Technological and microstructural characterization of mortars and plasters from the Roman site of Qasr Azraq, in Jordan

Abstract This work presents the analytical results of the mortars and plasters characterization from Qasr Azraq, located in the city of Azraq (north-eastern Jordan). The castle has undergone several interventions and modifications during its service life; the archaeological surveys have shown that the actual building is a medieval reconstruction of a Roman fort, still reflecting the original structure. This research paper encompasses 64 samples from different historical periods and structures of the monument, aiming to reconstruct the timeline of different phases and to highlight technological choices. Conclusions are drawn on the basis of interpretation and integration of in situ observations, historical data and analytical data. The mortars were characterized following a multidisciplinary approach, combining macroscopic observation with petrographic examination, mineralogical analysis (XRD), microstructural and chemical analysis (SEM-EDS) and quasi-quantitative chemical analysis (pXRF) of mortar samples. Moreover, microstructural and mechanical properties of representative samples were studied. The results indicate the use of five different types of mortars, grouped based on composition and characteristics of binder and aggregates, ranging from pure lime mortars to hydraulic, gypsum-lime and earthen mortars. Overall, this paper contributes to the better understanding of building techniques and mortar production technology in the Near East during time.