Engineering Commons^™

Evaluating The Permeability Of Porous Aggregate Concrete Using Electrical Resistivity-Based Measurements, Ariel Miguel Mendez Aragoncillo

Theses and Dissertations

Recycled concrete aggregates (RCA) and lightweight aggregates (LWA) are popular alternative aggregates for concrete. However, due to their highly porous structure, concrete with RCA and LWA shows a different microstructure and higher permeability than conventional concrete. Thus, the existing relationships used to evaluate the permeability and, consequently, the durability of concrete are not applicable in concretes with RCA and LWA. This research examined the permeation properties of recycled aggregate concrete (RAC) and lightweight aggregate concrete (LWAC). The relationships between electrical resistivity-based measurements in RAC and LWAC and their permeation properties were determined and compared to that of normal weight aggregate …

Perfusion Pressure-Flow Relationships In Synthetic Poroelastic Vocal Fold Models, Cooper B. Thacker

Theses and Dissertations

The purpose of this research was to study perfusion pressure-flow relationships in self-oscillating synthetic poroelastic vocal fold (VF) models before, during, and after vibration. This was accomplished by developing a custom ultra-soft poroelastic material, incorporating the poroelastic material as the cover layer in a synthetic VF model, and studying the model vibratory response and the flow rate of fluid perfused through the cover layer while undergoing flow-induced vibration. The custom ultra-soft poroelastic material was developed using the method of direct templating with sucrose spheres as the sacrificial template and silicone as the infiltration medium. The average modulus of elasticity of …

3d Permeability Characterization Of Sheared Fiber Reinforcement For Liquid Composite Molding Process Simulation, Collin William Childs

Theses and Dissertations

Resin transfer molding (RTM) is an infusion-based closed-mold manufacturing process where resin is injected into a preform of dry reinforcement to create a net shape part. Often, when a preform is draped over a mold with complex geometry, such as the double curvature of a dome, a reorientation of the fibers takes place in the form of in-plane shear. This deformation of the reinforcement structure has the potential to adversely affect the resin flow and the filling of the mold during RTM if the manufacturer fails to properly account for the shear effects. Various process simulation tools are being developed …

Evaluating The Stabilization Of Gypseous And Gypsiferous Sands Using Different Chemical Additives To Mitigate Gypsum Dissolution, Mohammed Kamil Faris

Theses and Dissertations

Gypsum, which is dihydrate calcium sulfate, (CaSO4.2H2O), is widely available in different sizes, from the size of a rock to the size of a few micrometers as a mineral, in different types of soils. It is primarily found mainly in arid and semi-arid areas around the world at different depths. Soils with gypsum and even gypsum rocks are very hard in their dry state. However, these soils and rock will experience remarkable dissolution upon wetting.

The dissolution phenomenon, which takes place in soils that contain gypsum, creates different geotechnical problems within the soil’s profile, along with foundation issues for structures …

Lcm Permeability Characterization Over Mold Curvature, Benjamin Grant Betteridge

Theses and Dissertations

Composite flow simulation tools for LCM processing can be expensive and time-consuming but necessary to design a mold system with proper placement of resin inlets and vacuum outlets. Composites manufacturing engineers would benefit from data regarding the impact of mold curvature radius on resin flow. This could help determine whether or not a particular part and mold would require expensive simulation software designed to handle complex flow paths through curved fabric architectures exhibiting variable permeability over the curvature, or if simple flow modeling would provide accurate enough simulations for sound tooling setup decision making. Four molds, with double curvature having …

Experimental, Theoretical And Numerical Evaluation Of Wicking Models For Liquid Imbibition In Dry Porous Wicks, Mohammad Amin Faghihi Zarandi

Theses and Dissertations

Nowadays commercial wicks are utilized by consumer product companies in several important commercial applications including Tiki® Brand torches, the passive lubricants of machine gears, propellant management device, and fragrance dispersion units. Spontaneous imbibition of a liquid into porous wicks, also called wicking, is modeled using the single-phase Darcy’s law after assuming a sharp flow-front marked by full saturation behind the front. An analytical expression for the height of the wicking flow-front as a function of time is tested through comprehensive experiments using different wicks and an oil as the wicking liquid. We proposed a model based on sharp liquid-front where …

Permeability Characterization And Fluorescent Void Flow Monitoring For Processing Simulation, John Caleb Lystrup

Theses and Dissertations

Liquid composite molding (LCM) is growing in importance alternative to traditional prepreg-autoclave methods for manufacture aerospace composites. The most significant roadblock to industry's implementation of LCM is the optimization of resin flow to ensure high quality parts. This study developed process optimization tools to foster the adaptation of LCM. The following dissertation characterized the permeability of reinforcement fabrics under various processing conditions, and investigated in-situ bubble flow with carbon fiber. The purpose of this research is to extend the understanding of LCM and push forward the state of the art via sub-studies captured in five chapters, or manuscripts. Research from …

Continuous Permeability Measurement During Unidirectional Vacuum Infusion Processing, David Wayne Hoagland

Theses and Dissertations

Composite materials have traditionally been used in high-end aerospace parts and low-end consumer parts. The reason for this separation in markets is the wide gap in technology between pre-preg materials processed in an autoclave and chop strand fiberglass blown into an open mold. Liquid composite molding has emerged as a bridge between inexpensive tooling and large, technical parts. Processes such as vacuum infusion have made it possible to utilize complex layups of reinforcement materials in an open mold style set-up, creating optimal conditions for composites to penetrate many new markets with rapid innovation. Flow simulation for liquid composite molding is …

Durability Of Mechanically Loaded, Freeze Thawed Concrete Determined By Water Absorption, Brian Daniel Mitchell

Theses and Dissertations

The design of concrete bridges is primarily focused on strength characteristics. However, it is often the case that durability characteristics, specifically early deterioration of the bridge deck, requires expensive repairs before the designed service life of the bridge can come to term. Lin et al. (2012) identified the development of microcracks as a possible source of this early deterioration. He proposed that these microcracks propagated due to high local compressive stress induced by overweight trucks. The resulting permeability increase caused by the propagation of these microcracks is not significant enough to cause the kind of early deterioration of bridge deck …

Experimental And Numerical Characterization Of Scalable Cellulose Nano-Fiber Composite, Bamdad Barari Barari

Theses and Dissertations

Fiber-reinforced polymer composites have been used in recent years as an alternative to the conventional materials because of their low weight, high mechanical properties and low processing temperatures. Most polymer composites are traditionally made using reinforcing fibers such as carbon or glass fibers. However, there has been recent interest in making these reinforcing fibers from natural resources. The plant-derived cellulose nano-fibers (CNF) are a material with remarkable mechanical properties at the nano-scale that are much superior to the mechanical properties of the traditional natural fibers (such as jute, hemp, kenaf, etc) used in the natural-fiber based polymer composites. Because CNF …

Frost Susceptibility Of Base Materials Treated With Asphalt Emulsion, Noelle Anderson

Theses and Dissertations

The objective of this research was to investigate emulsion-treated base (ETB) frost susceptibility in terms of both freeze-thaw cycling and frost heave. The research performed in this study involved laboratory testing of ETB materials sampled from both the Redwood Road and 7800 South reconstruction projects in northern Utah. The effects of freeze-thaw cycling were evaluated by comparing the stiffness and strength of tested specimens to the same properties of control specimens not subjected to freeze-thaw cycling. Frost heave testing enabled evaluation of the effects of emulsion content and degree of curing on the volumetric stability of ETB materials during sustained …

Internal Curing Of Concrete Bridge Decks In Utah: Mountain View Corridor Project, Joseph Michael Yaede

Theses and Dissertations

The objectives of this research were to 1) monitor in-situ moisture and diffusivity for both conventional concrete and concrete containing pre-wetted lightweight fine aggregate (LWFA), 2) compare deck performance in terms of early-age cracking, compressive strength, and chloride ingress, and 3) compare concrete properties in terms of compressive strength, chloride permeability, elastic modulus, and water content in the laboratory using cylinders cast in the field at the time of deck construction. The research involved field and laboratory evaluations of four newly constructed bridge decks located in northern Utah, two constructed using conventional concrete and two constructed using pre-wetted LWFA to …

Hydraulic Conductivity Of Cement-Treated Soils And Aggregates After Freezing, Michael Scott Shea

Theses and Dissertations

Improvements in the strength and durability of frost-susceptible soils and aggregates can be achieved through chemical stabilization using portland cement, where the efficacy of cement stabilization for improving durability depends on the degree to which hydraulic conductivity is reduced. Hydraulic conductivity is commonly estimated from basic soil properties using Moulton's empirical equation. However, the hydraulic conductivity estimation does not consider the detrimental effects of freezing or the benefits of cement stabilization. The purpose of this research was to derive new equations relating hydraulic conductivity after freezing to specific material properties of cement-treated soils and aggregates stabilized with different concentrations of …

Scaffold Permeability As A Means To Determine Fiber Diameter And Pore Size Of Electrospun Fibrinogen, Scott Allen Sell

Theses and Dissertations

The purpose of this study was to construct a flowmeter that could accurately measure the hydraulic permeability of electrospun fibrinogen scaffolds, providing insight into the transport properties of electrospun scaffolds while making the measurement of their topographical features (fiber and pore size) more accurate. Three different concentrations of fibrinogen were used (100, 120, and 150mg/ml) to create scaffolds with three different fiber diameters and pore sizes. The fiber diameters and pore sizes of the electrospun scaffolds were analyzed through scanning electron microscopy and image analysis software. The permeability of each scaffold was measured and used to calculate permeability-based fiber diameters …

Accelerating Whole-Cell Biocatalysis By Enhancing Outer Membrane Permeability, Ye Ni

Theses and Dissertations

Whole-cell biocatalysts are preferred in many biocatalysis applications. However, cell envelope often represents a formidable permeability barrier. As a result, reactions catalyzed by whole-cells are reportedly orders of magnitude slower than those of by their free enzyme counterparts. The present research addresses this critical issue by using membrane engineering approaches. Two E. coli strains with genetically altered outer membrane structures were used in the study, a lipopolysaccarides (LPS) mutant SM101 and a Braun's lipoprotein mutant E609L. The effects of outer membrane mutation on the permeability of substrates differing substantially in size and hydrophobicity were investigated by combining the mutant cells …