Evaluation of swelling pressure of bentonite/claystone mixtures from pore size distribution

Abstract

The swelling behaviour of expansive clays is strongly related to the interaction between clay particles. In this paper, a series of constant-volume swelling pressure and mercury intrusion porosimetry (MIP) tests were carried out on MX80 bentonite/Callovo-Oxfordian (COx) claystone mixtures with different bentonite fractions and dry densities. Results show that the swelling pressure increased linearly with the increase of dry density. Additionally, at a given dry density, the larger the bentonite fraction, the larger the swelling pressure. From the MIP results, the inter-particle pore volume decreased with the increases of bentonite fraction and dry density.To link the macroscopic swelling behaviour with the microstructure features, a new method was proposed, allowing the determination of the average inter-particle distance from the pore size distribution. Moreover, a linear relationship was identified between the swelling pressure and the average inter-particle distance in a semi-logarithmic plane, regardless of the bentonite fraction and montmorillonite content.

Research Progress on the Influence of Thermo-Chemical Effects on the Swelling Pressure of Bentonite

“…Hydration causes an increase in the interlayer pore volume of clay minerals, leading to the swelling of clay particles and, thus, to the formation of clay aggregates [60]. The bentonite swelling potential is influenced by the water content due to the coupling of micro-and macro-structures caused by hydration [61].…”

“…Clay represents a complex porous structural body, with clay layers and interlayer pores composing a basic unit of clay particles, such as montmorillonite lamellae and interlayer pores, as shown in Figure 9 [60]. Water in clay soils includes microstructural water and macro-structural water [64].…”

“…Nevertheless, the limitations of the MIP technique itself [69][70][71], combined with the differences in clay types, led to different pore size measures. For example, when the specimen was a mixture of bentonite and Callovo-Oxfordian (COx) claystone with low dry density, the average pore sizes of its three main pore groups were 10-22 µm for macro-pores, 0.17-0.52 µm for mesopores, and about 25 nm for small pores [60].…”