Artificial ground freezing as a method to temporarily stabilize and create hydraulic sealing in urban as well as in rural areas has been used in a number of Swedish construction projects, particularly during the last decade. One problem with the freezing of soil and rock is that fine-grained clayey types of soils have showed a tendency to under certain circumstances, during the thawing process, create a pore water overpressure and to consolidate, despite a change in the external loading conditions. In certain cases, this condition can be a desired effect as the soil mass after a freeze- and thaw cycle acquires overconsolidated properties. The main objectives of this study are, to describe and review the knowledge and current state of practice of artificial ground freezing, to increase the understanding about the conceptual behaviour for prognosis of the vertical deformation concerning artificial ground freezing and to compare and discuss results from laboratory and field studies concerning vertical deformation during thawing process for Bothnia soil. The field studies and the laboratory tests in this research study have been performed with soil from the freezing of the Bothnia Line in the vicinity of Stranneberget. The Bothnia Line is the railway link between Nyland, north of Kramfors, and Umeå. This thesis relates to a part of the Bothnia Line. It deals with the behaviour of soil during thawing by means of temporary stabilization and hydraulic sealing of fine-grained soil through artificial freezing using brine as the cooling agent. However, the reason behind the problem consists of the final deformations due to the thawing process. The general conclusions of this study are; the Bothnia soil water content decreased in mean approximately 14 % after a freeze-thaw cycle, which approximately corresponds to; wth = 0.8w – 1.5 the decrease of the water content has no correlation to the depth below ground surface, in contrast, there is a strong correlation between the undisturbed soil water content and the magnitude of the decrease in water content the soil liquid limit decreases after a freeze-thaw cycle, simultaneously as the relative share of clay and fine silt grains decreases while the relative share of more coarse grains increases the coarser and denser soil created after a freeze-thaw cycle obtains an increased preconsolidation pressure and an increased undrained shear strength. / QC 20100721

Slurry infiltrated fiber concrete (SIFCON) was first produced in 1979 in the USA, by incorporating large amounts of steel fiber in molds to form very dense network of fibers. The network is then infiltrated by a fine liquid cement-based slurry or mortar. The steel fiber content can be as high as 30 % by volume. This percentage usually does not exceed 2 % in normal fiber reinforced concrete (FRC) for reasons related to mixing and workability. Due to its high fiber content, SIFCON demonstrates unique and superior mechanical properties in the areas of both strength and ductility. Most of previous research work on SIFCON has focused mainly on investigating the mechanical properties of this material. On the other hand, the studies carried out in the field of durability of SIFCON are quite limited. v Therefore, it seemed that it would be worth to study the various durability aspects of SIFCON. In view of the above, the objectives of this study are to investigate and provide information about durability of SIFCON, mainly permeability, resistance to chloride penetration, freezing and thawing and drying shrinkage. This information will help in providing the necessary database and knowledge about the ability of SIFCON to withstand the conditions for which it has been designed without deterioration, especially when it is intended to be used in aggressive environments The investigations included studying the effects of the following on durability of SIFCON: (i) matrix type (slurry or mortar), (ii) fiber contents (7%, 9.5%, and 12% by volume), and (iii) steel fiber geometry (hooked or crimped). The results obtained indicated that SIFCON, especially when prepared using mortar not slurry, has shown good durability characteristics in spite of its apparent high water absorption. The SIFCON made with the highest possible fiber volume fractions showed the best results. However, it was concluded that SIFCON needs to be protected with suitable low permeability overlays to ensure ideal improved performance by protecting the steel fibers exposed on the surfaces especially against chloride attack.

A comprehensive study was conducted on the effects of de-icer and anti-icer chemicals on cement-based materials. Portland cement mortars and concretes were exposed to over 16 chloride-based and non-chloride-based generic and commercial products and changes in cement-based material properties were measured. Deleterious chemical actions of several types of these products on cement-based materials were observed, departing from the well-known position that attributes the concrete damage from such salts mainly to physical actions under freezing and thawing exposure. Independent of freezing and thawing exposure, mortars and concretes exposed to concentrated calcium chloride and magnesium chloride solutions were found to undergo severe deterioration whereas those exposed to sodium chloride did not. The mechanisms of deterioration are complex with factors such as concentration, temperature, and availability of calcium hydroxide playing important roles. It was found that the formation of calcium oxychloride of the form 3Ca(OH)2.CaCl2.12H2O, and the 3- and 5-form magnesium oxychloride, 3Mg(OH)2.MgCl2.8H2O and 5Mg(OH)2.MgCl2.8H2O, were the main causes for the severe deterioration, and to a lesser extent brucite, gypsum, and magnesium silicate hydrate (M-S-H). The instability of these oxychloride compounds when subjected to conditions normally encountered in sample preparation is suggested as the reason why field investigations have failed to relate distressed concrete to chemical attack by such de-icer and anti-icer chemicals. Concentrated solutions of calcium magnesium acetate were also found to be harmful to cement-based materials by dissolution of calcium hydroxide and formation of calcium acetate hydrate, whereas low concentrated solutions tended to cause slow deterioration by magnesium attack forming brucite, gypsum, and M-S-H. Potassium acetate chemicals did not cause significant deterioration in mortars when these products were diluted (25% by mass), but undiluted products (50% by mass) caused considerable distress in concrete specimens. The combined effect of chemical attack impairing concrete mechanical properties and subsequent salt scaling damage was proposed as the most likely mechanisms of field deterioration.

Made available in DSpace on 2016-08-15T20:31:37Z (GMT). No. of bitstreams: 1 ThiberioSC_DISSERT.pdf: 700205 bytes, checksum: 7a5563445307116480b9ce4be88608c4 (MD5) Previous issue date: 2010-03-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / We evaluated the effect of centrifugation and the use of Tris-based extender supplemented with different sugars as well as different rates of thawing on the kinematic pattern of motility and other characteristics of frozen-thawed semen from captive collared peccaries. Semen from 13 collared were collected by electroejaculation and evaluated subjectively for motility, vigor and by computer analysis (CASA). Other features such as sperm viability, membrane integrity and morphology of spermatozoa were also evaluated. Semen was divided into four portions: two were subjected to centrifugation and then diluted in a tris plus fructose and the other in tris supplemented with glucose, the other two forms were immediately diluted in the same way. Egg yolk (20%) and glycerol (6%) were added to all groups. The samples were frozen in liquid nitrogen and thawed using two thawing rates (37ºC/1min and 55°C/7s). The results showed a reduction in total motility immediately after the dilution using both extenders and interference in some kinematic parameters such as BCF, LIN and STR for the samples centrifuged, , in addition, an increase in the number of total and secondary morphological defects were observed in centrifuged samples, independent to the sugar used (P <0.05). No significant differences among the extenders supplemented with fructose or glucose were verified at any time (P> 0.05). Furthermore, no interaction between the supplementation of sugar and thawing rates were observed for any semen parameter evaluated (P> 0.05). In conclusion, it is not necessary to centrifuge the semen from collared prior to the procedure of freezing and thawing, which can be achieved through a Tris-based extender supplemented with either fructose or glucose, as well as using different thawing rates (37ºC/1min and 55°C/7s). / Avaliou-se o efeito da centrifugação e da utilização de diluentes a base Tris suplementados com diferentes açúcares além de diferentes taxas de descongelação sobre os padrões cinemáticos de motilidade e outras características do sêmen congeladodescongelado de catetos em cativeiro. O sêmen de 13 catetos foi coletado por eletroejaculação e avaliados subjetivamente e através de análise computadorizada (CASA) para motilidade, vigor. Outras características como viabilidade espermática, integridade da membrana e morfologia dos espermatozóides também foram avaliadas. O sêmen foi dividido em quatro alíquotas: duas foram submetidas à centrifugação e em seguida diluídas, uma em tris acrescido de frutose e a outra em tris acrescido de glicose, as outras duas forma imediatamente diluídas da mesma forma. Gema de ovo (20%) e glicerol (6%) foram adicionados para todos os grupos. As amostras foram congeladas em nitrogênio líquido e descongeladas usando duas taxas de descongelação (37ºC/1min e 55ºC/7s). Os resultados demonstraram uma redução na motilidade total imediatamente após a diluição em ambos diluentes para as amostras centrifugadas, bem como em alguns parâmetros cinemáticos como BCF, LIN e STR além do aumento no número de alterações morfológicas totais e secundarias independente do açúcar utilizado (P<0,05), tendo em vista não ter apresentado diferenças entre os diluentes suplementados com frutose ou glicose em nenhum momento (P> 0,05). Além disso, nenhuma interação entre a suplementação de açúcar e as taxas de descongelação foi observada para qualquer parâmetro seminal avaliado (P> 0,05). Em conclusão, não é necessário centrifugar o ejaculado de catetos antes dos procedimentos de congelação e descongelação, para os quais pode-se utilizar um diluente a base de Tris suplementado tanto com frutose ou glicose, bem como utilizando taxas de descongelação diferentes (37ºC/1min e 55ºC/7s).

O desenvolvimento de um concreto de alto desempenho aplicado a sistemas de processamento e armazenagem de alimentos em baixas temperaturas teve por objetivo atender às indústrias de alimentos no Brasil que se utilizam da tecnologia do frio em seu processo industrial. A hegemonia mundial do mercado de carnes é brasileira, sendo que nossas indústrias são responsáveis por 33% desse mercado. A ausência de estudos para aprimorar e tornar as plantas industriais mais duráveis e condizentes com a importância do setor foi determinante na delineação do tema desta tese. Desenvolveu-se um concreto de alto desempenho frente às possíveis situações em uma planta industrial: baixas temperaturas em ambientes secos e baixas temperaturas em ambientes sujeitos à umidade. A temperatura mínima a qual foram submetidos os concretos analisados foi de 35°C. O método de dosagem e as diretrizes calcadas no reforço da matriz da pasta de cimento e refinamento de poros mostraram-se como uma alternativa para vencer as agressividades causadas pelas baixas temperaturas ao concreto. Até então, estudos sugeriam um sistema de ar cujos vazios teriam diâmetros em torno de 250 µm espaçados com esta mesma distância entre eles e com conteúdo de 6±1% para a proteção de concretos expostos a baixas temperaturas. A produção de um concreto coeso, com teor de ar de 3,5%, poros com diâmetro médio de 0,02 µm e com área específica de 2,84m²/g, provaram ser duráveis quando expostos ao congelamento e a ciclos de gelo e degelo. O fator de durabilidade para esses concretos foi de 97%. Além da durabilidade, o projeto de dosagem contemplou o aspecto econômico, produzindo 1MPa com 7,8 kg de cimento por metro cúbico de concreto. Os resultados foram obtidos por meio de ensaios dinâmicos, microscopia eletrônica de varredura, porosimetria por intrusão de mercúrio, absorção de água por imersão, além dos ensaios mecânicos de resistência à compressão, à tração na flexão e módulo de elasticidade. / Brazil has rapidly emerged as one of the world\'s leading meat exporters, being responsible by 33% of this market. In face of that, a high performance concrete (HPC), that can be applied to storage and processing system buildings at low temperatures, has been developed with the aim of answering the needs of brazilian food manufacturers that use cooling technology during industrial process. The lack of studies to improve industrial plants and make them more durable was determinant to delineate this thesis subject. A high performance concrete was designed to resist to low temperatures at dry environments as well as at moist ones. Concrete was exposed to a target temperature of -35°C. The dosage method and the guidelines based on the strengthening of bulk cement and the porous refinement showed to be an alternative to overcome the aggressiveness caused by low temperatures to concrete. To this day, studies have suggested air voids systems to protect concrete from low temperature effects. According to them, the air voids should have about 250 µm of diameter, spaced from each other this same distance and with an air content of 6±1%. However, making a cohesive concrete, with 3,5% of air content and an average diameter porous of 0,02 µm with an specific surface of 2,84m²/g, resulted in a durable concrete, even when exposed to frost / thawing cycles. The durability factor of these concretes achieved 97%. Besides durability, the dosage design brought economical advantages, producing 1 MPa with 7,8 kg of cement per cubic meter of concrete. The results were obtained through dynamic tests, scanning electron microscopy, mercury intrusion porosimetry and water absorption by immersion. In addition, tests of compression, tension strength and elastic modulus were carried out.

Two measures of air temperature trends across southern Yukon and northern British Columbia were modelled based on measurements from 83 monitoring sites across seven areas, operating for up to 14 years. Both mean monthly air temperature (MMAT) and freezing and thawing degree days (FDD and TDD, respectively) were modelled across this area (59 °N to 64.5 °N) at elevations ranging from 330-1480 m asl. Lapse rates in this region show inversions in the winter months (November - March) varying in inversion strength and length in relation to degree of continentality. The spatial and elevation range of these sites allowed for regional lapse rate modelling at the monthly scale for MMAT and at the annual scale for FDD and TDD. Lapse rates below treeline were found to be correlated (p < 0.1) with degree of continentality in the colder months (November - April) and August. In these months, lapse rates were modelled using kriging trend surfaces. In months where degree of continentality was not found to have a significant impact on lapse rates (p > 0.1) (May - October, excluding August), an average lapse rate calculated from the seven study regions was used across the study region. A combination of lapse rate trend surfaces, elevation, and temperatures at sea level were used to model MMAT and F/TDD below treeline. A treeline trend surface was created using a 4th order polynomial, allowing for temperatures at treeline to be determined. MMAT and F/TDD above treeline were calculated using a constant lapse rate of -6 °C/km, elevation, and temperature at treeline. The above and below treeline models were combined to create continuous models of MMAT and F/TDD. Modelled MMAT showed a high degree of homogeneity across the study region in warmer months. Inversions in lapse rates are evident in the colder months, especially December through February, when colder temperatures are easily identified in valley bottoms, increasing to treeline, and decreasing above treeline. Modelled MMAT values were validated using 20 sites across the study region, using both Environment and Climate Change Canada and University of Ottawa sites. The RMSE between modelled and observed MMAT was highest in January (4.4 °C) and lowest in June (0.7 °C). Sites below treeline showed a stronger relationship between modelled and observed values than sites above treeline. Edge effects of the model were evident in the northeast of the study region as well as in the ice fields in the southwest along the Alaska border. The new MMAT maps can be used to help understand species range change, underlying permafrost conditions, and climate patterns over time. FDD values were found to be highly influenced by both degree of continentality as well as latitude, whereas TDD values were mainly dependent on elevation, with degree of continentality and latitude being lesser influences. FDD and TDD were validated using the same 20 sites across the study region, with FDD showing a larger RMSE (368 degree days) between modelled and observed values than TDD (150 degree days). TDD modelling performed better on average, with a lower average absolute difference (254 degree days) between modelled and observed values at the validation sites than FDD modelling (947 degree days). The models of FDD and TDD represent a component of temperature at top of permafrost (TTOP) modelling for future studies. Two mean annual air temperature (MAAT) maps were created, one calculated from the MMAT models, and the other from the F/TDD models. Most of the study region showed negative MAAT, mainly between -6 °C and 0 °C for both methods. The average MAAT calculated from FDD and TDD values was -2.4 ºC, whereas the average MAAT calculated from MMAT values was -2.8 ºC. Models of MAAT were found to be slightly warmer than in previous studies, potentially indicating warming temperature trends.

Résumé : Le développement des matériaux composites et leur utilisation dans le domaine du génie civil ont fait l’objet d’une recherche extensive sur le renforcement des structures en béton armé. Dans ce contexte, les études sur la compréhension du comportement structural des tubes en matériaux composites (Polymère renforcé en Fibre, PRF) sont indispensables. De fait que les matériaux composites sont innovateurs, cela nous exige de procéder à des investigations expérimentales approfondies pour vérifier les hypothèses et les théories, avant de les produire à échelle industrielle. Ce projet présente une étude expérimentale approfondie sur l’évaluation des propriétés physiques et mécaniques des nouveaux tubes en matériaux composites (PRF), et des tests sur la durabilité du matériau utilisé, et permet d’étudier l’influence de quelques facteurs environnementaux sur ces propriétés mécaniques, ces conditions sont simulées par une immersion prolongée en milieu aqueux et l'exposition à des cycles gel-dégel en milieu humide. Les tubes considérés sont produits par le procédé d’enroulement filamentaire à l’aide des fibres de verre (E) et de résine (Vinyle-Ester). Les expérimentations seront effectuées sur des échantillons normalisés prélevés à partir du tube. Les résultats de cette étude sont d’une importance cruciale pour comprendre le comportement structural (avant et après un vieillissement accéléré) des nouveaux tubes fabriqués entièrement en polymères renforcés de fibres par le procédé de l’enroulement filamentaire. // Abstract : The development of composite materials and their integration in the field of civil engineering has been the subject of extensive research on strengthening reinforced concrete structures. In the perspective of strengthening concrete structures by tubes made of composite materials. In this context, the need for knowledge of the structural behaviour of tubes made from fibre reinforced polymer (FRP) composite materials is prominent. The large using of innovativeFRP required extensive theoretical and experimental investigations. This project presents an experimental study to evaluate both the physical and mechanical properties of FRP-composites tubes, and to investigate the impact of some environmental factors on their mechanical properties. The tubes are produced by a filament winding process using fibre (E)-glass and vinyl-Ester resin. The experiments will be performed on standardized samples of the tube. The main objective of this project is to assess the physical and mechanical properties of laminated FRP composites, and then test the durability of the material used in the manufacture of the tubes. It leads to the study of the effects of some environmental factors on the mechanical properties of material. These conditions occur during an immersion in an aqueous medium and exposure to freeze-thaw cycles. The results of this study are crucial to understand the structural behavior (before and after accelerated aging) of new FRP tubes made by filament winding process.

The standard ASTM C672 de-icer salt scaling resistance test has been found to be overly aggressive to concretes containing slag cement. It was compared to the newly proposed ASTM WK9367 method, based on the Quebec BNQ test, as well as several modifications, including use of an accelerated curing regime developed in Virginia (VADOT). Sixteen concrete mixtures were studied using high-alkali cement, low-alkali cement, grade 100 slag and grade 120 slag with slag contents of 0%, 20%, 35% and 50%. Vinsol resin air-entraining admixture was compared to Micro Air®. Reducing the water cement ratio from 0.42 to 0.38 had the biggest impact on improving scaling resistance of slag concretes. In general, increased slag contents increased scaling regardless of the test method used. The Micro Air® admixture provided a lower air void actor and higher hardened air content compared to Vinsol resin.

The standard ASTM C672 de-icer salt scaling resistance test has been found to be overly aggressive to concretes containing slag cement. It was compared to the newly proposed ASTM WK9367 method, based on the Quebec BNQ test, as well as several modifications, including use of an accelerated curing regime developed in Virginia (VADOT). Sixteen concrete mixtures were studied using high-alkali cement, low-alkali cement, grade 100 slag and grade 120 slag with slag contents of 0%, 20%, 35% and 50%. Vinsol resin air-entraining admixture was compared to Micro Air®. Reducing the water cement ratio from 0.42 to 0.38 had the biggest impact on improving scaling resistance of slag concretes. In general, increased slag contents increased scaling regardless of the test method used. The Micro Air® admixture provided a lower air void actor and higher hardened air content compared to Vinsol resin.

On s'intéresse dans le présent travail au comportement au gel des sols fins limono-argileux traités à la chaux seule, sols valorisables qui sont couramment rencontrés sur les chantiers de terrassement. Trois sols appartenant aux classifications A1, A2, A3 selon la norme NF P 11300, ont été choisis pour cette étude. Ces sols sont traités à 3 dosages en chaux correspondant à 3 objectifs : 1) amélioration (dosage en chaux minimal), 2) stabilisation et insensibilité à l'eau (dosage en chaux intermédiaire), 3) stabilisation et résistance au gel (dosage en chaux le plus élevé). Les sols traités sont ensuite conservés pendant quatre périodes de cure : 7 jours, 28 jours, 90 jours et 365 jours. Les deux processus de gel - le géligonflement et la gélifraction sont étudiés, parallèlement à l'évaluation des performances mécaniques, hydrauliques et microstructurales. Les résultats expérimentaux ont montré que les propriétés hydrauliques (la succion au front de gel, sp et la conductivité hydraulique à l'état non-saturé, kunsat) sont les paramètres qui gouvernent le phénomène de géligonflement des sols, traités ou non. Les résultats ont également mis en évidence le lien direct existant entre la microstructure (la distribution porale) et les propriétés hydrauliques du sol, principalement en termes de capacité de rétention d'eau et conductivité hydraulique. Le traitement augmente les performances mécaniques des sols d'une part, et amène d'autre part à des modifications de leur microstructure ; ceci induit des changements vis-à-vis de leur sensibilité au gel. Les sols sont plus gélifs directement après le traitement, cette sensibilité au gel diminuant avec le temps de cure. Une modélisation simple permettant d'estimer le gonflement au gel à partir de la succion au front de gel et de la valeur de conductivité hydraulique à l'état non-saturé a été proposée et validée. Vu que la détermination de la conductivité hydraulique à l'état non-saturé n'est pas un essai couramment pratiqué au sein de la plupart des laboratoires, un critère basé sur la succion au front de gel, sp, et la conductivité hydraulique à l'état saturé, ksat a été proposé pour évaluer la sensibilité des sols au gel. L'essai de gélifraction consiste à évaluer un coefficient de résistance de l'éprouvette de sol après 10 cycles de gel/dégel, RFT (%) - « retained strength factor after freeze-thaw testing ». Les résultats expérimentaux montrent que la valeur RFT des sols traités varie de 0% (lorsque les éprouvettes de sol perdent totalement leur résistance à la compression simple et sont détruites après 10 cycles de gel/dégel) à 90%. Quand RFT ≥ 60%, aucune dégradation visuelle de la surface des éprouvettes des sols traités n'est constatée. Ainsi, cette valeur est proposée comme critère d'acceptation des matériaux constitutifs d'une couche de forme subissant le gel avant son recouvrement. L'étude de l'effet du nombre des cycles de gel/dégel montre une diminution importante de la performance mécanique (RFT) durant trois premiers cycles de gel/dégel, et ce paramètre se stabilisant après 10 cycles. A l'aide de la technique de µ Tomographie X, l'endommagement interne des éprouvettes de sol ayant subi des cycles de gel/dégel a été quantifié. Une corrélation directe entre la diminution de performance mécanique et l'augmentation de l'indice de l'endommagement de l'éprouvette a été mise en évidence. Enfin, un modèle d'endommagement permettant d'évaluer la dégradation de la performance mécanique avec l'augmentation de l'indice d'endommagement a été établi / The present work deals with the behaviour of fine-grained silty and clayey soils treated with lime under frost. Those soils are frequently encountered in earthworks. Three soils corresponding to A1, A2, A3 classes according French NF P 11-300 standard were chosen for this study. These soils were treated with 3 lime dosages corresponding to three objectives: 1) improvement (minimum dosage), 2) stabilization and insensitivity to water (intermediate dosage), 3) stabilization and frost resistance (highest dosage). Lime-treated soils were subsequently cured for different times: 7, 28, 90, 365 days. Two frost processes, frost heave and freeze-thaw cycles, were applied in parallel with the assessment of mechanical, hydraulic and microstructural properties. Experimental results evidenced that it is the hydraulic properties (suction at frost front, sp and unsaturated hydraulic conductivity, kunsat) that govern the frost heave phenomenon of soils, treated or not. In addition, this study demonstrates the direct link between the microstructure (the pore size distribution) and the hydraulic properties (water retention curve and hydraulic conductivity). The treatment on one hand improves the mechanical performances of soils, and on the other hand modify their microstructure, and thus changes their frost sensitivity. The frost susceptibility increases directly after treatment, and then decreases with curing time. Based on the suction at frost front and the unsaturated hydraulic conductivity, a simple model was proposed and validated allowing to estimate the frost heave. Considering that the determination of unsaturated hydraulic conductivity is not a test commonly performed by most laboratories, a criterion based on the suction at frost front and the saturated hydraulic conductivity was proposed to estimate the frost sensibility of soils. The second frost resistance test consists of measuring the retained strength factor after 10 freeze-thaw cycles, RFT (%). The results obtained show that RFT of lime treated soil varies from 0% (when soil specimen completely loses its resistance and collapses after 10 freezethaw cycles) to 90%. When RFT is higher than 60%, no visual damage was observed on the specimen surface; consequently, this value is proposed as a criterion for acceptance of lime treated soil in capping layer before covering. In addition, the study of effect of freeze-thaw cycles showed a significant decrease of mechanical performance (RFT) during the first three cycles, and a stabilization after 10 cycles. Using X-ray Tomography, the intern damage of specimens due to freeze-thaw cycles was quantified. A correlation between the decrease of mechanical performance and the increase of damage index was evidenced. A model was then developed to evaluate the degradation of mechanical performance with the increase of damage index