Study On Effect Of Freeze-thaw Damage To Chloride Ion Penetration Performance

Concrete structure is the most widely used structure form, its durability has been thefocus of attention. Under different working environment, all kinds of concrete durabilitydamage occurred. and single factor of concrete durability deterioration has been deeplydiscussed in in the field of civil engineering. However, in practical project, the matter ofconcrete durability was complicated, it was almost coupling effected by two or morefactors, these factors work together, promote each other and affect each other instead ofbeing a simple superposition.In "three north" area-the northeast, north and northwest china, concrete durability wasseriously affected by freeze-thaw action. At the same time, concrete durability damage incoastal and offshore and winter deicing salt environment was dominantly influenced bychloride ion penetration. Obviously, cold area offshore concrete structures in cold regionwere coupling effected by freeze-thaw and chloride ion penetration, and chloride ionpenetration was effected by freeze-thaw damage to a certain extend. On the foundation,through the experiment research chloride ion permeability was compared before and aftersuffering freeze-thaw deterioration, and the finite element numerical simulation wascombined to analysis the process of concrete freeze-thaw deterioration under temperaturefield, in which way to explore the influence of concrete freeze-thaw damage on chlorideion permeability.In this paper, the relevant test and numerical simulation were made to study the effectof concrete freeze-thaw damage on chloride ion penetration. The main research content areshown as follows: firstly, the fast freeze-thaw test method was applied, the appearancechange, quality loss and compressive strength changed of concrete were explored underdifferent freeze-thaw cycles and different strength concrete grades, in order to study therelationship between freeze-thaw cycles and the performance index; meanwhile, thesoftware of finite element analysis of ABAQUS was applied to the study,and numericalsimulation of concrete freeze-thaw cycles was made by using the heat conduction principle,in order to analysis the changed of concrete stress, strain and the strength under the actionof temperature, and compared with the experimental results to analysis and verify the performance of concrete after freeze-thaw damaged. On this basis, different mixture ratioof concrete after suffering0,50,100,150times of freeze-thaw cycles. Rapid ChlorideMigration Test (RCM method) was applied to measure the chloride ion diffusioncoefficient before and after freeze-thaw damage, in order to explore the the influence offreeze-thaw damage on chloride ion permeability, so that the relationship betweenfreeze-thaw damage parameter and the chloride ion diffusion coefficient was established.The analysis shows: The appearance of concrete damage is more and more seriouswith the increase of freeze-thaw cycles; Overall, the mass loss increases along with theincrease of freeze-thaw cycle times; The compressive strength of concrete is declining withthe increase of freeze-thaw cycles and it is a good linear relationship; The chloride ionmigration coefficients of different strength grades of concrete enhance along with theincrease numbers of freeze-thaw cycles, the relationship is nonlinear, and the permeabilityresistance of high strength grade concrete is relatively good. In brief, the concretefreeze-thaw damage provides convenient conditions for chloride ion penetration.