Resistance of plain and blended cement mortars exposed to severe sulfate attacks

► Plain and blended cement mortars were immersed into Na2SO4 and MgSO4 solutions. ► From the aspect of chemical attacks, MgSO4 solution is more damaging than Na2SO4. ► Conversely, Na2SO4 is more harmful than MgSO4, when physical attacks are considered. ► The addition of pozzolan improved mortar resistance to Na2SO4. ► However, pozzolan mortars are aggravated by MgSO4 from a chemical standpoint. To emphasize the effect of physical sulfate attack on pozzolanic additions, the resistance of plain and blended cement mortars was investigated using 10% Na2SO4 and MgSO4 solutions under four exposure regimes which included the standard conventional exposure and field-like exposures that created the physical sulfate attack. Although the performance of blended cement mortars was observed to be better under a conventional exposure regime, the damage in blended cement mortars was more severe under the exposure regimes that promoted the physical sulfate attack in a Na2SO4 environment. However, the physical attack by MgSO4 was not apparent. Overall, MgSO4 was found to be more damaging than Na2SO4 from the aspect of chemical attack; however Na2SO4 was more harmful than MgSO4 as far as the physical attack is considered.