Effectiveness of Two Sequential Mixing of Lime -Portland Cement in Stabilizing Expansive Soils

The existence of expansive soils in the study area that undergo swelling and shrinkage when subjected to moisture variations has caused major deterioration and distresses on lightweight construction such as shallowly founded structures ad roads founded on them. Unfortunately, the treatment of these highly plastic clay soils has attracted minimal attention despite the damages they are able to induce. Stabilization of highly plastic clay soils with lime or cement alone is generally not satisfactory. While significant increase in workability and adequate strength can be achieved by lime treatment, the process is characterised by brittleness. On the other hand, soil treatment with cement alone can somehow increase strength but with the danger of leaving pockets of uncemented material in the modified mass. Therefore, substantial increase in both unconfined compressive strength (UCS) and tensile-split strength can be achieved through a two sequential mixing operation whereby soil brittleness is reduced by providing smaller loss of post-peak strength. The operation is carried out by firstly treating the soil with lime, leaving it to mellow for some hours to ensure adequate workability and then secondly treating it with cement to obtain lime-cement treated soil with adequate strength and durability. The analysis of test results of the two sequential lime-cement treated soils showed markedly improvement in the unconfined compressive strength at a large strain when highly plastic soils were first treated with lime followed with cement treatment. This indicates that the use of two-sequential lime-cement soil stabilization is the cost effective techniques that effectively improves the engineering properties of expansive problematic soils.