## 2 Materials and Methods
### Materials
#### 2.1.1 Fluvial Sediment
The workability chart proposed by [PERSON] and [PERSON] [22] concerns clays used to produce ceramics, but it enables us to assess a priori whether the water-sediment mixture in this study is workable and to estimate the difficulties relating to grain size (low cohesion) and shrinkage after drying and firing. We can observe in Figure 3a that the points representing fluvial sediment are found between the recommended zone A and the limit zone B, but on the left, indicating a lack of cohesion but a moderate shrinkage. [PERSON] [23] used the Casagrande chart to define the optimum (zone C) and limit (zone D) extrudability zones for ceramic pastes. In the chart in Figure 3b, it can be seen clearly that the points representative of the sediment investigated are at the limit (zone D), or even outside the extrudability zone, showing average plasticity. These points are found on the boundary (A line) between clays and silts. If we refer to Table 1, we can see that the amount of clay remains low compared with the high percentages of fine sands, which justifies the lack of cohesion and average plasticity. The plasticity of fluvial sediments is affected by the presence of organic matter and some pollutants, the ratio of clay/sand that causes difficulties in the molding (formation of lumps, laminations and cracking), and the drying process (cracks and shrinkage). This extrudability chart can be extended to cover the molding of unfired bricks. A simplified zone (in blue, Figure 3c) was added for compressed earth blocks (CEB), rammed earth blocks (REB) and adobe, according to results reported by [PERSON] and [PERSON] [24]. This zone lies between the A line of Casagrande and its parallel passing through the origin O. The points representing the sediment are found at the border of the blue zone, but they may be suitable for the implementation of unfired bricks, i.e., sediment-based bricks, in this study. Other parameters remain to be fixed, such as the water content of the water-sediment mixture, depending on the brick production process (adobe, CEB or REB). Whatever the method used to produce unfired bricks, one of the objectives is to obtain the maximum density, i.e., the minimum of voids within the material. A chart proposed by [PERSON] and [PERSON] [25], and adopted by other authors [24], was established as a function of the dry density and water content of the molding mix, as shown in Figure 4. It shows the recommended zones for the optimum values obtained from the Proctor test. The widest zone is for the manufacturing of adobe, where the water content of the mold varies from 5% to 40%. We can also see that the maximum densities are obtained for CEB and REB  
Figure 2: Particle size distribution graphs for river sediment from Rouen and its suitability for raw earth bricks according to current standards (MOPT, [19]; AFNOR, [20]; Houben, [21]). bricks. The optimum moisture content obtained from the Proctor test is often proposed for the molding of unfired bricks. The representative points of the fluvial sediment are at the limit of the zone recommended for adobe; see Figure 4.  
Figure 3: Position of 3 samples of the river sediments in (**a**) chart of workability with optimal zone A and possible zone B; (**b**) chart of extrudability with optimal zone C and possible zone D; and (**c**) chart of molding.