Yukihito ASANO
Environment of corrosion and corrosion prediction of weathering steel bridge
Eiji Iwasaki
The decrease of the life cycle cost is an important problem in the steel bridge.A lot of bridges of the weathering steel have been constructed.The weathering steel material is appropriately used.It is a weathering steel material that has an excellent anticorrosion property for a long term.The steel material can be used under amount of marine is salt less than 0.05mdd(mg/dm2/day).The situation of corrosion is different because of the part and the position in the bridge where weathering steel was used.The important factor for corrosion of weathering steel is marine salt that occur in splash area of seaside.The humidity in nearby surface of girder, dew by the difference between temperature on surface of girder and temperature in moist air and dew by deliquescence due to salinity are factors of corrosion.To construct corrosion prediction system for anticorrosion design in bridge, the relation between corrosion and corrosive factors are investigated based on the observation of corrosive environment and deduction of thickness of test piece made on weathering steel in Niigata Prefecture.To observe corrosive environment, thermometer, hygrometer, ACM sensor and dry gauze type and Doken type apparatuses to collect airborne salt are set in bridge section.
The obtained results in this study are as follows.(1)The difference of corrosion in each part of the bridge was observed by results of thermometer, hygrometer, ACM sensor and dry gauze type apparatus.(2)Under on the lower side of web and the upper side of web, the relation of the corrosion speed during year was shown from the quantity of electricity of ACM sensor and airborne salt measured by dry gauze method.(3)The lower side and upper side of web in which airborne salt almost the same,factor other than the cause of airborne salt is observed because corrosion speed is different.(4)ISO wet time and ACM wet time are different. It became it as well as a past research.(5)Investigation of thickness of Decreasing amoun rust, thickness of board and forecast of quantity of rust was done.(6)Small test pieces, the corrosion of the lower surface is slower than that of the upper surface.(7)By result of the survey of small test piece of two years, It is pointed out that corrosion speed parameter BSMA was different in the current forecast procedure.
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