STUDY ON CORROSION OF REINFORCING BAR IN RECYCLED CONCRETE

摘要

Studies on utilization of recycled aggregate to concrete structures have been performed increasingly in the decade in Japan in order to reduce the environmental load. Applying recycled aggregate made from structures' concrete in Chugoku district, it is indispensable to investigate how much chloride is contained in recycled aggregate and how chloride contained in recycled concrete affects corrosion in reinforcing bars, because sea sand was used widely in the same district from 1960's to 1980's, chloride of which was not sufficiently washed off. In the present study, internal chloride content of recycled aggregate produced in Chugoku district was investigated, and then the influence of the internal chloride on corrosion of reinforcing bar in concrete was studied in which NaCl equivalent to 3-kg/m~3-chloride ion is added in order to accelerate corrosion. Major parameters were water-cement ratio and combination of aggregates, i.e., whether recycled coarse and/or fine aggregates are mixed or not. All concrete specimens were exposed to 40℃ and one day-salty rain every week. The results indicated that recycled aggregate contained water-soluble chloride of 0.2 kg/ton for coarse aggregate and 0.36 kg/ton for fine aggregate, and that lower water-cement ratio was effective in reducing corrosion area not only in normal concrete but also in recycled concrete.