Clayey soil having low shear strength and high compressibility cannot be used for sub grade as it's CBR value will not be in permissible standard. So it's needed to be modified when required to use for sub grade under pavements. To modify, stabilization or ground modification technique is required. In this regard we are making an attempt to modify the properties feasible to be used as sub grade material. Here we are using Fly ash as admixture to stabilize and improve the properties. Many attempts were made using fly ash, here we are attempting an study of fly ash stabilization under curing period as the fly ash is being used as an substitute of cement in concrete which gains strength with curing.