Study Of Polyurethane Waterproofing System Used In High-Speed Railway Bridge

High-speed railway which has developed in many countries is the result of achievements owning to modern science and technology, and also is an important symbol of railway modernization. More and more countries have chosen it as the most important way of passenger transport. In order to protect bridges made of reinforced concrete used in the railway from corrosion, a variety of measures have been taken. Duing to the high frequency impact vibration of vehicles, expansion-shrinkage caused by all kinds of climate fators, defects are inevitable. With external water entering the cracks appearing on the surfaces of bridges, a lot of problems need solving such as strength degradation and frature of reinforced concrete and reinforcement corrosion. It is high time that meaurses be taken to prolonge service life, keep running safe and reduce operation maintenance cost. Spraying waterproof material on the serface of the bridge deck is a better way according to engineering practice than thickening concrete during the design and construction.According to the layout of Chinese government, passenger dedicated lines named "four vertical and four horizontals" and intercity passenger travel system in the densely populated area have been planed.16,000 km high-speed passenger line will be put into operation in 2020 as planed. The area of waterproof layer can reach over 100 million square meters and a huge market will appear.The designed life of the high-speed railway is as long as 100 yuears. On the purpose of ensuring safety and durability of the high-speed railway the speed of which is as high as 250 km/h-300 km/h, waterproof layer is very important.Therefore, a kind of dedicated high-performance coating used in waterproof is needed urgently. It should satisfy all kinds of standards such as high strength, high elongation,aging resistance,acid and alkali resistance, light fastness and high tear strength.Bridge waterproof is a system engineering which is not only related to different positions and products, but also related to construction procedures and different components. Waterproof products involve deck waterproof coating, beam-end expansion joint, drainage slope inlet and so on.Related operations include installing bridge deck with six-face slope layer, sliding layer, rail plate and fastener.The difficulties of bridge waterproof mostly involve: 1. Because wettability between waterproof layer and concrete base is low, abscission is common.2. The strength of waterproof layer is not high enough to afford the rolling of follow-up process.3. The waterproof material in expansion joint comes off easilyThe subject aims to develop a series of products about waterproof system used in high-speed railway bridges, including polyurethane waterproof material used on bridge decks, polyurethane expansion joint filler with low modulus and high elongation used on beam-end and surface treatment agent of concrete. With the use of viscoelastic theory, a novel elastic molecular structure of polyurethane is designed,and the affects of raw material and synthesis technologis are also studied. Two new kinds of polyurethane material and three new sorts of products are got which have satisfied related standards of Ministry of Railway and also experienced pilot test and field applications.