SPECIAL ISSUE Experimental and numerical study of hygro-thermo-mechanical properties of ‘‘Schilfsandstein’’ from Baden-Wu ¨ rttemberg J. Oz ˇbolt Æ G. Grassegger Æ P. Van der Veken Æ G. Peris ˇkic ´ Æ H.-W. Reinhardt Received: 25 April 2008 / Accepted: 25 June 2008 / Published online: 22 July 2008 Ó Springer-Verlag 2008 Abstract In the present paper the results of experimental and numerical investigations of hygro-thermo-mechanical properties of ‘‘Schilfsandstein’’ from Baden-Wu ¨rttemberg are presented and discussed. The aim of the study was to investigate the influence of extreme environmental condi- tions causing severe damage that can often be observed on various monuments during restoration and reconstruction process. In the experimental investigations the stone specimen was exposed to extreme hygro-thermal condi- tions, which caused significant damage (cracking). During the experiment the ultrasonic and acoustic emission anal- yses were performed. Subsequently, a 3D finite element analysis was carried out using a coupled hygro-thermo- mechanical model for stone. The experimental and numerical results indicate that wetting in combination with either decrease or increase of temperature lead to severe damage. The most critical locations for initialization of cracks are sharp spikes (notches), or acute angles that are inward or outward oriented (corners). Stiff but brittle lay- ers, like late diagenetic iron cementations, might be a weak point for the initialization of crack. Furthermore, the bed- ding direction (anisotropy) seems to be a preferred direction for crack propagation. The results of the numer- ical analysis are in relatively good agreement with experimental observations. Keywords ‘‘Schilfsandstein’’ from Baden-Wu ¨rttemberg  Extreme environmental conditions  Damage  Experiments  3D hygro-thermo-mechanical model  Finite element analysis Introduction During restoration and reconstruction process on various monuments, e.g. Monrepos Castle/Ludwigsburg, Kilians Church/Heilbronn, sudden ruptures of working pieces occurred (Fig. 1). The damage could be observed after transportation, after being transported by work-loading equipment on the scaffolding and also during storage (Fig. 2). Similar behaviour such as sudden cracking shortly after exploitation could also be observed. Reasons dis- cussed as possible causes of damage are: not appropriate storage, stresses caused by transportation, internal stresses due to climatic loading (temperature and moisture), rock cutting and related release of confinement stresses or rea- sons due to the rock producing-equipment. Common causes for cracks like weathering or ageing could be excluded, because the material was freshly cut out of the quarry (Grassegger 1998). To clarify the possible reasons for this severe damage on sandstone (Schilfsandstein) specimens, experimental and numerical investigations are carried out. The results of these experimental and numer- ical studies are presented in the present paper. Petrographic properties of Schilfsandstein from Baden-Wu ¨ rttemberg The Schilfsandstein in Baden-Wu ¨ rttemberg is a fine-grained lithic (arenite) sandstone to feldspar arenite-sandstone J. Oz ˇbolt (&)  P. Van der Veken  G. Peris ˇkic ´  H.-W. Reinhardt Institut fu ¨r Werkstoffe im Bauwesen, University of Stuttgart, Pfaffenwaldring 4, 70569 Stuttgart, Germany e-mail: ozbolt@iwb.uni-stuttgart.de G. Grassegger Materialpru ¨fungsanstalt (MPA), University Stuttgart, Pfaffenwaldring 4, 70569 Stuttgart, Germany e-mail: gabriele.grassegger@mpa.uni-stuttgart.de 123 Environ Geol (2008) 56:535–546 DOI 10.1007/s00254-008-1467-x