Effect of carbonation curing on durability of cement mortar incorporating carbonated fly ash subjected to Freeze-Thaw and sulfate attack

High-calcium fly ash (HFA) is available in large quantity produced by coal-based electrical power plants. Up to now, the utilization of HFA in construction materials is limited. In this research, carbonation treatment of HFA in association with carbonation curing was applied for stabilization of hazardous residues and CO₂ sequestration. The improvement on durability of carbonation-cured cement mortar incorporating carbonated HFA against coupled freeze–thaw and sulfate attack was investigated. The results show that the synergy of carbonation treatment and carbonation curing mitigated the deterioration of relative dynamic elastic modulus and compressive strength caused by coupling action of freeze–thaw and sulfate attack. The collaborative carbonation treatment and carbonation curing can also reduce the content of expansile free-CaO, as well as the components that would expand under sulfate attack conditions, such as CH and aluminates. On the other side, the results of MIP show that carbonation curing improved the pore structure and decreased the permeability of cement mortars specimens.