Abstract Three‐dimensional quantitative image analysis from synchrotron X‐ray microcomputed tomography indicated a coarsening of the microstructure of magnesium potassium phosphate cements driven by crystallization of K‐struvite from the first amorphous product. Porosity and pore surface area increased because of the progressive build‐up of a network of elongated/tabular crystal domains, with density higher than the amorphous. The known increase in strength with time is thought to occur thanks to the overwhelming contribution of a developing interlocked lath‐shaped microstructure. Combined X‐ray and neutron diffraction texture analysis indicated that at least a fraction of K‐struvite nucleates at the surface of MgO grains, suggesting the intervention of more than one crystallization mechanism. The detected weak texture, compatible with a nearly random orientation of crystallites, and the isotropic pore fabric, are beneficial with respect to crack propagation.
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