The article presents the results of a preliminary investigation carried out to determine the effect of a small amount of potassium chloride (KCl) on the efficiency of fine slag (FS) used for treatment of expansive soil. The quantity of KCl has been varied from 0,5 to 1,5 %, while FS was varied from 5 to 15 % of the soil weight. It is found that the plasticity and differential free swell of the soil reduces with the addition of KCl as well as FS. KCl is more competent in reducing the plasticity and swelling of soil compared to FS. Whereas, the enhancement in strength and maximum dry density is relatively large in case of FS as compared to KCl added to the soil. The efficiency of fine slag to alter the properties of expansive soil increases significantly in the presence of a small quantity of KCl. The predictive models were also developed to find out the improved properties of expansive soil.