Validação de modelos de penetração de cloretos e CO2 em concreto na cidade de Pelotas/RS.

Abstract

Concern is growing over the loss of durability and performance of concrete structures.These characteristics are directly related to the requirements of design, execution and maintenance, so it is of fundamental importance to consider the environmental action in the building, since the concrete behaves differently due to the location in which it will be exposed.Among the forms of deterioration can be cited as the main action of chlorides and CO2 that can compromise the functionality and useful life of concrete structures. As a way of evaluating the action of these aggressive agents and the various factors that influence the deterioration process, prediction models were developed to estimate the durability of the concrete structures after a certain time.Thus, this research had as objective to verify the compatibility of models of prediction of useful life, existent in the literature with the process of carbonation and penetration of chlorides in concrete structures, exposed in the city of Pelotas / RS.For this purpose, the natural test was performed by exposing 60 specimens (cylindrical 10 cm in diameter and 20 cm in height) in five different locations of the city (in the Center, Porto and Fragata and two sites in the TrêsVendas neighborhood) where they were implanted 12 specimens in each locality.After a predetermined time of 4, 8, 12 and 16 months of exposure, a sample with 3 elements from each site was taken to the laboratory for cutting and subsequent application of silver nitrate and phenolphthalein to determine the depth of chlorides and CO2, respectively. Then the model of Bob (1996) for comparison and analysis of chlorides and models of Smolczyk (1976), Vesikari (1988), Morinaga (1990), Helene (1997) and Possan (2010) for carbonation were applied.As a result, significant values were found for both chloride and CO 2 penetration, mainly due to the city climate that favored these processes. It was noticed a tendency of increase between the first and last measurement for all the analyzed places, however the penetrated depth did not have a linear behavior, being the time variable that interfered significantly in the result.The application of the model of Bob (1996) presented differences between the values obtained with its application and the data of the natural test, however it was adequate for some situations, showing great potential in describing the behavior of the depth of chlorides over time to the city of Pelotas, requiring some adjustments in the input parameters.Regarding the carbonation process, with the application of the models of prediction of useful life, it was possible to observe that the model of Helene (1997), despite the differences between the values obtained with its application and the data of the natural test, represented satisfactorily the penetration of CO2 over time, quite possibly due to the characteristics of the concrete used.