Behavior of Sandstones Under Heat Treatment

• Published in: International journal of thermophysics 2017-04, Vol.38 (4), p.1-9, Article 60
• Main Authors: Keppert, M., Fořt, J., Trník, A., Koňáková, D., Vejmelková, E., Pokorný, J., Svora, P., Pavlík, Z., Černý, R.
• Format: Article
• Language: English
• Subjects: Calcite; Classical Mechanics; Clay minerals; Composition; Compressive strength; Condensed Matter Physics; Cracking (fracturing); Geophysics; Heat treatment; Humidity; Industrial Chemistry/Chemical Engineering; Mechanical properties; Moisture and Thermal Measurements in Industry and Science; Physical Chemistry; Physics; Physics and Astronomy; Porosity; Porous materials; Porous media; Quartz; Residual strength; Sandstone; Sedimentary rocks; Temperature dependence; Tempmeko 2016; TEMPMEKO 2016: Selected Papers of the 13th International Symposium on Temperature; Thermodynamics; Tunnel construction
• ISSN: 0195-928X; 1572-9567
• DOI: 10.1007/s10765-017-2191-0

Knowledge of materials behavior under heat treatment is of high importance in construction and safety engineering; tunnels represent a special field because of their specific safety issues. In the case of fire, tunnel structure and surrounding rock are subjected to extreme temperatures which induces irreversible changes in the material’s microstructure and consequently its mechanical properties. Significant portion of the Earth’s crust is formed by sandstones; this group of sedimentary rocks is highly variable in structure, composition and engineering properties. Quartz grains (alternatively together with other minerals) form the clastic part of sandstones; the space between clasts is filled by variable amount of cement and matrix which can contain particularly clay minerals, quartz and calcite. The porosity of sandstones is again highly variable from a nearly compact material to a highly porous one. The paper aims to find out and explain differences in response of various kinds of sandstones to heat treatment. The behavior of a representative set of sandstones under heat treatment was studied by TG/DSC, thermodilatometry and residual strength measurement. These experiments were accompanied by SEM and porosimetry measurement. The effect of increased temperature on the compressive strength was found to be crucially dependent on the nature of the cement and matrix present in the individual rock. The rocks with calcite cement which had high initial strength and low porosity were damaged by calcite decomposition. The siliceous sandstones were damaged by cracking due to thermally induced volume changes. In contrary, the strength of the clayey sandstones was even improved after the heat treatment. It can be concluded that behavior of sandstone under heat treatment is controlled by its composition and diagenesis.