Expansive soils are those soils whose volume changes when subjected to change in moisture content. This behaviour of expansive soil has the potential to affect the integrity and functionality of the superstructure. The soil should be treated or replaced by a suitable material to improve its mechanical property before any construction work is undertaken. The engineering properties of expansive soils are conventionally improved through the use of additives. In this study bagasse ash is used to reduce the amount of cement and lime from an economic point of view. Bagasse ash of percent varying from 4 to 16 percent (by dry weight of the soil) is used to investigate the effect of bagasse ash on cement and lime treated expansive soils. In order to evaluate the engineering properties of the soil, natural moisture content, wet sieving, compaction test, unconfined compressive strength test, specific gravity, free swell index and Atterberg limit tests were conducted. The f ree swell has decreased and the plasticity index of the stabilized soil has improved with the addition of 8% cement and 8% lime. So to get the required goal 4% cement and 6% lime is used to reduce the amount of cement and lime by subst ituting bagasse ash to be economical. The soil-water characteristic curve (SWCC) of unsaturated soils has considerable importance in the analysis of geotechnical engineering problems involving soils that remain under partially saturated conditions throughout any given year. The SWCC is a graphical representation of the mathematical relationship between the matric suction of a soil and its water content and it is a very fundamental property of unsaturated soils. The SWCC of treated and non-treated expansive soils was measured to investigate the applicability of SWCC in checking the effectiveness of treatment methods. The SWCC of expansive soils from Worota City were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 33-1,400kPa. The measured results were then analyzed using Fredlund and Xing (1994) SWCC model equation. The SWCC results are used to interpret the expansive soil behavior due to stabilizer treatment. The air-entry parameter is related to the soil air-entry value, which is the matric suction for which air starts to enter the largest pores in the soil. With an increase in the percentage of stabilization dosage the air-entry value correspondingly decreases because bonding from chemical reactions between clay particles forms aggregates and increases pore sizes in soil structure. The research data and interpretation analysis presented here can be extended to understand volume change behaviors of other stabilized expansive soils using the SWCC test data.