Swell–shrink behaviour of fly ash-stabilised expansive soils

Class C fly ash, a byproduct of thermal power plants, is often preferred for the stabilisation of expansive soils. However, improper optimisation of the stabiliser may lead to the premature failure of treated soils during wet–dry cycles. This  study demonstrates the volume change behaviour of fly ash-stabilised expansive soils subjected to wet–dry cycles. Furthermore, the effect of class C fly ash and lime–class C fly ash on the physical and engineering properties is also studied. The experimental results showed that addition of 20% fly ash to the expansive soil reduced the swell potential to 0% from an untreated swell value of 10.5%. However, when it was subjected to five wet–dry cycles, the initial cementitious effect of the fly ash on controlling the swell was partially lost, and therefore the volumetric deformation of the stabilised expansive soil increased from 0 to 14.5%. Furthermore, among the different additive combinations used for the treatment of expansive soils, it was observed that the combination of 4% lime and 20% fly ash resulted in the volumetric deformation of only 2.05% even after the fifth wet–dry cycle. Besides, the percentage of desiccation cracks has also reduced significantly from 29 to 0.5%.