*2.5. Evaluation of Water Absorptivity of Cement Paste Samples*

The water absorptivity of the cement paste samples was evaluated as follows: the mass 'A' of cement pastes was measured after removing all uncombined water through drying the samples to a constant weight. Subsequently, the samples were placed in the vessel with water. Immediately after the samples were removed from the vessel, their surfaces were carefully dried with a cloth. After that, the mass 'B', corresponding to the maximum saturated cement paste samples, was measured. The water absorptivity was calculated as the difference between B and A in relation to A, and is expressed in percentages.

#### *2.6. Evaluation of Microstructure of Cement Paste Samples*

The microstructure of the surface of the cement paste samples was observed using scanning electron microscopy (SEM JEOL model JSM-6610A) with secondary electron mode.
