Investigation of old Building Concrete(13. Four school gymnasiums，42-47 years old)

Investigations were carried out on the deterioration of four reinforced concrete gymnasiums built at the beginning of Showa era. They were located in Hokuriku district of centra1 Japan. The investigation revealed crack distribution， degree of carbonation of concrete and corrosion of reinforcing stee1. They are important factors for estimating the durabi1ity of the structures ・It was a1so found that the graded size aggregate mortar finish (ca11ed Araidashi in Japanese) was very effective for keeping concrete from carbonation and plaster was poor for the protection effect. The durability of reinforced concrete is stil1 to be clarified based on the compiled investigation of old bui1- dings