Archaeometric study of Roman bricks and cocciopesto aggregates from the ancient city of Nysa, Western Anatolia

The aim of this study is to identify the similarities and differences in the raw material properties and manufacturing processes of the building bricks and cocciopesto aggregates present in the lime mortars and plasters from the ancient city of Nysa. For this purpose, X-ray diffraction, Fourier transformed infrared spectroscopy, X-ray fluorescence spectroscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, and thermogravimetric analysis were used to determine their pozzolanic activities, chemical and mineralogical compositions, and microstructural properties. The XRF results were evaluated to determine differences in the chemical composition of the building bricks and cocciopesto aggregates using empirical statistical analyses. Analyses included descriptive statistics, scatter plots, and hierarchical clustering. The bricks were only partially sintered and did not contain high temperature products such as mullite, indicating moderate firing temperatures (<900 °C). The cocciopesto aggregates used in the mortars exhibit good pozzolanicity, unlike the building bricks, mainly due to their higher content of amorphous products. This suggests that pozzolanic cocciopesto aggregates were intentionally produced for the purpose of obtaining hydraulic mortars. The significant statistical differences in major oxide and trace element compositions suggest that the use of raw materials with different chemical compositions in the production of bricks and aggregates. The results reveal that pozzolanic cocciopesto aggregates were intentionally manufactured differently to building bricks to create hydraulic lime mortars.