH4 of Area X in the Bredasdorp Basin, offshore South Africa. The three wells were studied using methods including core description, petrophysical analysis, seismic facies and multivariate statistics in order to evaluate their reservoir potential. The thesis includes digital wireline log signatures, 2D seismic data, well data and core analysis from selected depths. Based on core description, five lithofacies were identified as claystone (HM1), fine to coarse grained sandstone (HM2), very fine to medium grained sandstone (HM3), fine to medium grained sandstone (HM4) and conglomerate (HM5). Deltaic and shallow marine depositional environments were also interpreted from the core description based on the sedimentary structures and ichnofossils. The results obtained from the petrophysical analysis indicate that the sandstone reservoirs show a relatively fair to good porosity (range 13-20 %), water saturation (range 17-45 %) and a predicted permeability (range 4- 108 mD) for Wells E-S3, E-S5 andF-AH4. The seismic facies model of the study area shows five seismic facies described as parallel, variable amplitude variable continuity, semi-continuous high amplitude, divergent variable amplitude and chaotic seismic facies as well as a probable shallow marine, deltaic and submarine fan depositional system. Linking lithofacies to seismic facies maps helped to understand and predict the distribution and quality of reservoir packages in the studied wells. Multivariate statistical methods of factor, discriminant and cluster analysis were used. For Wells E-S3, E-S5 and F-AH4, two factors were derived from the wireline log data reflecting oil and non- oil bearing depths. Cluster analysis delineated oil and non-oil bearing groups with similar wireline properties. This thesis demonstrates that the approach taken is useful because petrophysical analysis, seismic facies and multivariate statistics has provided useful information on reservoir quality such as net to gross, depths of hydrocarbon saturation and depositional environment.

>Magister Scientiae - MSc / With the latest advancements in the Pletmos Basin it is imperative to understand and study how sandstone reservoirs are affected by clay minerals. Clay minerals are an influential component in sandstone reservoirs worldwide and thus have an impact on the reservoir quality and petrophysical properties. The present research was aimed at assessing the effects of clay minerals on the petrophysical properties of sandstone reservoirs from the Offshore Pletmos Basin. This was done by integrating geological (wireline logs and core analysis), geochemical (XRD and pore water chemistry) and petrographical (QEMSCAN and thin section petrography) analysis to highlight the effects of clay minerals on the intrinsic properties (porosity, permeability and fluid saturation) on reservoirs encountered within the two wells (Ga- Q1 and Ga – S1). The results highlight pervasive quartz cementation as well as the presence of clay minerals: Glauconite (Illite group), Kaolinite (Kaolinite group), Clinochlore (Chlorite group) as the dominant clay minerals and Calcite as the dominant cement in both well Ga – Q1 and well Ga – S1. The most abundant clay mineral in both wells is Glauconite. This clay mineral had a more profound effect on the petrophysical parameters compared to the other clay minerals. The clay minerals occur as pore–filling Kaolinite and pore–bridging Glauconite and pore–lining Clinochlore. As a result, the clay minerals affected the pore connectivity (permeability) more than the pore spaces (porosity). This is confirmed by the petrophysical analysis where both wells have extremely low permeability and good porosity values. The study concludes that the presence of Glauconite, Kaolinite, Clinochlore and Calcite in both wells (Ga-Q1 and Ga-S1) had an adverse effect on the permeability more compared to the porosity in sandstone reservoirs. Due to the high volume of clay and high clay mineral content in well Ga-Q1, the petrophysical parameters were more adversely affected compared to well Ga-S1. As a result, we see better petrophysical properties (porosity and permeability) in the sandstone reservoir from well Ga-S1 due to intense bioturbation. The reservoir quality of well Ga-S1 is much better compared to well Ga – Q1 because water saturation averages at 42% and gas saturation averages at 58%, has decent porosity averages at 12% but low permeability ranges of 0, 1 – 4mD. / 2021-09-30

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

This investigation provides a comprehensive experimental dataset and kinetic model for biomass gasification, over a wide temperature range (1150-1350 °Ï¹) in CO2, H2O and the combination of these two reactant gases over the mole fraction ranges of 0 to 0.5 for H2O and 0 to 0.9 for CO2. The data come from a unique experimental facility that tracks continuous mass loss rates for poplar wood, corn stover and switchgrass over the size range of 6-12.5 mm. In addition, the data include char size, shape, surface and internal temperature and discrete measurements of porosity, total surface area, pore size distribution and composition. This investigation also includes several first-ever observations regarding char gasification that probably extend to char reactivity of all types and that are quantified in the model. These include: the effect of ash accumulation on the char surface slowing the apparent reaction rate, changes in particle size, porosity and density as functions of burnout, and reaction kinetics that account for all of these changes. Nonlinear least-squares regression produces optimized power-law model parameters that describe gasification with respect to both CO2 and H2O separately and in combination. A single set of parameters reasonably describes rates for all three chars. Model simulations agree with measured data at all stages of char conversion. This investigation details how ash affects biomass char reactivity, specifically the late-stage burnout. The ash contents ratios in the raw fuels in these experiments are as high as 40:1, providing a clear indication of the ash effect on the char reactivity. The experimental results definitively indicate a decrease in char reaction rate with increasing initial fuel ash content and with increasing char burnout -- most pronounced at high burnout. This investigation postulates that an increase in the fraction of the surface covered by refractory material associated with either higher initial ash contents or increased burnout decreases the surface area available for reaction and thus the observed reaction rate. A quantitative model that includes this effect predicts the observed data at any one condition within the data uncertainty and over a broad range of fuel types, particle sizes, temperatures, and reactant concentrations slightly less accurately than the experimental uncertainty. Surface area, porosity, diameter, and density predictions from standard models do not adequately describe the experimental trends. Total surface area increases slightly with conversion, with most of the increase in the largest pores or channels/vascules not measurable by standard surface area techniques but most of the surface area is in the small pores. Porosity also increases with char conversion except for abrupt changes associated with char and ash collapse at the end of char conversion. Char particle diameters decrease during these kinetically controlled reactions, in part because the reaction is endothermic and therefore proceeds more rapidly at the comparatively warmer char surface. SEM images qualitatively confirm the quantitative measurements and imply that the biomass microstructure does not appreciably change during conversion except for the large pore diameters. Extant char porosity, diameter, surface area, and related models do not predict these trends. This investigation suggests alternative models based on these measurements.

This investigation provides a comprehensive experimental dataset and kinetic model for biomass gasification, over a wide temperature range (1150-1350 °Ï¹) in CO2, H2O and the combination of these two reactant gases over the mole fraction ranges of 0 to 0.5 for H2O and 0 to 0.9 for CO2. The data come from a unique experimental facility that tracks continuous mass loss rates for poplar wood, corn stover and switchgrass over the size range of 6-12.5 mm. In addition, the data include char size, shape, surface and internal temperature and discrete measurements of porosity, total surface area, pore size distribution and composition. This investigation also includes several first-ever observations regarding char gasification that probably extend to char reactivity of all types and that are quantified in the model. These include: the effect of ash accumulation on the char surface slowing the apparent reaction rate, changes in particle size, porosity and density as functions of burnout, and reaction kinetics that account for all of these changes. Nonlinear least-squares regression produces optimized power-law model parameters that describe gasification with respect to both CO2 and H2O separately and in combination. A single set of parameters reasonably describes rates for all three chars. Model simulations agree with measured data at all stages of char conversion. This investigation details how ash affects biomass char reactivity, specifically the late-stage burnout. The ash contents ratios in the raw fuels in these experiments are as high as 40:1, providing a clear indication of the ash effect on the char reactivity. The experimental results definitively indicate a decrease in char reaction rate with increasing initial fuel ash content and with increasing char burnout -- most pronounced at high burnout. This investigation postulates that an increase in the fraction of the surface covered by refractory material associated with either higher initial ash contents or increased burnout decreases the surface area available for reaction and thus the observed reaction rate. A quantitative model that includes this effect predicts the observed data at any one condition within the data uncertainty and over a broad range of fuel types, particle sizes, temperatures, and reactant concentrations slightly less accurately than the experimental uncertainty. Surface area, porosity, diameter, and density predictions from standard models do not adequately describe the experimental trends. Total surface area increases slightly with conversion, with most of the increase in the largest pores or channels/vascules not measurable by standard surface area techniques but most of the surface area is in the small pores. Porosity also increases with char conversion except for abrupt changes associated with char and ash collapse at the end of char conversion. Char particle diameters decrease during these kinetically controlled reactions, in part because the reaction is endothermic and therefore proceeds more rapidly at the comparatively warmer char surface. SEM images qualitatively confirm the quantitative measurements and imply that the biomass microstructure does not appreciably change during conversion except for the large pore diameters. Extant char porosity, diameter, surface area, and related models do not predict these trends. This investigation suggests alternative models based on these measurements.

Indiana University-Purdue University Indianapolis (IUPUI) / Chronic kidney disease (CKD) currently affects ~37 million Americans and causes substantially increased risk of skeletal fracture and fracture-related mortality. Current methods to treat CKD-related bone loss remain alarmingly ineffective. Skeletal fragility in CKD is predominately driven by deteriorations in cortical bone, highlighted by significant cortical porosity development. It is hypothesized that cortical porosity is largely driven by chronically high levels of parathyroid hormone (PTH), which alters the balance of bone remodeling in favor of rampant osteoclast activity and bone resorption. Restricting cortical bone deterioration and the development of cortical pores is likely essential to improve CKD patients’ bone health and reduce their fracture risk. The goal of this series of studies was to answer the following key questions: (1) to what degree do bisphosphonates, an approved pharmacological agent used in metabolic bone disease, accumulate in the skeleton of animals with CKD; (2) can smaller and more frequent doses of bisphosphonates alter skeletal accumulation and improve cortical architecture and the mechanical integrity of bone; (3) can non-bisphosphonate pharmacological interventions more specifically affect cortical bone deterioration. Utilizing epi-fluorescence and two-photon microscopy, our results show that bisphosphonates accumulate more in rats with renal impairment and fractionating bisphosphonates lowered skeletal accumulation irrespective of disease state. Further, studies in both rat and mouse models of CKD demonstrated different bisphosphonate treatments alone do not recover declines in cortical microarchitecture or mechanical properties in CKD. These findings demonstrate that a single intervention is not sufficient in managing CKD-induced bone alterations. Utilizing individual pore tracking analysis, we demonstrated cortical pores can be modulated with therapeutic interventions and can infill, despite the presence of CKD. Potent suppression of PTH led to significant pore infilling while more subtle reductions in PTH, via a calcimimetic, had less striking effects on bone. Calcimimetics mitigated cortical microarchitecture deterioration and reduced the rate of cortical pore expansion. Overall, these findings highlight the importance of PTH management for treating cortical deterioration in CKD. Although bisphosphonates can be utilized in ways that reduce skeletal accumulation, they appear to need co-therapies to reduce skeletal fragility associated with CKD.

Increasing use of rock materials like shale in building, roofing, embankment filling, brick manufacturing, and in other civil structure application makes it an important rock to consider in construction engineering. Knowledge of thermal and physical properties of shale as building material is required to predict the rock's strength and permanence against weathering. Inconsistent heat capacity of anisotropic rock can result in differential heat flow. This tendency can expand the building materials leading to reduction in strength and initiate disintegration. Authors have studied various thermo-physical properties of anisotropic shale from Tennessee, which is commonly used as building stones and bricks. Experiment was designed to measure the basic thermal property, 'heat capacity' of shale. Series of laboratory tests including durability, strength, specific gravity, moisture content, and porosity were conducted to determine the physical and mechanical behavior of the samples. Results indicated that properties like porosity, strength and heat capacity varied significantly within samples, where as specific gravity and moisture content yielded steady values. Multivariate regression analysis was performed to evaluate possible correlations among the tested properties. Strong positive relationship was evident between heat capacity, and porosity. Heat capacity and Unconfined Compressive Strength of shale were inversely related. This study emphasized that physical and thermal properties of shale are directly linked with strength and durability of the rock mass.

No description available.

Improving the design of flow channels in a liquid-cooled heat sink is critical for boosting the capabilities of electronic components as well as reducing energy usage by the pump. This work explores the use of topology optimization to minimize the pressure difference across a heat sink and consequently, the energy used to supply the liquid. Topology optimization involves solving mathematical equations to obtain the optimal design for a defined cost function, here the total pressure difference between the inlet and outlet. A design variable called the porosity is defined for each cell in the mesh. The porosity features in a sink term in the momentum equation, which 'solidifies' cells by velocity suppression when deemed to be counterproductive to the cost function. The adjoint method of topology optimization, in particular, is a well-established tool for use in flow network problems and includes non-physical parameters such as the adjoint velocity and pressure. The method isn't without its drawbacks, such as the numerical instability of the adjoint equations, and the absence of boundary layers or wall functions at the interface of high and low porosity. The strength of the adjoint method lies in the ease with which it calculates the gradient of the cost function with respect to the porosity. When applied to the geometries in this work, it is observed that the problem is non-convex and results in multiple optimums with similar cost values. Thus the objective becomes seeking solutions with the simplest shape and at the same time having a minimized pressure difference. Interesting techniques are tested, namely an interpolation function, a velocity tolerance, and a volume constraint. The work is accomplished by modifying an existing adjoint optimization solver in the open-source CFD software, OpenFOAM.