Study On The Mechanical Propertie Of Concrete Exposed To High Temperature And Water-cooling And The Characteristics Of Acoustic-electric During Loading Process

In this paper,uniaxial compression experimental system for concrete deformation and fracture is established.The influence of water cooling system and one side heating method on the residual compressive strength of concrete is mainly studied and the change law of the main frequency of acoustic emission and the potential signal in the process of deformation and fracture is analyzed.The experimental results show that under the conditions of heating temperature less than 400oC,the single side heating method is weak to the deterioration of the compressive strength of concrete,but the difference of deformation at different positions is gr eat,the closer to the hotter surface,the greater the axial deformation ability.At the same time,due to the uneven distribution of temperature field,with the increase of temperature,the heterogeneity of the internal structure of concrete increases,and the strain localization is serious during the process of compression deformation.The effect of water cooling on the compressive strength of concrete is multifaceted.On the one hand,it can promote the hydration process of the gel when the temperature i s low,and it is beneficial to the enhancement of the strength.On the other hand,the rapid cooling effect of water makes the internal micro cracks in the concrete structure increase and the strength of concrete decrease.The higher the temperature is,the more obvious the deterioration.At the same time,the change law of the surface potential signal and the strain field of the surface of the concrete after the single side heating are analyzed.With the increase of the stress level,the distribution pattern of the surface potential field and the strain field changes.In the loading process,the stress state at different locations of concrete specimens is changed with the increase of applied stress,and the distribution of strain field shows strong localization characteristics.Moreover,the change of the stress state may lead to the change of the polarity of the charge on both sides of the piezoelectric material,which leads to the opposite sign of the surface potential field.Combined with the change of main frequency and the multi-fractal analysis of acoustic emission signals,it is found that the small fluctuations in the whole deformation and rupture process of concrete occupy the main position.With the increase of the experimental temperature,the low frequency signal in the compression process is obvious increasingly,and its main frequency is characterized by the typical low frequency and high energy characteristics;by statistical analysis,the energy released by low frequency signals accounts for more than half of the total release energy.By comparing and analyzing the acoustic emission and potential signals,it is believed that the acoustic emission signal can reflect the damage of the whole specimen well,but it cannot well describe the local dama ge change caused by the strain localization in a certain region,and the surface potential signal has a good response to the local breakage,and the surface damage area can be retrieved through the position of the electrode.Therefore,it is necessary to further study the accuracy of the measurement and improve the existing testing methods,so that the result is of more reference.