The stress-strain curves attained from unconfined compressive strength tests are depicted in Figure 2 for bagasse ash treated expansive soil and Fig.3 for hydrated lime-bagasse ash combination treated expansive soil after 7 days curing. As can be seen from Fig. 2, the stress-strain behaviour of untreated expansive soil are compared with that of bagasse ash treated expansive soil with various bagasse percentages up to 25%. The untreated expansive soil reached a peak stress of 138 kPa and at a strain of 3.5%. With the addition of bagasse ash, however, the peak stress and strain increased progressively with the increasing bagasse content up to 18% and then followed by a drop slightly to 25% bagasse ash content. It can be noted that the peak stress and strain at 18% bagasse ash were 183kPa and 6.5%, respectively, which reveal an increase of 33% in stress and a significant improvement of 87% in strain. This means when bagasse ash added to expansive soil, the treated expansive soil is very much better in terms of material ductility. In general, there was a considerable improvement in mechanical properties of bagasse ash treated expansive soil. Nonetheless, the unconfined compressive strength of treated expansive soil specimen reduced slightly when the bagasse ash content used was added up to 25%, which indicates that 18% bagasse ash content was the optimum bagasse ash dosage. In addition, Fig. 3 illustrates the Influence of different hydrated lime-bagasse ash contents on stress-strain behaviour of expansive soil after 7 days curing. It is obviously observed that the peak stress increased dramatically with an increase of hydrated lime-bagasse ash content and the stabilized expansive soil also displays a marked stiffness and brittleness. To be more specific, at 25% hydrated lime-bagasse ash addition, the failure stress and strain of treated expansive soil specimens were about 475 kPa and 1.05%, respectively, which shows a substantial increase of 247% in stress and an enormous reduction of 70% in strain. The failure strain is so much smaller in comparison with that of untreated expansive soil.