Enhancing chloride ion penetration resistance into concrete by using graphene oxide reinforced waterborne epoxy coating

To prevent early failure of concrete due to infiltration of chloride ions from
environment, epoxy resin nanocomposites modified with graphene oxides (GOs) were prepared using a solution blending process and then sprayed onto testing blocks of concrete. Microstructural analysis revealed that the GOs were uniformly dispersed inside the epoxy matrix, and covalent cross-links were formed between the GO and epoxy matrix. Water surface contact angles of concrete coated with the nanocomposites coatings were found to increase firstly but then decrease with the increase of the added GO contents. When the GO content was 0.3 wt%, the contact angle was 96.1°±0.3°, whereas that of pure epoxy resin was 77.5° ±0.3°. At the same GO content, water absorption and chloride diffusion coefficient of the coated concrete are much lower than those of the uncoated samples. The enhancement mechanisms for the chloride ion penetration resistance are attributed to the formation of cross-linking in the composite coating, improved hydrophobicity and shielding effects of the GOs.