Surface protection of concrete by new protective coating

Abstract

This work aims at enhancing the concrete performance using a new protective coating named as asphaltic polyurethane (As/PU) coating, which prepared at different NCO/OH molar ratios (1, 1.1, 1.2, 1.3 and 1.4). As/PU coating was prepared by the reaction of a fixed amount of methylene diphenyl diisocyanate (MDI) with the equivalent weight of mixed polyol (80% asphalt and 20% polyester). The performance of the prepared coatings was examined by the determination of curing time, dry film thickness (DFT), adhesion strength, and flexibility. The formulated coatings were applied on 28-days-cured concrete. The coated and uncoated concrete samples were evaluated regarding contact angle, water absorption, and chloride permeability. The resistivity of coated and uncoated concrete against sulfuric acid and sodium chloride solutions was evaluated. The preliminary results proved that the increase of NCO/OH molar ratio results in a remarkable increase in DFT, adhesion strength accompanied by decrease in curing time and flexibility of the prepared coatings. The concrete sample coated by As/PU with NCO/OH molar ratio of 1.4 demonstrates the highest contact angle associating with the lowest water absorption and chloride permeability. In addition the increase in NCO/OH molar ratio of the applied coating has a positive impact on the mechanical properties of concrete. The coated concrete samples recorded higher resistivity against acid and salt attack compared to uncoated one. This proves the eco-efficient use of the prepared As/PU as an innovative protective coating for concrete.