Abstract: An Artificial reef characterized by its high strength was prepared. Its cementitious material is composed of -0.088 mm steel slag stabilized by a hot-simmering method and blast furnace slag from Ansteel company; its fine and coarse aggregates are also steel slag stabilized by a hot-simmering method with sizes from 0.088 mm to 19 mm. By analyses of X-ray diffraction, field emission scanning electron microscope, differential thermal and infrared absorption spectrum for the hydration characteristic of the cementitious material, it can be found that a large amount of calcium silicate hydrate which mainly contributes to the early strength characterized by its low-alkalinity and a small amount of ettringte are both formed at early hydration stage. With the development of the hydration process, the calcium silicate hydrate and ettringite which is filling in the gaps of the hydration system are increasing continually. Therefore, the long-term strength can be improved by calcium silicate hydrate and ettringite. 

Key words: Artificial reefs, Steel slag concrete, Cementitious material, Hydration characteristic, Calcium silicate hydrate, Ettringite