Study On Damage Characteristes Of Reinforced Concrete Bonding Under Microwave Irradiation

With the acceleration of China’s urbanization process,it is necessary to dismantle a large number of reinforced concrete structures every year to complete the alternate renewal of new and old buildings.The drawbacks of traditional demolition methods,such as high noise,dust and inefficiency during demolition,have made their use in cities today more and more limited Microwave-assisted mechanical demolition can weaken the bond between steel and concrete in advance,so as to achieve efficient and environmentally-friendly demolition of urban buildings Therefore,it is necessary to study the damage of reinforced concrete adhesion caused by microwave irradiation.The development of technology is of great significanceIn this paper,microwave irradiation test,thermal imaging test,temperature rise characteristic test and standard pull test are carried out on reinforced concrete speecimens Combined with damage mechanics theory and finite element analysis method,the bond damage characteristics of reinforced concrete after microwave irradiation are studied.The main research contents and results are as follows(1)Thermal imaging test and temperature rise detection test of reinforced concrete specimens under 1000W,1500W,2000W and 2500W microwave irradiatio,for 5min,thedispersion of surface temperature distribution of reinforced concrete after microwave irradiation increases with microwave power On the other hand,the optimum irradiation time corresponding to the critical point of temperature rise is significantly shortened as the microwave power is increased(2)The tensile test of 10 kinds of reinforced concrete specimens under microwave irradiation was carried out and the failure mode was analyzed.It was found that with the increase of microwave power,the overall failure mode of the specimens gradually deternoratedl due to the cracking failure.The number and width of cracks at the external and bonding interfaces decrease with the increase of microwave power.Finally,the statistical analysis shows that the microwave power above 3000W is a reasonable illumination power.(3)Four-stage analysis of the bond slip curve of reinforced concrete drawing test after 10 kinds of power microwave irradiation was carried out,and the bond slip curve and its corresponding fitting equation under each microwave irradiation condition were obtained.Finally,the analysis curve was passed.The feature points have a better energy efficiency ratio when the microwave power is 3500W.(4)The bond damage of reinforced concrete after microwave irradiation was studied.The damage curve of damage variable was drawn by the calculation of damage amount D.Based on the damage theory,the constitutive model relationship considering interface damage was established by regression analysis.(5)The ANSYS finite element simulation software was used to numerically calculate the reinforced concrete drawing test under four kinds of microwave irradiation conditions.It was found that the bond-slip curve bond strength characteristic points τA,τB,τC and τD corresponded to the steel bars under four kinds of microwave irradiation.The shift test value agrees well with the simulated value,which proves the correctness of the constitutive model.