Absolute Dating of Mortars – Integrating chemical and physical techniques to characterize and select the mortar samples Roald Hayen 1 , Mark Van Strydonck 2 , Elisabetta Boaretto 3 , Alf Lindroos 4 , Jan Heinemeier 5 , Åsa Ringbom 6 , Sophie Hueglin 7 , Danuta Michalska 8 , Irka Hajdas 9 , Fabio Marzaoili 10 , Francesco Maspero 11 , Anna Galli 12 , Gilberto Artioli 13 , Christophe Moreau 14 , Pierre Guibert 15 and Marta Caroselli 16 1 Royal Institute for Cultural Heritage, Belgium, roald.hayen@kikirpa.be 2 Royal Institute for Cultural Heritage, Belgium, mark.vanstrydonck@kikirpa.be 3 Weizmann Institute, Israel, elisabetta.boaretto@weizmann.ac.il 4 Åbo Akademi University, Finland, alindroo@abo.fi 5 Aarhus University, Denmark, jh@phys.au.dk 6 Åbo Akademi University, Finland, aringbom@abo.fi 7 Newcastle University, United Kingdom, sophie.hueglin@newcastle.ac.uk 8 Adam Mickiewicz University, Poland, danumich@amu.edu.pl 9 ETHZ, Switzerland, hajdas@phys.ethz.ch 10 CIRCE and Seconda Università degli Studi di Napoli, Italy, fabio.marzaioli@unina2.it 11 Università degli Studi Milano-Bicocca, Italy, francesco.maspero@mater.unimib.it 12 Università degli Studi Milano-Bicocca, CNR-IFN & INFN, Italy, anna.galli@unimib.it 13 Università di Padova, Italy, gilberto.artioli@unipd.it 14 LMC14, France, christophe-r.moreau@cea.fr 15 CNRS - Université Bordeaux Montaigne, France, pierre.guibert@u-bordeaux-montaigne.fr 16 Univ. of Applied Sciences of Southern Switzerland, Switzerland, marta.caroselli@supsi.ch Abstract. Absolute dating of mortars is crucial when trying to pin down construction phases of archaeological sites and historic stone buildings to a certain point in time or to confirm, but possibly also challenge existing chronologies. It should become a standard tool for archaeometric research as it contributes considerably to the historical, artistic, social, cultural and touristic valorisation of our built heritage. To compare on the one hand the different methods – radiocarbon and OSL – as well as to evaluate the best method of how to prepare samples for radiocarbon dating, an intercomparison study amongst various laboratories was set up. The results of radiocarbon dating of mortars depend very