Análise de influência da carbonatação do concreto nos ensaios de esclerometria e ultrassom em concreto

Abstract

Evaluation of hardened concrete quality using nondestructive testing methods has been more widely used in Brazil. Among the many types of non-destructive testing, the ultrasonic pulse velocity method and the rebound test are those most applied ones due to their low cost and usability. However, many factors can have considerable influence on nondestructive tests results. For that reason, a proper analysis of the results is necessary for a good interpretation of the data. During its using life, concrete is susceptible to chemical and physical changes that can affect its properties and quality negatively. Concrete carbonation is an example of how a chemical reaction can act over concrete properties. It is a complex reaction that basically occurs due to carbon dioxide penetration through concrete pores. As the carbonation penetrates the concrete, the layers of carbonated concrete have an alkalinity decrease. On the other hand, concrete carbonation leads to a decrease of concrete porosity, what can be positive under some perspectives. This project aimed to analyze if changes on concrete properties due to carbonation reaction have any influence over ultrasonic pulse velocity and rebound test results. Cylindrical concrete specimens and concrete cubes were molded and then split into two groups. One of this groups was placed into a chamber with high concentration of carbon dioxide in order to induce and accelerate carbonation reaction. The other group was placed in the laboratory atmosphere and used as control sample. Both groups were then tested using ultrasonic pulse velocity and rebound test methods. Then the carbonation depth of the cylindrical concrete specimens and concrete cubes were measured and analyzed. The top and the bottom of the cylindrical specimens had low rate of carbonation and the measured depth was of only few millimeters. The same was observed in the concrete cubes, where the carbonated surface was less than five millimeters deep. Under the circumstances of concrete carbonation of this project, no influence over the results of the nondestructive testing methods applied was noticed