Compressibility effect in evaluating the pore-size distribution of kaolin clay using mercury intrusion porosimetry

Abstract

The objective of the present research is to quantitatively evaluate the compression that can occur during the evaluation of pore-size distribution of cohesive soil using mercury intrusion porosimetry (MIP). A new experimental procedure was developed that can be routinely used to evaluate the corrections associated with the compressibility for porous solid samples using MIP. The approach used in this study involves performing mercury intrusion tests on dehydrated kaolin samples using freeze-dried and oven-dried techniques, and on identical samples confined by low-porosity latex membranes. Corrections for latex intrusion and issues related to dehydration of samples are addressed. The measured contact angle of mercury with kaolin clay using the sessile drop technique was used in the data reduction. Repeatable test results were obtained throughout the testing program. The procedure for obtaining volume-change behavior under isotropic conditions for a large range of pressures using the mercury porosimeter is also presented for oven-dried samples. Scanning electron micrographs for intruded and compressed specimens are presented along with a discussion on the observed hysteresis in MIP test data. The test results for kaolin samples show substantive initial compression before the occurrence of actual intrusion. This resulted in errors associated with the interpretation of pore sizes with diameters in the range of 0.4-200 µm.Key words: mercury intrusion, clay, compression, correction, pore-size distribution, high pressure.

Influence of magnetic impurities on proton spin relaxation of water in clay

“…The shape of the T~ distribution curve is often regarded as corresponding to the distribution of pore sizes [13]. Indeed, the shape of the spin relaxation spectrum with no magnetite -a major component and a broad component comprising the tail -is consistent with pore size data obtained by mercury porosimetry of kaolin clay [14]. For up to 1 mg of magnetite added, the curves did not change significantly.…”

Microstructure Investigation in Unsaturated Soils: A Review with Special Attention to Contribution of Mercury Intrusion Porosimetry and Environmental Scanning Electron Microscopy

“…However, this cannot be the case during low-pressure application and before the initial intrusion takes place in compressible materials. The occurrence of substantive initial volume change due to isotropic compression in clayey samples prior to intrusion was reported by Penumadu and Dean (2000), though for some initially compacted clays the volume change indicated by porosimetry is a good estimate of the macroscopic volume change (Simms and Yanful 2004). Yet another consideration is the deformation of the sample container, which may cause an overestimate of the pore volume of the smaller pores-this deformation can be measured by running blank samples in the porosimeter (for a recent example on the degree of error that can result see Simms and Yanful 2004).…”

“…The value n = 4 is often used in MIP. The contact angle, which is very sensitive to surface roughness, is usually taken between 139°and 147°for clay minerals (Diamond 1970), although Penumadu and Dean (2000) have reported higher values with kaolin clay using the sessile drop technique (advancing angle of 162°and receding angle 158°).…”

“…Prior to freeze drying, soil samples must be cut into cubes less than 1 cm 3 in size to maximize heat transfer. Detailed accounts of freezedrying techniques have been given by Ahmed et al (1974), Delage et al (1982), Delage and Pellerin (1984), , Penumadu and Dean (2000), Mitchell and Soga (2005), and others.…”

A four elements porous model to estimate the strength of unsaturated soils

“…Porosimetry tests show that, in general, soils exhibit a bimodal structure meaning that both large and very tiny pores coexist (see for example: Simms and Yanful 2001;Penumadu and Dean 2000;Delage et al 1996). Also, it is known that clay particles aggregate in pellets, generating the microstructure of the soil where very tiny pores appear.…”