Multi-technical characterization of Roman mortars from Complutum, Spain

This paper provides a multi-technical characterization of mortar samples from the Roman city Complutum. It aims to contribute to future conservation projects as well as archaeological research on Roman construction techniques. Archaeological mortar samples were analysed via binder aggregate ratio, grain size distribution and POM, XRD, SEM/EDS, TGA/DSC, XRF and isotope analysis (δO and δC). The analyses provided information on how mortar was prepared by Roman builders. Sub-rounded sand aggregates collected from Henares riverbank and Tertiary-age limestone were used in lime production. To make the mortar hydraulic, ceramic dust, fly ash, chamotte, and charcoal were used. Generally, a planned and consistent mortar manufacture can be deduced. In two construction phases there exist slight differences in mortar production. In the second phase more aggregate were preferred after empirical knowledge gained about crack formation. The combined measurement techniques utilized in this study permitted relative dating of the mortar based on compositional types