Swell–shrink behaviour of lime precipitation treated soil

Abstract

Previous investigation showed that sequential mixing of calcium chloride and sodium hydroxide solutions with an expansive soil resulted in lime precipitation in the soil mass, which controlled the swelling potentials and increased the unconfined compressive strength of treated specimens through strong modification and pozzolanic reactions. However, expansive soils in the field are subjected to cyclic wetting and drying due to environmental conditions, which affects the swell–shrink behaviour. Therefore, the present investigation examines the efficacy of the lime precipitation technique in controlling the swell–shrink potentials and strength characteristics of expansive soils subjected to cyclic wetting and drying. Expansive soil is mixed sequentially with different concentrations of calcium chloride and sodium hydroxide solutions to yield a range of lime precipitation contents, and cured for different time periods. The cured specimens were subjected to cyclic wetting and drying in modified odeometer cells, and the swell–shrink potentials were monitored. The unconfined compressive strength of cured specimens was also determined after different cycles of wetting and drying in a sand bath. The laboratory results showed that the second swell potential was the maximum for untreated and lime precipitation treated specimens, in comparison with other wetting cycles. The equilibrium state was reached after about four to five cycles of wetting and drying. The equilibrium bandwidth reduced as the percentage lime precipitation and curing period increased. The unconfined compressive strength reduced with wetting and drying cycles, which indicated the loss of cementation after one wetting and drying cycle.