| The Beijing-Shanghai High-Speed Railway (abbr. as BS), also known as the Jinghu High-Speed Railway, is a 1,318 kilometres (819 mi) long high-speed railway that will connect two major economic zones in the People's Republic of China: the Bohai Sea Rim and the Yangtze River Delta. The bridge concrete was long-term subjected to natural environment (air corrosion, variational temperature and humidity) and service environment (increased frequency loading, material and structure fatigue), the durability of bridge concrete had long been the focus of engineering and academic. Polyurea technology (Spray Polyurea Elastomer, abbr. as SPUA) is recognized as most effective way of coating protection for the bridge concrete. The complicated ambient condition of BS made severe challenge to the performance and application of SPUA coating. In this paper, SPUA conventional coating performance both in jobsite and laboratory simulation was studied, the crack patten, water absorption, adhesion, choloride content, rebar corrosion of SPUA coated concrete subjected in load-NaCl immersion was also discussed. The main conclusions are as follows:Firstly, the development trend with time of curing time, tensile properties, adhesion and chemical resistance of BS jobsite samples were analysised, it showed that, this sample was fast set SPUA type, the curing time and chemical resistance conforms to the―BS Temporary Technology Standard‖, after 4 days, tensile property and adhesion meets the requiments of―BS Temporary Technology Standard‖, which is 16 MPa tensile strength, 400% Elongation, 2.5 MPa.Secondly, Jobsite samples of CangZhou, Jinan, Xuzhou, Bengbu, Changzhou and Kunshan section of BS were investigated, tesile performance development trend under diffirent T and RH was researched, It was showed that, diffirent section under different ambient condition, the tested time was diffirent, Changzhou (>35°C) was 2days, Bengbu (<0°C) was 4days, Kunshan (RH>95%) was 5days, Jinan(>35°C) was 6days, Cangzhou and Xuzhou (<0°C) was above 7days.Thirdly, the comparative study of performance of three kinds of surface preparation system jobsite samples were studied, the results confirmed: epoxy was dependent on environmental temperature and humidity, compatibility with SPUA in low temperature was poor, BS SPUA surface preparation sysem should use polyurethane surface preparation system.Fourthly, self-bending load - chloride immersion test device was used to study the interaction of load and on the SPUA chloride coating and concrete coating of SPUA, the results were as follows: 1) The crack width of SPUA coating concrete was 0.021~0.376mm, uncoated concrete crack width was 0~0.319mm, when the bending load ratio was 0.1, SPUA can inhibit the development of cracks on the concrete surface and it can effectively inhibit the closure of cracks and crack propagation, which can effectively increase durability;2) Water absorption test showed that: water absorption of SPUA coating concrete was 0.62% ~ 1.35%, water absorption of uncoated concrete was 5.86% ~ 7.89%, the water absorption of SPUA coated concrete was 16% to uncoated concrete. SPUA coating can effectively prevent water intrusion, thereby enhancing the durability of concrete bridges;3) Adhesion test showed that: when bending load ratio was 0, the adhesion of SPUA coated concrete was 2.8MPa ~ 5.27MPa, when bending load ratio was 0.5, the adhesion of SPUAcoated concrete was 1.25MPa ~ 2.7MPa, bending load can reduce the adhesion of SPUA coated concrete;4) Chloride ion content test showed that: bending load-NaCl immersion after 90d, the chloride content of SPUA coated concrete was 1E-4~0.3481, uncoated concrete was 0.15 to 0.8564, after immersed 150d, the chloride content of SPUA coated concrete was 1E-4~0.453, uncoated concrete was 0.466~1.4622, it indicating that SPUA has good resistance to chloride ion diffusion capacity;5) Resistivity of concrete and half-cell potential test results showed that: steel corrosion of uncoated concrete in concrete probability was > 95%, SPUA coated was about 5% probability. SPUA protective coating can effectively prevent steel corrosion in BS bridge concrete, It can effectivity enhanced the durability of concrete bridges;Finally, the construction of BS SPUA construction technology was discussed, comparing different construction scheme, surface preparation system, spraying proportioner equipment and spray gun, designed special SPUA spray trailer for BS SPUA application; and evaluated the comprehensive technical economic of two kinds of construction plan.Through the above experiments and academic analysis, this paper provides a scientific and reasonable test data for Beijing-Shanghai High Speed Railway, establishes foundation for the application of SPUA technology in the protection of bridge concrete structure, also supplies reference for the congener bridge engineering construction. |
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