Concrete properties can be greatly improved with the advanced mineral admixtures such as steel slag powder. Used in combination with Super-plasticizer admixture, steel slag powder can lead to economical high performance concrete with enhanced durability and reduced cement content. The effectiveness of steel slag powder on suppressing Alkali Aggregate Reaction is analyzed. The effectiveness of steel slag powder on suppressing AAR expansion was assessed using the method of ASTM C441 and accelerated test method. Results show that mineral admixtures with steel slag powder as partial replacement for Portland cement in concrete is an effective means for controlling expansion due to AAR. At most a 50% decrease in expansion rate of mortar bars can be found.