Compression experiments were carried out by applying uniaxial pressures of 100 or 500 MPa onto the powder with water (wet) or under dry conditions. This initial pressure was reached by applying a constant displacement rate in the first stage of the compression test. After this maximum pressure was reached, the sample was allowed to relax under the initially imposed displacement (stage 2, Fig.3c). The results of the compression experiments show a significant effect of the presence of water on the stress relaxation behavior of the vaterite compacts. A stress drop of 40% was observed in the presence of water for samples subjected to an uniaxial pressure of 500 MPa. By contrast, the experiment with dry powder showed a stress drop of only 10% for this initial pressure. A similar trend was found for the specimens subjected to the initial stress of 100 MPa.