Research On The Evaluation Of Frozen Damage Of Concrete Based On Deformation

Concrete needs to resist the action of environmental media and maintain its good performance and appearance integrity for a long time,thus the ability for maintaining the safety and function of the concrete structure is called durability.In recent years,due to the lack of design for concrete durability,the cases of the destruction and the loss of service function of practical works are numerous.Therefore,monitoring the internal deformation of concrete under the effect of freeze-thaw cycle in different service environments in cold areas is of great theoretical significance and engineering application value for studying its damage and damage mechanism.First of all,the monitoring method of the internal freeze-expansion strain of concrete under the action of fast freeze-thaw and slow-speed freeze-thaw is studied and the test specimen are made.At the same time,the waterproof treatment of strain gauge,interface enhancement treatment between the strain gauge and the concrete are carried out.The internal deformation and temperature of C60 and C30 strength grade concrete in the process of freeze-thaw cycle were monitored in the experiment,and the measured data such as internal freeze-expansion strain and internal temperature were obtained.Then,according to the test and monitoring data,the influence law of concrete saturation degree,different areas inside,the number of different freeze-thaw cycles and the mechanism of freezing and thawing cycle on the internal freeze-expansion strain,as well as the distribution law of the internal temperature of concrete.The results show that the initial deformation of the concrete in the process of freezethaw cycle is reflected in the contraction deformation,with the increase of the number of freeze-thaw cycles,showing the characteristics of expansion deformation.The higher the strength level of concrete,the stronger the resistance to frost damage.It is obtained that the maximum tensile stress peak produced imside concrete at the corner under the effect of freeze-thaw is obtained.When the design value of the tensile strength is first reached,the concrete is destroyed first at the corner of concrete.And with the increase of the number of freeze-thaws,the concrete interior gradually degraded.Secondly,by sticking the strain gauge on the outer surface of the concrete,the difference of the early deformation characteristic curve between winter construction concrete and concrete at normal temperature is studied.The three-stage characteristics of early deformation of winter construction concrete are found,and the early freezing process of concrete can be characterized by the early deformation value of concrete under negative temperature.The law of frozen deformation of concrete after 24 hours of pre-curing is that the larger the water-cement ratio,the smaller the cold-shrink deformation of concrete,the greater the air content,the greater the cold-shrink deformation.There is a certain correlation between the early deformation of pre-curing concrete at negative temperature and the loss rate of concrete strength.