Degradation mechanisms of Portland cement mortar under seawater attack and drying-wetting cycles

This study investigates the degradation mechanisms of Portland cement mortar under multiple salts attack and drying-wetting cycle condition. The results indicate that the sulfate combined with chloride salts retard the chloride diffusion and mitigate the deterioration of mortar under drying-wetting cycles. However, the presence of sulfate, magnesium and chloride ion result in increased consumption of port-landite and causes the decalcification of C-S-H, thus aggravating the degradations. Microstructure analysis shows that the sulfate ion in chloride solution refines the pore structure, while the presence of sulfate and magnesium ion in chloride environment increases the porosity and pore volume, which accelerates the ingress of corrosive ions. (C) 2019 Elsevier Ltd. All rights reserved.