It is known that clayey soils with high plasticity absorb water several times as much as their weight. The swelling pressure and swelling potential are important swelling characteristics for safe and economic design of geotechnical application [1-3].   In this study, silica fume has been considered alternative additive material and its effects on the swelling characteristics compacted clay structures have been investigated under laboratory condition. All samples have been compacted at the optimum moisture content and then subjected to laboratory tests to determine their swelling characteristics.   The results show that silica fume improves the swelling characteristics such as swelling pressure and swelling potential. It is observed that the liquid limit and plasticity index values slightly decrease with increase in the silica fume. 
However, the plastic limit slightly increases with increase in the silica fume contents. The silica fume decreases the swelling percentage, swelling pressure and swelling potential of compacted clayey soil samples. It is seen that silica fume decreases the compressibility and low compressibility values are yielded in the silica fume-modified clayey soil as compared to those of natural clayey soil samples.   Consequently, it is concluded that silica fume can be successfully used to modify the swelling characteristics of compacted clayey soils.