Current design guidelines for reinforced soil walls and slopes recommend the use of granular soils such as gravels and sands as select fills. Cost savings could potentially be realized by using on-site clays and silts. Some clays are swelling and silts are frost susceptible. When considering the use of swelling clays and frost susceptible silts as fills, environmental loading due to swelling-shrinkage and freeze-thaw effects from environmental changes could become a design issue. To examine the hypothesis that consideration of environmental loading during design will produce improvements in the performance of geosynthetic-reinforced soil structures that use clays or silts as fill materials, experimental and numerical studies were undertaken. Geosynthetic-reinforced clay specimens were subjected to wetting and drying in a model test apparatus developed and commissioned for this study. In separate test set-up, reinforced silt specimens were subjected to freezing and thawing. Tests on unreinforced specimens were also performed in otherwise identical conditions for comparison purposes. Movements of the specimens, soil strains, reinforcement strains, soil suctions and soil temperatures were monitored during the application of environmental loading in addition to mechanical loading from external stresses. The results of the laboratory model tests showed that reinforcements reduced horizontal displacements of the clay specimens during wetting and drying. The same is true for the case of silt during freezing and thawing. The environmental loading induced strains, and therefore stresses in the reinforcements. The measured geogrid strain during the wetting-drying of reinforced clay specimen was up to 0.75%. Similarly, the measured geogrid strain in the reinforced silt specimen during freezing-thawing cycles was up to 0.57%. The strains were greater than the strains generated by mechanical loading for the range of applied stresses used in this study. Numerical models were developed to simulate wetting only induced swelling of reinforced clays and freezing only induced expansion of reinforced silts specimens. They were used to simulate the results of laboratory model tests. The performance of geosynthetic-reinforced soil slopes with swelling clay fills and frost susceptible silt fills was evaluated. Parametric studies were performed to determine important parameters affecting the performance of reinforced clay and silt slopes.

Current design guidelines for reinforced soil walls and slopes recommend the use of granular soils such as gravels and sands as select fills. Cost savings could potentially be realized by using on-site clays and silts. Some clays are swelling and silts are frost susceptible. When considering the use of swelling clays and frost susceptible silts as fills, environmental loading due to swelling-shrinkage and freeze-thaw effects from environmental changes could become a design issue. To examine the hypothesis that consideration of environmental loading during design will produce improvements in the performance of geosynthetic-reinforced soil structures that use clays or silts as fill materials, experimental and numerical studies were undertaken. Geosynthetic-reinforced clay specimens were subjected to wetting and drying in a model test apparatus developed and commissioned for this study. In separate test set-up, reinforced silt specimens were subjected to freezing and thawing. Tests on unreinforced specimens were also performed in otherwise identical conditions for comparison purposes. Movements of the specimens, soil strains, reinforcement strains, soil suctions and soil temperatures were monitored during the application of environmental loading in addition to mechanical loading from external stresses. The results of the laboratory model tests showed that reinforcements reduced horizontal displacements of the clay specimens during wetting and drying. The same is true for the case of silt during freezing and thawing. The environmental loading induced strains, and therefore stresses in the reinforcements. The measured geogrid strain during the wetting-drying of reinforced clay specimen was up to 0.75%. Similarly, the measured geogrid strain in the reinforced silt specimen during freezing-thawing cycles was up to 0.57%. The strains were greater than the strains generated by mechanical loading for the range of applied stresses used in this study. Numerical models were developed to simulate wetting only induced swelling of reinforced clays and freezing only induced expansion of reinforced silts specimens. They were used to simulate the results of laboratory model tests. The performance of geosynthetic-reinforced soil slopes with swelling clay fills and frost susceptible silt fills was evaluated. Parametric studies were performed to determine important parameters affecting the performance of reinforced clay and silt slopes.

<p>There is consistent research evidence that shows improvement of the engineering properties of subgrade soils treated with lime or cement. However, limited information is available on the effect of climatic changes on the subgrade stiffness. The thesis studies the effects of changes in soil moisture content and temperature on the resilient modulus of treated and untreated subgrades in Indiana. Two types of soils were tested: A-6 and A-7-6, from two locations in Indiana: Hartford City and Bloomington, respectively. When existing standards ASTM D559/559-15 and ASTM D560/560-16 for wetting/drying (WD) and freezing/thawing (FT) processes, respectively, were followed, the treated and untreated samples failed through the process of preparation due to the stringent procedures in the standards. Appropriate test conditions were investigated, as part of the research, to develop new protocols more appropriate to the field conditions in Indiana. Two new test protocols were developed and successfully applied to the treated soils. A total of 26 resilient modulus, M_R, tests were conducted following the standard AASHTO T307-99. The M_R results showed that the repeated action of WD and FT cycles reduced the stiffness of the chemically-treated soils down to values similar to or lower than those of the untreated soils. However, when the amount of chemical was doubled, with respect to the optimum, the M_R of the treated soils improved over that of the untreated soils, even after the wetting-drying cycles.</p>

Diss. (sammanfattning) Swedish University of Agricultural Sciences : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Soft soil stabilization frequently uses cement, lime, fly ash, etc., but very limited studies were conducted on the long-term durability of stabilized soil. The present research work deals with the long-term durability of commercially available soil (i.e., EPK clay) stabilized with ordinary Portland cement and polypropylene fiber using a realistic approach, where the effect can be noticed in each weathering cycle. In the present study, two different tests (i.e., wetting-drying and freezing-thawing) were conducted to analyze the long-term durability of stabilized soil. Cycles of higher temperature followed by rainfall, which generally occurs in southern states of the US, were analyzed by the wetting-drying test; and on the other hand, cycles of freezing temperature followed by normal temperature, which generally occurs in northern states of the US and Canada, were analyzed by the freezing-thawing test. For the mid-continental region where freezing, normal, and higher temperature followed by rainfall are expected to occur, hence both the test method i.e., wetting-drying and freezing-thawing, were suggested. Laboratory experimental investigations were conducted to find the percentage loss of stabilized soil during wetting-drying and freezing-thawing tests, which were used as a durability indicator for cement and cement-fiber stabilized soil. Stabilized samples were subjected to harsh environmental conditions in a laboratory set up, and their deterioration was observed and studied after each wetting-drying and freezing-thawing cycle. In the real world, stabilized soil encounters seasonal cycles of monsoon and summer in long run of its service life which was simulated in rapid weathering cycles in laboratory setup. EPK clay samples were stabilized with different percentages of cement, and a mix of cement-fiber combination and were subjected to 12 cycles of wetting-drying and freezing-thawing cycles separately to determine the percentage loss of soil in accordance with the ASTM standards. Finally, based on percentage loss of soil of those stabilized samples which survived up to 12 cycles of weathering action, the optimum content of stabilizing agent was determined for wetting-drying and freezing-thawing tests. Results of wetting-drying tests indicate that EPK clay stabilized with ordinary Portland cement and fiber combination survived up to 12 cycles, but only 10% cement + 0.5% fiber was durable against wetting-drying based on percentage loss. For all the samples stabilized with 10% cement + 0.5% fiber combination, the percentage loss of soil when subjected to durability test was less than 7%, which satisfy the Portland Cement Association’s (PCAs) durability specification. The results of freezing-thawing tests indicate that the EPK clay stabilized with 10% cement, 5% cement + 0.5% fiber, and 10% cement + 0.5% fiber survived up to 12 cycles and were durable against freezing-thawing based on percentage loss of soil i.e., less than 7% which satisfy the Portland Cement Association’s durability specification.

Yes / The focus of the construction industry has shifted towards the development of al-ternative, eco-friendly and green construction materials due to the energy-inefficient and carbon-intensive nature of Portland cement (PC) production and aggregate quarrying. Meanwhile, increased number of repetitive re-pair/renovation/maintenance activities and demolition operations for the end-of-life buildings generate significant amounts of construction and demolition waste (CDW). For the purposes of sustainability and upcycling wastes into high-value-added materials with improved greenness, components from CDW streams can be used in producing geopolymer concretes without using PC and natural aggre-gates, given the rich aluminosiliceous nature of CDW components. The focus of current work is therefore on the analysis of durability of aspects (i.e., drying shrinkage and resistance against sulfate attack, cyclic freezing-thawing, and chlo-ride penetration) of geopolymer concretes made entirely of CDW. Different types of bricks, tile, concrete, and glass were used in mixed form as precursors for ge-opolymerization while different-size grains of waste concrete were used as recy-cled aggregates. As alkali activators, sodium hydroxide, calcium hydroxide and sodium silicate were used. In a companion mixture, CDW-based precursors were replaced with slag and class-F fly ash. Results showed that sulfate and cyclic freeze-thaw exposure did not cause any noticeable weight and compressive strength loss in CDW-based geopolymer concretes, while chloride penetration was found comparable to PC-based concrete. While drying shrinkage was found high in entirely CDW-based geopolymer concrete and resulted in surface mi-crocracks, it was possible to lower the drying shrinkage substantially via substi-tution of CDW-based precursors with fly ash and slag. / The authors also wish to thank the support of Scientific and Technical Research Council (TUBITAK) of Turkey provided under projects: 218M102 and 117M447. / This paper is from the fib Symposium 2023, Building for the future: Durable, Sustainable, Resilient. 5-7 Jun, Istanbul, Turkey.

Orientador: Marcelo Ganzarolli de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T16:07:51Z (GMT). No. of bitstreams: 1 Simoes_MairaMartinsdeSouzaGodoy_D.pdf: 6359705 bytes, checksum: 9fb71ed44e3423b6b245f6b70134e270 (MD5) Previous issue date: 2011 / Resumo: O Poli(álcool vinílico) (PVA) é polímero biocompatível que pode ser usado como matriz para a incorporação de S-nitrosoglutationa (GSNO), que é uma molécula endógena que exerce todas as funções bioquímicas do óxido nítrico (NO). Os principais objetivos deste trabalho foram a obtenção de filmes sólidos de PVA capazes de eluir GSNO localmente, que pudessem ser utilizados para aplicações tópicas e para o recobrimento de stents. Os filmes de PVA foram reticulados fisicamente através de ciclos de congelamento/descongelamento (C/D). Verificou-se que a aplicação de 1 a 5 ciclos C/D leva a um aumento da cristalinidade dos filmes comparada aos filmes não submetidos a C/D. Este efeito está associado ao aumento do raio de giro de estruturas espalhadoras de raios X e com a redução do coeficiente de difusão da GSNO. A liberação tópica de GSNO a partir de filmes de PVA na pele de voluntários levou a um aumento significativo do fluxo sanguíneo dérmico, medido por fluxometria com laser Doppler. Demonstrou-se que a aplicação de ciclos C/D pode ser usada para controlar a velocidade e a intensidade de aumento de fluxo sanguíneo. Filmes de PVA/GSNO aplicados como revestimentos de poços de placas de cultura de células mostraram atividade bactericida dose e tempo-dependentes contra cepas de S. aureus e P. aeruginosa, sendo capazes de esterilizar completamente estas duas bactérias multi-resistentes após 6 h de incubação. Filmes de PVA/GSNO permitiram a obtenção de revestimentos aderentes sobre a superfície de stents intracoronários de aço inox levando a uma redução significativa da adesão plaquetária após incubação com sangue total. Estes resultados permitem propor o uso de filmes de PVA/GSNO fisicamente reticulados para aplicações tópicas no tratamento de lesões infectadas, para promover a vasodilatação de tecidos isquêmicos e para a melhoria das propriedades hemocompatíveis de dispositivos de contato sanguíneo / Abstract: Poly(vinyl alcohol) (PVA) is a biocompatible polymer that can be used as a matrix for incorporation of S-nitrosoglutathione (GSNO), an endogenous molecule that exerts all the biochemical functions of nitric oxide (NO). The main objectives of this work were to obtain solid PVA films capable of releasing GSNO locally, which could be used in topical applications and for the coating for stents. PVA films were physically crosslinked through freezing-thawing cycles (F/T).It was observed that films subjected to 1 to 5 cycles shows higher crystallinity than films not subjected to F/T. This effect is associated with an increase in the gyration radius of the X-ray scattering structures an with a decrease in the GSNO diffusion coefficient. Topical GSNO release from PVA films on the skin of volunteers led to a significant increase of dermal blood flow, measured by laser Doppler flowmetry. It was shown that F/T cycles can be used to control the rate and intensity of blood flow increase. PVA/GSNO films applied as coatings of cell-culture plate wells showed dose and time-dependent bactericidal activities against S. aureus and P. aeruginosa, being able of completely sterilizing these mult-resistant bacteria after 6 h of incubation. PVA/GSNO films allowed the formation of adherent coatings on the surface of intracoronary stainless steel stents, and lead to a significant reduction of platelet adhesion after incubation with whole blood. These results allow suggesting the use of physically crosslinked PVA/GSNO films in topical applications for the treatment of infected lesions, for promoting the vasodilation of ischemic tissues and for improving the hemocompatible properties of blood contact devices / Doutorado / Físico-Química / Doutor em Ciências

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.

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.