Gypseous Soils are distributed in many regions in the world including Iraq, which cover about
(31.7%) of the surface area of the country. Existence of these soils, some times with high gypsum
content, caused difficult problems to the buildings and strategic projects due to dissolution and
leaching of the gypsum slates by the action of water flow through the soil mass.
In this study the effect of treatment with Dihydrate Calcium Chloride (CaCl2.2H2O) as water
solution on compaction, compressibility, leaching, permeability and shear strength characteristics of
Gypseous soil is investigated. It is found that the maximum dry unit weight increases while optimum moisture content decreases with the increase in the concentration of calcium chloride in the molding water. It is concluded that the engineering properties of the samples are highly improved when the
samples are soaked in calcium chloride solution at (20%) concentration. Where, considerable
reduction is observed in compressibility, collapsibility, coefficient of permeability, percentage of
dissolved gypsum and leaching strain. Also, the treatment minimizes the reduction in cohesion
component (c) upon soaking in water and slightly decreases the angle of internal friction (f).
Analysis of the tests results showed that the using of calcium chloride solution in improvement the gypseous soil is more efficient than using it in any other form (powder).