Long-term performance of concrete surface coatings in soil exposure of marine environments

The present research addresses the performance of coated concrete samples after 88 months of natural exposure to coastal soil of the Persian Gulf. A concrete mixture proportioned with water-to-cement ratio of 0.5 was used for casting the reference and all coated specimens. Five types of surface coatings were investigated. Samples were extracted at different ages of 9, 36, and 88 months to monitor carbonation depth and chloride ion penetration into concrete. Slight signs of carbonation are observed for the reference concrete and specimens coated with cementitious coatings. Chloride ion concentration profiles are analyzed during the exposure period. Chloride ion diffusivity is investigated for each sampling time. Surface chloride build-up is also monitored. Time to corrosion initiation is calculated and incorporated as a means of ranking coating efficiencies. Among all studied coatings, aliphatic acrylic and polyurethane are proved to reduce chloride ion concentration most effectively. This resulted in increasing the simulated time required for corrosion initiation in soil exposure at marine environments.