Enhanced Long-Term Resistance of Concrete with Marine Sessile Organisms to Chloride Ion Penetration

Yuichiro Kawabata, Ema Kato and Mitsuyasu Iwanami

Journal of Advanced Concrete Technology, 10, 151-159, 2012

Reinforced concrete (RC) structures in marine environments are generally affected by harsh marine environmental actions, resulting in early performance degradation mainly due to chloride-induced deterioration. In such conditions, corrosion of rebar progresses rapidly, and also the cross-sectional area of rebar is reduced and consequently structural performance of RC structures will be degraded. In contrast, the surface of concrete structures is often covered with many marine sessile organisms under marine tidal and submerged conditions. These marine sessile organisms have been empirically known to enhance the durability of concrete though the effectiveness is not appropriately evaluated.
This paper describes the long-term resistance of concrete with marine sessile organisms to chloride ion penetration in concrete. The effect and its sustainability of marine sessile organisms on chloride ion penetration in concrete were investigated through field exposure test and laboratory test. From the test results, the basal membrane, which is a matrix of marine sessile organisms, adheres to concrete strongly on a long-term basis though some gaps between concrete and the basal membrane can be observed. In addition, experimental results and simplified simulation clarified that the attachment of marine sessile organisms can enhance the long-term resistance of concrete to chloride ion penetration.

The authors' efforts on conducting long-term real exposure tests on the effect of marine sessile organisms on chloride penetration are appreciable. Though more results are required for quantification in order to be able to incorporate it into the design process, it is among the first of its kind for this topic.
(Prof. S. Tangtermsirikul)