Improving the Characteristics of Expansive Subgrade Soils Using Lime and Fly Ash

This paper investigates the improvements in the properties of expansive soils, as road subgrade stabilized with lime and fly ash in varying percentages. Laboratory tests were undertaken to study the swelling and strength characteristics of expansive soils stabilized with lime, fly ash and a combination of both. Lime and fly ash were added separately to expansive soil at ranges 0-15% and 040%, respectively. Index property, compaction, California Bearing Ratio (CBR), Unconfined Compression Strength (UCS), free swell and swelling pressure tests were performed on natural and treated soil samples. For the investigated admixture lime-fly ash; the amount of lime added 5% and 8% combined with the fly ash content 0%, 5% and 10%. Comparing the results obtained of the natural and treated samples, the CBR and UCS of lime-fly ash treated samples increased significantly, coupled with the swelling reduction, depending on additive content. It could be concluded that stabilization of expansive subgrade soils by lime-fly ash admixture is successful and more economical.