This paper discusses about deterioration of plain concrete structures constructed approximately fifteen to fourty-four years ago. Structures have been exposed to sea water and sea breeze.
　Tests in the fields consisted of surface observation and compressive strength done by way of Schmitt hammer and ultra sonic method. Unit volume weight absorption ratio, average depth of neutralization, compressive strength were experimented from core specimens at the laboratory. Some specimens were used for estimation of mix proportioning and salt content in concrete.
　Results of surface observation showed the degree and reasons of visible deterioration. Based on the laboratory work, deterioration of concrete was classified according to the standard of evaluation proposed.
　It was concluded that the method of casting, vibrating and curing might be more important factor affecting deteriration of concrete.