*3.3. Compressive Strength and Elasticity at Room Temperature*

Average pace of compressive loading was equal to 4 Mpa/s. The photos of the specimens were taken during the tests from one or two perpendicular directions in order to determine the strains with the use of DIC software after the tests. The virtual tensiometers with the length of approximately 10 mm were used.

The stress–strain relations for each specimen in compression were calibrated with the use of linear function, where modulus elasticity at compression was assumed as a directional coefficient of these functions. If two digital cameras were used, moduli of elasticity values were calculated on each direction separately.

Compressive strength was calculated as the force at failure divided by the crosssection area.
