Publication: Oedometric Small-Angle Neutron Scattering

Rex Hjelm of the New Mexico Consortium has a new publication accepted by Environmental Science and Technology titled “Oedometric Small-Angle Neutron Scattering: In Situ Nano-Pore Structure During Bentonite Consolidation and Swelling in CO2 Environment”.

In this paper, results of oedometric consolidation experiments linked with small-angle neutron scattering (SANS) measurements are presented, using SWy-2 Wyoming bentonite clay in dry and water-bearing N2 and CO2 atmospheres.

Oedometric SANS involves deforming a porous sample under uniaxial strain conditions using applied axial force and internal pore pressure control, and combines with SANS for in situ observation of pore structure evolution and interaction.

Scattering from both the interlayer (clay intra-aggregate) and the free (inter-aggregate) pores is observed. This shows decreasing pore size with dry consolidation and interactions between interlayer and free pore types with swelling and consolidation.

Introducing dry liquid CO2 at zero effective stress (axial stress minus pore pressure) produces large shifts in interlayer scatterers, but is reversible back to pre-CO2 levels upon decreasing pore pressure and increasing effective stress. On the other hand, introduction of wet liquid CO2 produces large, but irreversible changes in interlayer scatterers, which are interpreted to be the combined result of CO2 and H2O intercalation under hydrostatic conditions, but which diminish with application of effective pressure and consolidation to higher bentonite dry densities.

Consideration of CO2 intercalation in smectite-bearing CO2 caprocks needs to include effects of both water and nonhydrostatic stress.

To learn more see:

Dewers, T., Heath, J., Bryan, C., Mang, J., Hjelm, R., Ding, M. and Taylor, M., "Oedometric Small-Angle Neutron Scattering: In Situ Nano-Pore Structure During Bentonite Consolidation and Swelling in CO2 Environments", Environmental Science & Technology, (2018, in press).

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