An approach to develop suitable criteria for cob and adobe techniques

The use of earth in the building industry offers the opportunity to reuse soil whiles meeting the challenges of circular economy through soil reuse and low embodied energy. However, the lack of standardized criteria for soil classification, suitability and a comprehensive understanding of the interactions between soil properties and construction techniques remain a significant barrier to widespread adoption. This study aims to propose criteria for evaluating and optimizing soil classification and suitability in earthen construction through experimental analyses. For this, the study will use three different soils, sampled from three different regions in France. Straw- fibred and non-fibred cylindrical specimen will be prepared in laboratory using the cob and adobe techniques. The prepared specimens will be dried at 40 °C and conditioned in a climatic chamber at 20 °C and 50 % relative humidity. The variation in dry densities, and Unconfined Compressive Strength (UCS) of the cob and adobe specimens will be observed. The impact of soil properties and implementation parameters such as water content, mineralogical composition (calcite and dolomite content) on these variations will be analyzed. To underline the contribution of these parameters, a principal component analysis (PCA) will be conducted on all the results to identify the most dominant factors affecting mainly the dry densities and soil strength. Future work will study the microstructure evolution in the specimens using the Brunauer – Emmett – Teller (BET) and the Mercury Intrusion Porosimetry (MIP) tests. The mechanical behaviour and microstructure evolution will be combined into developing new criteria for soil suitability considering the implementation process parameters and soil properties for earth construction.