Development and validation of a mix design procedure for extruded earth bricks with cementitious stabilisation

Raw earth as a construction material is showing potential for significant development with the involvement of earth-stabilisation to improve the water resistance properties of unfired earth materials as well as enhancing the mechanical performances. However, the addition of a cementitious component as a stabilising agent can lead to rapid rheological changes including stiffening and loss of plasticity. This challenge hinders the industrial scale implementation of extrusion manufacturing process for stabilised earth bricks. To maintain the extrudability of these new clayey materials for longer period, the addition of admixtures is studied. However, there is a wide variety of products available. In this study, an experimental procedure is proposed to evaluate the performance of admixtures according to two criteria: the final water content of the formulation and the rheological evolution of the mixture observed after resting for 1 h. The results are presented in the form of a performances map. Finally, the formulations that best meet the established criteria were tested experimentally through extrusions, and a discussion was opened on the relevance of admixture on stabilised clay materials.