Study On Fine Damage Of Concrete Based On Acoustic Emission And CT Image

The recycling and utilization of construction waste is an essential aspect for building a green,economical and developmental society.To find out the relationship between meso-damage and macroscopic properties of concrete,meso-damage test of recycled concrete is very necessary.Therefore,the meso-damage test of recycled concrete when the replacement rate of recycled aggregate is optimal is based on acoustic emission technology and electron microscope scanning,and the CT scanning test of concrete samples and the numerical simulation of three-dimensional model near real structure based on CT image are as follows:(1)Based on acoustic emission technology,the whole process of uniaxial compression of recycled concrete test block is collected.Based on the macroscopic performance of failure process,the stress level is taken as the basis of division.It is of great significance to use four peak frequency characteristic intervals to predict the damage deterioration of recycled concrete in the future.(2)According to the acoustic emission analysis method,different acoustic emission parameters are used to characterize the damage evolution process,damage failure state,damage failure type and crack evolution process of recycled concrete.The change trend of b value can accurately evaluate the development process of cracks in concrete.The sudden decrease of b value is the precursor characteristic of concrete instability failure,and the continuous fluctuation decreases to the macroscopic failure characteristic of recycled concrete.According to the correlation between acoustic emission activity and damage development,a damage evolution model of recycled concrete is established,which is based on the cumulative energy of acoustic emission.It provides the basis for the deeper theoretical research and practical use of recycled concrete.(3)Through scanning electric mirror,found that recycled concrete has disturbed cracks and original cracks,cracks generally occur at the interface junction.There are many holes in the interface transition area.EDS observation is found that the ITZ area is rich in hydration products but loose microstructure.ITZ is generally a weak link of recycled concrete.(4)The CT technology is used to scan the concrete under different loads.After processing the results,a three-dimensional model is established by MIMICS software,and the numerical simulation calculation is carried out with ABAQUS tools.The simulation results are consistent with the scanning test results.The model can fully display the mesoscopic damage characteristics of concrete specimens and prove that the modeling method is feasible.Different modeling methods are provided for numerical simulation to study the mesoscopic failure form and mechanism of concrete.