Soil–water characteristic curve of lime treated gypseous soil

The determination of water holding capacity variations with environmental conditions, in particular relative humidity (suction), is essential in the assessment of the behaviour of gypseous soil. The relationship between suction and moisture content is expressed by the soil-water retention curve (SWRC) or soil-water characteristic curve (SWCC). This relationship was determined for the first time for lime treated gypseous soil, using tensiometric plate, osmotic membrane and vapour equilibrium techniques, in the suction pressure range of (10–1,000,000 kPa). Soil samples containing (0, 5, 15 and 25%) gypsum were treated with 3% lime and cured for 28, 90 and 180 days at 20 °C and 40 °C. Results showed that the water holding capacity of the soil samples increased with increasing gypsum content, curing period and curing temperature. The effect of gypsum content on SWCC was greater than the effect of curing conditions, although microstructural properties of the treated soil samples showed that curing conditions also had a significant effect on the SWCC. All the experimental data fitted well to the Fredlund and Xing (1994) and Van Genuchten (1980) models for SWCC.