Publication: Modificaciones estructurales del gel C-S-H irradiado con láser continuo de CO₂
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2019-01-10
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Universidad Complutense de Madrid
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Abstract
El principal componente del cemento hidratado, responsable de sus propiedades mecánicas y resistentes, es un silicato cálcico hidratado de naturaleza amorfa denominado, según la nomenclatura de la Química del Cemento, gel C-S-H. La estructura de este compuesto se asemeja a la de los minerales tobermorita y jenita. Sin embargo, mientras que el gel C-S-H presenta una estructura en forma de cadenas finitas de tetraedros de silicio con estequiometría no definida, los otros dos minerales poseen una estructura en forma de cadenas infinitas y estequiometrías concretas, siendo Ca5Si6O16(OH)2·4H2O para la tobermorita y Ca9Si6O18(OH)6·8H2O para la jenita.La estructura y la composición del gel C-S-H han sido estudiadas por múltiples autores desde principios del siglo XX hasta la actualidad a través del desarrollo de diferentes modelos estructurales, coloidales y computacionales. Todos ellos presentan varios aspectos en común, como la versatilidad a la hora de determinar características fundamentales del gel C-S-H, como las diferentes relaciones Ca/Si y los valores de longitud media de cadena. Asimismo, estos modelos deben poder explicar su estructura laminar y fibrosa, y la incorporación de cationes extraños dentro de su estructura. Todas estas características del gel C-S-H se modifican en función de las condiciones de síntesis, la composición inicial del cemento, el tiempo de hidratación, la temperatura de curado y la presencia de adiciones, entre otras variables. Así, la relación Ca/Si puede oscilar entre 0.5 y 2.3, la longitud media de cadena tomar valores de 2 e, incluso, mayores de 20...
The main component of hydrated cement, to which the material owes its mechanical properties and strength, is an amorphous calcium silicate hydrate known, in Chemistry of Cement nomenclature, as C-S-H. Its structure is reminiscent of but not identical to the minerals tobermorite and jennite. The differences between them consist in the nature of their silicon tetrahedral chains, finite and with an undefined stoichiometry in the gel, and infinite and with a specific stoichiometry in the minerals: Ca5Si6O16(OH)2·4H2O for tobermorite and Ca9Si6O18(OH)6·8H2O for jennite.C-S-H gel structure and composition have been the object of ongoing research since the early twentieth century, for which structural, colloidal and computational models have been developed. All such models share a number of features, such as versatility when determining the essential characteristics of the gel, including its Ca/Si ratio and mean chain length. They must also be able to explain its laminar and fibrous nature, as well as the uptake of extraneous cations in its structure. All these characteristics of C-S-H gel vary depending on synthesis conditions, initial cement composition, hydration time, curing temperature and the presence of additions, among others. The Ca/Si ratio, for instance, may range from 0.5 to 2.3 and mean chain length may be 2 or greater than 20...
The main component of hydrated cement, to which the material owes its mechanical properties and strength, is an amorphous calcium silicate hydrate known, in Chemistry of Cement nomenclature, as C-S-H. Its structure is reminiscent of but not identical to the minerals tobermorite and jennite. The differences between them consist in the nature of their silicon tetrahedral chains, finite and with an undefined stoichiometry in the gel, and infinite and with a specific stoichiometry in the minerals: Ca5Si6O16(OH)2·4H2O for tobermorite and Ca9Si6O18(OH)6·8H2O for jennite.C-S-H gel structure and composition have been the object of ongoing research since the early twentieth century, for which structural, colloidal and computational models have been developed. All such models share a number of features, such as versatility when determining the essential characteristics of the gel, including its Ca/Si ratio and mean chain length. They must also be able to explain its laminar and fibrous nature, as well as the uptake of extraneous cations in its structure. All these characteristics of C-S-H gel vary depending on synthesis conditions, initial cement composition, hydration time, curing temperature and the presence of additions, among others. The Ca/Si ratio, for instance, may range from 0.5 to 2.3 and mean chain length may be 2 or greater than 20...
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Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Química Inorgánica, leída el 22-06-2018