GBFS (granulated blast furnace slag) has a hydraulic property in natural environment by its hydration reaction. In this study, in order to investigate the progress of hardening and self-restoration characteristics of GBFS under different conditions such as plain water, seawater and Ca(OH)2 solution, the change in the unconfined compressive strength and the percentage of hydration reaction of GBFS were observed. It can be seen from test results, the strength of GBFS cured in seawater and Ca(OH)2 solution increases in the early stage due to the rapid hydration reaction which occurs earlier in comparison with the plain water. In addition, in the same level of hydration reaction, the restoration of strength depends on the condition of curing water. Furthermore, based on the relation between the strength and the hydration reaction of GBFS which was taken from the test embankment constructed 11 years ago, it is clarified that the strength of GBFS under long term curing in natural condition also increases with the hydration reaction.
