Original Paper(Vol.61 No.10 pp.837-844)

An Evaluation of the ASR-Degenerated Condition for the Footings Based on the Long Term Exposure Tests under the Actual Condition

Tetsuya KOHNO, Shoichi NAKATANI, Takashi YAMAMOTO and Toyoaki MIYAGAWA

Abstract:In these days, the footings degenerated due to Alkali Silica Reaction (ASR) have been discovered in Japan. To perform an appropriate diagnosis for those footings, a lot of knowledge for the footings degenerated due to ASR have to be obtained, such as the occurrence condition of ASR in footings, the internal degradation conditions. Accordingly, the road administrator canft maintenance them, and this is a big problem to carry on safe road network. So, the long term exposure test has been done under the actual condition up to now, and the crack and strain of the footings, temperature and water level of the exposure environmental have been measured to get those knowledge. At first, we analyzed the difference of the degradation of footings cased by environmental condition, in water, air and under the ground, from measured data, and we examined the reason of the difference. And we showed that the strain of steel is affected by reflection from temperature. Further out, we identified the internal degradation mechanism in footings. Finally, the characteristic value, for example temperature, needed for the occurrence of ASR and the evaluation of the degenerated condition in the footings are revealed.

Key Words:RC footings, Hygrothermal environment, Strain behavior over time, Ultrasonic determination, Maintenance