Assessing shrink/swell properties of two argillaceous soils from the Paris Basin: a comparison of cation exchange determination methods

A comparison between three methods of determining cation exchange capacity values has been undertaken in order to evaluate the applicability of methylene blue for characterization of clayey soils. The Argiles vertes de Romainville, Marnes bleues d’Argenteuil (two very plastic, loamy soils from the Paris Basin which are known to experience shrink/swell) were tested in their natural and purified states, as well as samples of smectite, illite and interstratified illlite/smectite. The results from the methylene blue, turbidimetric and cobalt hexamine methods were similar, although the methylene blue gave slightly higher values. It is concluded that the differences seen are likely to be due simply to the degree of accuracy available with the various methods. Hence, the quicker and more convenient methylene blue method was realistic for use by geotechnical engineers. However, attention is drawn to the need to continue these tests to the “end point” which is some 24 h after the solution has stabilised.