This diploma thesis deals with the characterization of rheological properties and biodegradation of a poly(3-hydroxy-co-4-hydroxybutyrate), a copolymer produced by a strain of Cupriavidus malaysiensis. The theoretical part focuses on the rheology and degradation of polymers in general. It also contains the basic characteristics of polyhydroxyalkanoates and deals in more details with the description of the studied copolymer, its properties, synthesis, decomposition and possibilities of its applications. In the experimental part, the given copolymer was investigated in its native form and also in the form of copolymer mixtures filaments, which were enriched with additives (stabilizers and plasticizers). In terms of rheology, the samples showed pseudoplastic behaviour, which was slightly limited by the plasticization of the material. The highest thermal stability observed as a function of changes in complex viscosity over time was observed in a sample of a copolymer mixture containing stabilizers and plasticizer Citrofol BII. The plasticization also caused significant changes in thermal properties, especially crystallinity, which decreased compared to the native copolymer. In vitro degradation studies of samples in the form of films prepared by dissolving copolymer mixtures in chloroform were performed in phosphate buffer with lipase, in simulated body fluid and in synthetic gastric juice. The course of the process itself was characterized by the method of determining the molecular weight (SEC-MALLS) and the weight loss over time (gravimetrically). The results showed that the analysed samples are subject to degradation in all used environments. The most considerable molecular weight loss after 105 days (76 %) was observed in the sample containing stabilizers and plasticizer Citrofol BII in the environment of synthetic gastric juice. The most extensive gravimetric weight loss was attributed to the sample with stabilizers and without plasticizers, in the environment of phosphate buffer with lipase, specifically by 79%.

Self-Consolidating concrete (SCC), a highly flowable concrete, is gaining wide acceptance in the concrete industries due to a higher productivity, lower energy consumption, improved working environment and increase quality. SCC is susceptible to segregation and therefore a balance between flow-ability and stability is required. The absence of a comprehensive SCC mixture composition design guidelines merits investigating the effects of SCC mixture variables on the properties affecting its performance, namely flow and stability. An experimental and analytical study were carried out to study the influence of 5 design variables, namely water to binder ratio (w/b), percent addition of silica fume (SF), percent addition of Ground Granulated Blast Furnace Slag (GGBFS), bulk volume of coarse aggregates and binder content, on the workability and rheology of SCC. Workability measurements, specifically the slump flow, T50, L-Box and segregation column, and rheological properties, namely plastic viscosity, yield stress, and thixotropy were measured to evaluate SCC’s performance. A revised modified Bingham model was proposed to adequately account for the linear and non-linear responses of the concrete flow. It postulates that the flow is divided into a linear and non-linear part. The revised model is found to provide more consistent and precise estimate of the rheological properties. Using regression analyses, yield stress and plastic viscosity models that account for the statistically significant variables were derived from experimental test data. Yield stress is found to depend on the bulk volume fraction of the coarse aggregate, Silica Fume content, High Range Water Reducing Agent (HRWRA) and Viscosity Modifying Agent (VMA), and plastic viscosity on w/b, HRWRA and Average Paste Thickness (APT). / Thesis / Master of Applied Science (MASc)

Vertebroplasty is a new technique in orthopedic surgery for stabilizing fractured vertebra. In this technique acrylic bone cement as a biocompatible material is injected through a cannula inside of vertebra. There are several concerns in this technique that the most serious one is cement leakage out of vertebra. The main reasons are improper viscosity and lack of visibility. Clinicians who practice vertebroplasty use commercial highly concentrated radiopaque acrylic bone cement (more than 25%BaSO[subscript 4] or ZrO[subscript 2]) or a cement with manually added radiopaque agents. High density materials with attenuation under X-ray are good alternatives compared to conventional radiopaque agents (BaSO[subscript 4] or ZrO[subscript 2]) in acrylic bone cement for application in vertebroplasty. In the first part of this study, thermal and rheological properties of modified acrylic bone cement with conventional radiopaque agent (Barium Sulfate, BaSO[subscript 4]) are studied. Additions of barium sulfate are in the form of substitute or excess. In substitute formulation, barium sulfate is replaced with the same weight of powder and liquid to powder ratio kept constant. In the excess formulation, barium sulfate added as excess and liquid to powder ratio decreased. In the second part of this study, high density radiopaque agents are used as alternative radiopacifier. Experimental design technique is used to study the effect of X-ray conditions, concentration, type, and size of radiopaque agents on the visibility of bone cement. The visibility of bone cement was quantified by the measurement of contrast index. In the first project, it was found that the setting time increased with the increase of concentration of radiopacifier in substitute formulation of barium sulfate bone cement. With increase of barium sulfate concentration, excess formulations showed higher residual monomer but for substitute cement, we had a decreasing trend. Acrylic bone cements with excess formulation had higher initial viscosity compared to reference or substitute but the variation of viscosity with time was lower for substitute formulation and cements had higher working time. In the second project, contrast index was the same for barium sulfate, tungsten, and zirconium in the lower voltage but in higher voltage of X-ray lamp, tungsten and zirconium gave higher contrast index. Variation of current in X-ray lamp changed the contrast index of cement slightly compared to the effect of voltage. Bone cement with nano tungsten had higher contrast index compared to the cement with micro size tungsten although micro size zirconium as radiopacifier gave higher contrast index than nano size zirconium.

The objective of this study was to evaluate the reduction on the levels of mycotoxins in wheat products and by-products: deoxynivalenol (DON) in whole wheat flour, wheat bran and the efluent from wet milling of wheat flour, and zearalenone (ZEN) in wheat bran. Firstly, the reduction of DON contamination was studied on whole wheat flour, naturaly contaminated, and considering different moisture levels, as well as in wet milling effluent of wheat flour. Further, the impact of the ozonation process on the rheological properties of the processed flour was evaluated. Secondly, the wheat bran naturally co-contaminated with DON and ZEN was studied, considering the degradation of both mycotoxins and the impact of the ozonation process on the bran phenolic compound content and on the antioxidant capacity. The DON degradation in the whole wheat flour increased with both processing time and moisture content. By changing these process parameters, it was possible to obtain products in accordance with the legal limits of Brazil and the European Union, even starting with concentration 2-4 times higher than the legal limits. However, the rheological properties of the whole wheat flour were affected by the process, probably due to protein modifications. The DON concentration on the wet milling effluent was linearly reduced by the ozonation. In wheat bran naturally contaminated and in its equilibrium moisture, the ozonation reduced both DON and ZEN contamination. The degradation of ZEN was higher and faster than the degradation of DON, which could be explained by their molecular structures. It was also observed that the ozonation process did not negatively affect the phenolic compounds and the antioxidant capacity, which is high desirable from a nutritional point of view. Consequently, this work concludes that the ozonation process was effective in reducing DON and ZEN in different wheat products and efluent. It is noteworthy that the results obtained are promising for future studies and to elucidate the mechanism of action of ozone on mycotoxins and constituents of food. / O objetivo deste estudo foi avaliar a redução nos níveis de micotoxinas em produtos e subprodutos de trigo: desoxinivalenol (DON) em farinha de trigo integral, farelo de trigo e efluente de moagem da farinha de trigo e zearalenona (ZEA) em farelo de trigo. No primeiro momento, a redução da contaminação por DON foi estudada em farinha de trigo integral, naturalmente contaminada e considerando diferentes níveis de umidade, bem como no efluente de moagem úmida da farinha. Além disso, o impacto do processo de ozonização nas propriedades reológicas da farinha processada foi avaliado. Em segundo lugar, estudou-se o farelo de trigo naturalmente co-contaminado com DON e ZEA, considerando a degradação de ambas as micotoxinas e o impacto do processo de ozonização no conteúdo do composto fenólico do farelo e na capacidade antioxidante. A degradação de DON na farinha de trigo integral aumentou tanto com o tempo de processamento quanto com o teor de umidade. Ao alterar esses parâmetros de processo, foi possível obter produtos de acordo com os limites legais do Brasil e da União Européia, mesmo com a concentração 2-4 vezes superior aos limites legais. Contudo, as propriedades reológicas da farinha de trigo integral foram afetadas pelo processo, provavelmente devido a modificações de proteínas. A concentração de DON no efluente de moagem úmida foi linearmente reduzida pela ozonização. Em farelo de trigo naturalmente contaminado e em sua umidade de equilíbrio, a ozonização reduziu a contaminação DON e ZEA. A degradação do ZEA foi maior e mais rápida que a degradação do DON, o que poderia ser explicado pelas suas estruturas moleculares. Observou-se também que o processo de ozonização não afetou negativamente os compostos fenólicos e a capacidade antioxidante, o que é altamente desejável do ponto de vista nutricional. Consequentemente, este trabalho conclui que o processo de ozonização foi efetivo na redução de DON e ZEA em diferentes produtos de trigo e efluentes. Vale ressaltar que os resultados obtidos são promissores para futuros estudos e elucidar o mecanismo de ação do ozônio sobre micotoxinas e constituintes dos alimentos.

A argamassa de revestimento é um material largamente utilizado na construção civil. Após a década de 90, as construtoras necessitaram introduzir inovação no processo construtivo, como um diferencial de mercado, a fim de aumentar a produtividade e qualidade, juntamente à redução do custo final. Em consequência disso, ao longo do tempo, houve a evolução do subsistema de revestimento, apresentando como maior mudança a substituição da aplicação manual por projeção mecânica. Acredita-se que, devido ao fato desta tecnologia propiciar a redução da interferência da mão de obra e possibilitar o fluxo contínuo durante a execução, permite atingir maior produtividade, qualidade e redução de perdas excessivas. Porém, verifica-se elevada incerteza e variabilidade na produção e aplicação da argamassa em canteiros de obras com a inexistência de controle das variáveis envolvidas ao processo, juntamente à carência de normativas e recomendações para projeção mecânica. Além disso, a falta de controle tecnológico e carência de conhecimento técnico, com elevado grau de empirismo nas etapas do processo resultam, muitas vezes, no desencadeamento de manifestações patológicas e perda de desempenho do revestimento. Sendo assim, buscando-se um melhor entendimento das variáveis existentes no sistema e a influência de sistemas distintos para projeção de argamassas, o principal objetivo desta pesquisa consiste em verificar a influência de variáveis com baixo ou inexistente controle no processo de produção da argamassa em relação às propriedades, no estado fresco e endurecido. Para que seja possível atingir esse objetivo a pesquisa foi dividida em duas etapas: a etapa 1, em campo e em laboratório, e a etapa 2, em laboratório. Na etapa 1, em campo, buscou-se o conhecimento e caracterização das edificações, bem como peculiaridades e práticas executivas adotadas em canteiros de obras. Os resultados desta etapa mostraram a variabilidade na produção e aplicação do revestimento, principalmente relacionado à quantidade de água adicionada e sentido de aplicação. Em relação à etapa 1, em laboratório, foram coletadas e transportadas as argamassas produzidas e utilizadas em canteiros de obra desta etapa, em campo. Foram realizados ensaios de caracterização, no estado fresco e endurecido, a fim de observar a influência da mistura (sistema) e do aumento da vazão. Através deste estudo, verifica-se que distintos sistemas apresentam diferença estatística significativa em algumas propriedades no estado fresco, tais como índice de consistência aos 50 minutos e retenção de água, e endurecido, através do coeficiente de capilaridade e resistência à tração na flexão, da argamassa. Além disso, pode-se afirmar que com o incremento da quantidade de água, apenas o teor de ar incorporado decresce, sendo as demais propriedades diretamente proporcionais ao aumento da vazão. Quanto à etapa 2, em laboratório, foram avaliados três fatores controláveis (vazão, sentido de aplicação e altura do substrato) em relação à resistência de aderência à tração e permeabilidade. Pode-se afirmar que a totalidade dos fatores controláveis estudados, bem como a interação entre a totalidade das variáveis (com nível de confiabilidade de 93%) influenciam na resistência de aderência à tração. Entretanto, em relação à permeabilidade, apenas o efeito isolado da vazão e a interação entre os fatores controláveis exercem influência estatisticamente significativa. / Rendering mortars are widely used in civil construction. In the 1990s, construction companies were pressed to introduce innovations in their processes to gain market advantages, increase quality and productivity and reduce costs. As a result, rendering systems underwent major improvements, the most important of which being the adoption of mechanical shotcrete systems to replace manual processes. As mechanical systems reduce operator interference and offer better flow control during application, they are believed to deliver higher productivity and quality while reducing losses. However, the reality of construction sites still shows that the process is subject to the great variability and uncertainty associated with the lack of standards and guidelines for shotcrete application. In addition, this lack of technological control and the limited technical expertise are compounded by the adoption of empirical approaches, which often result in pathological manifestations and impaired rendering performance. To provide a better understanding of existing variables and the influence of different shotcrete systems, this study investigated the influence of mortar production variables that are subject to no or limited control on the properties of fresh and hardened mortar. The study was designed as a two-phase program, in which phase 1 was carried out both in situ and in the lab and phase 2 in the lab only. In the in situ section of phase 1, information was collected on the features of constructions and on the specific characteristics and application techniques used in construction sites. The results of this stage show huge differences in shotcrete production and application practices, particularly regarding the amount of water added and the direction/orientation of application. In the lab section of phase 1, the mortars collected in the construction sites were taken to the lab for the characterization of fresh and hardened mortar in order to determine the influence of mixing processes (system) and flow rates. The study shows that different systems result in statistically significant differences in some properties of fresh mortars, such as the consistency at 50 minutes and water retention. In the hardened mortar, differences were observed in capillarity coefficients and flexural strength. In addition, it was observed that higher water amounts cause only the entrained air content to decrease, while all other properties increase as the flow rate increases. In stage 2 in the lab three controllable factors were studied (flow, direction/orientation of application, and depth of substrate vis-à-vis bond strength and permeability). It is possible to say that all controllable/control variables studied as well as the interaction between them (with a confidence level of 93%) affect bond strength. However, in the case of permeability only the isolated effect of flow and the interaction between the controllable/control factors have a statistically significant influence.

No description available.

Drilled shafts are cylindrical, cast-in-place concrete deep foundation elements. Their construction involves drilled excavation of soil or rock using large diameter augers, and placement of the necessary reinforcing steel in the excavation followed by concreting. Where a high water table is encountered, drilling slurry is used to support the excavation walls and concreting is tremie-placed. Even though the history of drilled shaft construction goes back to the 1950s, the occurrence of anomalies persists in the form of soil inclusions, reduction in shaft cross-sectional area and exposure of reinforcement. One of the main reasons for the anomalies is attributed to the kinematics of concrete flowing radially from within the reinforcing cage to the surrounding annulus/concrete cover region. In view of this radial component of concrete flow and thus radially flowing interfaces between the concrete and slurry, the region outside the cage is more likely to contain veins of poorly cemented or high water-cement ratio material. These veins contain trapped slurry, which oftentimes consists of bentonite, jeapordizing the integrity of the shafts. This research program focuses on the numerical evaluation of self-consolidating concrete (SCC) for drilled shaft application by taking into account realistic non-Newtonian concrete flow properties and the shaft structural blockages. For this objective, a 3-D computational fluid dynamics (CFD) model of the concrete flow in the shaft excavation is developed in ANSYS-Fluent. As a precursor to 3-D modeling, 2-D CFD modeling is carried out using COMSOL Multiphysics. In both 2-D and 3-D models, the Volume of Fluid method is used for computing the motion of the interface between the concrete and the drilling slurry. The models predict the flow patterns and volume fraction of concrete and slurry. The results are encouraging as the flow pattern from the simulation shows both horizontal and vertical creases in the concrete cover region. Moreover the flow pattern shows the concrete head differential developed between the inside and the outside the reinforcement cage. Further, the 3-D model is evaluated by studying the influence of the size of drilled shaft and arrangement of the bars and the results obtained are realistic. With this 3-D model developed as a tool, the simulation of SCC and the normal standard concrete (NC) flow in drilled shaft concreting are studied in terms of creases and concrete head differential encountered in the flow. From the simulation, it is observed that in the flow pattern of SCC, the creases are very few compared to the one obtained from the flow pattern of NC. Moreover, the concrete head differential in the flow pattern of SCC is much less, than the head differential obtained from the flow pattern of NC flow. In the case of SCC, the head differential encountered about one inch. In the case of NC, the concrete head differential is 4-inch when the vertical rebars are spaced at 7-inch apart and 10-inch when the rebars are placed at 3.5-inch apart. Based on this numerical evaluation of SCC flow in the drilled shaft excavation, it is concluded that the performance of SCC is better than the performance of NC in filling the cover annular region of drilled shafts.

In the beginning of this study, Molecular dynamics simulation is utilized to investigate the behavior of water molecules confined between two Au plates of (001) planes separated by gaps of 24.48, 16.32, 12.24, 11.22, and 10.20 . The simulation results indicate that the arrangements of the water molecules are dependent on the gap size. An inspection of the variation of the self-diffusion coefficients with the gap size suggests that the difference between the dynamic properties of the water molecules in the z-direction and the x-y plane decreases as the distance between the two Au plates increases. Moreover, we discuss the effects of different lattice structures, (100), (110) and (111)¡Aon the water molecules. The simulation results indicate that the arrangements of the water molecules are dependent on Au plate surface structures. The adsorption of the plate creates flat water layers in the proximity of each plate surface for (100) and (111) cases, but wave-like water layer for Au (110) plate. The absorbed water layer is the most close to plate surface for (110) lattice structure. Moreover, the self-diffusion coefficient in the z-direction for (110) case is the largest, meanwhile, the water molecules have a greater ability to diffuse in the x-y plane for (100) case. Finally¡Athe density distribution, velocity profile, and diffusion coefficients of the water film in a Couette flow are studied. Shear viscosity and its dependence on the shear rate of the water film are also examined in the present research. The diffusion of the whole film increases dramatically as the shear rate greater than a critical value. The shear viscosity decreases as the shear rate increases, especially for the water film with a small thickness, which implies the shear-thinning behavior for viscosity of the nanoconfined film. Moreover, increase in shear viscosity with a decrease in the film thickness can also be found in the present study.

Slurry wall is a geotechnical engineering application to control the migration of contaminants by retarding groundwater flow. Sand-bentonite slurry walls are commonly used as levees and containment liners. The performance of bentonite slurry in sand-bentonite slurry walls was investigated by studying the rheological properties of bentonite suspensions, the penetration length of bentonite slurry into clean sand, and stability of the trench under in-situ hydraulic gradients. In this study, the rheological parameters of bentonite suspensions were measured at various bentonite fractions by weight from 6 to 12% with 0-3% of sodium pyrophosphate; an ionic additive to control the rheological properties of the bentonite slurries. The penetrability of the bentonite slurries through Ottawa sand was studied by injecting the slurries into sand columns at different bentonite fractions. The injection tests were performed with the permeameters having different diameters to eliminate any bias on test results due to the different size of permeameter. An empirical correlation for predicting the penetration length of bentonite slurry based on apparent viscosity, yield stress, effective particle size, relative density, and injection pressures was updated by taking into account the effects of the permeameter diameter size. Moreover, the stability of sand-bentonite slurry walls was inspected by studying the hydraulic performance of sand permeated with bentonite suspensions under increasing hydraulic gradients. The critical hydraulic gradient at which washing out of bentonite suspensions is initiated was examined. For specimens with bentonite contents less than the threshold value, the flow occurred through the sand voids and minimal washing out occurred. On the other hand, when the bentonite content was high enough to fill up all the void space between the sand particles, the flow was controlled by the clay void ratio. In this case, washing out did occur with increasing gradients accompanied by an increase in hydraulic conductivity. Accordingly, a relation between the yield stress of bentonite suspensions and the critical hydraulic conductivity was developed. / text

No description available.