The article focuses on the analytical characterization of ancient mortars from the Roman archaeological site of Pisões in Southern Portugal. Various analytical techniques such as X-ray diffractometry, thermogravimetry, microscopy, potentiometry, and combustion analysis were employed to study the composition and conservation state of the mortars.
The mortars exhibited a calcitic matrix with low magnesium content, likely derived from burning calcareous stone at temperatures below 800-900°C. Local aggregates and ceramic fragments were used in mortar formulation, with some mortars containing lime lumps. The Roman builders may have sourced limestone from a nearby quarry for binder production.
The study revealed that the mortars were non-hydraulic, with hydraulicity potentially introduced through ceramic or pozzolanic materials. The composition of the mortars varied based on their location and use within the archaeological site, aligning with findings from other studies on Roman structures in the Iberian Peninsula.
The presence of hydraulic products and recrystallized calcium carbonate contributed to the good cohesion, mechanical strength, and long-term durability of the mortars. Additionally, no significant amounts of detrimental compounds like soluble salts were detected, indicating a favourable state of conservation.
The data obtained from this study can be valuable for developing compatible repair mortars and formulating an appropriate conservation strategy for the Pisões archaeological complex. Overall, the careful selection of raw materials and skilled craftsmanship by the Roman builders played a crucial role in the preservation and durability of the ancient mortars at the site.
