Abstract: In order to study the internal deformation of the early-age recycled aggregate concrete in the process of uniaxial compression，recycled concrete specimens under different axial loads，which respectively possesses the recycled coarse aggregate replacement rates of 0，30% and 50%，were scanned by means of Xray industrial computed tomography ( CT) ． Then，by taking the grayscale distribution in CT images as a speckle pattern and the CT images captured before and after the loading as the carrier of deformation information of the specimens，the internal realtime displacement fields and strain fields of the recycled concrete specimens were obtained via MatchID， and the corresponding deformation contours were drawn to visually reveal the evolution of the internal micro-deformation of recycled concrete specimens in the compression process． It can be shown that there is a positive correlation between the internal deformation of the specimens and the replacement rate of recycled coarse aggregate under the same loading conditions，and that the localization deformation characteristics of specimens with the same recycled coarse aggregate replacement rate become obvious with the increase of axial load． The proposed method combining CT images and MatchID algorithm provides a new approach to exploring the micro-deformation of recycled aggregate concrete． 

Key words: recycled aggregate concrete, uniaxial compression, CT scanning, MatchID analysis system, deformation contour, deformation localization