*2.2. Sample Preparation*

To prepare the cement paste mixes, the graphite powder and cement were dry-mixed first, in a laboratory bench-scale mixer, for 2 min, and then water was added. Immediately, when the water was added, the mixer was started at a slow speed for 60 s and high speed for 30 s. Then, the mixer was stopped for 90 s, and during the first 30 s, the paste adhering to the walls and bottom of the bowl was removed with a scraper and placed in the middle of the bowl. Mixing was then continued at high speed, for a further 60 s. It should be noted that no chemical admixtures were used to aid the dispersion of the graphite. When mixing was completed, the fresh paste was cast in three layers of equal thicknesses, in oiled stainless-steel moulds. For compressive strength, the specimens had a size of 40 <sup>×</sup> <sup>40</sup> <sup>×</sup> 40 mm3; for micro-indentation, the cylindrical specimens were 50 mm diameter and 100 mm height; and for electrical conductivity, the prismatic specimens had a size of 40 <sup>×</sup> <sup>40</sup> <sup>×</sup> 160 mm3. The specimen size was reduced by half (20 <sup>×</sup> <sup>20</sup> <sup>×</sup> 80 mm3) for electrical impedance spectroscopy testing. The specimens were demolded after 24 h and cured in a water tank, at temperatures of 20 ± 2 ◦C and a relative humidity 60%, until testing.
