Elevated temperature causes changes in mechanical properties of rock, due to thermal effect and mineralogical transformations, which show great varieties for different lithologies. The present paper provides information on seven different sandstones. The studied predominantly quartz sandstones show different petrology from fine-grained to coarse-grained with silica, carbonate and clayey cement. The changes in rigidity as a function of temperature were documented. The analyzed data set includes the uniaxial compressive strength and indirect tensile strength measured at 22°C, 150°C, 300°C, 450°C, 600°C, 750°C and at 900°C, respectively. The test results allowed determining the changes in rigidity. Brinke number was also calculated and clearly show a trend with increasing temperature. The Brinke number of the studied sandstones was in the range of 5–20, showing the higher values at higher temperatures. Constants were calculated for equations describing the trends in changes of rigidity. Our results indicate that the rigidity of sandstone depend on thermal conditions and show different rate of changes depending on the micro-fabric and petrological characteristics of sandstone.
Recently, the influence of the heating on the physical and mineralogical composition of stones is in the focus of research. Due to heating shock the petrophysical constants of the rocks show some changes (e.g. Brontóns et al. 2013, Tian et al. 2012; Tian et al. 2014). Studying the relationships between the heating temperature and the rock mechanical parameters is an important issue in understanding the material behavior in fire related accidents, such as tunnel fire (Smith & Pells 2008).
Many of the publications focused on the mineral and color changes of sandstones after heating (e.g. Hajpál & Török 2004, TÖrÖk & Hajpál 2005, Hajpál 2006, 2007, 2008), some recent papers dealt with other parameters, too (Kompaníková et al. 2014). In this paper we analyzed and recalculated the published results of Hajpál (2002).
Both non-destructive and destructive tests were carried out by Hajpál (2002). The effect of heat was studied on seven different German sandstones. From the sandstone blocks nearly 1500 cylindrical specimens (40 mm in diameter and 40 mm to 80 mm in length) were core-drilled.