Use of Chemically Stabilized Soil as Cushion Material below Light Weight Structures Founded on Expansive Soils

Among the several remedial techniques suggested to combat the damages caused by expansive soils, the use of sand cushion and cohesive nonswelling (CNS) soil cushion were widely accepted, especially for light weight structures such as floorings, pavements, and canal linings, which cover large areas. CNS cushion is preferred to sand cushion in view of the sceptical performance of sand cushion at several work sites. However, various investigators have reported the nonavailability of suitable CNS materials at many project sites and in such circumstances, it is also suggested to prepare the artificial CNS materials by mixing suitable admixtures to the native clay. The present work deals with the modification of black cotton soil using Ca Cl2 and rice-husk-ash (RHA), which resulted in two favorable combinations of soil +0.5% Ca Cl2 +8% RHA and soil +1% Ca Cl2 +6% RHA with nonswelling properties, while retaining high unconfined compressive strength values. The mix of soil +0.5% Ca Cl2 +8% RHA was taken for further study in view of its economy due to lower Ca Cl2 content. The field heave measurements of footings, pavement slabs, and canal lining panels cushioned with the proposed chemically stabilized soil (CSS) mix revealed that the CSS cushion can effectively reduce their heave and hence it can be recommended as an alternative to conventional CNS cushion in localities of scarcity for suitable CNS materials.