Phase composition and temperature dependence of Young’s modulus and damping of natural basalt and its melt cast product

Natural basalt (rock) and its melt cast product (tile) are compared with respect to phase composition, density and porosity, as well as Young’s modulus and damping. Although the phase composition of the rock (pyroxene, olivine, anorthite, nepheline, spinel, < 11 % glass phase) is much more complex than that of the corresponding tile (pyroxene, olivine, < 44 % glass phase), both materials have similar Young’s moduli at room temperature (around 107 ± 5 GPa, significantly lower than the lowest predictions, 122–137 GPa). However, the temperature dependence of Young’s modulus and damping is completely different: while the rock exhibits severe microcracking during thermal cycling to 800 °C (but only in the first cycle, without significant damage accumulation in repeated cycles), the tile does not exhibit microcracking during thermal cycling at all and behaves in a completely reversible manner. Damping is much lower in the tile than in the rock.