Research Of Concrete Performance Under The Coupled Action Of Freeze-thaw Damage And Chloride Salt Erosion

Freezing-thawing damage and chlorine ions corrosion both have serious effect on durability of concrete.Due to peculiar environment,the bridge the bridges in the cold regions or at the particularly windy spots are often under combined action of freezing-thawing and chloride ion erosion.Both the two erosion ways will cause great damage to concrete structure and be enhanced because of each other’s participation,which leads to the concrete structure failure before it’s service deadline,and leads to a grate economic loss.Therefore,in order to investigate the above problems and determine damage mechanism and mechanical performance degradation of concrete under the combined effect of chlorine ion corrosion and freeze-thaw damage,the main work is as follows:(1)114 concrete blocks were made to conduct the rapid freezing-thawing damage test with chlorine ion corrosion and investigate the effect of different freeze-thaw damage times on surface flaking,the saturation water content and other properties,and determined the breakaway law of surface concrete in structure under freezing-thawing damage.(2)Uniaxial compression test of concrete with different cycle times was conducted to study the degradation of mechanical properties under the freezing-thawing damage and the combined effect of compression and freezing-thawing damage.The effect of freezing –thawing on the peak stress and strain of concrete was analyzed,and a stress-strain model of concrete under freezing-thawing damage was established based on fitting analysis of test data.(3)Rapid chloride ion permeability test of concrete with different freezing – thawing times was designed.On the basis of the test,penetration law of chloride ion at surface in concrete under freezing-thawing damage was determined,and the impact of freezing-thawing damage of concrete on chloride ion diffusion coefficient was explored and prediction model of chloride ion permeability coefficient in concrete under freeze-thaw damage was established;(4)Taking the change law of chlorine ion permeability coefficient for concrete under freezing – thawing damage into consideration,setting a goal as no chlorine ion corrosion of concrete structure in service life,A calculation model of minimum thickness of concrete protective layer for concrete structure under the combined effect of chlorine ion corrosion and freezing-thawing damage was established.