ABSTRACT
Experimental work, done in laboratory, which is described in this paper, consisted of determination of the steel reinforcement corrosion using the electrical resistance method. The reinforcement was in the form of the steel bars, which were embedded in the concrete beams 50 mm x 50 mm x 340 mm (Fig. 1). Concrete beam with embedded steel bar. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig266_1.tif"/>
Results of the non-destructive measurements were compared to data from subsequent destructive tests in the laboratory conditions. The steel bars were removed from each concrete beam to detect the real corrosion decrease of cross section by weight decrease evaluation process.
Laboratory testing of reinforcements were realized particularly for verification of the procedures for measuring the electrical resistance, and for verifying the suitability of the method for realistic use in monitoring of in-situ corrosion in the next period.
The next part of research was focused on corrosion simulation of reinforcement in reinforced concrete with the program ATENA 3D. The results from experiment and corrosion simulation were used for modeling of a real corrosion on bridge structure.
From obtained results, it is possible to conclude that the methods for the detection rate (quantity) of reinforcement corrosion can used as a major criterion in the decision-making process, of reinforced concrete structures redevelopment. These quantitative methods are useful for determining the rate of steel reinforcement attack embedded in the monitored reinforced concrete structure with a known input electrical resistance.
The numerical modeling of reinforcement corrosion confirms that already the small corrosion, namely the small percentage of corroded surface causes the formation of cracks within the cross section near the reinforcement. The increase of corrosion products (rust) causes the connection of cracks from the inside to outside due to increase of the radial tensile stresses. Those cracks weaken the bond between concrete and reinforcement and cause the subsequent concrete cover dropping out.
From results of the 3D models (model 1 – without transverse stirrups, model 2 – with transverse stirrups) follows that the stirrups (transfers stiffeners) did not influence greatly the crack pattern at crosssection – in both models approximately the same crack development was obtained. However, according to expectation, the stirrups did influence the crack width. Using the stirrups causes the crack width to decrease in longitudinal direction about 11% (direction x). Nevertheless, the limit crack width was exceeded in both models, without using the vertical loading induced bending stresses. The crack width in the vertical direction (direction z) was not markedly changed.
In practice, it means that it is necessary to place the greater emphasis on diagnostics in cases where the corrosion of reinforcement was identified. Moreover, it means to verify the rate of concrete cover damage and the decrease of the bond. Based on the diagnostics and analysis, it is necessary to consider carefully whether it is possible to retain moderately damaged parts of concrete cover and repair them, or is it necessary to replace one by the new layer.
In conclusion, it is important to emphasize the need for a combination of different methods in monitoring the state of the steel reinforcement in terms of obtaining, if possible, the most comprehensive quantitative and qualitative information. Therefore, increasing knowledge related to the further development of research in this area has justification.
