Abstract
Cracks in reinforced concrete structures exposed to a marine environment or de-icing salts can cause major durability issues due do accelerated ingress of chloride ions. In this study, the influence of autonomous crack healing by means of encapsulated polyurethane on the chloride ingress perpendicular to cracks was evaluated. This was done quantitatively by determining perpendicular-to-crack chloride profiles by means of profile grinding followed by potentiometric titration and qualitatively through visualization of the chloride penetration front by means of the AgNO3 spray method. The resulting chloride profiles showed that the healing mechanism was able to reduce the chloride concentrations in the direct vicinity of the crack to a large extent and to reduce the perpendicular-to-crack chloride penetration, especially further away from the exposed surface. Visualization of the chloride penetration front showed some variation in crack healing. For some healed samples almost no additional chloride ingress was found compared to uncracked samples, others showed a slightly enhanced ingress at the crack location but less perpendicular-to-crack chloride penetration compared to untreated cracked samples. Generally, the reduced amount of chlorides present in the concrete matrix due to crack healing will enhance the durability and service life of concrete structures.
Highlights
Crack appearance is one of the leading causes of durability problems in reinforced concrete structures
The chloride profiles for the uncracked samples (UNCR) samples are in all three areas more or less constant and independent from the distance to the cut surface
When the crack is healed by polyurethane, only in the first layer (0-2 mm distance from the crack surface) an elevated chloride concentration can be noticed compared to the UNCR series
Summary
Crack appearance is one of the leading causes of durability problems in reinforced concrete structures. For structures which are exposed to a marine environment or de-icing salts, the presence of cracks provides accelerated pathways for chlorides to enter the concrete matrix [1,2,3,4]. This leads to an accelerated onset of reinforcement corrosion and further deterioration [5,6,7]. The ideal way of dealing with the unavoidable appearance of cracks in concrete would be to modify the concrete to give it the ability of restoring cracks by itself This idea of creating a so called self-healing concrete grew during the last two decades. At the moment of crack appearance, one or more of the capsules break, causing a release of the healing agent in the crack
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