Study on material properties of concrete structures exposed to extremely high temperature due to severe accident

In March 2011, the Fukushima Nuclear Power Plant suffered a severe accident because of the tsunami waves when the Great East Japan Earthquake occurred and because of this accident the containment vessel was exposed to high temperatures. However, studies related to concrete with extremely high temperature exposure are very few. For this reason, the aim of this study is to understand the structural soundness of the concrete structures exposed to high temperature by conducting heating experiments of concrete specimens which were made to reproduce the concrete structure of the Nuclear Plant. From the test results, cracks were observed at the specimen surface and they grew with the increase of temperature. Additionally, it was observed that concrete crack volume grew to temperatures around 800°C, but this growth saturated more than this temperature to 1000°C. It was observed that the amount of water content inside concrete decreased with temperature. Moreover, the chemical composition change of concrete was accompanied with the water content decrease. Results on other material properties are also to be presented. (author)