Evolution of nano-pores in illite-dominant clay during consolidation

Abstract

In this paper, the evolution of nanoscale pores, covering inter-particle pores and inter-layer pores, in illite-dominant clay during consolidation is monitored using small angle X-ray scattering (SAXS) and nitrogen gas adsorption (N2GA) techniques. No obvious change observed in the characteristic peaks of SAXS intensity curves during consolidation suggests that the intra-particle structure of the clay, including interlayer spacings, is not affected by mechanical loading, at least up to 4 MPa. The N2GA test results show that the volume of inter-particle pores inside the aggregates does decrease gradually as the compression proceeds, which is accompanied by a gradual reduction in specific surface area, probably due to the rearrangement of the particles composing the aggregates. The inter-particle pores are compressed as a whole during consolidation instead of the progressive collapse in an ordered manner, from the larger to the smaller. By comparing the pore-size distributions of illite-dominant clay obtained by MIP (mercury intrusion porosimetry) and N2GA techniques, it is found that the shapes of the two distributions in the common measurement range are obviously not matched, essentially due to the sequential nature of the drying and wetting processes. While filling the research gap in the evolution of intra-aggregate pores during consolidation, this study also shows that the N2GA technique and SAXS measurement used in conjunction with each other appear as a powerful approach for clay nano-pores identification.