Sandstone Colour Change due to the High Temperature Exposure

Abstract

An analysis of colour change in sandstone under the influence of heat is presented in this paper. The colour change observed is primarily a result of transformations occurring within the material. The colour change may be used to reveal the exposure temperature of stone elements subjected to fire, from which the corresponding damage can be estimated. The paper presents the results of tests carried out on sandstone with a clayey-ferruginous binder. The colour change was investigated using Scion Image v.4.0.3, an image analysis software package (Scion Corporation ©, USA). In the proposed method the digital image is split into three RGB colour components: red, green and blue, which are then presented as a histogram using counts of pixel intensity. The histogram results show colour distributions in unheated sandstone material and in material heated to temperatures ranging from 200 to 1000 °C. The significant colour changes in tested stones was observed and attributed to the presence in sandstone structure of minerals with iron compounds.