Optimizing Subgrade Soil Stability through Cow Dung Ash and Rice Husk Ash Incorporation

The stability and load-bearing capacity of subgrade soils play a crucial role in the construction and maintenance of transportation infrastructure. In many regions, subgrade soils exhibit poor engineering properties, leading to detrimental effects such as excessive settlement, differential settlement, and pavement distress. Consequently, there is a pressing need to develop cost-effective and environmentally friendly solutions to enhance the stability of subgrade soils. This research investigates the feasibility of utilizing agricultural waste materials, namely cow dung ash (CDA) and rice husk ash (RHA), as soil stabilizers to improve the mechanical properties of subgrade soils. CDA and RHA are abundant byproducts in many agricultural communities and have the potential to be utilized as sustainable alternatives to traditional stabilizers. The experimental program involved characterizing the physical and geotechnical properties of the subgrade soil, CDA, and RHA. Various proportions of CDA and RHA were mixed with the subgrade soil to create stabilized soil mixtures. Tests were conducted to evaluate the effects of the additives on the compaction characteristics, California Bearing Ratio (CBR), and unconfined compressive strength (UCS) of the stabilized soils. Preliminary results indicated that the addition of CDA and RHA led to significant improvements in the engineering properties of the subgrade soil. The CBR values and UCS of the stabilized soils increased with increasing proportions of CDA and RHA, demonstrating enhanced load-bearing capacity and resistance to deformation. The improvements were attributed to the pozzolanic properties of CDA and RHA, which facilitated cementitious reactions and the formation of stable soil-aggregate bonds.