Research On The Application Of Polyurea Protective Technology For Hong Kong-Zhuhai-Macao Bridge Concrete

Hong Kong-Zhuhai-Macao Bridge is located in Lingdingyang waters, linkingHong Kong, Macao and Zhuhai.The engineering construction mainly includes:the mainbridge and the undersea immersed tube tunnel. The undersea immersed tube tunnel issoaked by seawater for a long time. The sea area is in tropical marine climate with hightemperature and salinity. The service environment is complex. The design life of thebridge is120years and its durability issues has always been concerned.The technology of spray polyurea elastomer is considered to be one of the mosteffective ways of the bridge concrete protection, which has been successfully applied inprotecting the Beijing-Shanghai high-speed railway and Qingdao Jiaozhou Bay Bridge.But with combined structure by bridge and tunnel and complex environment conditions,Hong Kong-Zhuhai-Macao Bridge has put forward the severe trial to the performanceand construction technology of polyurea coating.This paper mainly studies influences of temperature, humidity, soak of acid, alkaliand salt on polyurea coating and the mechanics performance of geotextile polyureacomposite coating and the influences of different thickness of coating on frost resistanceof coating concrete under simulated condition in the laboratory. The conclusions are asfollows:(1) The study of influences of temperature on polyurea coating and geotextilepolyurea composite coating indicates: Under the condition of-30℃, the coating canreach the stable mechanical property value on the45th day, and the tensile strength,elongation at break and tearing strength of polyurea coating shows:16.62MPa,449.49%and77.69N/mm; under the condition of25℃and50℃, the coating can reach stablemechanical property value on5th day and2th day. Under above temperature, themechanical property value is higher than the demanded value in the actual project.(2) The study of influences of humidity on polyurea coating and polyureageotextile composite coating shows: Under the condition of normal temperature and60%humidity, the coating can reach stable mechanical property value on the6th day.For the polyurea coating, the tensile strength, elongation at break and tearing strengthshows:16.98MPa,481.27%and78.31N/mm; when the humidity is80%, the elongationat break and tearing strength of polyurea coating shows:509.51%. The result shows thatits elongation at break and tearing strength increases with the increase of humidity andthe mechanical property value can satisfy the demand in the actual project. (3) When the polyurea coating is soaked in seawater, the wear quality has noobvious change with the increase of the soaking time. After soaking120days andAkron abrasion machine reaching1.61km, the coating’s wear quality is0.1102g. Theresult shows that the polyurea coating has a good wearing resistance and can satisfy thedemand in the actual project.(4) The mechanical property of polyurea coating and polyurea geotextile compositecoating is reduced in different degree by soaking in corrosive mediums. The changetrend mechanical property is almost unanimous after soaked in three corrosive mediums.Although the mechanical property declines, it remains at a high level and can satisfy thedemand in the actual project.(5) The frost resistance of coating concrete is related to the thickness of coating.When the thickness of coating is1mm and the freezing-thawing cycles reach400times,the relative dynamic modulus of polyurea protective begins to decline; when thethickness of coating is2mm, the relative dynamic modulus of concrete does notdecrease. It shows that the frost resistance of concrete has improved significantly whenthe thickness of coating is2mm.(6) It discusses the technology of immersed tube tunnel polyurea protection. Inorder to prevent zero elongation of polyurea in seams, sticking the geotextile in advanceto make sure the enough polyurea can participate in swell-shrink deformation, whichavoids polyurea tearing.Through above experimental research and analysis, it can provide theoreticalsupport and corresponding experimental data for the construction of the HongKong-Zhuhai-Macao Bridge and lay a foundation for the future application of polyureatechnology in the field of concrete protective.