| Epoxy resin has been widely used in fiber reinforced polymer (FRP) strengthening concrete structures. This kind of resin, however, has the disadvantages of low light and heat-resistances as well as poor fire-resistance. Even in a normal environment, the life cycle of epoxy resin is only from 30 to 50 years. In order to improve the durability and safety of strengthened structures at a low cost, an attempt to replace epoxy resin with fire and heat-resistant magnesium oxychloride cement (MOC) was proposed.The primary compositions, process and mechanism of hydration and hardening of MOC were reviewed. The water-resistance and existed modifying methods of MOC were summed up in detail. According to the former experimental result, the relatively better mix ratios of MOC might be obtained by following principles. Under the premise of flowability and reaction, the water/cement ratio should be as low as possible, with modifying materials of phosphoric acid 1%, silicon powder 10%～15%, durafiber 0. 05%～0. 1%, a molecular ratio of 6 to 8 for active magnesia and magnesium chloride. Base on this, the influence of urea formaldehyde resin on the water resistance of MOC was investigated through an experimental study with strength and water-resistance as evaluation indexes. The test results showed that urea formaldehyde resin could improve the water-resistance of MOC, and the modifying effect of urea formaldehyde resin powder was better than that of liquid urea formaldehyde resin. The rational content of urea formaldehyde resin was obtained and the modifying mechanism was discussed. In order to greatly improve the long-term water resistance of MOC, a high water-resistant epoxy resin was used to coat the MOC by the author. The influence of epoxy resin coat on the strength of the coated specimens immersed in water was investigated through an experimental study. The test results indicated that epoxy resin...
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