The diffraction pattern is a reflection of the crystal structure state in which the compound is in. So, as long as the compound maintains the same lattice structure, the diffraction pattern should remain the same. In the instance that adding to the water content of your cement compound only expands the lattice without changing the structure pattern, then you will notice a shift in the peak position of the diffraction pattern reflecting a change in the d spacing. But, in the instance that increasing the water content of your cement compound the lattice structure pattern will change, then the diffraction pattern will be different. These cement compounds are characterized by an ability to retain water and swell; to my understanding, their structures do not change, but rather just swell. If you wish to learn further on this topic, I would recommend contacting a materials chemist who would know much more on ceramics and their structures.