The type and amount of clay present in soil are very important factors controlling engineering properties of the soils. The significance of the changes in these properties due to contaminant-clay interaction in the soils as a result of improper waste disposal and industrial activities also needs to be investigated. In this study, kaolinite, which has very low swelling capacity, has been contaminated with 10 000 ppm solutions of Pb²⁺, Zn²⁺, and Cu²⁺ (solid: solution ratio, 1:10) and amount of change in swelling percentages of the contaminated kaolinite has been determined using oedemeters. Swelling percentages have been investigated on oven dried samples which were compacted to have 1.16 gr/cm³ densities. For uncontaminated kaolinite, the amount of swell in vertical direction has been determined as 2.2 %. For Pb-contaminated, Zn-contaminated, and Cu-contaminated kaolinite, these values reached to 5.8%, 5.3%, and 5.4%, respectively. Besides heavy metals, effect of hydroxides (released to environment from paint and paper industries) on swelling properties of the kaolinite resulting from clay-alkali interaction has also been investigated. For this, kaolinite has been contaminated with 4 N NaOH (1:2). The biggest change in the amount of swelling has been obtained from NaOH-contaminated kaolinite which is 13.9 %.

These results show that contamination can significantly change the swelling capacity of the kaolinite as in the case of NaOH-contamination. Further studies needs to be carried out on different clay types for different types of contaminants for through understanding of the contaminant effect.