Study On Damage Process And Infrared Characteristics Of Concrete Under Different Loading

The increase in urban construction demand has been opened up a broad space for the application of concrete buildings.Due to the different functions of concrete buildi ngs,there are differences in the strength and stress state of concrete required for differ ent locations of buildings.In order to improve the safety of buildings in the process of use and discover the hidden dangers in buildings,it is necessary to detect the damage of concrete under different stress environments and explore the damage evolution pro cess of the concrete under different stress environments or stress states,which has im portant practical significance for the damage detection and early warning of concrete under different stress.In order to explore the damage evolution process of concrete structures with the different strength under different stress states,the uniaxial compression tests of the co ncrete specimens with different strength at different loading rates were carried out by using the RMT-301 rock and concrete mechanical loading device.During the loading process,the specimens were monitored by infrared thermography and the acoustic em ission,Stress-strain,macroscopic failure,acoustic emission and infrared characteristi cs of concrete with different strength under different loading rates were analyzed.The main conclusions of this paper are as follows :(1)The uni-axial compression tests of C20,C25,C30 and C35 concrete specime ns at loading rates of 0.0001mm/s,0.0005mm/s,0.001mm/s and 0.005mm/s were carr ied out.The macroscopic damage process of concrete with different strength under un iaxial compression at the same loading rate is analyzed.It is found that with the decre ase of concrete strength,the macroscopic damage degree of concrete is more obvious.In addition,the damage degree of concrete specimens with the same strength under u niaxial compression with different loading rates was explored,it was found that,with the increase of loading rate of concrete specimens,the macroscopic damage degree of specimens after loading failure was more obvious.(2)The acoustic emission characteristics of concrete specimens under uniaxial c ompression were analyzed,and it was found that the acoustic emission ringing count o f concrete specimens increased rapidly when the stress limit of instability failure was about to occurring.In addition,the acoustic emission ringing counts of concrete speci mens is positively correlated with the accumulated energy of specimens at the same lo ading rate.The peak time points of acoustic emission energy is related to the strength of the loaded concrete specimen.With the decrease of the strength of the concrete spe cimen,the energy accumulation period of the specimen absorbed by the loading comp ression becomes shorter,and the peak energy of acoustic emission decreases.(3)The infrared monitor on the surface of concrete specimens during uniaxial lo ading were analyzed,It was found that infrared radiation can well reflect the energy a ggregation on the surface of compressed concrete specimens.The distribution of the maximum temperature scatter diagram on the surface of concrete specimens is used to predict the failure location of concrete.The same strength concrete specimens,with th e specimens subjected to the loading rate increases,the internal energy accumulation of concrete is increasing trend;different strength of the concrete specimen surface of t he high-temperature points show the distribution of location with the decrease in conc rete strength and the more scattered.