Research Of Durability Of Surface-film-forming Protective Coating On Marine Concrete

Concrete is the most important structural material in marine basic construction. However, marine concrete works for a long period in the bad environment, which cannot achieve the expected service life. Surface-film-forming protective coatings applied over the concrete surface, can effectively protect the concrete against all kinds of corrosion and infringement of environment, improve the durability of concrete, and prolong its service life. But protective performance of coatings may be down for the long-term ocean environmental impact. Therefore, it is important and significant to research the durability of different protective coating.This paper selected four kinds of surface-film-forming protective coatings, referred to as A, B, C, D coating. Indoor simulation experiments were tested on different concrete, including single corrosion factor and multiple corrosion factor experiment. The durability of different types of protective coatings were evaluated by comparing the variation of water absorption, compression strength, breaking strength, chloride ion diffusion coefficient of the benchmark specimen and specimen with coatings. The following can be obtained:(1) Coatings on concrete can improve the resistance of concrete specimens to chemical erosion, coatings have better anti-acid erosion ability in the early, and then weakened ability to resist acid erosion for peeling off with the growth of the immersion time; the acid erosion of B coating is the stongest. The alkali of B, C, D coatings are all well. Four kinds of coating are on different certain levels against the erosion of sulfate solution, where D coating has the best sulfate corrosion resistance ability.(2) B and D coatings have the better freeze-thaw resistance capability. Coatings on concrete can significantly reduce the quality rate in the process of freeze-thaw cycle, and improve the compression strength, breaking strength retention of the concretes after the freeze-thaw cycle.(3) The performance of protective coatings is influenced by photo and thermal aging, and the aging properties of different coatings are significantly different. The ageing resistance of coatings is as follows:D coating is best, B, C coatings take second place. (4) Compared with the thermal aging, photoaging has more serious impact on the performance of coatings, which is due to the each other promote role of ultraviolet light and heat. Infrared spectra of acrylic polyurethane coating shows that ultraviolet light aging can lead to the breaking of C-N and-NH-COO-bonds in the coating, with the degradation of the coating.(5) Wet and dry cycles result in cracking and falling off of coatings and concrete. After the same cycle of multiple corrosion factor experiment, the water absorption of specimens with D coating is much smaller than others, and compression and breaking strength much bigger. In summary, D coating shows better resistance to multiple corrosion factor.(6) Photo and thermal aging contributs to the turbidity and crack of coatings as well as internal structural damage. As a result of wet and dry cycles and freeze-thaw cycles after photo and thermal aging, the damage compound factors effect occured, which accelerated the aging of coatings. Consequently, the influence of multiple corrosion factor on performance of coatings is more obvious than that of single corrosion factor(ultraviolet light, heat, acid, alkali, salt and so on).