Mineral and mechanical characterization of earthen building materials from Argentina

Abstract

The use of sediments for the construction of earthen buildings was a technological development used in every continent, from prehistoric times until the present. Earthen building techniques are varied, and they can be classified in three general types: monolithic systems (rammed earth), brickworks (adobe o mudbrick), mixed systems (wattle and daub) and earthen plasters and mortars. Nevertheless, the recognition of archaeological evidence indicative of these kind of buildings is problematical, because this kind of architecture is vulnerable to destruction by weathering, especially by wind and water erosion. Rainer (2008) emphasized that, in addition to environmental variables, the type of building material is a key factor affecting their composition and deterioration. The presence of swelling clays, hydrolytic weathering of minerals, mechanical erosion produced by rain drops, meteo-climatic factors, and discontinuities produced by the geological materials are among the major causes that produce the physical and chemical deterioration of the earthen architecture. The determination of texture, plasticity and mineralogy is important to understand the behaviour of earthen building materials (Spengler et al. 2011). However, detailed mineral and petrographic investigations on the earthen building materials from Andean prehispanic cultures are scarces, and over NW Argentine cultures were never carried out. The aim of this contribution is to fill in part this gap. A petrographic classification of the earthen building materials will certainly contribute to understand their weathering and decay processes, and to define parameters for their determination in archaeological contexts.