Selection of Consolidants for Use on the Tower of Belem / Auswahl eines Steinfestigers für den Turm von Belem

During the exterior conservation project of the Tower of Belem, Lisbon, it was noticed that although most of the Lioz limestone used in its construction was in good condition, some specific areas presented severe powdering and flaking deterioration patterns. These are mainly due to the effect of natural weathering, including anthropogenic air-pollution, on poorer quality Lioz limestone. Since the deterioration affects mainly the immediate surface and subsurface of the stone blocks, the application of stone consolidants was considered as the most appropriate solution for this problem. This paper describes the difficulties encountered in the evaluation of the tested consolidants-an ethyl silicate ester, an acrylic resin and an epoxy resin-appliedin situ.The laboratory and on-site testing used in the final selection are described as well as the actual approach to consolidating the different areas that required this treatment.