Study On The Deterioration Of Bearing Capacity Of Concrete Under Freeze-thaw Cycles

Because of the low temperature,the hydraulic concrete structure in northern cold area will suffer from the damage of freezing and melting again and again.Finally,freezethaw damage will occur,which will cause a great influence on the safety and stability of the structure.Frost resistance is one of the most important aspects of the durability of concrete structures,which determines the ability of concrete to resist freeze-thaw damage.This paper uses the method of laboratory experiment,choosing five groups of concrete specimens,focuses on the study of concrete freeze-thaw cycle under the action of bearing capacity degradation characteristics,the research content and the main conclusions are as follows:(1)The internal stress wave velocity of concrete subjected to different freeze-thaw cycles was measured by impact echo method.The results show that for the same set of specimens,with the increase of the number of freeze-thaw cycles,the P wave velocity of concrete will decrease,and the change of concrete with different ratio is not the same.At the same times of freeze-thaw,the velocity of the concrete with small water cement ration decrease slower compared with the high water cement ratio concrete,the concrete which add air entraining agent compared with the concrete without air entraining agent shows the same regular too.(2)The ultimate compressive strength and stress-strain curves of concrete under different freeze-thaw cycles are studied by uniaxial loading test.The results shows that,for the same set of test blocks,with the increase of the number of freeze-thaw cycles,the compressive strength of the concrete limit will decrease,for the concrete with the same strength,in the same number of freeze-thaw cycles,the small water cement ratio concrete compressive strength limit decrease slower compared with high water cement ratio concrete.Although the air entraining agent will reduce the strength of concrete when the mixture ratio is the same,the change of ultimate compressive strength is a little slower than that of concrete without adding air entraining agent.With the increase of the number of freeze-thaw cycles,all the concrete shows the decrease of ultimate compressive strength and the increase of peak strain.(3)For the same set of specimens,the relationship between the P wave velocity and the strength of concrete subjected to different freeze-thaw cycles was studied.The data were fitted by power function and exponential function.It is found that the ultimate compressive strength of concrete subjected to freeze-thaw damage has a good correlation with the internal P wave velocity.(4)When develop the concrete uniaxial compressive test,use VIC-3D system shot the loading progress from the beginning to the concrete is destructed.And then,the pictures are progressed by software,research on freeze-thaw and regularity of concrete surface changes and the failure process of loading.