Experimental Study On Creep Property And Prediction Model Of High Durability Concrete In Coastal Environment

The concrete structures are often affected by adverse environmental factors such as seawater,salt spray,wet-dry cycles and other factors in coastal environment.In actual projects,there often appear some early failure and destruction of structures due to lack of durability,and the socio-economic losses are enormous.Concrete creep has a significant impact on the long-term performance of concrete structures,which is mainly reflected in the influence of the stress and deformation of the bridge,causing the deflection of the bridge,the excessive loss of prestress,the cracking of the web of the box girder and the uneven settlement of the support,premature loss of function.Among the problems related to the durability of high performance concrete,creep problems have drawn the attention of researchers.In this paper,based on a long-span railway cable-stayed bridge in Wenzhou,Zhejiang,on the basis of concrete compressive test,concrete against chlorine infiltration performance test and hydration heat test,the optimization of the incorporation amount of high durability concrete mineral admixtures was optimized design;through the compression creep test of concrete block and the heaped load creep test of beam members to study the creep properties of high durability concrete materials and components;through comparison and analysis of three concrete creep prediction models and experimental data to study the long-term creep prediction model applicable to the long-span railway cable-stayed bridge;through compared and revised the ACI209 creep prediction model,CEB-FIP90 creep prediction model and B3 creep prediction model to obtain a long-term creep prediction model suitable for the long-span railway cable-stayed bridge.The main conclusions of the paper are as follows:(1)According to the practical requirements of the project,the optimal mix ratio of slag and fly ash for the high durability concrete of the long-span railway cable stayed bridge is determined to be 11%;(2)The effects of fatigue load and chloride ion erosion will significantly change the law of the shrinkage and creep of concrete,which is reflected in the overall increase in the shrinkage and creep of the concrete,shortening of the loading time for entering the smooth development period of creep,and increasing the rate of increase of the creep value after entering the stationary period of development;(3)The development law of the mid-span deflection and creep coefficient of beam members heaped load creep test in general laboratory environment and simulation environment of Wenzhou is similar.Both of beam members heaped load creep test have higher growth rate in the early stage and lower growth rate in the later stage,but the former creep into the smooth development period of age slightly delayed loading;(4)The CEB-FIP90 concrete creep prediction model is more similar to the experimental data.The model was selected and modified to obtain a high durability concrete creep prediction model applicable to the long-span railway cable-stayed bridge in Wenzhou.