The use of quarry by-products can enable the commercialization of a clay building material (reconstituted earth) thanks to minimal valorized and perennial stocks of materials. This study shows that quarry by-products can be used to mix design a clay-based building material for the manufacture of CEB. These soils are composed of quarry tailing and clayey muds. Proctor and dry compressive strength tests have shown that the proportion of mud that achieves the highest possible compressive strength is a balance between increasing density through the aggregate arrangement, increasing clay activity, and decreasing density through the increase in water content. These tests resulted in the formulation of materials with compressive strengths of 5.8 MPa and 8.4 MPa at densities of 2135 kg/m³ and 2178 kg/m³. The influence of mud incorporation on the material granulometry and on its characteristics was also studied. Moreover, a model allowing us to link the compressive strength, the clay activity, and the dry density is proposed for the materials composed of quarry by-products. This model enables us to facilitate the mix design and the standardization of the earth material.

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.