Experimental Study On Mechanics Properties Of Concrete Corroded By Chlorine Salt After High Temperature

In the construction of reinforced concrete and prestressed concrete bridge across the sea coast,Chloride ion and chloride ion in concrete raw material penetrate into steel bar.After reaching a certain concentration,the chloride ion destroys the passive film of the steel bar and cuts the effective section of the steel bar.These damages will lead to the deterioration of the macro and micro structures of steel and concrete,which will affect the bearing capacity and fire resistance of the bridge.In this paper,three experiments were carried out to study the mechanical properties of concrete after chloride corrosion and high temperature.Mainly includes the following work:The mechanical properties test of concrete corroded by chloride corrosion after high temperature was carried out.In this study,two kinds of chloride corrosion methods were used.One method was carried out on 30 dry wet cycles;In addition,the three groups were immersed in Na Cl solution 60 d,180d and 360 d.And complete the test of high temperature,The constant temperature is 200 ?,400 ?,600 ?,800 ? respectively.The mechanical properties test was carried out after the natural cooling of concrete.The research shows that,the strength of concrete will be enhanced in the early stage of corrosion,the strength of concrete decreases with the increase of temperature.Coupling accelerates the degradation of mechanical properties of concrete,which is not a simple superposition of the two factors.The mechanical properties test of corroded steel bars after high temperature was carried out.Steel bars embedded in concrete slabs.Use electricity to make steel rust,then start the high temperature test,The constant temperature is 300?,500?,700?.The actual corrosion of steel bars is reflected by the mass loss rate of steel bars.The research shows that,the deformation load curve of the steel bar changes,with the increase of the corrosion degree,theyield point of the reinforcement decreases,After the high temperature effect,there are still obvious yield stage and strengthening stage,and the yield stage of steel bars is not obvious before 500 ?,and the yield point and the ultimate strength of the steel are decreased obviously at 700?.The experimental study on bond behavior between concrete corroded by chloride corrosion and steel bar after high was carried out.Corrosion of steel bars by electrochemical accelerated corrosion test,the power time was 15,30,45 d.The control group was also designed;the influence of the diameter of steel bar,the thickness of concrete cover and the shape of steel bar on the bond performance of reinforced concrete is studied.The constant temperature of high temperature test is 300?,500?,700?.The pull-out test was carried out after a week of natural cooling.The research shows that,when the corrosion rate of steel bar is small,the bond strength increases,and the bond strength decreases obviously with the increase of corrosion degree.With the increase of temperature,the peak value of the bond slip curve decreases and the amount of slip increases when the ultimate bond stress increases.