Sulphates usually affect calcium aluminates in cements. Sulphate ions might have negative effects on cement hydration and it would be a reason of decrease in cement strength. In this study, the effects of Na2SO4 solution on the concretes made from OPC with oil shale ash (OSA) addition (0, 15 and 30%) were investigated Concretes with 15% OSA gave the lowest value of Length Change Factor (LCF). Addition of an optimum amount of super-plasticizer increases positive properties of the concrete with 15% OSA addition, binds free Ca(OH)(2) in OPC, makes its composition more effective, prevents massive alkali-aggregates reactions showing that this addition rate is proper.