Performance of bio-mortar under elevated temperatures

The microbially induced calcite precipitation was used to bind sand grains, yielding consolidated material known as bio-mortar. An aerobic, urease-active and nonpathogenic Sporosarcina pasteurii microorganism was used for the induction of calcite precipitation. Three different temperatures (250, 500 and 750 °C) were applied to examine the firing resistivity of bio-mortar. The results showed that the organic fiber of died bacterial cells completely dissociates at 500 °C, causing a moderate compressive strength reduction and mass loss increment in bio-mortar. The exposure of bio-mortar to 750 °C leads to a significant compressive strength regression, due to the thermal decomposition of CaCO₃ as confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and differential thermal analysis (TG and DTA) as well as scanning electron microscopy.