STUDY ON DAMAGE TO CONCRETES ATTACKED BY SULFATES

The damage processes of an ordinary concrete and a high strength concrete, attacked by solutions of 10% Na2 SO4 (in mass, the same below), 10%MgSO4 and Qinghai salt lake solution in cycles of drying-immersion are studied. The results show that the damage process of concretes attacked by Na2 SO4 exhibits a decreasing stage followed by improved performance stage, finally the failure stage because the SO2- 4 ions lead to expansion damage to concrete. Abrasion and mass loss of concrete are the main deterioration form when concrete exposed toMgSO4 solution or to Qinghai salt lake solutions, its relative dynamic elastic modulus and mass decreased first, then kept stable, lastly to failure. Moreover, corrosion elements of concretes attacked by sulfates are studied by SEM, EDS and XRD.