Effect of Water Pressure Increase Speeds in Mortar on Mechanical Behavior Under High Water Pressure

In recent years, the shortage of energy and mineral resources and global warming have become problems. As a solution to these problems, the effective utilization of the deep sea is attracting attention. In Japan, methane hydrate has been discovered at a depth of 1,000 m, and rare earths have been discovered at depths of 4,000 to 6,000 m, indicating the existence of abundant deep sea resources. In addition, carbon dioxide capture and storage in the deep sea is being considered as a solution to global warming. In order to make stable use of these resources, it is necessary to develop infrastructure facilities on the seabed. Therefore, it is necessary to clarify the behavior of cement concrete, in the deep sea environment. Previous studies focusing on high water pressure indicate that the effect of water movement is significant on the mechanical properties of concrete under high-water pressure action. In this study, mortar specimens with different water-cement ratios were applied water pressure at different water pressure increase speeds. The strain behavior of the mortar specimens under high water pressure action was evaluated. The results show that under constant water pressure action, an increase in compressive strain occurs for W/C = 0.3, while a relaxation of compressive strain occurs for W/C = 0.7. The magnitude of compressive strain and the timing of the onset of relaxation of compressive strain at different water pressure increase speeds under constant water pressure action were found to be different.