Waterproof, hydraulic or natural hydraulic? – Characterization of a set of historic mortars from Paphos (Cyprus)

Abstract

Defining the hydraulic properties of historic lime mortars is a complicated task: chemical processes related to both the nature of the material and its degradation heavily influence the possibility of correctly assessing the existence and the extent of hydraulic components. Furthermore, terminological issues contribute to the confusion and uncertainty, with terms such as waterproof, hydraulic, natural hydraulic, natural cement, and watertight being used improperly, especially in the field of traditional archaeology. This paper aims at offering an interpretation of the hydraulicity degree in a set of historic mortars collected from the modern-day district of Paphos (Cyprus) through an interdisciplinary analytical approach. Eventually, determining the hydraulic character of a historic mortar is a matter of careful evaluation of multiscale data, starting with the interpretation of the context and ending with the characterization of the mixture components.

The samples collected from key archaeological sites near Paphos all pertained to water-related structures, although their hydraulic character could not be properly addressed; after the analytical procedure, we were able to categorize and define their physical and chemical properties in relation to their water containment function. At least two different types of renders for water-related structures were used in Paphos between the Late Bronze Age and the Roman time: one group consists of air lime binder with pozzolanic materials, while the second is a lime-based mixture with higher hydraulic properties.