Assessing the performance of earth building materials: a review of recent developments

After being almost abandoned in Europe at the end of the Second World War, raw earth is currently regaining the interest of civil engineers and architects worldwide. Raw earth (unfired 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 main reasons preventing dissemination of raw earth into mainstream construction practice is the lack of commonly agreed protocols for assessing engineering performance. In this context, the RILEM Technical Committee 274‐TCE is critically examining current experimental procedures to propose appropriate testing methods that could be adopted as standards. The present paper summarizes the main challenges faced by the committee and describes some of the existing procedures for measuring the engineering properties of earth materials. The main issue identified by the committee is that laboratory protocols do not accurately reproduce field conditions. The representativeness of laboratory samples is also questionable due, for example, to different degrees of material homogeneity with respect to the field. Finally, the paper identifies some possible routes to reduce the discrepancies between laboratory testing and field conditions in relation to the thermo‐hygro‐mechanical characterization of earth materials.