Abstract—The life of any structure depends on strength of the soil and load on the structure. The soil is not uniform through-out the world. Generally the poor soil having low load bearing strength (CBR) value less than 2% is replaced by good quality soil material. This paper deals with the improvement in various properties of Black Cotton soil for pavement sub-grade by using soil stabilizer. The stabilizer like RBI Grade 81is used to improve the properties of Black Cotton soil for pavement sub-grade purpose. From CBR test, it is found that the soaked CBR value of soil is improved by 745.54% i.e. 2.02% to 15.06% by stabilizing soil 4% RBI Grade 81. The various mixes of Black Cotton soil: RBI Grade 81 for the different proportions was tested for Atterberg¡¯s limit, Shrinkage limit, Free Swelling Index, Compaction (OMC & MDD) and 4 day¡¯s soaked CBR value.