Einfluss von Temperaturänderungen auf die mineralogischen und physikalischen Eigenschaften von Sandstein. Ergebnisse von Untersuchungen im Labor / Effect of Temperature Changes on the Mineralogy and Physical Properties of Sandstones. A Laboratory Study

Fires and high temperatures cause changes in the physical properties and mineralogical composition of sandstones that are commonly used in monuments. To assess these changes cylindrical specimens of seven German and three Hungarian sandstones were tested in the laboratory by submitting the samples to increasing temperatures, from room temperature to heating at 150 °C, 300 °C, 450 °C, 600 °C, 750 °C and 900 °C. The pétrographie analyses (polarizing microscope, XRD, SEM) and physical parameters (density, porosity, water absoφtion, ultrasonic sound velocity, uniaxial compressive and indirect tensile strength) have shown that quartz sandstones of various cement and grain size behave differently after heating to high temperatures. The heat resistance depends on the type of the cementing mineral, the amount of cement, and the grain size. The strength of clayey and clayey ferruginous sandstones generally decrease less than that of some silica-cemented ones. Carbonate-cemented sandstones often disintegrate at temperatures above 900 °C due to portlandite reactions. The fine-grained matrix-rich sandstones have the best physical parameters after being subjected to elevated temperatures while the coarse-grained matrix-poor sandstones represents the lower end of the physical spectra.