Soil stabilization is a technique to improve soil properties. Currently many methods are available to stabilize soils and improve their engineering properties. The soil type,soilstructure and economic factors govern the decision to select an appropriate single or a combination of two or more methods. The stabilization of soil can be accomplished by adding cementing material, or some other chemical material to change engineering property of soil. After this addition of stabilizer to soil, engineering properties of soil such as increases strength, load bearing capacity, durability, workability and etc. Stabilization can be achieved by mechanically mixing the natural soil and stabilizer together to reach desired improvement. There are many types of additives which can be used for stabilization. There are Portland cement, lime and fly ash. This project focuses on the effectiveness of fly ash as stabilizer. Fly ash is a waste material produced by combustion of pulverized coal in thermal power plants. Since many years fly ash has been used as a construction material. Thermal power plants produce two kinds of fly ash; class F and class C. Class F fly ash is more popular than class C and contains less amount of lime. Class C fly ash has a large amount of lime, (more than 20%), so it has a better cementing characteristic. Class F ash are used in Portland cement production. While class C fly ash is more suitable in soil stabilization because of high percentage of lime and its cementing characteristics. In this project we used fly ash of class C as soil stabilizer, by adding a varying proportions of fly ash we determined the basic geotechnical properties such as, specific gravity, plasticity, compaction characteristics, unconfined compression strength and stress-strain modulus. Addition of small percentage of fly ash (about 3 %) decrease plasticity characteristics of clay. Beyond this percentage, addition of fly- ash tends to increase the plasticity. Harvard Miniature Compaction Tests indicate that maximum dry density increases with increasing fly ash content and optimum moisture contents decrease with increase in ash contents. Unconfined compressive tests were conducted on compacted specimens corresponding water content of optimum moisture contents (OMC), OMC-2%, and OMC +2%. The unconfined compressive strength (qu) and consequently the undrained shear strength (Su) which is half the unconfined compressive strength show a steep increase at 6% fly ash, beyond that increased moderately with increasing fly ash content for all the 3 moisture content conditions. However, the stress-strain moduli with increases with increasing fly ash contents. However it appears that there is no correlation between the modulus of elasticity ant the unconfined compressive strength. The result analysis of this study, it appears that fly ash class "C" is not an effective stabilizer to stabilize clay. This may be due to the fact that both clay particles and fly-ash particle have approximately same size. This might result in poor gradation that is deficient in particle interlocking in clay-fly ash mixtures. Another important property required for effective stabilization is plasticity. Unlike Lime, fly ash is a low non- plastic material and is not effective in binding the soil particles together.