In order to solve the problem of natural aggregate exhaustion, several types of industrial waste have been studied for recycling of construction materials. In general, steel slag has been used as aggregate in concrete, however, steel slag has a problem of causing volume expansion by F-CaO. Therefore, in this study, the expansion properties are compared with aging period to solve the problem of the steel slag expansion. According to the test results, the expansion of the steel slag decreased regardless of the types of steel slag during aging period. And, the Electronic Arc Furnace Oxidizing Slag(EAF) had the better reduction in expanding than the Converter Slag(CS).