Physico-chemical Properties of Expansive Soils from Sudan and their Effects on Intrinsic Swelling and Shrinkage

Abstract

Intrinsic swelling was evaluated for seventeen potentially expansive clay samples obtained from
different parts of Sudan. A swell percent test, where the test samples were statically compacted at air dry
temperature to the same dry density (1.35 g/cm3) and allowed to swell was used as a measure for intrinsic
swelling. Physico-chemical properties were measured for all the samples to assess the effect of these properties on
intrinsic swelling. The physical properties included, gradation (clay, silt and sand contents), Atterberg limits (LL,
PL and SL), linear shrinkage and free swell whereas the chemical properties included cation exchange capacity
CEC, exchangeable sodium percent ESP and sodium absorption ratio SAR. The investigation has shown that
intrinsic expansiveness is well related to linear shrinkage and that linear shrinkage alone is a good candidate for
assessing both the swelling and shrinkage potential of clay soils. However, clay activity is found to be a poor
indicator of intrinsic expansiveness if the well known evaluation standards are adopted. Intrinsic expansiveness is
well related to LL, PI and SI and these parameters could be used for its assessment. The CEC showed poor
relationship whereas ESP and SAR showed no relationship with intrinsic expansiveness