Evaluación de la carbonatación en hormigones elaborados con cemento de bajo carbono LC3
Fecha
2018-06
Autores
Lorenzo Ulloa, Danitza
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Editor
Universidad Central “Marta Abreu” de Las Villas. Facultad de Construcciones. Departamento de Ingeniería Civil.
Resumen
La presente investigación evalúa el comportamiento de los procesos de carbonatación en especímenes de hormigón fabricados con cemento de bajo contenido de carbono (LC3), respecto a los producidos con cemento Portland (P-35), situados en dos sitios de exposición (Punta Matamoros y Sede Universitaria, ambos en Cayo Santa María), con condiciones ambientales diferentes, el primero en una zona marina tropical con un nivel de agresividad ambiental muy alta, y el segundo en zonas aisladas con un nivel de agresividad ambiental alta. Para la determinación de la profundidad carbonatada se emplea la técnica de la fenolftaleína, según la NC 355:2004. Para entender este fenómeno se tienen en cuenta parámetros como el tipo y contenido de cemento, la estructura de poros del material y el sitio de exposición.
Generalmente los elementos elaborados con cementos ternarios resultan más sensibles a la carbonatación que los producidos con Cementos Portland, debido al efecto de la sustitución de clínker con la consecuente reducción de la alcalinidad, así lo corresponde los resultados de los ensayos realizados en el sitio de exposición de la Sede.
Por otro lado, al evaluar los hormigones situados en Punta Matamoros, se obtiene que los elementos elaborados con LC3 muestran una profundidad carbonatada menor respecto a los hormigones producidos con cemento Portland, situación atípica, que puede deberse, a que los hormigones producidos con cemento Portland tienen una mayor cantidad de compuestos solubles que lixivian con el agua de mar y afecta la estructura de poros del mismo, quitándole compuestos que le proporcionan la alcalinidad al material.
En cuanto a los iones cloruro, en el sitio de exposición de la sede universitaria, según la NC 120:2014, las concentraciones de cloruros presentes en las muestras no superan el 0,20 %, por lo que no existe riesgo de corrosión en estos momentos. En el sitio de exposición en Punta Matamoros, la muestra M-32 (cemento P-35), presenta concentraciones de iones cloruro superiores, con respecto a la muestra M-381 (cemento LC3), esto puede deberse a la difusión de los iones cloruro hacia abajo desde la superficie de la losa, pues como la superficie de la losa se seca varias veces, la disminución de agua en los poros centraliza los iones cloruro en la superficie, lo que causa la difusión acelerada de los mismos hacia abajo.
The present investigation evaluates the behavior of the processes of carbonation in concrete specimens manufactured with cement of low carbon content (LC3), with respect to those produced with Portland cement (P-35), located in two exposure sites (Punta Matamoros and University Headquarters, both in Cay Santa Maria), with different environmental conditions, the first in a tropical marine zone with a very high level of environmental aggressiveness, and the second in isolated areas with a high level of environmental aggressiveness. For the determination of the carbonated depth, the phenolphthalein technique is used, according to NC 355: 2004. To understand this phenomenon, parameters such as the type and content of cement, the pore structure of the material and the exhibition site are taken into account. Generally, the elements made with ternary cements are more sensitive to carbonation than those produced with Cement Portland, due to the effect of the clinker substitution with the consequent reduction of alkalinity, so corresponds the results of the tests carried out at the exhibition site of the Headquarters. On the other hand, when evaluating the concretes located in Punta Matamoros, it is obtained that the elements made with LC3 show a lower carbonated depth compared to the concretes produced with Portland cement, an atypical situation, which may be due to the fact that the concretes produced with Portland cement they have a greater amount of soluble compounds that leach with seawater and affect the pore structure of the same, removing compounds that provide alkalinity to the material. As for chloride ions, in the exhibition site of the university headquarters, according to the NC 120: 2014, the concentrations of chlorides present in the samples do not exceed the 0,20 %, so there is no risk of corrosion at this time. At the exposure site at Punta Matamoros, sample M-32 (cement P-35), presents concentrations of higher chloride ions, with respect to sample M-381 (cement LC3), this may be due to the diffusion of ions chloride down from the surface of the slab, because as the surface of the slab dries several times, the decrease in water in the pores centralizes the chloride ions on the surface, which causes the accelerated diffusion of them downwards.
The present investigation evaluates the behavior of the processes of carbonation in concrete specimens manufactured with cement of low carbon content (LC3), with respect to those produced with Portland cement (P-35), located in two exposure sites (Punta Matamoros and University Headquarters, both in Cay Santa Maria), with different environmental conditions, the first in a tropical marine zone with a very high level of environmental aggressiveness, and the second in isolated areas with a high level of environmental aggressiveness. For the determination of the carbonated depth, the phenolphthalein technique is used, according to NC 355: 2004. To understand this phenomenon, parameters such as the type and content of cement, the pore structure of the material and the exhibition site are taken into account. Generally, the elements made with ternary cements are more sensitive to carbonation than those produced with Cement Portland, due to the effect of the clinker substitution with the consequent reduction of alkalinity, so corresponds the results of the tests carried out at the exhibition site of the Headquarters. On the other hand, when evaluating the concretes located in Punta Matamoros, it is obtained that the elements made with LC3 show a lower carbonated depth compared to the concretes produced with Portland cement, an atypical situation, which may be due to the fact that the concretes produced with Portland cement they have a greater amount of soluble compounds that leach with seawater and affect the pore structure of the same, removing compounds that provide alkalinity to the material. As for chloride ions, in the exhibition site of the university headquarters, according to the NC 120: 2014, the concentrations of chlorides present in the samples do not exceed the 0,20 %, so there is no risk of corrosion at this time. At the exposure site at Punta Matamoros, sample M-32 (cement P-35), presents concentrations of higher chloride ions, with respect to sample M-381 (cement LC3), this may be due to the diffusion of ions chloride down from the surface of the slab, because as the surface of the slab dries several times, the decrease in water in the pores centralizes the chloride ions on the surface, which causes the accelerated diffusion of them downwards.
Descripción
Palabras clave
Alcalinidad, Carbonatación, Cemento, Estructura de poros, Lixiviar, Iones, Alkalinity, Carbonation, Cement, Pore structure, Leaching, chloride ions