Expected performances for mosaic-grouting monitoring by GPR

Due to the 1999 Athens earthquake, both the masonry structure and the mosaics of the Katholikon of Dafni¿s Monastery have suffered severe damages. In order to design the appropriate intervention scheme for mosaic conservation, first for the detection and mapping of delaminated mosaic¿s areas, and second for the monitoring the movement of the grout during injection, using a non-destructive testing such as ground-penetrating radar, presents a great interest. Two experimental studies have been realized on the mosaics. The first one concerns GPR mapping on some mosaics in-situ, in order to find out the exact location of doubtful zones including delamination, changes of structures (i.e. recent repairs) or buried heterogeneities. The second one is focused on the GPR monitoring of mosaic grouting. Thus, a physical model has been built with old pieces of thick lime plaster put together with lime mortar, including known voids in order to develop the survey methodology and define the performances and limits that one can expect. Results show that one can follow the grouting spreading inside the physical model. This point enables us to forecast a methodology of grouting evaluation, in terms of quality, extension and quantity, for the ancient mosaics in-situ.