Swelling pressure of Na- and Ca-montmorillonites in saline environments: A molecular dynamics study

• Published in: Chemical physics 2020-01, Vol.528, p.110511, Article 110511
• Main Authors: Akinwunmi, Bukunmi, Hirvi, Janne T., Kasa, Seppo, Pakkanen, Tapani A.
• Format: Article
• Language: English
• Subjects: Bentonite; Dry density; Ionic strength; Salt solutions
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2019.110511

[Display omitted] •Salinity has a negative influence on swelling pressure of bentonite clays.•The influence of salinity on swelling pressure is dependent on dry density.•Type of exchangeable cation influences the behavior of clays in salt solutions. The swelling pressure of bentonite clay is an important characteristic that influences its use in nuclear waste disposal repositories. A molecular dynamics study was performed to investigate the influence of salt solutions of different concentrations on the swelling pressure of Na-montmorillonite and Ca-montmorillonite in NaCl and CaCl2 solutions, respectively. Na-montmorillonite shows a gradual increase in swelling pressure as the dry density increases, while Ca-montmorillonite shows a slow increase as the dry density increases, after which a steeper increase in swelling pressure was observed. There is an overall decrease in swelling pressure of Na- and Ca-montmorillonites as the salinity of the surrounding solution increases. The influence of ionic strength was most prominent for Na-montmorillonite at moderate to high dry densities. At low to moderate dry densities, the swelling pressure of Na-montmorillonite was greater than that of Ca-montmorillonite; however, at high dry densities and ionic strengths, Ca-montmorillonite exhibits the higher swelling pressures.