Strengthening Black Cotton Soil with Fly Ash and Moorum

One of the most effective and economical methods to strengthen clayey soils is addition of stabilizing agents such as fly ash to the soil. In this study, highly plastic clay was stabilized using fly ash. Geotechnical properties such as Atterberg limits, unconfined compressive strength (UCS), and the California bearing ratio (CBR) value of virgin black cotton soil and soil treated with fly ash were evaluated. Soil was stabilized with various proportions of fly ash, i.e., at 0%, 10%, 15%, 20%, and 30%. The UCS of black cotton soil–fly ash mixes is found to be at its maximum at 20% fly ash content and thereafter decreases with further increases in fly ash content. However, in the case of fly ash mixed with soil, the CBR value obtained was less compared with virgin soil. Furthermore, CBR was performed with two-thirds part fly ash soil mixed with one-third part moorum with better results. The maximum CBR value was found to be 5.03% at 20% fly ash content. These results are significant; they prove that we can use fly ash as subgrade material for the reason that in actual conditions, water does not easily enter into the subgrade layer because it is protected by a moorum (subbase) course.