Research On Mechanical Properties And Durability Of C50 Steel Fiber Reinforced Concrete

Steel fiber reinforced concrete(SFRC)is a new type of cement-based composite material made by adding a certain amount of short steel fiber into ordinary concrete.In this paper,the composition,working performance,mechanical performance and durability of steel fiber micro-expansive concrete are studied based on the continuous steel-box composite beam bridge-Yunnan manhaohonghe bridge,and the research results are also applied to the Yunnan manhahonghe bridge.Specific research work and main conclusions are as follows:(1)The mix ratio design method of SFRC was proposed,and the influence law of steel fiber content,expansion agent content,water-binder ratio,sand rate and other factors on the basic performance of concrete was proved through parallel and orthogonal tests.The results show that the suitable sand rate can improve the performance of SFRC,and it will decrease with the increase of the steel fiber content and the decrease of the water-binder ratio and the expansion agent has little influence on it.Steel fiber can effectively improve the mechanical properties of concrete,especially the splitting tensile strength.It is an effective way to improve the mechanical properties of steel fiber concrete to reduce the water-binder ratio,select the appropriate sand ratio and increase the content of expansion agent reasonably.(2)Based on the optimal mix ratio,the durability of SFRC against cracking,osmosis,chloride ion osmosis and carbonization in stage was studied.The results show that the steel fiber is beneficial to reduce the crack and improve the crack resistance.Whileinhibiting the cracks,it can also reduce the porosity,prevent the water migration in the concrete,reduce the capillary pressure,and improve the impermeability.An appropriate amount of steel fiber can inhibit chloride ion penetration.Within a certain range,the larger the content of steel fiber,the more obvious the inhibition effect.The strength of SFRC increases with the growth of the age of carbonization.(3)SFRC was applied to Yunnan manhaohonghe bridge with temperature characteristics of high temperature valley in service environment.The C50 steel fiber concrete was prepared to meet the requirements of construction and mechanical properties.The test showed that the concrete compacted steel box girder was in good service condition.