Study On The Mechanical Behavior Of Concrete Compression Members Subjected To Salt Corrosion And Frost Damage In The West Of Jilin Province

The western region of Jilin province is not only a typical season frozen zone of northeast region,but one of the regions with the most serious soil salination in Jilin province.In such region the major ingredient of the saline soil is carbonate?hydrogen?salt,with the bad physical and chemical properties and high PH value,the soil highly riches in salt and its composition is complex;containing CO₃^2-,HCO_3-,SO₄^2-,Cl^-,Na⁺,and Mg²⁺ plasma.Due to serious weather conditions,such a region of concrete structure engineering often suffer from various types of salt(CO3^2-,HCO_3-,SO₄^2-,Cl^-)of the dual role of erosion and freeze-thaw alternation cause a erosion destroy of the concrete,and aggravated the invasion of the corrosive medium in the surrounding environment,accelerate the expansion of steel corrosion in concrete cover and concrete crack,causing the failure of the bearing capacity of concrete member and structure and destruction,greatly shorten the service life of the concrete engineering.At present,domestic and foreign scholars pay more attention to the problems about deterioration of the bearing capacity of concrete compressive member under the effect of single factor such as freeze-thaw cycle,chloride salt corrosion,sulfate corrosion,and dual factors of salt corrosion and freeze-thaw action;pay less attention to the degradation of the bearing capacity of the concrete compressive member under the saline alkali soil environment in the western region of Jilin.Therefore,in the thesis the concrete projects in Da'an city of Jilin,one typical region with saline soil,are taken as the research object,then the studies are performed on the behavior damage of concrete compressive members after the action of salt corrosion and freeze-thaw cycles.The concrete components?120mm × 120 mm × 600 mm in size?are prepared for salt-corrosion and freezing-thawing test,and placed into the composite salts solution which the mass fraction is 0,3.4%,and 10% respectively.Through a series of tests,the main purpose is to find out the damage laws of bearing capacity of concrete columns with the times of salt-corrosion and freezing-thawing cycles.These results will provide reference for the safety evaluation and durability design of concrete structures under such environment.The main study contents in this paper include:1.In axial compression test,the concrete members are made to study the damage law of their bearing capacity under axial load after freeze-thaw cycle.The test shows that the mass loss of member,dynamic elastic modulus and the bearing capacity aredeclining,and the axial compressive strength of the concrete is decreased simultaneously.2.According to the type and content of soluble salts in the saline soil of Da'an city,three kinds of multi-salt solution are prepared to be as the erosion solution.In axial compression test,the concrete members are made to study the damage law of their bearing capacity under axial load after long-term immersion.The results show that concrete members under multi-salt erosion are damaged not severely,the decaying degree of the compressive capacity increases with increase of the mass fraction of the multi-salt solution.3.In axial compression test,the concrete members are made to study the damage law of their bearing capacity under axial load after the double factors of multi-salt erosion and freeze-thaw cycle.The results show that the surface layer of concrete is peeling off,and the internal structure is badly damaged,and the bearing capacity is decreasing obviously under the action of salt corrosion and freeze-thaw cycles.And the higher the salt solution concentration,the more serious the concrete member damage.In addition,the concrete members damage under the action of the salt corrosion and the freeze-thaw cycle far more seriously than single factor?salt corrosion,freeze-thaw cycle?action.4.The experimental data obtained by three groups of axial compression tests are fitted to calculate respectively the computational model of concrete members under compression bearing capacity,that under the effects of salt corrosion,freeze-thaw cycle,salt corrosion and freeze-thaw dual factors.