The factors which affect the engineering properties of calcium carbonate cemented soil are examined. The influence of calcium carbonate content, molding moisture content, and confining pressure on the strength characteristics of two types of soil is investigated in two distinct phases of the research. Type A soil, obtained from the University of Arizona Campbell Avenue Farm in Tucson, was used for the artificially cemented specimen stage. It is composed of sand and silt-size particles with some clay and is virtually free of calcium carbonate in its natural state. Sierrita soil, obtained from the Twin Buttes Open Pit Mine south of Tucson, was used for the reconstituted sample stage. It is naturally cemented with calcium carbonate and is composed mainly of sand, gravel, a small amount of silt, and occasional large-sized (boulder and cobble) particles. Specimens for triaxial compression testing were compacted for each phase of the study under carefully controlled conditions. Three test series were carried out on Type A soil artificially cemented with calcium carbonate. Three percentages (0%, 15%, and 30%) on a dry weight basis of the soil were used. Two molding water contents, one dry and one wet of optimum moisture content, were established for each test series. Unconsolidated undrained triaxial compression tests were carried out on oven-dried specimens at three different confining pressures to obtain shear strength parameters. The fabric characteristics of selected specimens were then defined by viewing them under a scanning electron microscope. The results indicate that the strength of the calcium carbonate cemented soil depends on the distribution and not necessarily the content of the cementing agent within the soil mass. Visual examination of the various microstructures of the artificially cemented soil confirmed the hypothesis that strength gain occurs when the calcium carbonate particles are concentrated at the points of contact between soil grains. Visual examination of the fabric of the naturally cemented Sierrita soil showed the microstructure to be highly compressed with weathered calcium carbonate particles dominating the soil structure. The calcium carbonate content was found to range from 14 to 23%. Because of sampling difficulties, an in situ cohesion value for the Sierrita soil could not be obtained from conventional laboratory tests. Therefore, the value was obtained by back analysis of the stability of actual slopes existing at Twin Buttes Mine. Slope stability analyses using Bishop's Modified Method with a search routine based on the Simplex Method of Nelder and Mead were performed. Stability analyses were also performed using strength properties of artificially cemented Type A soil. These analyses showed the relationships among cohesion, friction angle, safety factor, and calcium carbonate content for a specified slope geometry.

The use of soil cement as a growth medium was examined in this study. During the monitoring, green soil cement revealed diverse ecological values. The survival rates of plants in each soil conditions were higher than 80%,which was very promising. Furthermore, the survival rates dropped when the soil density reached95%, which means soil density might influence the survival rate of plant. Plant growth rates in sandy soil were higher than that in soil cement. In particular, low soil density facilitated plant growth in sandy soil, whereas density effect was not clear to plant growth performance in soil cement. Experiments were undertaken to study the soil-water characteristics of sandy soil and soil cement in field and laboratory condition. The influence of vegetation and material density on the development of negative pore water pressure (PWP) and degree of saturation (Sr) in the studied materials was investigated. The field planting experiments proved a promising survival rate of Schefflera heptaphylla in both types of materials while sandy soil promoted better growth of the seedlings than the soil cement. From the field study, PWP and Sr of sandy soil responded noticeably and promptly to natural drying and wetting cycles. However, the responses in soil cement were relatively mild. When subjected to the same drying-wetting cycles, PWP responded more slowly and to a smaller magnitude compared with that of soil cement. In addition, Sr changed little in soil cement. An increase in the density of the sandy soil promoted rapid development of negative PWP, while an opposite trend was observed for soil cement. Attempts have been made to explain the observations from the perspectives of material permeability and change in water content during a drying period in both soil types. Furthermore, in sandy soil, the development of PWP (with a measurement limit of -90 kPa) was minimally affected by the presence of vegetation, while vegetation noticeably helped the development of negative PWP in the soil cement. Bounds of the soil-water characteristic curve of the studied materials were presented based on estimates from the drying and wetting scanning curves derived from the field monitoring. A complementary laboratory study was carried out in an environmental chamber with controllable temperature and humidity. Monitoring results from the laboratory agreed well with that obtained from the field. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

No description available.

No description available.

Thesis (Ph.D.)--Texas A & M University, 1986. / Includes bibliographical references (leaves 115-120).

Made available in DSpace on 2014-06-11T19:25:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-09-24Bitstream added on 2014-06-13T20:32:46Z : No. of bitstreams: 1 berte_sdd_me_ilha.pdf: 1473291 bytes, checksum: 61382a3a1bac42cdf44d0975ecac5ff5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esta dissertação trata de uma pesquisa sobre a otimização e o comportamento do SCAA – Solo-Cimento Auto-Adensável tanto no seu estado fresco quanto no seu estado endurecido, confeccionando-se misturas com variação nos teores de cimento, água e aditivo superplastificante. A proposta visa analisar e compreender os desafios de se obter a auto- adensabilidade em misturas de solo-cimento, bem como o comportamento deste material no que diz respeito aos finos do solo e o cimento frente à água, envolvendo a coesão ou dispersão das partículas de solo, na tentativa de determinar qualitativamente ou quantitativamente a fluidez, a homogeneidade, a exsudação, a segregação, a resistência à compressão mecânica e a absorção de água do material. A pesquisa foi dividida em três etapas, sendo elas: o Estudo Preliminar (EP) que contou com 5 misturas, o Estudo de Otimização (EO) que contou com 27 misturas e o Estudo de Aperfeiçoamento (EA). No EP e no EO, com o material no estado fresco, foram efetuados os ensaios do Funil, de Espalhamento, de Segregação e de Adensamento e Moldagem em corpos-de-provas cilíndricos de 5 cm de diâmetro e 10 cm de altura e em formato de estrelas. No EO, os cilindros, no estado endurecido, foram submetidos a ensaios de Resistência à Compressão Mecânica e Absorção de Água, sendo que os resultados de resistência à compressão mecânica de todas as misturas apresentaram valores entre 2,0 e 7,5 MPa, atendendo assim a norma de solo-cimento; e quanto aos valores obtidos de absorção de água, 3 das 27 misturas apresentaram valores superiores ao que a norma estipula como máximo de 20% e as demais misturas apresentaram valores bem inferiores a este. No EA, foi eleita a mistura otimizada, sendo esta repetida e, com ela, confeccionados 20... / This paper is a study on the optimization and behavior of SCSC – Self-Compacting Soil Cement both in its fresh state as in its hardened state, using mixtures with variation in levels of cement, water and superplasticizer. The proposals are to analyze and understand the challenges of attaining a self-compacting soil cement as to understand the behavior of this material, especially the fine part of the soil and cement plus water, involving the cohesion or dispersion of the particles of the soil, in an attempt to determine the flowability, homogeneity, exudation, segregation, the mechanical compressive strength and the water absorption of the material. The research was divided into three stages: the Preliminary Study (PS), which featured five mixtures, the Study of Optimization (SO), which included 27 mixtures, and the Study and Improvement (SI). In PS and SO, during the fresh state of the material, there were performed the tests of Funnel, Scattering, Segregation and molding cylinders of 5 cm in diameter and 10 cm height and some in shape of stars. In the SO, the cylinders, in the hardened state, were tested for compressive strength and water absorption. The results of mechanical compression resistance of all blends showed values between 2.0 and 7.5 MPa, thus according to the standard of soil-cement. On the water absorption test, 3 of the 27 mixtures showed higher values than the standard provides (a maximum of 20%) and the other mixtures showed values well below this. In the SI, the mixture with better results on the tests was selected. With this mixture, it was made 20 cylinders of 5 cm diameter and 10 cm in height, which were tested for compressive strength. Also in SI, the selected mixture was again repeated. This time it was used to assess the feasibility of gravity flow through the passage of the mixture through a funnel... (Complete abstract click electronic access below)

Orientador: Marco Antonio de Morais Alcântara / Coorientador: Antonio Anderson da Silva Segantini / Banca: Sergio Augusto Mello da Silva / Banca: Obede Borges Faria / Resumo: Esta dissertação trata de uma pesquisa sobre a otimização e o comportamento do SCAA - Solo-Cimento Auto-Adensável tanto no seu estado fresco quanto no seu estado endurecido, confeccionando-se misturas com variação nos teores de cimento, água e aditivo superplastificante. A proposta visa analisar e compreender os desafios de se obter a auto- adensabilidade em misturas de solo-cimento, bem como o comportamento deste material no que diz respeito aos finos do solo e o cimento frente à água, envolvendo a coesão ou dispersão das partículas de solo, na tentativa de determinar qualitativamente ou quantitativamente a fluidez, a homogeneidade, a exsudação, a segregação, a resistência à compressão mecânica e a absorção de água do material. A pesquisa foi dividida em três etapas, sendo elas: o Estudo Preliminar (EP) que contou com 5 misturas, o Estudo de Otimização (EO) que contou com 27 misturas e o Estudo de Aperfeiçoamento (EA). No EP e no EO, com o material no estado fresco, foram efetuados os ensaios do Funil, de Espalhamento, de Segregação e de Adensamento e Moldagem em corpos-de-provas cilíndricos de 5 cm de diâmetro e 10 cm de altura e em formato de estrelas. No EO, os cilindros, no estado endurecido, foram submetidos a ensaios de Resistência à Compressão Mecânica e Absorção de Água, sendo que os resultados de resistência à compressão mecânica de todas as misturas apresentaram valores entre 2,0 e 7,5 MPa, atendendo assim a norma de solo-cimento; e quanto aos valores obtidos de absorção de água, 3 das 27 misturas apresentaram valores superiores ao que a norma estipula como máximo de 20% e as demais misturas apresentaram valores bem inferiores a este. No EA, foi eleita a mistura otimizada, sendo esta repetida e, com ela, confeccionados 20... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This paper is a study on the optimization and behavior of SCSC - Self-Compacting Soil Cement both in its fresh state as in its hardened state, using mixtures with variation in levels of cement, water and superplasticizer. The proposals are to analyze and understand the challenges of attaining a self-compacting soil cement as to understand the behavior of this material, especially the fine part of the soil and cement plus water, involving the cohesion or dispersion of the particles of the soil, in an attempt to determine the flowability, homogeneity, exudation, segregation, the mechanical compressive strength and the water absorption of the material. The research was divided into three stages: the Preliminary Study (PS), which featured five mixtures, the Study of Optimization (SO), which included 27 mixtures, and the Study and Improvement (SI). In PS and SO, during the fresh state of the material, there were performed the tests of Funnel, Scattering, Segregation and molding cylinders of 5 cm in diameter and 10 cm height and some in shape of stars. In the SO, the cylinders, in the hardened state, were tested for compressive strength and water absorption. The results of mechanical compression resistance of all blends showed values between 2.0 and 7.5 MPa, thus according to the standard of soil-cement. On the water absorption test, 3 of the 27 mixtures showed higher values than the standard provides (a maximum of 20%) and the other mixtures showed values well below this. In the SI, the mixture with better results on the tests was selected. With this mixture, it was made 20 cylinders of 5 cm diameter and 10 cm in height, which were tested for compressive strength. Also in SI, the selected mixture was again repeated. This time it was used to assess the feasibility of gravity flow through the passage of the mixture through a funnel... (Complete abstract click electronic access below) / Mestre

No description available.

A base de solo-cimento é um material de alta qualidade e durabilidade empregada na pavimentação rodoviária. Atualmente no Brasil, sua dosagem é realizada a partir de ensaios mecânicos, de forma a definir um valor mínimo de cimento que apresente resistência satisfatória. O foco da pesquisa consiste no estudo de prováveis diferenças na forma da adição do cimento: (i) mistura realizada com o solo seco, procedimento comumente adotado para dosagem, ou ainda (ii) mistura realizada com solo úmido, condição que representa o processo de produção em pista, ou usina. Ensaios mecânicos de resistência e rigidez foram realizados para as duas condições de umidade de mistura e para quatro tempos de cura (3, 7, 14 e 28 dias). As amostras moldadas a partir da umidade higroscópica apresentaram maiores valores de resistência à compressão simples e módulo de resiliência, porém menores de valores de resistência à tração por compressão diametral. O grau de saturação obtido na compactação Proctor das amostras de solo mostram que o solo compactado na umidade de campo atinge menores índices de vazios, resultando em massa específica aparente seca superiores ao solo compactado a partir da umidade higroscópica. Através do acompanhamento de um trecho experimental, foram realizadas medidas de bacias de deflexão com equipamento FWD, com o objetivo de retroanalisar os módulos resilientes das camadas constituintes da estrutura do pavimento. Os valores de módulo de resiliência retroanálisados apresentaram variações quando comparados com as determinações de rigidez determinadas em laboratório. / The soil-cement base-layer is a high quality and durable material employed in construction road. In Brazil, the soil-cement mix design is based on mechanical tests, in order to define a minimum cement content to assure satisfactory strength. The aim of this research is to study possible differences in the way cement is added to the mixture: (i) soil in the dry moisture condition (hygroscopic), common procedure adopted in laboratory for the mixture design, or (ii) soil in the wet moisture condition, common procedure during the road construction, or in the mix plant. Mechanical tests for strength and stiffness measurement were performed using both initial moisture conditions, and for four curing times (3, 7, 14, and 28 days). The sample compacted in the hygroscopic moisture condition showed higher strength in ultimate compressive strength (UCS) and resilient modulus (RM) tests. The degree of saturation calculated for the soil samples from the compaction test (Proctor) showed that the soil at wet moisture condition decreased the air voids. It resulted in higher dry density when compared with the soil at the dry moisture condition. One experimental test site, with soil-cement in the base layer was constructed and monitored. Its structural evaluation with Falling Weight Deflectometer (FWD) was used for backcalculation of the resilient modulus of the pavement layers. The backcalculated resilient modulus results were smaller than the values obtained from laboratory sample testing.

A base de solo-cimento é um material de alta qualidade e durabilidade empregada na pavimentação rodoviária. Atualmente no Brasil, sua dosagem é realizada a partir de ensaios mecânicos, de forma a definir um valor mínimo de cimento que apresente resistência satisfatória. O foco da pesquisa consiste no estudo de prováveis diferenças na forma da adição do cimento: (i) mistura realizada com o solo seco, procedimento comumente adotado para dosagem, ou ainda (ii) mistura realizada com solo úmido, condição que representa o processo de produção em pista, ou usina. Ensaios mecânicos de resistência e rigidez foram realizados para as duas condições de umidade de mistura e para quatro tempos de cura (3, 7, 14 e 28 dias). As amostras moldadas a partir da umidade higroscópica apresentaram maiores valores de resistência à compressão simples e módulo de resiliência, porém menores de valores de resistência à tração por compressão diametral. O grau de saturação obtido na compactação Proctor das amostras de solo mostram que o solo compactado na umidade de campo atinge menores índices de vazios, resultando em massa específica aparente seca superiores ao solo compactado a partir da umidade higroscópica. Através do acompanhamento de um trecho experimental, foram realizadas medidas de bacias de deflexão com equipamento FWD, com o objetivo de retroanalisar os módulos resilientes das camadas constituintes da estrutura do pavimento. Os valores de módulo de resiliência retroanálisados apresentaram variações quando comparados com as determinações de rigidez determinadas em laboratório. / The soil-cement base-layer is a high quality and durable material employed in construction road. In Brazil, the soil-cement mix design is based on mechanical tests, in order to define a minimum cement content to assure satisfactory strength. The aim of this research is to study possible differences in the way cement is added to the mixture: (i) soil in the dry moisture condition (hygroscopic), common procedure adopted in laboratory for the mixture design, or (ii) soil in the wet moisture condition, common procedure during the road construction, or in the mix plant. Mechanical tests for strength and stiffness measurement were performed using both initial moisture conditions, and for four curing times (3, 7, 14, and 28 days). The sample compacted in the hygroscopic moisture condition showed higher strength in ultimate compressive strength (UCS) and resilient modulus (RM) tests. The degree of saturation calculated for the soil samples from the compaction test (Proctor) showed that the soil at wet moisture condition decreased the air voids. It resulted in higher dry density when compared with the soil at the dry moisture condition. One experimental test site, with soil-cement in the base layer was constructed and monitored. Its structural evaluation with Falling Weight Deflectometer (FWD) was used for backcalculation of the resilient modulus of the pavement layers. The backcalculated resilient modulus results were smaller than the values obtained from laboratory sample testing.