In Japan, many RC structures are damaged by chloride attack under marine environments. Based on this situation, establishment of “Repair Design System” for damaged structures and “Durability Oriented Design System” for newly constructed structures is strongly required. The indispensable information in these design systems is a quantitative evaluation of environmental conditions, in which structures are exposed. However, enough research data on this topic are not obtained. In this study, 2 years' exposure test of small size mortar specimens in 19 ports located from Hokkaido to Okinawa was carried out. From test results and their analysis, quantitative evaluation of environmental factors, affecting deterioration of mortar specimens is discussed. Through a series of experimental work, several environmental factors are selected as key factors that affect the steel corrosion in mortar and mortar deterioration.
