A Study on the Historical Materials of the Apollo Pythios Temple in Rhodes and the Evaluation of Potential Restoration Materials

The Temple of Apollo Pythios, built in the Hellenistic era (3rd–1st century BC), is located in the ancient Acropolis of Rhodes. It was excavated during the Italian occupation and reconstructed by the Italians in the period 1937–8. The method of the “scenographic” restoration was the “mixed structure” technique using a core of reinforced concrete in combination with new biocalcarenite stones and the integration of very few ancient architectural members. Its proximity to the sea and the corresponding salt decay phenomena, aggravated by the erroneous reconstruction methodology and materials, have further deteriorated its state of preservation. Today, the four columns, epistyle and entablature of the Italian interventions demand immediate restoration actions to ensure the monument’s sustainability. This can only be achieved through a combined study of the performance of potential restoration materials and assessment of their compatibility with the historical materials. In the present study, the characteristics of the Temple’s historical porous stones are presented along with the characteristics of five quarry stones, aiming to evaluate which quarry stone is the most appropriate for use in the upcoming restoration. Restoration mortars are designed and evaluated in respect to both the historical materials and the quarry stones, aiming to select the optimum restoration mortar, which can achieve the required level of performance and compatibility and ensure sustainability of the structure as a whole.