Improvement of swell and dispersive characteristics of problematic soils which are present at various places in the world is an important topic of research in engineering applications. In recent years, industrial side products are often used to improve engineering features of problematic clay soils and both environmentalist and economic benefits are obtained. In the present study, it is aimed to improve the high plasticity clay soil, which is determined to have both high swelling potential and dispersive features, by using silica fume (SF) as a by-product material and lime (L). The minimum lime quantity that is required for the pozzolanic reaction is fixed as 3% and experiments are made with SF additive mixtures of increasing percentages (0, 1, 3, 5, 10, 15, and 20%). Within this context, the swell percentage, swell pressure, crumb, pinhole, and unconsolidated-undrained (UU) triaxial compression tests with different curing periods were conducted on the soil samples that are prepared by compressing at compaction characteristics that are specified at each additive level at standard proctor energy. In addition to these tests, in order to examine the changes caused by additives on soil structure, scanning electron microscopy (SEM) analyses were performed. As a result of this study, it is found out that swelling and dispersive features of the clay soil improved and that curing period of first 7days was more effective on the strength improvement and optimum stabilization was achieved at an addition of 3% lime combined with 10% silica fume.