An experimental program was undertaken to study the individual and admixed effects of lime and fly ash on the geotechnical characteristics of expansive soil.Lime and fly ash were added to the expansive soil at 4%-6% and 40%-50% by dry weight of soil,respectively.Testing specimens were determined and examined in chemical composition,grain size distribution,consistency limits,compaction,CBR,free swell and swell capacity.The effect of lime and fly ash addition on reducing the swelling potential of an expansive soil is presented.It is revealed that a change of expansive soil texture takes place when lime and fly ash are mixed with expansive soil.Plastic limit increases by mixing lime and liquid limit decreases by mixing fly ash,which decreases plasticity index.As the amount of lime and fly ash is increased,there are an apparent reduction in maximum dry density,free swell and swelling capacity under 50 kPa pressure,and a corresponding increase in the percentage of coarse particles,optimum moisture content and CBR value.Based on the results,it can be concluded that the expansive soil can be successfully stabilized by lime and fly ash. An experimental program was undertaken to study the individual and admixed effects of lime and fly ash on the geotechnical characteristics of expansive soil. Lime and fly ash were added to the expansive soil at 4% -6% and 40% -50% by dry weight of soil, respectively. Tented specimens were determined and examined in chemical composition, grain size distribution, consistency limits, compaction, CBR, free swell and swell capacity. The effect of lime and fly ash addition on reducing the swelling potential of an expansive soil is presented.It is revealed that a change of expansive soil texture takes place when lime and fly ash are mixed with expansive soil. Plastic limit increases by mixing lime and liquid limit decrease by mixing fly ash, which decreases plasticity index. As the amount of lime and fly ash is increased, there are an apparent reduction in maximum dry density, free swell and swelling capacity under 50 kPa pressure, and a corresponding increase in the percentage of coarse particles, optimum m oisture content and CBR value.Based on the results, it can be concluded that the expansive soil can be successfully stabilized by lime and fly ash.