Crack propagation measurements using Digital Volume Correlation for an in situ Wedge Splitting Test on mortar

Abstract

Facing global warming, nuclear energy allows us to progressively develop solutions without having to depend on fossil fuel. However, it also induces other ecological challenges such as nuclear safety against radiations and incidents, which are directly related to the cracking of concrete sealing. Nowadays, crack propagation in concrete is the subject of research such as, in this study, mechanical constraint but also aging, drying or temperature effects. A common difficulty for crack propagation measurements within quasi-brittle materials such as concrete or mortar is its instability. The presented work consists in the exploitation of an in situ Wedge Splitting Test to assess crack propagation for a chosen mortar when subjected to a splitting load. The presented in situ Wedge Splitting Test was performed taking different tomographic scans at different loading steps. This type of test allowed us to interrupt loading at different steps, with stable cracking conditions, to scan the material bulk. Regularized Finite Element based Digital Volume Correlation (DVC) on the different scans enabled 3D displacement fields to be measured during crack propagation. It consists in measuring the displacement fields by minimizing the gray level differences between a reference volume and deformed volumes. The presence of the major crack was investigated thanks to the elementary strain fields and the voxel-wise registration residuals. Measurement uncertainties were also assessed via DVC on a repeated scan. Furthermore, the high brittleness of the material involved very small displacement levels during crack propagation. Given the low uncertainties associated with regularized DVC, it was possible to obtain satisfying results for the investigated test.