Abstract
After being almost abandoned at the end of the Second World War, the use of raw earth is currently regaining the interest of architects, engineers and policy makers for the construction of dwellings in industrialised countries. This renaissance is driven by growing ecological awareness and the promotion of construction techniques that minimize energy consumption and carbon emissions. Raw earth displays very interesting thermo-hygro-mechanical properties, which can contribute to the reduction of the environmental impact of buildings not only during construction but also during service life. Nevertheless, one of the reasons that still prevents dissemination of raw earth into construction practice is the lack of commonly agreed procedures for assessing material performance. The RILEM technical committee TCE 274 has been established as a first step for overcoming this obstacle. The objective of the technical committee is to critically examine current testing procedures in order to propose suitable experimental standards. The results of this work will be presented in future publications while the present paper summarizes the main challenges faced by the committee and briefly describes some of the existing procedures for measuring the engineering properties of earth materials.
Highlights
Humans have used raw earth in various forms during millennia for the construction of dwellings
A good understanding of these two aspects requires taking into account the large variability of earth materials which is mainly due to: a) the different geological characteristics of the sites from where the earth is sourced and b) the different construction techniques, which can vary depending on soil types and manufacturing tools
The results presented in [106] and [107] are comparable to earlier estimations of the erosion rate of unstabilised uncoated adobe walls in New Mexico (USA) in [108], which indicated a reduction in thickness of 1 inch over 20 years
Summary
Humans have used raw earth in various forms during millennia for the construction of dwellings. The high water affinity of clays, and possibly embedded fibres, facilitates the capillary condensation and adsorption of water inside the porous network This combination of moisture transport, condensation and sorption mechanisms confers a marked hygroscopic nature to earth materials and a great ability to regulate indoor relative humidity. The high hygroscopicity of raw earth has an impact on the mechanical properties as a consequence of the interaction between the pore water and the clay fraction This interaction can result in swelling or shrinkage [4,5] and can cause the reduction of strength and stiffness. The term “hygrothermal” is commonly used to denote the couplings between mass transfers of water phases, including their phase changes, and heat transfer These two concepts are linked together, and a material with good moisture buffering capacities will show good hygrothermal properties. Trivial, since they can be strongly influenced by both temperature and relative humidity
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