Partículas de sílice modificadas orgánicamente como adiciones para la matriz de concreto hidráulico: síntesis, formulación y propiedades
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Fecha
2023
Tipo
tesis doctoral
Autores
Mora Castro, Ernesto José
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Las estructuras de concreto hidráulico en sus elementos de borde (como fachadas, losas de techo, muro, entre otras) están expuestas al medio ambiente, por esto en lugares muy lluviosos o húmedos, es conveniente disminuir la permeabilidad de estos elementos para mejorar tanto su durabilidad como su funcionabilidad. El presente trabajo describe la mejora de matrices de materiales de cementicias, y posteriormente concretos, dotándolos de hidrofobicidad. Esta modificación hidrofóbica de los materiales se realiza de forma integral (externa e internamente), en contraposición a los tratamientos superficiales que sólo modifican las superficies de borde. El anexo B1 describe la construcción y el uso de nuevos moldes antiadherentes basados en politetrafluoroeteno (Teflon®, PTFE). El anexo B2 reporta la síntesis y caracterización de micropartículas de sílice funcionalizadas con grupos n-dodecilo (-C12H25) y luego su incorporación a matrices de concreto. El carácter hidrófobo de los materiales derivados se consiguió en los especímenes formulados incluso al utilizar pequeñas proporciones de las micropartículas de sílice modificadas. Los ensayos de resistencia a la compresión confirmaron que la estabilidad mecánica de cubos de mortero relacionados, no se ve afectada por su modificación con sílice hidrofóbica. Por último, el anexo B3 ofrece una aproximación a la aplicación de la técnica desarrollada para formular concretos hidrófobos, al incorporar agregados gruesos con rasgos de absorción de agua extremos, como es típico en la práctica de la construcción. El principal resultado de este estudio fue que el carácter hidrófobo se incrementó en todos los casos, independientemente del tipo del agregado grueso. Sin embargo, se confirmó que las características de absorción de agua de los materiales de concreto ciertamente dependen de las características de absorción de agua de los agregados gruesos elegidos. También se comprobó que una impregnación previa de los componentes gruesos, con una suspensión líquida de micropartículas de silice hidrófobas, mejora en gran medida el carácter hidrófobo del concreto derivado.
Hydraulic concrete structures are often exposed to the environment, in very rainy or humid places, it is desirable to decrease the permeability of concrete materials to water to improve both their durability and their functionality. The present work describes the enhancement of concrete materials by endowing them hydrophobicity. This hydrophobic modification of concrete materials is performed integrally (externally and internally), in contraposition to surface treatments which only modify external surfaces of concrete. Hydrophobic concrete materials needed to be prepared without using demolding oils that could lead to false positive results of hydrophobicity. Thus, the first chapter describes the construction and use of new anti-adherent molds based on polytetrafluoroethene (Teflon®, PTFE). The second chapter reports the synthesis and characterization of silica microparticles functionalized with n-dodecyl (-C12H25) groups and their incorporation into concrete composite matrices. The hydrophobic character of the derived concrete materials was achieved even using small proportions of the modified silica microparticles in the formulations. Compressive strength tests confirmed that the mechanical stability of concrete composite mortars is not affected by their modification with hydrophobic silica. Finally, third chapter offers an approximation to the application of the developed methodology to formulate hydrophobic concrete, using common coarse aggregates having varied water absorption traits as is ubiquitous in the construction practice. The main outcome of this study was that the hydrophobic character was enhanced in all the cases regardless of the use of a particular coarse aggregate. However, the water absorption characteristics of the final concrete materials depend on the water absorption traits of the chosen coarse aggregates. It was also proven that a preliminary impregnation of the coarse aggregates with a liquid suspension of hydrophobic silica microparticles greatly enhanced the hydrophobic character of the derived concrete materials.
Hydraulic concrete structures are often exposed to the environment, in very rainy or humid places, it is desirable to decrease the permeability of concrete materials to water to improve both their durability and their functionality. The present work describes the enhancement of concrete materials by endowing them hydrophobicity. This hydrophobic modification of concrete materials is performed integrally (externally and internally), in contraposition to surface treatments which only modify external surfaces of concrete. Hydrophobic concrete materials needed to be prepared without using demolding oils that could lead to false positive results of hydrophobicity. Thus, the first chapter describes the construction and use of new anti-adherent molds based on polytetrafluoroethene (Teflon®, PTFE). The second chapter reports the synthesis and characterization of silica microparticles functionalized with n-dodecyl (-C12H25) groups and their incorporation into concrete composite matrices. The hydrophobic character of the derived concrete materials was achieved even using small proportions of the modified silica microparticles in the formulations. Compressive strength tests confirmed that the mechanical stability of concrete composite mortars is not affected by their modification with hydrophobic silica. Finally, third chapter offers an approximation to the application of the developed methodology to formulate hydrophobic concrete, using common coarse aggregates having varied water absorption traits as is ubiquitous in the construction practice. The main outcome of this study was that the hydrophobic character was enhanced in all the cases regardless of the use of a particular coarse aggregate. However, the water absorption characteristics of the final concrete materials depend on the water absorption traits of the chosen coarse aggregates. It was also proven that a preliminary impregnation of the coarse aggregates with a liquid suspension of hydrophobic silica microparticles greatly enhanced the hydrophobic character of the derived concrete materials.
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Palabras clave
CONCRETO, HIDRÁULICO, PARTÍCULA, SILICIO