Comparative Analysis of Physico-Chemical and Potassium Sorption Properties of Sensitive Clays

The paper analyses physico-chemical and geotechnical characteristics of four Scandinavian sensitive soils formed under different environmental depositional conditions, with the main aims to contribute to the knowledge of sensitive soils and assess the potassium sorption capacity among the investigated soils, as a basic characteristic to evaluate the effectiveness of treatment with KCl and to analyse potassium migration in such soils. The results show that, although the chemical composition of the four soils is very similar, their sensitivity is significantly different. The correlation from literature linking the specific surface, mineralogy, and plasticity in sensitive clays of Eastern Canada, was found to be qualitatively valid for the investigated Scandinavian sensitive clays, too. The highest value of the sensitivity index among the tested soils was found to be related to the lowest cation exchange capacity and to a limited amount of amorphous minerals. These characteristics contribute to explaining the highly sensitive behaviour of that soil affecting the structure formation during the deposition stage. The potassium sorption capacity has been experimentally investigated through batch tests specifically performed on the sensitive soils, as the first step to quantify the maximum sorption capacity and identify the main factors affecting it. The maximum potassium sorption capacity was always lower than that estimated by the cation exchange capacity, and it increased with the cation exchange capacity, plasticity index, and activity of the soils, as well as with the amount of phyllosilicates and amorphous minerals.