Research On The Mechanical Properties And Micromechanism Of Concrete Under The Coupling Of Freezing And Corrosion

The concrete bridges under salt-freezing environment suffer both freeze-thaw damage and corrosion damage.The mechanical properties and damage mechanisms of concrete materials under this environment are the basis for studying such problems.This article takes concrete,cement mortar,cement paste as the research object.Based on the freeze-thaw,corrosion,freeze-thaw-corrosion coupling environment,through uniaxial compression test,Zeiss microscope observation test,specific surface area and aperture analysis test,the system is systematic Analyzing the physical mechanics and micro damage law of concrete bridges in salt-freezing environment,the result shows:(1)Freeze-thaw action and freeze-thaw-corrosion coupling effects The damage of cement paste,cement mortar,and concrete in all aspects is similar,but the three materials have obvious physical damage under the freeze-thaw-corrosion coupling and three materials under corrosion the change is not significant.(2)Under the action of freeze-thaw,freeze-thaw-corrosion coupling,the slurry on the surface of the cement slurry has fallen off in a large area,and the slurry on the surface of the cement mortar has fallen off locally,the change is not significant,the concrete aggregate is completely exposed,and the quality is reduced;but the freeze-thaw effect The lower structural integrity is better and the quality is generally lower.The structural integrity is lower and the quality decline rate is faster under the coupling of freeze-thaw corrosion.The three changes are not significant under the effect of corrosion,but the quality increases slightly.(3)The compressive strength of the three materials under the freeze-thaw,freeze-thaw-corrosion coupling environment gradually decreases with the increase of the number of times,and the compressive strength decreases the most under the freeze-thaw-corrosion coupling environment.The compressive strength first increases and then decreases,and the change range is small.(4)Pore volume and strength are closely related in the freeze-thaw and freeze-thaw-corrosion coupled environments.The pore volume increases as a whole,and the compressive strength decreases as a whole.The pore volume of the three materials in a corrosive environment is generally correlated with its strength.(5)In the freeze-thaw,freeze-thaw-corrosion coupled environment,the reduction of 10 ~ 50 nm pores in cement pastes,the increase of> 100 nm pores has the largest contribution to the decrease in strength,and the decrease of 50 ~ 100 nm pores in cement mortar,> 100 nm pores increases.The greatest contribution to the reduction in strength.(6)The decrease of 10 ~ 50 nm pores and the increase of 50 ~ 100 nm pores of concrete under freeze-thaw are the main reasons for its strength reduction.The increase of the number of pores of concrete> 50 nm under freeze-thaw-corrosion coupling is the main reason for its strength decrease.The internal small holes are reduced,and the large holes are obviously increased.The freeze-thaw-corrosion effect mainly causes the increase of the mesopores and the large holes,and the changes of the small holes are not significant.(7)The damages of the three materials are similar to the freeze-thaw coupling and the freeze-thaw-corrosion coupling,but the physical damage of the three materials is obvious under the freeze-thaw-corrosion coupling,indicating that the corrosion has a catalytic effect;The physical and quality loss of the paste is the most obvious,and the strength is the most obvious.The concrete is the second,and the cement mortar is the least.The connection between the material and the gelling material makes it the best in strength,but destroys its uniformity,resulting in a decrease in its stability.