Rammed earth: feasibility of a global concept applied locally

Abstract

Rammed earth is an ancient building technique that has been continuously reinvented in the dynamic movement of people all over the world, where it has been used to build from dwellings to enormous fortresses and city walls. In the particular case of Portugal, the inhabitants have been closely related to earth construction. From one region to another, rammed earth, adobe and wattle-and-daub buildings are frequently found. The rammed earth construction is mainly found in the southern part of Portugal and is almost absent from the north. However, the relatively low seismic hazard of the north of Portugal plus the sustainability of earth as a building material encourages the development of this technique in the region. The suitability of the typical granite residual soils from the Minho region for rammed earth construction was assessed by means of an experimental program, in which three representative soils were subjected to expeditious and laboratory tests that evaluated the characteristics of the soils and the performance of rammed earth built with them. The results showed that the granite residual soils tested fulfil most of the requirements needed for rammed earth construction, being the low compressive strength its main limitation. In this way, an innovative and sustainable stabilization technique based on alkaline activation of fly ash is proposed.