Analysis and restoration of an exterior plaster floor of the 19th Century

The article describes a case study aimed at analysis of an ancient exterior plaster floor at Karlstejn Castle and the development of a repair mortar of similar characteristics. The floor was cast in situ during extensive restoration works at the end of the 19th century and exhibits surprisingly high durability and strength. The first part of the paper describes a series of tests which were carried out in order to attain a better knowledge of the material. In designing new material to replace the heavily damaged plaster floor of a medieval castle rampart with a similar durability, attention has been paid to fibrous additives and mainly to pozzolan or latent hydraulic admixtures. Some non-standard testing methods were developed and used.