Influence of cracks on chloride penetration in concrete
Audenaert, K.; De Schutter, G.; Marsavina, L. (2009). Influence of cracks on chloride penetration in concrete, in: Denton, S. et al. (Ed.) Concrete: 21st century superhero: building a sustainable future: proceedings of the annual international fib symposium. pp. 8
In: Denton, S.; Clark, G. (Ed.) (2009). Concrete: 21st century superhero: building a sustainable future: proceedings of the annual international fib symposium. The Concrete Society: Camberley. ISBN 9781904482604. , more
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Document type: Conference paper
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Concrete, Chloride penetration, Cracks, Durability, Service life |
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- Audenaert, K., more
- De Schutter, G., more
- Marsavina, L.
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| Abstract |
Chloride initiated reinforcement corrosion is the main durability problem for concrete structures in a marine environment. If the chlorides reach the reinforcement steel, it will depassivate and start to corrode in presence of air and water. Since the corrosion products have a larger volume than the initial products, concrete stresses are induced, leading to spalling and degradation of the concrete structures. If cracks, caused by early drying, thermal effects, shrinkage movements or overstress, are present in the concrete, the penetration of chlorides is much faster than in uncracked concrete. In this way, the corrosion process is initiated earlier and the service life is decreased drastically. In order to investigate the influence of existing cracks in concrete structures on the penetration of chlorides and the resulting service life, a test program was set up at the Magnel Laboratory for Concrete Research of Ghent University, Belgium in cooperation with the "Politehnica University of Timisoara", Romania. Part of the testing program was carried out on concrete specimens with artificial cracks. These artificial cracks were manufactured using thin copper plates with a thickness of 0.2 mm or 0.3 mm. The copper plates were positioned inside the fresh concrete for a depth of 5, 10, 15 or 20 mm and removed after approximately 4 hours. In order to study the influence of the amount of cement, two types of concrete were considered with a different amount of cement and a constant W/C ratio. From the age of 28 days, diffusion test were carried out in a 3.5 % NaCl solution. Each month, during 10 months, the chloride penetration depth was measured on 2 concrete specimens. The specimens were split and on eacht of the freshly split sections, a 0.1 MAgNO3 solution was sprayed. The chloride penetration depth is measured at 19 points, visually checking the presence of white silver chloride precipitation. With these penetration profies, the influence of the cracks on chloride penetration was quantified by comparing the cracked zone of the specimens with the uncracked zone. The ratio of the chloride diffusion coefficient of the cracked concrete zone to the chloride diffusion coefficient of the uncracked zone was called the crack influence factor, depending on the crack depth. The crack width was not taken into account because for crack widths of 0.2 mm and 0.3 mm no influence was found of the crack width. |
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