A case study of ancient mortars and concretes from Umm al-Jimal, Jordan with implications for archaeological site conservation

The excavation at Umm al-Jimal, a Late Roman-Byzantine site in northeast Jordan, yielded large amounts of fragmented mortar and concrete. These materials are relevant both to the archaeological context and to the continued care and management of the site. An analysis of the mortars and concretes can reveal the geologic origin of the raw materials, how they were processed, and how technology changed over time. This information, when viewed within the context of the inhabitational history of the site, contributes to an understanding of the site's historic development. It may also shed light on various social, economic and technological aspects of the people who manufactured these materials.; The management of archaeological sites is usually designed as an afterthought to archaeological research. Unfortunately one result is that valuable information can be lost or remain uncollected. There is often a great deal of useful information present in the archaeological record which could be helpful to archaeological site conservators, engineers and planners. Specifically, a complete understanding of the site's original architectural materials provides a basis for decisions regarding the preservation and management of existing site features. Stabilization of existing standing structures cannot be accomplished without an understanding of the original materials used in their construction.; In order to maximize the information available to archaeological site managers, a comprehensive site management plan must be an integral component of the archaeological research design and implementation. This requires integrating an investigation of construction materials into the original archaeological research model. The origin, manufacture, use and subsequent deterioration of these materials, as well as their archaeological context are important to the conservation plan.; Ancient mortars and concretes from Umm al-Jimal proved to be complex mixtures containing both raw geologic, biological and human processed components. This formulation gave the original mortars and concretes specific qualities of physical strength and durability. These compounds are markedly different from modern materials, such as Portland cement, frequently used to “stabilize” archaeological structures. Analysis indicates that all of the materials used in the manufacture of the ancient mortars and concretes were locally available to the historic occupants of Umm al-Jimal.