| Qingdao Bay Bridge under construction (hereinafter referred to as the bridge) in the north cold salt sea is the first large bridge cluster subject of our country, in order to avoid the influence of sea water, salt fog corrosion, freeze-thaw damage and other marine environment factors, Polyurea coating protection technology was applied to improve the durability and safety of the bridge. According to the environment characteristics of the bridge, the marine corrosion resistance of a novel Spray Polyurea Elastomer (Spray Polyurea Elastomer, referred to as SPUA) such as water absorption, adhesion resistance, frost resistance, resistance to chloride ion penetration were tested by macroscopic and microscopic methods, the main contents are as follows:Firstly, the strength development of the novel SPUA material with curing age was explored. According to environment of the bridge, the macro performance of SPUA was tested by the methods such as sealed immersion,dry-wet circulation,freeze-thaw cycle and salt fog, and the micro-topography of SPUA was analyzed by scanning electron microscope (SEM). Research results show that, the novel SPUA system cured very fast, and suitable for constructing in marine environment. After 180 day exposure under corrosion environment above, the tensile strength of SPUA was respectively decreased by 4.0%, 6.4%, 9.0% and 25.7%. Macro and micro test results show that SPUA has good Marine corrosion resistance.Secondly, water absorption and adhesion of SPUA coated concrete in different corrosion medium were studied. The results of water absorption test show that concrete protective coatings could markedly decrease water absorption of concrete. After concrete was dealed with Epoxy and SPUA protective coatings, the water absorption were decreased by 94.4% and 96.3%. They also show that water absorption could availably evaluate the waterproof ability and resistance to acid and alkali corrosion of concrete protective coatings. The results of adhesion test show that freeze-thaw cycle affects the adhesion of Epoxy coated concrete seriously. Epoxy coating fell off after 600 times, while the adhesion of SPUA coated concrete was 4.02MPa, only dropped by 3.6%. Thirdly, the frost resistance of Epoxy and SPUA coated concrete in 3.5% salt solution was studied. Research results showed that SPUA coated concrete has better frost resistance compared to Epoxy coated concrete, the frost resistance would dropped greatly if there were defects on concrete protective coatings. Curing age of SPUA coated concrete has little influence on frost resistance. After 600 times freeze-thaw cycling, the surface of 1d-cured SPUA coated concrete was intact, and the quality and relative dynamic elastic modulus remained unchanged.Fourthly, the resistance to chloride penetration of concrete protective coating of polyurea and epoxy by rapid chloride penetration test (RCP), nature soak and dry-wet circulation was studied. Research results show that, RCP method has correlation to nature soak method. Both methods could evaluate resistance to chloride diffusion of the above coated concrete effectively. In the condition of RCP method, concrete protective coatings could improve the resistance to chloride penetration of concrete. And the resistance value increased with the thickness. In the condition of nature soak method, compared with concrete, the chloride diffusion coefficient of SPUA coated concrete after immersion is 0.724×10-12m2/s, reduced by 67.9%. In the condition of dry-wet circulation method, the chloride diffusion coefficient of concrete with no coating increased by 40.6% compared with nature soak, but SPUA coated concrete remained unchanged.Finally, the construction process of SPUA technology in Qingdao bay bridge was introduced, also discussed the application of the new construction process that prefabricating protective coating in template lining before pouring concrete.Through the above experiments and academic analysis, this paper provides a scientific and reasonable test data for Qingdao bay bridge, establishes foundation for the application of SPUA technology in the protection of marine concrete structure, also supplies reference for the congener marine engineering construction. |
