Experimental Study On The Durability Of Shotcrete Under The Coupling Effect Of Chloride Ion And Freezing Thawing

Shotcrete is commonly used in tunnel engineering,underground engineering and repairing engineering,etc,but got eroded frequently under the rugged environment,like frost and chloride erosion,which may lead to the lack of durability and further affect the normal use of the structure.However,there are limited researches on the chloride resistance of shotcrete.So it is of great significance to carry out the experimental research of chloride freezing resistance of shotcrete.With the consideration of the binder ratio,the dosage of steel fiber and the forming method,rapid salt freezing experiment of shotcrete is conducted in order to explore the effects of cyclic salt freezing time on appearance of shotcrete,mass loss rate and relative dynamic elastic modulus and compressive strength loss rate.What’s more,the conclusion that mass loss rate is the most suitable index to judge the degree of salt resistance of shotcrete is got,and the mass loss rate variation of shotcrete with the change of cyclic salt freezing time on the influence of the water cement ratio and steel fiber content is established.In addition,it was concluded that salt freezing damage is far greater than that of water freezing damage;water binder ratio,or the steel fiber volume fraction is smaller,the resistance of salt freezing erosion the shotcrete is better,and it is concluded that shotcrete does better than the normal concrete.In addition,experimental research on the ability of free chloride ion diffusion properties and surface chloride ion content on the influence of water binder ratio,dosage of steel fiber and forming method before and after salt freezing cycle experiment is conducted,and find that cycle of salt freezing accelerated chloride ion diffusion in shotcrete,and that the higher water binder ratio or the lower content of steel fibers are not conducive to the diffusion of chloride ion,and the degenerative ability of resistance to chloride ion erosion performance of steel fiber reinforced shotcrete freeze-thaw cycle is the most obvious.Finally,the equation on chloride ion diffusion after cyclic salt freezing affected by water binder ratio,content of steel fiber content is built.