Processing methods for optimising the mechanical strength of raw earth-based materials

In the last few years, raw earth construction has recovered much consideration due to its low environmental impact, local characteristics and recyclability. However, the strength of this material fluctuates in reality due to the variability of soils and the different methods used in vernacular earth construction. The aim of this study was to identify the mechanisms that increase the strength of this material. Optimisation of the processing method of raw earth blocks was sought in order to obtain better strength for different sorts of soils systematically. Soils were extracted from the same region, Brittany, France, in order to keep the local character of this material. The soils were mixed with water only or water and a dispersant (sodium hexametaphosphate or tannins). The rheological behaviour of each soil changed with different processing methods. Thus, the processing method and the use of dispersant can be efficient ways to enhance the mechanical properties of the selected soils. This study highlights that some of these methods could be used in the near future at a semi-industrial scale to produce a structural material that can achieve compliance with modern standards without hydraulic binders.