Abstract This paper presents a pipeline for investigating crack development and strain changes in concrete beams that are reinforced with a glass fiber-reinforced polymer (GFRP) rebar using 4D image data. Concrete beam samples were loaded and imaged simultaneously using computed tomography at several load stages. The displacement fields were estimated from the resulting time series of images using the MorphFlow method. Individual cracks were segmented and analysed at selected stages of their formation. The method shows high potential for early detection of very thin cracks at the sub-voxel level. Additionally, the adopted image processing approach provides a detailed distribution of crack widths. The crack widths measured in the experiment are consistent with numerical results and with standards specific to FRP reinforcement, such as the Canadian ISIS standard. Image analysis results also indicate that the local crack width at the rebar level differs significantly from the crack width at the sample surface.
Grzesiak et al. (2026) studied this question.