What fixes architect's reason and sense? Materials study of CTU facade mosaic mortar

摘要

A bedding mortar of the stone mosaic Architect's Reason and Sense situated on the facade of the Faculty of Civil Engineering, CTU in Prague was characterized by microscopic techniques, thermal analysis and gas chromatography. The mortar is based on Portland cement. Polymict concrete sand was used as an aggregate. The mortar was strongly carbonated. The choice of inorganic materials used in the mortar bed as well as the mosaics fixation on reinforced concrete panels corresponds to a common technique of mosaic installation of the time. However, the presence of 8 wt% of organics consisting predominantly of stearic, palmitic and erucic fatty acids in the mortar was unexpected. It indicates that the mosaic mortar was probably modified with a water repellent based on water-dispersed fatty acid salts to improve durability of the mortar. Such dispersions were available in Czechoslovakia at the time of the mosaics origin (1970s).