Kotaro KOIKE

Construction of Mesoscale Model for Crack Formation of Concrete due to Corrosion Expansion of Rebar

Takumi SHIMOMURA

This study was focused on a methodology to estimate the corrosion amount if reinforcement steel of concrete structures, based on the relationship between corrosion cracks and rebar corrosion observable at surface in finite-volume regions. Previous studies, characteristics of corrosion cracks and reinforcement corrosion were only locally related. This research aims to correlate the corrosion cracks and rebar corrosion within finite volume regions. Three topics were studied in this research.
As start, Electrochemical corrosion tests, using several concrete specimens, were conducted to reveal a spatial non-uniformity on corrosion cracks and rebar corrosion.
Secondly, to understand the expansion behavior of corrosion, cylindrical concrete specimens were made with a ring attached on its outer edges and its expansion strain was measured.
Thirdly, a numerical simulation regarding the occurrence and progress behavior of corrosion cracks was carried out, and this was compared with experimental results of previous researches, which had study the influence of internal cracks behavior. In addition, a corrosion cracks prediction model considering these three topics was evaluated.
As a result, it was found that the occurrence sequence of surface cracks and internal cracks changes with the changing ratio of concrete coverage and rebar space. Therefore, two types of prediction models, one considering ratio of concrete coverage and the other considering rebar space, were proposed. By using these model, it was confirmed that the corrosion amount of rebar, predicted from the behavior of corrosion cracks on the concrete surface, has a correlation with the actually measured corrosion amount. From this, it was confirmed that the mesoscale model, averaging material degradation, such as cracks and corrosion amount, in units of several tens of centimeters is an effective method to predict corrosion amount of reinforcement steel of concrete structure by considering corrosion cracks.