Archaeometric study of natural hydraulic mortars: the case of the late roman Villa dell’Oratorio (Florence, Italy).

This paper shows the results of the study of the mortars from the late roman Villa dell’Oratorio (4th-6th A.D.), an aristocratic mansion built in the lower Valdarno (Florence, Italy) (Alderighi et al., 2011). Thirty-one bedding and plaster mortar samples were analyzed through optical microscopy, thermogravimetric analysis, X-ray powder diffraction and scanning electron microscopy with energy dispersive spectroscopy, while their main physical properties were measured with geotechnical procedures. The collected data shows that the analyzed mortars are made up of very fine to coarse sandy aggregates and white to yellowish white natural hydraulic lime binders consisting mainly of mixtures of calcite and CSH phases. The aggregates were recognized to be selected Arno sand, while the binders are the firing product of a local clay-rich limestone (Alberese), a stone that has been historically used for the production of lime (Fratini et al., 1994). Therefore, in the lower Valdarno, the mortars of the Roman Villa dell’Oratorio are an interesting case of natural hydraulic lime obtained by firing marly limestones.