Avaliação do comportamento eletroquímico do concreto auto adensável exposto ao ataque de cloretos

Abstract

The selection of construction materials requires knowledge and responsibility. Selfcompacting concrete is considered a successful innovation in the construction industry as it dispenses the conventional process of vibration or compactation due to its ability to flow and fulfill the spaces of the moulds only by its own weight, resulting in a more compact material, with less pores. Self-compacting concrete has been widely used in Japan and Europe. In Brazil, its use is still restricted, due to the limited availability of standards and mixing design methods, as well the limited professiona knowledge regarding the material behaviour. The aim of the present work is to investigate mechanisms of degradation in self-compacting concrete exposed to chloride attack by electrochemical impedance spectroscopy (EIS) the, in order to prescribe the influence of using self-compacting concrete on the durability of reinforced concrete structures. Also this study evaluated the influence of curing time on the transport of chloride in self-compacting concrete, the corrosion processes of the reinforcement and diffusion coefficient of chlorides in concrete. For the analysis of the penetration of chlorides in the material, the specimens were subjected to wet and dry cycles in an accelerated test for a period of two years. The results showed distinct patterns in relation to durability, where the self-compacting concrete showed greater durability compared to conventional concrete. The chloride diffusion coefficient was in the order of 10-12, in general the diffusion coefficient of conventional concrete was superior in relation to self-compacting concrete, and the difference between both concretes reduced with exposure time and curing age.In the lastest ages - around two years of exposure, there is an increase in the diffusion coefficient in both concretes probably related to the increase in the size of pores and microcracks caused by penetration of the chloride and by the increase in the concentration gradient