Limestone calcined clay cements are being widely researched, and they are starting to find field applications. Most chemical hydration reactions and their durability features are being reported. However, due to the large variability in the mineralogy and textural properties of the clays, it is important to have a wide portfolio of techniques to understand their hydration behavior. Here, we contribute to the LC3 hydration understanding by using synchrotron and laboratory X-ray microtomography (μCT). On the one hand, μCT allows determining microstructural features like microporosity (mainly amount, size(s) and connectivities). However, porosity can only be measured for sizes larger than the attained spatial resolution, usually 1–2 μm at best. Therefore, only a fraction of capillary porosity is currently being measured by even synchrotron μCT where currently the best true spatial resolution is ~ 1 μm. On the other hand, and for in situ experiments, where the same capillary is measured with time, μCT has the potential to follow the volume decrease (i.e. reaction/hydration) of amorphous phases like metakaolin. For synchrotron μCT measurements, the detector can be placed at a certain distance from the samples (here 5.5 mm) and phase-propagation increases the visibility between components with similar attenuations to the X-rays. The Paganin phase retrieval algorithm resulted in augmented contrast. Here several preliminary examples of the use of μCT in LC3-related binders are reported and discussed.