Physical characteristics identification of the concrete interfacial transition zone via 3D image scanning

The interfacial transition zone (ITZ) is the weakest link in concrete materials. The physical characteristics of the ITZ, such as its microhardness and thickness, significantly influence the mechanical properties and durability of concrete. Typically, microhardness testing is employed to identify the physical features of the ITZ through line measurements with a certain degree of randomness. In order to accurately describe ITZ physical characteristics, this study proposes a novel physical characteristics identification method via three-dimensional (3D) image scanning. The fundamental principle of this method lies in the varying hardness of each concrete phase, resulting in different surface elevations after polishing. As the polishing abrasiveness changes from coarse (240 mesh) to fine (800 mesh), the ITZ can be clearly observed in the 3D point cloud images of the experimental concrete. The ITZ geometrical information (thickness and different surface heights) can be easily identified using 3D scanned images. It was also found that there was a considerable linear regression relationship between the height difference and the relative microhardness variation; thus, the ITZ microhardness could be indirectly recognized through surface measurements. The physical characteristics of ITZ can be statistically analysed, effectively mitigating the bias inherent in traditional test results and significantly improving identification efficiency and accuracy.