Abstract: In order to promote the application of steel slag in cement concrete, the cementitious properties of steel slag were investigated by XRD, nonevaporable water content determination of hydration products, strength test and particle size analysis. The influence of fineness on cementitious properties of steel slag was studied. The results show that the pure steel slag paste can harden slowly, however its cementitious properties is weak. The hydration process of cement and steel slag is similar. In early age the hydration rate of steel slag is much lower than that of cement, whereas in later age the hydration rate of steel slag is higher than that of cement, especially after 90 d. The hydration rate of steel slag is improved to a certain extent by increasing the specific surface area before 90 d in contrast with a reduced rate after 90 d. The hydration degree of different fineness steel slag reaches to a similar extent after 180 d.

Key words: converter steel slag, cementitious properties, cement, hydration, specific surface area