Whereas the high longitudinal strai

Whereas the high longitudinal strains developed within the wet compacts clearly illustrate the strong effect of water on the densification process, elucidating the origin of the observed internal displacements requires further systematic experiments. We address this question by measuring the deformation of the compact at two different length scales using instrumented indentation tools. Indentation tests at the nanoscale are carried out to quantify the deformation of the assembly of nanoparticles within a single agglomerate, whereas measurements at the microscale are conducted to assess the deformation of the assembly of agglomerates at a larger length scale. The experiments were performed under wet or dry conditions by first loading the specimen at a constant force rate, followed by a creep test at a target fixed force (Fig. 6a,d). The evaluated specimen was prepared by cold sintering the nanovaterite powder with water at 500 MPa to obtain a 11mm diameter disc with a final relative density of 87%. Scanning electron microscopy images of imprints generated upon indentation confirm that the selected micro or nano-indenters could be appropriately positioned to probe either the assembly of agglomerates or the assembly of nanoparticles, respectively (Fig. 6c,f). The micro-imprints were typically 100 nm wide and 10 nm deep, whereas the nano-imprints exhibited width of 1 nm and depth of 100 nm. These dimensions are at least 10-fold larger than the average size of a single agglomerate (10 nm) and an individual nanoparticle (50 nm), which validates our experimental protocol as a means to probe the deformation of assemblies of agglomerates and particles at two different length scales.