Swelling Behaviour of Super-absorbent Laponite Hydrogel under One-dimensional Loading

Because of the inherent rheological property of transparent gel, laponite has been proposed for soil densification to withstand seismic events. Since the swelling behaviors of laponite could affect the soil-nanoparticle structure, one of the most important research topics is the swelling capacity of nanoparticles, particularly laponite. Hence, the objective of this study is to investigate the swelling properties of fresh laponite and sand treated with different contents of laponite. The swelling characteristics of compacted laponite hydrogel were investigated using a one-dimensional consolidation test setup. Results showed that the swelling strain of compacted laponite increased with time and as the concentration of laponite increased in specimens. The initial swelling of fresh laponite took around 4 weeks to attain equilibrium, while in the reswelling tests, laponite reached equilibrium within 60 h. The reswelling strain of laponite was higher than the initial swelling of fresh laponite, with a distinct reswelling behavior compared to other clay minerals. This swelling strain of laponite was found to be consistent with other clay minerals in which the swelling strain is caused by interlayer and double-layer forces. Scanning Electron Microscope images revealed that the structures of swollen laponite are continuous sheet-like irregular structures with pore size. Moreover, the swelling strain of the sand-laponite mixture with 3% laponite reached equilibrium after 40 h, whereas the swelling strain of sand-laponite with 5% laponite specimen did not reach equilibrium even after 50 h. In this study, the water retention ratio and changes in laponite hydrogel characteristics due to repeated drying and wetting processes were also investigated. In addition, the swelling pressure of compacted laponite hydrogel was also estimated, which varied in a range of 5.6-8.6 kPa throughout the experiment.