The Niokastro of Pylos: Conditions Survey through Microscopy, Imaging and Computing Technologies

Abstract

In the present study, structural condition survey of the castle of Pylos, (Niokastro castle), a historical monument dated in 15th century conducted. Stone and mortar samples from the masonries of the monument have been analyzed for the identification of their preservation state, physic-chemical characteristics, their manufacture techniques, and their provenance via microscopy, imaging techniques with the application of new technology computing program (ArcGIS). Fifteen historical mortar and sixteen building stones samples were collected from eight regions of the monument (perimetrical). The specimens include mortars from different construction phases of the monument. Optical microscopy (LED), grain size distribution analysis (in mortar samples), Scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDS), X-ray diffraction (XRD) technique, were performed in castle’s stone and mortar samples. In order to examine the provenance of the construction materials of the monument, samples PLs, Ptk, KsKd originated from Pylos, examined by SEM/EDS and XRD analysis. The obtained data reveal that the castle is mainly made of two types of local stones the gray limestone and the yellow sandstone. Between the two types of stones sandstones introduced in a more eroded state than lime-stones. Historical mortar samples are classified in five categories according their application (structural, structural for sandstone blocks, forehead-structural, renderings, and structural reconstruction mortars). Mortar samples that appear more contaminated are from the areas of initial gate of the monument, the western wall, the reconstruction mortars and these that belong to the external sides of the monument. Calcite is the most abundant mineral in the stone and mortar samples, was identified by XRD. Sulfur oxides presented in elemental composition mainly of mortar samples is due to dry and wet deposition of atmospheric SO2 and aerosol. Its reaction with the calcium carbonate constituting the binding component of the lime mortar, leads to the formation of gypsum (CaSO4.2H2O), as confirmed by the XRD data. The microscopic, mineralogical, chemical and physical data, collected on the bulk mortar and their binder material show the constant use of a high-quality lime. From the grain size distribution analysis, the binder aggregate ratio (B/Ag) was identified, range from 1/2 to 1/3. The most conspicuous differences between mortar samples lie in the aggregate content, that have similar mineralogical composition, but the granulometry is different, depending on the mortar function in the monument and the construction phase to which they belong. The coarser aggregates with grains up to 1.960mm have mostly siliceous composition and the finer grains are of calcareous composition both derive from local origins. Three thematic maps via computer mapping software (ArcGIS) to emerge the process and the outcomes of the research were created. The implementation of GIS achieves the goal, where a document remains usable and useful after its initial creation. Datasets used should meet four criteria: (1) that the dataset remain accessible by more than one person (2) that it can integrate with other types of data (3) that it is easily updated with future research, and (4) that it results in the creation of accompanying .