Resumen de Investigations of Hellenistic Mortar from Umm Qais (Gadara), Jordan
Ancient mortars have been widely studied, in connection with both diagnosis and applications required for restoration. This study is primarily based on analyses of different mortar samples from a Hellenistic temple. The study was done by means of a polarizing microscope equipped for observations in transmitted and reflected light; and X-ray powder diffraction (XRD). Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) were also used to confirm and supplement the microscopic data, and wet chemical analyses were performed on the acid filtrate for soluble oxides of Fe, Al, Ca, Mg, S, Na and K. Chemical and petrographic analysis were used to determine chemical composition and physical properties, which in turn provide an in-depth understanding of the structural behavior and durability characteristics as they relate to the composition. The results show that the plaster used was a lime-based mortar. The cementing binder was a lime (identified by spot test) with fossilized shell, very fine grain size quartz, and some other minerals as the aggregate. The EDS analysis showed the presence of calcium and a small proportion of magnesium; in addition, silicon, aluminum, potassium, and iron were detected. Possibly, the silicate compounds contributed to the hydraulic component. We found strong similarities among mortar samples used in the temple. Physical methods provided useful information on the mineralogical compounds and the surface structures of samples, allowing for the postulation of deterioration mechanisms and overall decay, including the identification and crystalline morphology of reaction products and salts. These results aid in both understanding the technology of historic mortars and planning the restoration of these mortars.
