Characterization of Late Antiquity mortars and plasters through the example of a Peristylli House around the Church of Laodikeia

Mortars and plasters, much like in contemporary civil engineering, are indispensable elements in ensuring the structural integrity and preserving the aesthetic character of historical monuments. These materials, through their functional performance during the construction phase and throughout the subsequent lifespan of a structure, play a pivotal role in the endurance of cultural heritage. Consequently, restoration and conservation interventions on historical buildings demand an exceptionally meticulous and scientifically grounded approach that respects the authenticity of the existing structure and aims for long-term sustainability. Past experiences in restoration projects have unequivocally demonstrated that the use of mortars and plasters prepared with inappropriate proportions or materials incompatible with the original structure can lead to irreversible physical and chemical degradation of ancient structures. To counteract these detrimental outcomes and to develop durable mortar and plaster solutions that seamlessly integrate with the historical fabric, a detailed characterization of the chemical composition and physical properties of the original binding and finishing materials is an absolute imperative. In this context, the present study aimed to comprehensively elucidate the properties of mortar and plaster samples obtained from the Church-Peristyle House in the ancient city of Laodikeia through extensive analyses. The advanced laboratory analyses conducted within the scope of this research include: X-ray fluorescence (XRF) for elemental composition analysis, petrographic analyses for the determination of aggregate and binder morphology, thermal analyses (TGA/DTA) for assessing the degree of carbonation and identifying the binder type, point load testing for mechanical strength determination, acid loss analysis for estimating carbonate content and binder-aggregate ratio, calcination analysis for quantifying volatile matter and carbonate loss, spot tests for identifying the presence of specific ions, conductivity measurements for determining soluble salt content, pozzolanic activity testing for evaluating the hydraulic properties of the binder, and porosity analyses for characterizing the pore structure of the material. The data acquired through these comprehensive analyses were rigorously evaluated within a scientific framework. Based on the insights derived from these in-depth analytical results, precise and authentic mortar recipes that are fully compatible with the architectural characteristics and environmental conditions of the Church-Peristyle House have been formulated. This methodological approach serves as a robust, scientifically-grounded guideline for future conservation and restoration interventions, marking a significant step in transmitting this important historical structure in Laodikeia to future generations.