Determinação do coeficiente de difusão de íons cloreto em concretos com fibra na condição saturada

Abstract

There are several pathologies related to structure of concrete that influence the durability and lifespan of such constructions, which are essential factors to the appropriate performance of these systems in their projectual functions. The chemical attack of ions chloride is one such pathology that is particularly aggressive to steel-concrete systems, especially in coastal environments, where structures are exposed to sea mist. This noxious agent, besides causing the dissipation of armature and eventual corrosion, alters the composition and initial properties of the concrete, which causes the shortening of its lifespan. To study the effects of such pathology on concrete, this project analyzes the penetration of ions chloride in structures with different resistant classes, fiber concentrations in each trace, and different contamination ages. Specifically, the project was conducted with resistant classes C20, C25 and C40, and for each class, two different steel fiber concentrations were used (0.38% and 0.77%); the samples were contaminated in different time intervals (223, 251, and 279 days). For the aforementioned study, the steel-concrete samples were submerged in a saline solution with concentration of 250 grams per cubic centimeter as in the Accelerated Modified Method developed by Helene Guimarães (2007), and the following aspects were investigated: chloride concentration in different depths (5, 10, 15, and 20 milliliters); superficial coefficient determined by chloride profiles obtained by depth concentration; and the diffusion coefficient of ions chloride, which indicates resistance of a specific concrete system to agent penetration. The results from titrations and concentration calculations indicated that neither presence of steel fibers nor the class of resistant influenced the process of chloride ions penetration in concrete samples; contamination time was the main factor to interfere with the chemical attack.