Properties of Roman structural mortars in the province of Asia (Turkey)

In this study, the properties of Roman structural mortars composed of lime and natural aggregates from twenty-three archaeological sites in Western Anatolia were determined in order to understand whether there was a common production technology of lime mortars in the Roman Empire by making a comparison between Europe and Western Anatolia. Their basic physical and mechanical properties, raw material compositions, microstructural and hydraulic properties, mineralogical and chemical compositions of their lime binder and fine aggregates were identified by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, thermal gravimetric analysis analyses, bulk density, total porosity and compressive strength of mortars. The results indicated that these mortars mortars were produced by combining fat or lean lime with coarse aggregates (quartz, tuff) and predominantly fine pozzolanic rhyolitic and dacitic tuff aggregates. The lime/aggregate ratios of the mortars generally exhibited a range of values between 1:4 and 1.5:1 by weight, which closely paralleled the lime/aggregate ratios in other Roman mortars published in literature. The presence of lime lumps within the mortar matrices, exhibiting a spongy texture, may suggest the use of the hot lime mixing method in the preparation of the mortars. The mortars are hydraulic, possessing compressive strengths comparable to those observed in natural hydraulic lime mortars (NHL2, NHL3.5 and NHL5 types). The results indicate that the production of structural mortars in the province of Asia was similar to that in other regions of the Roman Empire, although the raw materials are similar, small differences in raw material composition could be due to the use of local raw material sources. This may be evidence of a common lime mortar technology that deliberately used pozzolanic aggregates with almost pure lime throughout the Roman Empire.