Laboratory simulation of temperature changes by insolation and fire and their influence on physical properties of travertines

The influence of insolation and fire represents important factor for study of historical object destruction. The results have shown that temperature changes by insolation (60°C) and fire (200, 400, 600, and 800°C) significantly contributed to the change of physical properties of Slovak travertine from Spi ské Podhradie and Ludrová. Research was oriented not only on a visual change of rocks (colour change, brightness and surface roughness), but also on the quantitative and qualitative analyses of mineral composition, connected with structural changes as well as study of selected physical properties. The micropetrographic study indicated that increasing of temperature was followed by expand of fractures as reflected even change of true and specific bulk density. Significant increase of microcracks was determined at 600°C by optical microscopy. The macroscopic observation of microcracks was visible at 800°C subsequently followed by destruction of samples. By spectrophotometry was visible colour change by increasing of temperature. The brightness of travertine samples was decreasing till 600°C, but after 600°C it became markedly increasing. With increasing of temperature travertine surface samples had also change from a few hundred nanometres to several microns. The investigation of thermal decay by insolation and fire may lead to an improved assessment of natural building stones that have been used as building and decorative stone on ancient monument.