Lightweight cellular concrete (LCC) is a cement, water, and air entrained mixture that consists of 25-80% voids. The air voids reduce the material strength but also decrease the material weight. Due to its lightweight properties LCC is an attractive alternative to soil backfill for retained structures, such as mechanically stabilized earth (MSE) walls. Although LCC is widely used behind MSE walls, limited information exists regarding the pullout strength of MSE wall reinforcements in LCC backfill. This research attempts to fill the knowledge gap through performing pullout tests on welded wire and ribbed strip reinforcements in MSE walls to determine the pullout friction coefficient (F*), reinforcement pullout behavior, and LCC properties. A large-scale test box (10 feet wide x 12 feet long x 10 feet high) supported by a steel resisting frame, was constructed, and filled with LCC backfill. Both the west and east MSE wall faces consisted of concrete walls. The west wall was supported by 16 ribbed strip reinforcements, while the east wall was supported by nine short, welded wire reinforcements. After backfilling the MSE wall, pullout tests were performed of the 12 ribbed strip reinforcements and all nine welded wire reinforcements. To determine different pullout friction coefficients (F*), different surcharge loads were applied through LCC self-weight, concrete reaction beams, and hydraulic jacks at the top of backfill. After performing the pullout tests on the large-scale test box, additional pullout tests were performed in two smaller (10 feet wide x 6 feet deep x 30 in. tall) MSE walls, each containing four ribbed strip reinforcements to determine the F* of ribbed strip reinforcements at moderate surcharge pressures. Results from these tests produced F* recommendations for ribbed strip and welded wire reinforcements. Additionally, a total of 130 LCC cylinder specimens were used to identify LCC material properties. Results of these tests show that the unconfined compressive strength of LCC is greatly dependent on the cast and cured unit weight, as well as the sample maturity. Comparing the UCS results to other work reveals a wide variation of UCS versus cured density, even though the same ASTM standard was applied for all tests. An equation for the secant modulus of LCC was created using UCS data from this thesis and other research conducted at Brigham Young University (BYU). Direct shear tests were also conducted on LCC cylinders cut to fit the confinement of a direct shear machine. The direct shear test results from this thesis agree with other research conducted at BYU.

Made available in DSpace on 2015-03-26T13:27:58Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2671402 bytes, checksum: 5e8d1471c2dce03d8b3c04e46e23e3e4 (MD5) Previous issue date: 2010-12-13 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The adoption of the soil nailing technique in the project of slope stability once or excavations it is being more and more frequent. This with it is reguire a larger number of studies about the estimate of the the pullout resistance (qs) in function of parameters of field tests for the most varied types of Brazilian soils.The objective of this research was to propose correlations for the qs resistence in function of field tests, and also to compare the results also found in the pullout test with dear in existent formulations. The study was accomplished in a slope of young gneissic residual soil, Viçosa - MG.In the field test they occurred the standard penetration test (SPT), Menard pressuremeter test (PMT), Marchetti dilatometer test (DMT) and pullout test in twelve nails, only made with no injection procedures. The assembly of the pullout test system was different from the proposal for other authors and it was shown effective.The qs values obtained in the pullout tests and the correlations found for each nails were compared using appropriate statistics for each analysis. The parameters of the field test used in the proposed correlations Nspt, PL, and P0, were certain for the average of your magnitudes along the nails. The pullout resistance found for each nails and the parameters obtained in the field tests they were plotted in dispersion graphs us which lineal and no-lineal regressions were applied in the intention of to evaluate which mathematical model was adapted better to each proposition. For the correlation qs x Nspt the logarithmic model presented larger correlation coefficient (R2) and significance (p <0,05), in the relationship qs x p0 the quadratic form obtained larger R2, however the behavior of the curve was not suitable with the one of the soil, being accomplished the option by the logarithmic model that was highly significant (p <0,01). The correlation qs X PL didn't show any statistically significant and the choice of the format of the lineal curve was based on the behavior of the soil, same not presenting the largest value of R2. In the case to to the proposed correlations it s possible to conclude that they can be used as initial estimate of project being indispensable the execution of pullout tests to prove the safety with relationship to the values of adopted qs. / A adoção da técnica de solo grampeado no projeto de contenção de taludes ou escavações vem sendo cada vez mais freqüente, com isto se faz necessário um maior numero de estudos sobre a estimativa da resistência ao arrancamento (qs) em função de parâmetros de ensaios de campo para os mais variados tipos de solos brasileiros. O objetivo desta pesquisa foi propor correlações para a estimativa de qs em função de ensaios de campo, e também comparar os valores encontrados nos ensaios de arrancamento com estimados em formulações existentes. O estudo foi realizado em um talude de solo residual jovem de origem gnáissica, Viçosa MG. No campo efetuaram-se os ensaios de penetração (SPT), sondagem pressiometrica de Ménard (PMT), sondagem dilatometrica de Marchetti (DMT) e ensaios de arrancamento em 12 grampos, confeccionados somente com a bainha. A montagem do sistema de arrancamento foi diferente da proposta por outros autores e se mostrou eficaz. Os valores de qs obtidos nos ensaios de arrancamento e os encontrados pelas correlações existentes para cada grampo foram comparados através de estatísticas adequadas para cada análise. Os parâmetros dos ensaios de campo utilizados nas correlações propostas Nspt, PL, e p0, foram determinados pela média de suas magnitudes ao longo dos grampos. As resistências ao arrancamento encontrada para cada grampo e os parâmetros obtidos nos ensaios de campo foram plotados em gráficos de dispersão nos quais se aplicaram regressões lineares e não-lineares no intuito de avaliar qual modelo matemático se adequou melhor a cada proposição. Para a correlação qs x Nspt o modelo logarítmico apresentou maior coeficiente de correlação (R2) e significância estatística (p<0,05), na relação qs x p0 a forma quadrática obteve maior R2, porém o comportamento da curva não foi condizente com o do solo, sendo realizada a opção pelo modelo logarítmico que se mostrou altamente significante (p<0,01). Já a correlação qs X PL não apresentou nenhum modelo estatisticamente significante e a escolha do formato da curva linear foi baseada no comportamento do solo, mesmo não apresentando o maior valor de R2. Quanto às correlações propostas conclui-se que podem ser utilizadas como estimativa inicial de projeto sendo imprescindível a execução de ensaios de arrancamento para comprovar a segurança quanto aos valores de qs adotados.

An electrophoretic deposition (EPD) process of micro-quartz (MQ) powder is applied to carbon fibers (CFs) with the aim to enhance their interfacial bond to cementitious matrices and to investigate its influence on the microstructural and mechanical properties of the CFs itself. The electrophoretic mobility of the MQ particles with negative charge in aqueous media was confirmed by potential sweep experiments and zeta-potential measurements. High amounts of MQ were successfully deposited onto the fiber surface, as proven by scanning electron microscopy. Single-fiber tension tests and thermogravimetric analysis showed that EPD treatment had little impact on the tensile properties and thermal stability of the modified fibers. However, storing the CFs in cement pore solution impaired temperature stability of untreated and modified fibers. X-ray diffraction and Raman spectroscopy reveal specific changes of CF's microstructure upon EPD treatment and immersion in pore solution. Single-fiber pullout tests showed that the pullout resistance of MQ-modified CFs was enhanced, relative to untreated CFs. This augmentation can be explained by an enhanced interlocking mechanisms between CF and matrix due to the deposited quartz particles on the CF surface.