From material analysis to mortar design: conservation science investigations for the preservation of the Fortress of Bashtovë in Albania

The ruin of the Fortress of Bashtovë, built in the fifteenth century, is a significant example of Albanian cultural heritage. To assess the material characteristics and the state of preservation, mortar and stone samples were analyzed using various microscopic techniques. The results revealed well-preserved lime mortars and related binders with natural hydraulic properties, attributed to the use of a locally sourced, impure limestone, or lime sediment in its original construction. The condition and deterioration pattern of the building stones was strongly dependent on their petrological characteristics, position and the quality of historical and modern mortar systems. Based on in situ observations and the results of the analyses, an appropriate mortar system was developed and applied on-site during a conservation campaign. It was essential to formulate a recipe that could be easily mixed on-site while exhibiting optimal properties for the fortress’ walls. In addition, a workshop was conducted to ensure workers mastered the mortar preparation, application techniques, and curing practices crucial for the successful restoration of the fortress.