Thermal and phase analysis of Roman and Late Antiquity mortars from Bulgarian archaeological sites

Abstract

By using the methods of archaeological chemistry—thermal analysis, powder X-ray diffraction analysis, and Fourier transform infrared measurements, 13 mortar samples from the Roman age and Late Antiquity were investigated. The results of the investigation showed the phase composition and probable raw materials that were used. The defined composition, type, and properties of the mortars prove that the same production technology was used in both the Roman and Late Antiquity. The exponential dependence of temperature of the point of inflection (Tinfl) by mass loss (ML) of calcite decarbonation was found, specifying that the decrease in mortar structure homogeneity and compactness leads to a decrease in calcite decarbonation temperature. All studied samples were defined as non-hydraulic lime mortars without any hygroscopic properties. The samples are of different binder to aggregate (B/A) ratios, as no relation between the B/A ratio and the purpose of mortar use was established. The experimental results related to the geological setting of the area provide additional information about people's knowledge of the environment. The results obtained are of fundamental and practical use, helping a future archaeological interpretation.