In the Cracor project we make use of X-ray tomography to study the corrosion development at transverse cracks over time in reinforced concrete specimens. The specimens, containing an 8 mm rebar with varying concrete cover, are first cracked in tension and then immersed in a chloride solution. Multiple scans at different time points are conducted to allow for the tracking of the formation of corrosion products and the consequent fracture mechanisms. Why? Corrosion of reinforcement steel in concrete is a common, yet complex, problem. Exposure conditions, such as oxygen, moisture, pH variations, and damage at the steel-concrete interface, influence corrosion development. Furthermore, as the process takes place inside the concrete, the location of the anodic area is seldom known. During corrosion, iron oxides are produced as corrosion products. Iron oxides occupy more volume than the iron they originated from, leading to internal forces and microcracking. This damage mechanism is difficult to track, given that it occurs at the steel-concrete interface, up to the point where it leads to the formation of corrosion-induced cracks. Observing corrosion development and the consequent fracture mechanism in concrete is challenging. Destructive tests are by far the most common way to assess corrosion damage, thereby not allowing for the collection of data over time in the same sample. Corrosion currents and potential are often used for monitoring corrosion damage but can only give a rough estimation of damage distribution.