The pH influence on the index properties of clays

Three clay sediments, concerning Pliocenic clay, Chaotic Complex clay and commercial kaolinic clay, have been studied in order to verify the pH influence on the index properties. The analysed clays have been mineralogically characterized in natural, conditions, and in modified pH conditions. This last procedure, obtained respectively by adding NH₄OH or CH₃COOH 1 mol., in a pH range between 4.5–11.3 has been carried out. To verify the different experimental conditions the C.E.C. of exchangeable cations as K⁺, Na⁺, Ca⁺⁺ and Mg⁺⁺, has been measured. The index properties obtained show a different behaviour of the three clays. The kaolin is not much affected only a limited W_L% increase is recognizable when the pH decreases. The Chaotic complex clay evidence a considerable rise of the W_L with the pH uncrease. In the Pliocenic clay the W_L value increased with the pH. The described process can be related to the natural environment, connected also with various pollution phenomena.