Concrete construction methods and practices influence the final in-place quality of concrete. A low permeability concrete mixture does not alone ensure quality in-place concrete. If the concrete mixture is not transported, placed and cured properly, it may not exhibit the desired durability and mechanical properties. This study investigates the in-place permeation properties of low permeability concrete bridge decks mixtures used in the Commonwealth of Virginia. Permeation properties were assessed in both the laboratory and in the field using 4-point Wenner array electrical resistivity, surface air flow (SAF), and chloride ion penetrability (ASTM C 1202-97). Laboratory test specimens consisted of two concrete slabs having dimensions of 280 x 280 x 102-mm (11 x 11 x 4-in) and twelve 102 x 204-mm (4 x 8-in) cylinders per concrete mixture. Specimens were tested at 7, 28 and 91-days. Thirteen cylinder specimens per concrete mixture underwent standard curing in a saturated limewater bath. The simulated field-curing regimes used wet burlap and plastic sheeting for 3 (3B) and 7 days (7B) respectively and was applied to both slabs and cylinder specimens. Slab specimen were tested on finished surface using the SAF at 28 and 91 days, and 4-point electrical resistivity measurements at 1, 3, 7, 14, 28 and 91 days. Compressive strength (CS) tests were conducted at 7 and 28 days. Chloride ion penetrability tests were performed at 7, 28, and 91 days. Statistical analyses were performed to assess the significance of the relationships for the following: Total charge passed and initial current (ASTM C 1202-97); 3B resistivity and 7B resistivity; Slab and cylinder resistivity; Slab resistivity and ASTM C-1202-97 (Total Charge and Initial current); and Surface Air Flow and ASTM C-1202-97. Field cast specimens, test slabs and cylinders, were cast on-site during concrete bridge deck construction. The slab dimensions were 30.5 x 40.6 x 10.2-cm (12 x 16 x 4 in.), and the cylinders were 10.2 x 20.4-cm (4 x 8-in). In-situ SAF and resistivity measurements were taken on the bridge deck at 14, 42 and 91 days. In-place SAF and resistivity measurements on laboratory field cast slabs were taken at 7, 14 and 28-days. ASTM C 1202-97 specimens were prepared from field cast cylinders and tested at 7 and 28 and 42-days. The relationship between in-place permeation measures from field specimens was compared to laboratory data. Results indicated no difference in chloride ion penetrability (Figures 7.4 and 7.5) and 28-day compressive strength (Figure 7.2) with regard to differing simulated field curing regimes, for same age testing. There was no significant difference at the 95 % confidence level between 3B resistivity and 7B resistivity specimens tested at the same age (Figures 7.9 and 7.10). A well defined relationship was observed between total charge passed and initial current (Figure 7-6). An inverse power function was found to describe the relationship between charge passed/initial current and electrical resistivity for all laboratory mixtures used in this study (Figure 7.17 – 7.22). Field data was used to validate laboratory established models for charge passed/initial current and electrical resistivity. Laboratory established models were able to predict 30 to 50% of the field data (Figures 7.31 – 7.34). Results indicate that the SAF lacked the sensitivity to classify the range of concretes used in this study (Figure 7.24). / Ph. D.

Phenylindane monomers 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (DAPI), 5,6-diamino-1-(4-aminophenyl)-1,3,3-trimethylindane (TAPI) and 6-hydroxy-1-(4-hydroxyphenyl)-1,3,3-trimethylindane (DHPI) were synthesized and characterized. DAPI, as well as other diamines, were then utilized in solution step polycondensation with a number of commercially available dianhydrides using either the two-step ester-acid solution imidization or the high temperature solution imidization routes. High molecular weight soluble fully cyclized polyimides were successfully synthesized using a 1:1 molar ratio of dianhydride to diamine. The polyimides were film forming and were characterized by size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and selective gas permeation methods, as well as other techniques. The O2 permeation and O2/N2 selectivity values obtained for materials prepared in this thesis are discussed in relation to the concept of an "upper bound", as defined in the literature concerning gas separation membranes. The series of polyimides based on DAPI and several dianhydrides were found to have high glass transition temperatures (247°C-368°C) and very good short-term thermal stability as shown by TGA, despite the partially aliphatic character of DAPI. The 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis-1,3-isobenzenefurandione (6FDA)/DAPI system also exhibited low weight loss under nitrogen at 400°C, which was comparable to that of a wholly aromatic polyimide based on 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA)/4,4'-oxydianiline (ODA) which is known to have high thermal stability. In addition, the 6FDA/DAPI polyimides had a refractive index value of 1.571 from which the dielectric constant was calculated, giving an attractively low estimated value of 2.47. The rigid, bulky and isomeric structure of DAPI in the repeat unit imparted film forming characteristics that allowed production of solvent cast membranes which displayed a range of O2 permeability and O2/N2 selectivity characteristics. High O2 permeabilities were observed for polyimides in which the DAPI structure predominated in relation to the overall polymer repeat unit, i.e. in combination with low molar mass dianhydrides. The more flexible dianhydrides afforded a greater degree of molecular freedom and were thought to result in a more tightly packed polymer conformation which decreased the rate of gas penetration through thin films. The DAPI/3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) system showed the best combination of O2 permeability and O2/N2 selectivity values (2.8Ba and 7.3, respectively). Modest variations in the DAPI isomeric ratio did not significantly effect the gas permselectivity properties. High molecular weight polyimides based on DAPI and BTDA were synthesized by three different routes. The ester-acid and thermal imidization methods produced polyimides with the highest Tgs and best thermal stability in air, as compared to the chemical imidization procedure. For example, a Tg increase of 22°C and a 68°C increase in the 5% weight loss were found for the ester-acid imidized DAPI/BTDA polyimide over those found for the chemically imidized version. The higher Tg and 5% weight loss values were attributed to the elimination of residual uncyclized amide acid moieties. Polyimides derived from 6FDA were synthesized by the high temperature solution imidization method. Thin films, cast from NMP, were tough and creasable and afforded high Tg (>295°C) systems with good thermal stability. When combined with rigid diamines, 6FDA contributed to high O2 permeation and moderate O2/N2 selectivity. The high O2 permeability was ascribed to hindered interchain packing attributed to the bulky CF3 groups. The exceptionally high oxygen permeability and O2/N2 selectivity values of the 9,9-bis(4-aminophenyl) fluorene (FDA)/6FDA system, were near the desirable "upper bound" for gas separation membrane materials, while those of 3,7-diamino-2,8-dimethyl-dibenzothiophene-5,5-dioxide (DDBT)/6FDA were actually above the upper bound. High performance polymers based on 4,4'-bis [4-(3,4-dicarboxyphenoxy)]biphenyl dianhydride (BPEDA), 2,2'-bis [4-(3,4-dicarboxyphenoxy)phenyl] propane dianhydride (BPADA), 2,2-bis(3-amino-4-methylphenyl)hexafluoroisopropylidene dianhydride (Bis-AT-AF) and 3,7-diamino-2,8-dimethyl-dibenxothiophene-5,5-dioxide (DDBT) were also synthesized in this work. Additionally, they were characterized with regard to molecular weight, glass transition temperature, and thermal stability. Polyimide systems containing hydroxyl moieties in the repeat unit were also investigated. Incorporation of hydroxyl moieties in the repeat unit enhanced chain stiffness via intermolecular hydrogen bonding and showed Tg increases of ~30°C Hydroxyl moieties also decreased the thermal stability values typically observed for polyimides. High O2/N2 selectivity was achieved with all of the 4,4'-diaminobiphenyl-3,3'-diol (HAB) containing polymers. However, these materials also had low O2 permeabilities, which suggested a tightly packed structure, possibly facilitated by hydrogen bonding. In contrast to suggestions in the literature, the comparison between a polyimide having pendant hydroxyl groups and another having the same repeat unit without them did not reveal a significant change in permselectivity behavior. The synthesis, characterization and crosslinking behavior of functional polyimides containing phenol, amine and acetylene moieties are also described. A crosslinking reaction of oligomers containing phenol moieties with a tetrafunctional epoxy resin was achieved 100°C below the "dry" glass transition temperature and was attributed to residual solvent. Utilization of this crosslinking mechanism could allow membrane optimization by investigating the influence of a number of variables, such as the concentration of the phenolic moiety, epoxy weight percent, catalyst concentration and residual solvent content. / Ph. D.

Step-growth polymerization enabled the synthesis of novel polyester regioisomers and pendant functionalized polyetherimides (PEI)s. Novel monomers incorporated at targeted mol % produced series of polyesters and PEIs, suitable for systematic analysis of key polymer properties. Subsequent compositional, thermal, mechanical, and rheological characterization forged structure-property relationships to further understand the influence of composition on performance. Altering regiochemistry is a subtle way to maintain the same polymer composition but tune desired properties. Similarly, introducing functional pendant groups expands the property profile of common industrial polymers and installs a handle for secondary chemistry after synthesizing the main polymer. Both altering regiochemistry and adding pendant groups alters polymer properties without the need for large changes in synthetic requirements or reaction conditions, ideal for industrial adoption. Incorporation of a kinked bibenzoate (BB)-based diester monomers into the commonly utilized linear regioisomer afforded processable amorphous and semi-aromatic (co)polyesters. BB-(co)polyesters with ethylene glycol (EG) possessed improved barrier performance compared to poly(ethylene terephthalate) (PET) while improving on mechanical properties, including tensile and flexural modulus/strength, rivaling bisphenol-A polycarbonate (BPA-PC). Replacement of EG with 1,4-cyclohexanedimethanol (CHDM) improved thermal properties closer to BPA-PC, while enabling melt rheological analysis due to its amorphous morphology. Time-temperature superposition (TTS) analysis produced master curves provided insight into the entanglement molecular weight (Me) and entanglement density. More kinked structures possessed a lower Me and more entanglements. Introducing kinked monomers posed the question of cyclic speices generation during polymerization, common in step-growth reactions. Thus, systematic incorporation of meta-substituted hydroxyethylresorcinol and para-substituted hydroxyethylhydroquinone regioisomers into PET analogues enabled the characterization of cyclic formation due to monomer regioisomers. Increased meta substitution produced increased amounts of cylic species, analyzed by size exclusion chromatography (SEC). Adding functionality to high performance polyetherimides (PEI)s is difficult due to the high temperatures required for processing. The lack of thermal stability for commonly utilized H-bonding/reactive groups limits viable moieties. Utilizing the high temperture processing, PEIs incorporating pendant carboxylic acids reacted in the melt to form branched PEIs. These branched PEIs exhibited steeper shear thinning as well as improved flame resistance, limited in thin film commercial PEIs. / Doctor of Philosophy / My research focused on making new plastics (polymers) for use in consumer and performance markets. Typical applications utilizing these plastics include food packaging, consumer goods, automotive, aerospace, microelectronics, construction, and medical devices. Large changes such as intricate new chemicals used to make the plastics increase the difficulty in incorporating these new materials into existing synthesis and processing techniques and infrastructure. Thus, my research revolved around subtle changes to the chemical structure of the plastic, suitable for easy industrial adoption while also improving targeted properties necessary for the aforementioned applications. Polyesters are a class of polymers commonly used for food packaging and consumer goods. Thus, improving gas barrier performance and mechanical integrity/strength is crucial when designing new polyesters. Changing the bond angles through the linear versus kinked nature of the polymer chain imparts processability and improved gas barrier, compared to commercial poly(ethylene terepthalate) (PET), commonly used in food packaging applications. The density of the polyesters is also increased, which improves mechanical strength. The specific structures used also increased the thermal resistivity compared to PET. This higher thermal resistivity enables use in applications where high temperature cleaning such as steam sterilization and dish-washing could deform products or processing such as filling food packaging containers with hot foods. Similar types of polymers which possess much higher thermal resistivity are classified as high performance polymers. One class of these include polyetherimides (PEIs). The specific chemical structures and their high thermal resistance makes them great candidates for applications in automotive, aerospace, and microelectronic applications; although, these same properties make these polymers very difficult and expensive to process into the desired parts. Thus, adding functionality to the polymer by putting specific chemical groups off of the main chain enabled easier processing and improved other polymer properties. Adding the functionality to these polymers allowed them to react and change structure at high temperatures (during processing) to achieve a different shape, thus improving desired properties, such as how easy they flow like liquids at high temperatures and processing conditions. Another benefit realized from this change during processing was the improvement of flame resistance. Due to the chemical structure of the PEIs, they inherently possess resistance to catching on fire, remaining on fire, and dripping flaming material. Although PEIs typically possess good flame resistance, thin films or small parts made from these polymers do not possess the same flame resistance and can produce flaming drips, undesirable for applications requiring flame resistance. Chemically modifying these polymers with the aforementioned functionality and processing them increased the flame resistance to eliminate flaming drips and lessen the amount of time the polymer was on fire.

[pt] O fator fundamental que leva um poço de petróleo ao colapso é o processo transiente de elevação da pressão de poros ao seu redor, devido à penetração da lama de perfuração no interior da formação. Entre as propriedades da rocha, a permeabilidade é responsável pela determinação da velocidade de penetração, bem como da profundidade atingida. Quando são perfurados folhelhos, rochas de baixa permeabilidade, uma região de dano mecânico se desenvolve ao redor do poço. Esta região é caracterizada pela alteração das propriedades mecânicas e hidráulicas da rocha. O material aumenta de volume acompanhado do surgimento de fissuras, como resultado do descarregamento e subsequente carregamento desviador. Este comportamento do material foi representado neste trabalho através de um modelo de plasticidade não-associada. Este trabalho discute a influência das tensões e da escavação sobre a permeabilidade das rochas, testando a aplicabilidade de duas relações de permeabilidade ao problema da perfuração de poços de petróleo. Estas relações foram implementadas num simulador numérico baseado no método dos elementos finitos, capaz de modelar o processo acoplado de fluxo monofásico através de um meio poroso deformável. Os resultados obtidos mostram que a consideração da permeabilidade da região circunvizinha às paredes do poço como constante, durante e após a perfuração, é uma simplificação que pode levar a erros significativos. As relações de permeabilidade adotadas, embora ainda necessitem de comprovação experimental ou de campo, contribuirão para o melhor entendimento do estudo da estabilidade de poços. / [en] The underlying factor that leads the wellbore collapse is the porepressure transient process of elevation around the wellbore due to the penetration of the drilling mud. Among the rock properties, the permeability is responsible for determining penetration speed, as well as the reached depth. When drilling shales, wich are rocks of low permeability, a zone of mechanical damage is developed around of the wellbore. This zone is characterized by the alteration of the mechanical and hydraulic rock properties. There is a material volume increase, accompanied by microcracking, as a result of the unloading and subsequent deviatoric stresses. This behavior of the material was represented in this work by a model of non-associated plasticity. Here is discussed the stresses and excavation influence on rock permeability, by testing the application of two permeability relationships to drilling problem. These relationships were implemented in a numeric simulator finite element based, wich can model the coupled process of the single-phase flow through porous media.The obtained results show that the consideration of constant permeability on zone close to the wellbore as constant, during and after the drilling, is a simplification that can lead to significant mistakes. The permeability relationships adopted, although still need experimental or field validation, will contribute to a best understanding of the study of the wellbores stability.

Variabilities of hydraulic and solute transport properties of soil are examined at three scales: pore-scale, sample volume-scale, and field-scale. Undisturbed soil cores were taken at 19 subsites spaced logarithmically along a 150 m line transect in a Groseclose mapping unit near Blacksburg; Virginia. Three core sizes were taken at each subsite at the soil surface and 0.5 m depth. 'Small' cores were-40x54 mm; 'medium' cores were 60X100 mm; and 'large' cores were 100x150 mm. Macropore effects on solute transport were evaluated using monocontinuum and bicontinuum models. Bicontinuum-predicted solute breakthrough curves (BTC) closely agreed with observed BTC data with mean errors of reduced concentrations </- 0.05 for 97% of the samples, Monocontinuum predicted BTC's had comparable fits with 80% of the samples having mean errors </- 0.07. The simpler monocontinuum model was chosen for estimating dispersion coefficients for all samples on the basis that seven percent error in concentration is acceptable for the purpose of making field predictions in light of high spatial variability. Sample volume did not significantly affect the low variation (coefficients of variation, (CV) of 7-20%) soil properties bulk density or moisture retention characteristics in Ap or Bt horizons. Large cores are recommended for assessing high variation (CV of 60-280%) fluid transport parameters, saturated hydraulic conductivity (Ks), pore water velocity and dispersion coefficients (D) since they yielded less variance than the smaller cores. Ranges of about 25 m were determined for log-transformed Ks and D from semivariograms. Monte Carlo simulations were used to predict field-average BTC's. / Master of Science

The objective of this study is to characterize the properties of typically adopted drainage layer materials in VA, OK, and ID. A series of laboratory tests have been conducted to quantify the volumetric properties, permeability and mechanical properties of the laboratory-compacted asphalt treated and cement treated permeable base specimens. The modified test protocols to determine the dynamic modulus of the drainage layer materials have been provided, which can be followed to determine the dynamic modulus of the drainage layers as level 1 input in Mechanistic-Empirical (M-E) pavement design. The measured dynamic moduli have been used to calibrate the original NCHRP 1-37A model to facilitate its application on drainage layer materials for prediction of the dynamic modulus as level 2 input. The compressive strength of the cement treated permeable base mixture of different air void contents has also been quantified in laboratory. Numerical simulations are conducted to investigate the location effects and the contribution of the drainage layer as a structural component within pavement. The optimal air void content of the drainage layer is recommended for Virginia, Oklahoma and Idaho based on the laboratory-determined permeability and the predicted pavement performances during 20-year service life. / Ph. D.

Reservoir characterization is an essential step in the oil/gas exploration process and is of great significance in the evaluation of oil/gas resources. To evaluate the production potential of the Lower Huron shale in the central Appalachian Basin, matrix permeability, Raman spectroscopy, Fourier Transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM) were used in this study. According to the experimental results, matrix permeability is relatively high for a shale gas formation, suggesting great production potential of shale gas resources in this region. Additionally, four shale samples with varying thermal maturity were characterized by the complementary Raman and FTIR spectroscopy, and curve-fitting results successfully demonstrated the change of chemical structures with the evolution of thermal maturity. Raman spectroscopy results show that the curve fitted G band position and the band separation between the G band and D1 band tend to increase with the rise of thermal maturity level. Results of FTIR spectroscopy show that the aromaticity level and the condensation extent of aromatic rings show an increasing tendency with the increase of maturation level. Moreover, mechanical properties of these four shale samples were characterized by AFM. Results show that Young's modulus is in the range of 8.20 GPa - 12.94 GPa, which is in the normal range compared with the results from other shale formations. Additionally, scanned results show an increasing tendency for Young's modulus of the organic components with the rise of thermal maturity level in these shale samples. The potential reason for this phenomenon was also explored, specifically, the growth of aromatic groups and the decrease of the CH2/CH3 ratio may be possible reasons for the rise of Young's modulus of organic components in these shale samples. This work is meaningful for the evaluation of shale gas resources, especially emerging plays, in the central Appalachian Basin, and it also provides a valuable database for relevant research on shale matrix permeability, Raman, FTIR and AFM. / Master of Science / Reservoir characterization is important in evaluating the production potential of unconventional resources. The purpose of this work is to characterize key reservoir properties of shale samples from the central Appalachian Basin to provide support for improved shale gas production in this region. This work includes the analysis of matrix permeability testing, Raman and Fourier Transform infrared spectroscopy (FTIR) characterization, and atomic force microscopy (AFM) mapping. Matrix permeability testing results show that the matrix permeability of these six samples is relatively high for a shale gas formation, suggesting great production potential of shale gas resources in this region. Additionally, four shale samples with different thermal maturity were scanned using Raman and FTIR spectroscopy, and mineral components of these same four samples were also identified by the FTIR analysis. Processed Raman data show that two important measures, the G band position and the difference between the G band position and D1 band position, tend to increase with the rise of thermal maturity. FTIR results show that the aromaticity rings would likely be compressed due to the increased number of aromaticity rings. Also, AFM provides a high-resolution map for the Young's modulus, a measure of material stiffness, of these four samples. The modulus value is in the normal range compared with scans from other shale formations. In addition, the modulus value tends to increase with the increase of thermal maturity level. The increase of aromatic rings and the decrease of the CH2/CH3 ratio can be regarded as potential reasons for the change of modulus value. This work has potential to improve the production design of shale gas resources, especially emerging plays, in the central Appalachian Basin and can be regarded as a valuable reference for other similar research.

Yes / The water permeability constant, (Kw) is one of many important parameters that affect optimal design and operation of RO processes. In model based studies, e.g.within the RO process model, estimation of Kw is therefore important. There are only two available literature correlations for calculating the dynamic Kw values. However, each of them are only applicable for a given membrane type, given feed salinity over a certain operating pressure range. In this work, we develop a time dependent neural network (NN) based correlation to predict Kw in RO desalination processes under fouling conditions. It is found that the NN based correlation can predict the Kw values very closely to those obtained by the existing correlations for the same membrane type, operating pressure range and feed salinity. However, the novel feature of this correlation is that it is able to predict Kw values for any of the two membrane types and for any operating pressure and any feed salinity within a wide range. In addition, for the first time the effect of feed salinity on Kw values at low pressure operation is reported. While developing the correlation, the effect of numbers of hidden layers and neurons in each layer and the transfer functions is also investigated.

No / Piperacillin, a potent ß-lactam antibiotic, is effective in a large variety of Gram+ and Gram¿ bacterial infections but its administration is limited to the parenteral route as it is not absorbed when given orally. In an attempt to overcome this problem, we have synthesized a novel series of charged liposaccharide complexes of piperacillin comprising a sugar moiety derived from d-glucose conjugated to a lipoamino acid residue with varying side-chain length (cationic entity) and the piperacillin anion. A complete multiple reaction monitoring LC¿MS/MS method was developed to detect and characterize the synthesized complexes. The same method was then successfully applied to assess the in vitro apparent permeability values of the charged liposaccharide complexes in Caco-2 monolayers. / BBSRC

Yes / Dual submicromolar trypanocidal–antiplasmodial compounds have been identified by screening and chemical synthesis of 4-aminoquinoline-based heterodimeric compounds of three different structural classes. In Trypanosoma brucei, inhibition of the enzyme trypanothione reductase seems to be involved in the potent trypanocidal activity of these heterodimers, although it is probably not the main biological target. Regarding antiplasmodial activity, the heterodimers seem to share the mode of action of the antimalarial drug chloroquine, which involves inhibition of the haem detoxification process. Interestingly, all of these heterodimers display good brain permeabilities, thereby being potentially useful for late stage human African trypanosomiasis. Future optimization of these compounds should focus mainly on decreasing cytotoxicity and acetylcholinesterase inhibitory activity.