Abstract: Calcium carbide slag is a kind of industrial waste slag mainly composed of calcium hydroxide，and it features strong alkalinity，a large output and is easy to cause environmental hazards. To be utilized as a resource，calcium carbide slag is calcined to obtain active lime as it is an important auxiliary raw material for steelmaking or other industries instead of natural active lime. The physical phase and composition of calcium carbide slag before and after calcination are examined with XRF and XRD to determine the feasibility of converting calcium carbide slag into active lime. The physical and chemical changes that occur during the heating process of calcium carbide slag are investigated via differential thermal analysis. By setting different calcination temperatures and duration，the optimum calcination regime to obtain the lime with the best activity is determined. The study unveils that the lime obtained by calcining carbide slag at 900 ℃ for 1.5 h has the highest activity.

Key words: Calcium carbide slag, Calcination, Active lime, Physical and chemical changes, Activity