Intra-aggregate water content and void ratio model for MX-80 bentonites

Abstract This paper proposes a model to define the water content present in the intra-aggregate space (microstructure) of MX-80 bentonites with different sodium and calcium contents. Data from a broad number of water retention curves was considered, both from sodium-exchanged and calcium-exchanged MX-80 bentonites, as well as from natural samples. Models both for Na-exchanged and Ca-exchanged samples were first fitted. Then, a general model for natural bentonites was proposed based on the sodium and calcium content as exchangeable cations in the bentonite. The model was compared against a number of water retention data, achieving good fits. Given the one-to-one relationship between microstructural water content and void ratio, the model also allows characterising the microstructural deformability of the soil, which is an essential issue when using a double porosity approach to model the MX-80 bentonite behaviour.