Soil Stabilization Using Rice Husk Ash and Natural Lime as an Alternative to Cutting and Filling in Road Construction

Pavement construction tends to be relatively expensive in areas where expansive clay forms the bulk of the alignment soil. The common practice in Kenya is to remove the undesirable material and fill the space with more stable materials. The present study has developed a method for stabilizing expansive clay for Subgrade Class S2 pavement construction. A combination of 20% by weight of rice husk ash (RHA) and approximately 2% by weight of natural lime improved the California bearing ratio (CBR) of expansive clay soil by 800%, reduced the soil plasticity by approximately 90%, and decreased free swell by approximately 70%. It has been shown that use of RHA as a stabilizer is not only an affordable green technology, but also gives expansive clays the strength required for the Subgrade Class S2 pavement layer.