Experimental Study On Seawater Erosion Resistance Of High Performance Concrete After High Temperature

This thesis is based on the construction project of Shougang,which is planned to be built in Caofeidian Industrial Zone.One concrete structure of this project is designed to bear the internal heat and the corrosion from invading salt water.To meet the requirement of the safety and long-term performance of concrete structure,this thesis studies the effect of salt-water on the high performance concrete(HPC)after the high temperature impact.Current research is mostly focused on the durability of HPC under a single factor,such as seawater or high temperature.However,the hydration degree,the distribution of free water,and the mechanical characteristics of HPC may change due to the influence of high temperature.Therefore,the effect of salt-water on the HPC after high temperature aging could be different from that on the HPC without experiencing high temperature.In order to have a better understanding on the rules of the coupling effect of high temperature and seawater corrosion on the long-term performance of HPC,four different salt solutions are used in this thesis,namely chloride solution,sulfate solution,simulated sea water and real seawater.At the same time,three levels of the concentration of both chloride solution and sulfate solution are set to simulate the salinity changes in different sea areas,which provides a basis for the application of HPC to a certain sea area.Specifically,the effects of high temperature on the mechanical properties and apparent characteristics of HPC are studied in this thesis.Furthermore,the HPC specimens with high temperature aging are immersed in different simulated seawater and real seawater,respectively.Then the tests of residual compressive strength and chloride ion penetration depth are performed.The same indexes of HPC without high temperature damage are also obtained.Finally,the effects of temperature,aging period,and salt solution types on the HPC specimens are compared and analyzed.The main conclusions are as follows:(1)The water absorption of HPC soaked in different solutions after high temperature is tested.The results show that the water absorption of HPC soaked in chloride solution,sulfate solution,simulated seawater and real seawater decreases,and the water absorption of HPC increases obviously after high temperature.(2)The chloride ion penetration depth of high performance concrete after high temperature damage at 300℃ was determined by silver nitrate colorimetry.The results show that the penetration depth of chloride ion in high performance concrete is lower at 300℃.(3)The compressive strength of high performance concrete after 300℃ high temperature was tested.The compressive strength of concrete after 300℃ high temperature was improved,and the strength of high performance concrete compressive specimens under normal temperature was increased by 28%.(4)The compressive strength of high performance concrete specimens increases with the immersion age of chloride salt,and the compressive strength of specimens increases most at 3%chloride solution.(5)After immersion in the sulphate,the compressive strength of the high performance concrete specimen increases with the immersion age in 90 days,and the compressive strength of the specimen increases most in the 5‰ sulphate solution.After 90-180 days of soaking,the compressive strength of high performance concrete began to decline.The strength of the specimen after 300℃ high temperature damage is greater than that of the specimen without high temperature damage.(6)After immersion in simulated seawater and real seawater,the compressive strength of high performance concrete specimens increases with the age of the immersion.