Optimization of Black Cotton Soil Stabilization Using Lime and Bamboo Fiber Mixture for Sustainable Road Subgrade Construction

Black cotton soil is highly expansive in nature and exhibits significant swelling and shrinkage behavior due to variations in moisture content, making it unsuitable for construction purposes without proper stabilization. This study focuses on improving the engineering properties of black cotton soil by using lime and bamboo fibres as stabilizing agents. The experimental investigation was carried out to evaluate the effect of varying percentages of lime (0% to 8%) and bamboo fibres (2% to 8%) on the physical and mechanical properties of the soil. Laboratory tests such as sieve analysis, Atterberg limits, Standard Proctor test, California Bearing Ratio (CBR), and Unconfined Compressive Strength (UCS) were conducted to determine the changes in soil characteristics. The results showed that the addition of lime reduces the liquid limit and plasticity index while increasing the plastic limit, indicating improved soil stability. Compaction characteristics revealed a decrease in maximum dry density (MDD) and an increase in optimum moisture content (OMC) with increasing lime content. The strength parameters, including CBR and UCS, showed significant improvement up to an optimum lime content of 4%. Further enhancement in strength was observed with the inclusion of bamboo fibres, where optimum performance was achieved at 2% fibre content. The combined effect of lime and bamboo fibres resulted in increased load-bearing capacity, improved shear strength, and reduced swelling characteristics of black cotton soil. Based on the experimental results, the optimum proportions of lime and bamboo fibres were found to be 4% and 2%, respectively. The stabilized soil can be effectively used as a subgrade material in pavement construction, providing a cost-effective and sustainable solution for weak soil improvement.