Análise da deterioração do concreto por carbonatação natural com exposição às classes de agressividade ambiental marinha e respingos de maré

Abstract

Carbonation is one of the main phenomena to be avoided in the concrete, since it can degrade the concrete structures by itself, but it is also one of the ones responsible for the triggering of the process of corrosion of the reinforcement, through the depassivation of the steel present. Among the main factors that influence carbonation are the type and quantity of cement, water/binder ratio, quality in the execution, concentration of carbon dioxide in the atmosphere, relative humidity and temperature, that is, this phenomenon is influenced both by the composition of the factors related to the exposure environment. Within this context of exposure environment, it is necessary to know the classes of environmental aggression, and in the present study the classes evaluated are the marine, which represents a strong aggressiveness to the structure, and that of tide springs, which represents a very strong aggressiveness the structure. For the study, specimens of 15 cm x 15 cm x 50 cm were prepared, made of concrete classes C15 and C30, with water/cement ratios of 1.0 and 0.7, respectively. After the curing period, the beams were transported to the exhibition sites, located in the coastal city of Barra Velha / SC, most of the beams were allocated in a building in front of the sea, some on the ground floor and others on the 5th floor, while a beam was exposed on the stones of the beach, in an environment of very strong aggressiveness to the structure. After two months of exposure, a pH indicator, called phenolphthalein, was sprayed with a 5 cm cut in the beam with a circular saw and then sprinkled the phenolphthalein solution in the cross section of the beam. With the aid of a pachymeter the carbonation depth was measured and it was verified that there was a clear difference between the carbonation depth in the concrete of class C15 and that of the concrete of class C30, difference that, with two months of exposure, was not perceived Comparing the two classes of environmental aggressiveness. The introduction of the mathematical models in this study was important for the realization of the life expectancy and carbonation forehead prediction for many years of exposure, making an analysis and comparison between the mathematical models and a comparison between the test value and the theoretical value which would give two months of exposure. This study has a theoretical and practical bias, demonstrating the carbonation process, and concepts such as degradation, durability and useful life of reinforced concrete structures.