António Sousa Gago

Earth is a complex material with mechanical and physical behaviors that differ from modern building materials. The conservation of rammed-earth (RE) constructions presents specific difficulties that are challenging to overcome. A lack of knowledge about RE due to its abandonment for decades and interventions adopting materials and repair methodologies designed for conventional constructions have led to inadequate interventions. In the case of historic defensive constructions, the doubts and technical difficulties are even greater due to the nature of so-called military RE (with physical and mechanical characteristics which differ significantly from those of civil, more common RE) and, not least, due to the historical and cultural heritage value of these constructions. Some important interventions have been carried out recently, while others are underway or in the planning stage, and there is a constant lack of information and technical data regarding the best ways to intervene. To fill this gap, the state of conservation of defensive RE structures and the results of interventions carried out throughout history in the southwest of the Iberian Peninsula are being assessed. This article sets out a framework for the subject, identifies material and construction techniques and recognises the main causes of RE constructions’ deterioration and decay. With special focus on the most frequent damages detected in historic military defensive structures built with RE, it analyses and discusses the most common techniques that have been used for the repair and conservation of these particular structures.