Improvements of carbonation and chloride resistance of concrete treated with nano-modified coatings

For studying the influences of aging on the carbonation and chloride resistance of concrete treated with nano-modified coatings, three types of organic film-forming paints, such as polyurethane, epoxy resin, and chlorinated rubber, were selected, and nano-modified paints with the addition of 0.5, 1.5, and 3.0 wt.% of nano-SiO2 or nano-TiO2 particles were prepared and applied on concrete specimens. Ultraviolet irradiation, accelerated carbonation, and Coulomb electric flux experiments were performed on coated concrete specimens. Results indicated that carbonation and chloride resistance of concrete with polymer coatings deteriorates gradually with aging. The addition of nano-SiO2 or nano-TiO2 can substantially enhance coating density, alleviate the aging effects of coatings, thus increasing the carbonation or chloride resistance of coated concrete and extending the coatings' service lives. However, a suitable nano-SiO2 or nano-TiO2 dosage of about 1.5 wt.% exists. A new service life prediction model for coatings based on the carbonation or chloride resistance of coated concrete is established. Among three coatings, nanomaterials in the chlorinated rubber coating showed the most substantial promotion of service life, and nano-TiO2 is relatively more effective than nano-SiO2 in extending the service lives of coatings.