Abstract: Bentonite is commonly utilized as a waterproofing and buffering material due to its high expansibility and very low permeability. The cation exchange capacity is a crucial parameter that influences the microstructure of montmorillonite, thereby modifying its expansibility, hydraulic properties, and diffusion characteristics. Various montmorillonite samples with reduced cation exchange capacity were produced by heating lithium-modified bentonite at varying temperatures. By employing nuclear magnetic resonance and X-ray diffraction techniques, we acquired information on the distribution of pore water and interlayer spacing in montmorillonite with reduced cation exchange capacity under varying water content. Furthermore, we investigated the effect of cation exchange capacity on hydration in montmorillonite interlayers. The research demonstrates that a decrease in cation exchange capacity results in a reduction in the number of expandable layers, consequently lowering the liquid limit of bentonite. An preliminary approach for determining the proportion of expandable layers is suggested using the T₂ distribution curve derived from nuclear magnetic resonance. The results from this method closely align with the proportion of reduced exchangeable cations.

Key words: cation exchange capacity, reduced cation exchange capacity bentonite, interlayer hydration, number of expansive layers, nuclear magnetic resonance