Enhancing the Salt Frost Durability of Concrete with Modified Epoxy Composite Coating

We propose a durable and easy-to-operate treatment, modified epoxy composite coating (MECC)., as a potential alternative to traditional epoxy resin protectants to enhance the protection of concrete structures. This new material consists of epoxy resin as the base material, dimethyl carbonate as the solvent, and modified amines + polyaniline as a composite curing agent that reacts with epoxy resin to form a film over the surface of concrete, thus protecting concrete structures from surface cracking, peeling and spalling when exposed to chloride. Salt frost resistance test indicated that the MECC specimens had lower water absorption and much higher salt frost resistance. Compared with the non-coating (NS) specimens, after 200 freeze-thaw cycles, the relative dynamic elastic modulus (RDEM) was 21.62% higher and the mass loss was merely 19.14% of that of the NS specimens. Better performance was achieved as compared with ordinary epoxy resin coating (EC) and silicate coating (SC), too. After 120 days of erosion in 10.0% NaCl, the coating could effectively prevent environmental liquids and chloride from intruding through the cracks. The reason behind the increased salt frost durability is that treatment with MECC improved the internal structure of concrete and made its surface dense enough to prevent the intrusion of environmental liquids and chloride. Under repeated freezing and thawing, the degree of chloride-induced damage and the icing pressure inside the concrete were greatly reduced. This relieved the frost damage inside the concrete and elongated the service life of concrete.