Maintenance of concrete structures under severe environment in coastal zone of the Japan Sea

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1) Diffusion coefficient of chloride ions in mortar with admixtures was measured. Influences of kind and amount of admixtures on diffusion coefficient were investigated. Prediction equation of diffusion coefficient was proposed as a function of porosity and specific surface area of pore structure.2) Exposure test of mortar specimens was conducted. Specimens were exposed in more than ten points in Niigata Prefecture. It was revealed that part of chlorides that had reached concrete surface can penetrate into concrete. Long term chloride ingress can be predicted based on the result of short term exposure test.3) Local transport process of airborne salt around an actual concrete structure was measured. Numerical simulation method for transport process of airborne salt was developed.4) Damage of concrete structures in Ishikawa Prefecture was investigated. Deterioration grade, amount of airborne salt and chloride ingress were examined.5) Effectiveness of surface coating and water repellent was evaluated by laboratory test.6) Damage of concrete bridges by de-icing agent was investigated in Northern Tohoku region. It is clarified that damage by de-icing agent may be localized.7) Resistant of sprayed mortar against combined action of salt attack and frost damage was examined by electric migration test.