Suitable methods for enhancing the volume stability of steel slag utilized as fine aggregate were determined. The effects of steam treatment at 100 ℃ and autoclave treatment under 2.0 MPa on the soundness of steel slag sand were investigated by means of powder ratio, linear expan-sion, compressive and flexural strength. DTA, EDX, XRD and ethylene glycol methods were em-ployed to analyze both the treated slags and susceptible expansion grains. Experimental results indi-cate that powder ratio, content of free lime and rate of linear expansion can express the improvement in volume stability of different treated methods. Steam treatment process cannot ultimately prevent specimens from cracking and decrease of strength, but mortar made from autoclave treated slag keeps integration subjected to hot water of 80 ℃ until 28 d and its strength do not show significant decre-ment. The hydration of over-burn free lime and periclase phase are the main cause for the disintegra-tion or crack of untreated and steam treated steel slag’s specimens. Autoclave treatment process is more effective than steam treatment process on enhancement of volume stability of steel slag.
