Investigating the manufacturing technology and durability of lime mortars from Amaiur Castle (Navarre, Spain): A chemical–mineralogical and physical study

Abstract Mineralogical, chemical and physical characterization of archaeological lime mortars from different structures at Amaiur Castle (Navarre, Spain) was accomplished in order to comprehend their durability. Mortars from the south-west of the 16th century filling and bastion, and the south-east mortars of the17th century bastion are the most susceptible to deterioration due to their textural features. The high porosity and water absorption capacity, the poor interconnection of pores and slow drying are the main factors contributing to deterioration of mortar at Amaiur Castle. The mineralogical study enabled an approach to the technological knowledge used in the lime mortar manufacturing process at Amaiur Castle. Hydrotalcite and hydromagnesite identified in the mortar binder support the use of the traditional hot-mixing method during mortar manufacturing. This work provides valuable references for the formulation of compatible repair mortars to ensure suitable conservation of the castle as well as of other ancient structures built with similar materials.