Swelling pressure development and inter-aggregate porosity evolution upon hydration of a compacted swelling clay

Abstract

A specific oedometer cell has been set up to measure the swelling pressure of compacted montmorillonites at constant volume and to concomitantly visualize the evolution, upon wetting, of how the microstructure is organised through X-ray microtomography. The swelling pressure experiments were conducted with solvents of various natures. In addition to conventionally used water and saline solutions, we used an organic solvent (methyl methacrylate-MMA). We chose this to explore the effect of its different physical and chemical properties, and to differentiate the respective roles of crystalline and osmotic pressures on macroscopic swelling behaviour. The results, which combined both swelling pressure measurements and quantification of microstructure evolution upon hydration for the two different solutes, give sound understanding on the development of osmotic and/or crystalline swelling and their relative impact both on the microstructure and on the magnitude of the macroscopic swelling pressure of compacted montmorillonites.

5-year chemico-physical evolution of concrete–claystone interfaces, Mont Terri rock laboratory (Switzerland)

“…The method applied here using impregnation of 14 C-labelled PMMA combined with radiography is thought to be best suited (Gaboreau et al 2011). The acrylic monomer is a small molecule, mixes with water and has been shown to also penetrate clay-interlayers of smectites (Prêt et al 2004;Massat et al 2016). While the pore-geometry cannot be resolved at the relevant small scale, a quantification of local bulk porosity by radiography is possible (quantification involving post-processing of images and calibration is ongoing).…”

Porous space in Brazilian soils using X-ray computed tomography

“…Massat et al (2016) destaca a relevância no aumento de espaços porosos no solo em consequência de um aumento na hidratação do mesmo, levando a uma redução da porosidade inter-agregado.…”

“…A comprovação da relevância no uso da tomografia computadorizada de raios-X no avanço da compreensão das particularidades e especificidades da estrutura dos solos e suas implicações para a condução/acumulação de água, facilidades/dificuldades para o desenvolvimento de raízes de plantas, especialmente se tratando daquelas cultivadas, é extensamente encontrada na literatura abordando variados objetivos de aplicação (Pires et al, 2011;Beckers et al, 2014;Lu et al, 2014;Pires et al, 2014;Carducci et al, 2016;Massat et al, 2016;Prado et al, 2016;Robin et al, 2016).…”

Reactive Transport Modeling of Coupled Processes in Nanoporous Media

“…However, the concentration used for calculating the osmotic pressure may be different from the average concentration in the pore. In smectite osmotic swelling models, the reference concentration for this calculation is usually taken as the mid-pore concentration (Langmuir 1938;Warkentin and Schofield 1958;Blackmore and Miller 1961;Madsen and Müller-Vonmoos 1989;Liu 2013;Massat et al 2016), i.e., a parameter the value of which cannot be easily computed from a mean electrostatic potential modeling approach. It would be surprising in any case if the advective flow affects uniformly the entire porosity, especially in clayey rocks and cementitious materials that exhibit a large range of pore sizes from nanometer size (interlayer porosity) to few micrometers (macropores) (Curtis et al 2012;Kuila and Prasad 2013;Hemes et al 2015Hemes et al , 2016Gaboreau et al 2016).…”