Survey of repaired and artificial stones of the archaeological site of pella five years after application

Abstract

An extensive restoration project was realized in the Archaeological site of Pella, in order to consolidate ancient stone remnants by filling them with mortar and manufacture artificial units of stone for anastylosis purposes. Samples of ancient stones were analyzed, regarding their morphological, physico-mechanical and chemical properties. Based on the evaluation of the analysis results, repair mortars were designed and tested for their compatibility with old stones. An in situ monitoring of the repair works took place, while samples for testing were taken from the site 2 and 5 years after the interventions. In this paper the results of the analysis of an adequate number of repaired and artificial stones are presented. The survey showed some cracks on few large stone units (100 × 50 × 30 cm) precast or cast in place. The analysis followed comprised color determination, measurement of compressive strength, modulus of elasticity and porosity properties. Microstructure examination was made, assisted by stereoscope and SEM-EDS, while soluble salt content and residual resistance to wetting-drying cycles were also carried out. The results were compared with the previous ones at earlier age, as well as with those of the authentic stone of Pella. Based on them, it seems that properly designed mortars are effective for consolidating or for completing missing parts of old stones without problems related with the existing microstructure and the resisting environmental cycling of the area. The characteristics of the designed repair mortars seem to be compatible with those of the old stones. The cracks appeared in some artificial stone units could be attributed to thermal load effects, as well as to lack of adequate curing.