| Freeze-thaw cycle and salt-freeze cycle have greatly reduced the durability and strength of tyr concrete structures.As a very important load-bearing raw material,concrete structures have been widely used in most cold regions of China,so they are inevitably damaged by fr eeze-thaw cycle.At present,there are many researches and tests on the freeze-thaw cycle and salt-freeze cycle the damage of concrete,most of which focus on the freeze-t haw cycle mechanism,salt-freeze cycle the mechanism,the use of materials and additives in concrete,etc.Although there are many tre og t er domestic and foreign research tests on the mechanical properties of freeze-thaw cycle and salt-freeze cycle,there are still some syst ematic stud ies in some asp ects,such as the lack of the the oh systematic studies on the red uction of comp ressive strength and splitting te nsile strength of concrete after freeze-thaw cycle and salt-freeze cycle.However,this is quite different from the freeze-thaw cycle and salt-freeze cy cle of con crete in practical engine ering,and a large number the the of experi ments and res earches are needed.It is necessary to find out the att enuation law of be aring capac ity and compr essive cap acity of conc rete by m any fa ctors.Especially for the concrete of concrete in different type of protective coating,freeze-thaw cycles,influ ence fa ctors such as water cement ratio,concrete stre ngth under the a ction of freeze-thaw cycle and thef rost cycle effect con trast test rese arch,this is more for pre vention in the practical engineering to the recycle concrete freeze-thaw cycle and frost damage after freeze injury,to provide systematic the reality and theory support.The economic loss caused by the erosion of concrete structures by the saline solution environment acco unts for about 1%?5%of the nati onal economic aggregate,and about 30%-40%of concrete building materials are destroyed by freeze-thaw cycle and the the of damage salt-freeze cy cle every year.At pr esent there are two kinds of concrete construction the method of prote ction:one kind is the basic protection methods,such as the concrete building the structure of high performance concrete is made and be become,but the concrete structure itself is a ki nd of po rous material,it ha s certain permeability,can't comp let ely prevent the intrusion of moisture in the external env ironment and ero sion me dium.The se cond is the use of pr otective the co ating te chnology,o with prot ective coating tech nol ogy will make the Ma rine erosion the envi ronment of concrete bu ilding structure engin eering to achieve long-term service is possible,this is the resis tance to freeze-thaw cycle and salt cycle and oth er fields of bre akthro ugh.The or of main research content of this paper is as follows:(1)To ma ster the act ual eng inee ring situ at ion of fr eezin g-thaw ing cycl e of typ ical concrete conc rete structures in nor theast China and freezing-thawing cycle of salt.Based on the analysis of the ma in factors aff ecting the frost dam age of conc rete in practical engineering,the field investigation and testing of concrete Bridges in engineering are carried out.The du rability and failure mechanism of freeze-thaw and salt-freeze concrete were studied.(2)The influ encing factors w ere anal yzed,and the fre eze-thaw cycle co mparison tests were carri ed out un der the influence of diff erent freeze-th aw cycles,protective coa ting types,water-cement ratio,concrete strength and other factors,so as to measure the quality,compressive strength loss rate and moisture content of the freeze-thaw concrete.(3)This paper ana lyzed and stu died the comp arative test of salt free zing cycle of ogern concrete specimens under the infl uence of factors such as dif ferent water-cement ratio,concrete stren gth grade,num ber of times of salt freezing cyc le and ty pe of prote ctive coa ting,etc.,and measured the damage caused by salt fr eezing damage caused by mass loss rate,water absorption rate,spl itting tensile strength and NaCl concentration solution on con crete spec imens.NaCl the solutions with concentrations of 3%and 5%,me dium and low NaCl solutions,10%medium and high NaCl solu tions,and 15%high NaCl sol utions were sel ected,respect ively.Concrete of the word specimens with 5 diffe rent coating types of prote ction combinations and those without the or protective coating protection were compared in detail.After the salt freezing cycle of concrete blocks protected by different coating types was studied,the hydroscopicity of the concrete blocks was changed und er the cond ition of alk ali and ac id acce lerated corrosion,and the chloride ion the pen etration resis tance of the test blocks after salt free zing was anal yzed by the electric flux accelerated diffusion method(RCP). |
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