MORTAR AND PLASTER ANALYSIS AS A DIRECTIVE TO THE DESIGN OF COMPATIBLE RESTORATION MATERIALS IN FRANGOKASTELLO (CRETE)

Abstract

In this study the results of physico-chemical analysis for mortar and plaster specimens from Frangokastello castle in Sfakia (western Crete) and the subsequent designing of compatible restoration mortars are being presented, as part of a wider project for the sustainable management of the monument. In order to compose a compatible restoration mortar or plaster a reverse engineering process has been adopted. Primarily, a study of mortar and plaster specimens, that constitute a representative sampling from the monument, was performed. The analyses included macrosopic characterisation and microstructural examination using microscopy on samples and on fine polished cross-sections of them. Additionally, chemical and mineralogical analyses were executed including Fourier transformation infrared spectroscopy (FT-IR) and X-ray diffraction analysis (XRD). In the framework of thermal analysis, thermogravimetric and differential thermal analysis (TGA and DTA) were performed in order to obtain information regarding hydraulic components of the mortars. Finally, the granulometric curves of selected specimens were produced and contributed to the classification of samples in different groups and construction phases. Elaborating all these results and the state of the conservation, compatible raw materials were chosen, including hydraulic lime and other binder and aggregates. The designed mortars were subjected to durability tests, so that the mechanical behavior of the restoration mortar could be comparable to the historic ones. Subsequently, colouring experiments were carried out in order to approach one or more existing plasters for partial use. The result of this work aims to constitute a directive for the restoration of the monument, concerning the use of compatible mortars.