Cement hydration is a very complex set of processes. The evolution of the crystalline
phases during hydration can be accurately followed by X-ray powder diffraction data evaluated by
the Rietveld method. However, accurate measurements of some microstructural features, including
porosity and amorphous content developments, are more challenging. Here, we combine laboratory
X-ray powder diffraction and computed microtomography ( CT) to better understand the results
of the CT analyses. Two pastes with different water–cement ratios, 0.45 and 0.65, filled within
capillaries of two sizes, = 0.5 and 1.0 mm, were analysed at 50 days of hydration. It was shown
that within the spatial resolution of the measured CTs, ~2 m, the water capillary porosity was
segmented within the hydrated component fraction. The unhydrated part could be accurately
quantified within 2 vol% error. This work is a first step to accurately determining selected hydration
features like the hydration degree of amorphous phases of supplementary cementitious materials
within cement blends.