Mei KUDO

Experimental and Analytical Study on the Influence of Crack on Drying and Wetting Behavior of Concrete Members

Takumi SHIMOMURA

Water -induced reinforcement corrosion into concrete is one of the most serious problems affecting the durability of concrete structures. Therefore, a method to predict water penetration into concrete precisely is required. On the other hand, durability of concrete structures is deteriorated by the occurrence of cracks on the surface of concrete. Resistivity for water penetration into concrete is decreased by the crack. The purpose of this study is to evaluate the influence of crack on drying-wetting behavior of concrete members. 
At first, drying-wetting tests of concrete having a crack were carried out. Experimental results showed the amplitude of drying-wetting becomes larger as the crack width becomes larger. Based on the result, numerical simulation method was developed, which can well simulate drying and wetting behavior of concrete members with cracks.
Secondly, drying-wetting tests of concrete having a plurality of various patterns of cracks was carried out. As results, in the case of concrete with multiple cracks, it was found that the drying-wetting behavior of concrete can be predicted by the same way as a case of a single crack by using the average value of crack-width and crack-interval.
In additionCparametric numerical simulation of long-term behavior of concrete members with cracks revealed that the crack strain, which is defined as crack width divided by crack interval, is an effective index for the influence of crack on long-term drying and wetting behavior of concrete members and that monthly model of environmental action is acceptable to predict long term drying-wetting behavior of concrete under natural environment.
Finally, the validity of threshold value of crack width in current design code was evaluated based on analytical results. As results, it was confirmed that the critical crack width that has been used in practical design is reasonable from the viewpoint of permeation of water.