Repair mortars for the sandstones of the cathedral of berne

Abstract

Stone repair mortars used on the cathedral of Berne (Switzerland) have been re fi ned from existing recipes. These hydraulic mortars without any organic additions are prepared on the building site. They are applied as two different layers, a coarser ground layer (KMtl) and a fi ner surface layer (DMtl) which imitates the stone material. The investigations were undertaken to understand the overall good practical experiences with these materials, and to anticipate the long term performance of this mortar system under the rough exposure conditions on the cathedral. Laboratory investigations included, petrophysical measurements and thin section analysis, of the individual materials but also on the system of DMtl-KMtl-stone. The investigations suggest that the mortars used are in many ways well adapted to the sandstones on the monument, and that the diverse application methods only provoke small differences in the resulting mortars at an early stage. But only in-situ observations will be able to show whether these small differences will lead to problems after long exposure to the elements. © RILEM 2012.