Hygro-thermo-mechanical properties of earthen materials for construction : a literature review

Although earth has been used for construction for millennia and is still one of the most widely used building materials in the world, it is still difficult to find reliable values for the hygro-thermal and mechanical properties of earthen materials. Only little scientific research has been conducted on this material compared to the huge literature available concerning cementitious materials. Considering the literature available on earthen materials, a majority of studies deal with cement or lime stabilized earth for compressed earth blocks or rammed earth, and less has been done about natural unstabilized earth. The only existing comprehensive overview on the hydro-thermal and mechanical properties of earthen materials was authored by CRAterre-ENSAG and published 25 years ago. Now, for the second time in its thirty years of existence, CRAterre-ENSAG has undertaken the task of reactualizing this synthetic knowledge by writing a comprehensive review of the existing literature on the subject, thanks to the CRAterre laboratory documentation centre, which is the most complete source of information on earthen construction and architecture in the world (more than 20.000 references). In the present work, we intend to compile the most reliable experimental data on the hygro-thermal and mechanical properties of natural earth. We will inventory the performances determined by several research teams for rammed earth, compressed earth blocks, adobe, cob and mortar. We will discuss the reliability of the experimental techniques used. We will provide an overview on the state of knowledge concerning the different properties as well as on the lacking data. Finally, this literature review will also give some orientations for further scientific research