*Specific and apparent density*

The material's specific density and its drop after thermal exposure were determined using a helium pycnometer ULTRAPYCNOMETR 1000, Quantachrome, while the apparent density was determined by the geometrical method, using an electronic caliper (measuring accuracy up to 0.01 mm) and a RADWAG analytical balance, with a measurement accuracy of 0.001/0.01 g.

*Porosity*

Based on the specific and apparent densities, porosity can be evaluated by the formula 1:

$$P = 1 - \frac{\rho\_0}{\rho} \tag{1}$$

where *ρ*<sup>0</sup> *and ρ* are, respectively, apparent and specific density.
