Experimental Investigation for Stabilization of Subgrade Using Demolition Waste with Different Fibres

Subgrade soil stabilization is an important process in pavement construction on expansive soils such as black cotton soil. Expansive soil causes extensive damage to lightly loaded structures constructed over them. Also, in urban areas, borrow earth is not easily available which has to be hauled from a long distance. In this scenario expansive soil stabilization proves to be a better alternative. Past studies mentioned that extensive laboratory and field tests has been carried out which showed promising results for application of such soil after stabilization with agents such as cement, lime, and bitumen. The growing cost of traditional stabilizing agents has prompted an investigation into the stabilizing potential of demolition concrete waste in expansive soil. Also, an attempt is made to utilize different fibres in addition to the demolition concrete waste to stabilize the soil for pavement subgrade. The effect of bamboo fibre in varying percentages such as 0.2, 0.4, and 0.6 along with demolition concrete waste of 10, 20, and 30% in subgrade soil was studied. An optimum fibre content of 0.6% with 20% of demolition concrete waste was found to be very effective in stabilization of the expansive soil. It increased the maximum dry density (MDD) with decrease in optimum moisture content (OMC) and showed promising results for the stabilization of expansive soil. Similarly, the improvement of expansive soil was studied by adding polyester fibre in varying the percentage of 0.1, 0.2, and 0.3 with 10 and 20% of demolition concrete waste. The additions showed an improved result with an optimum of fibre content 0.2% with 20% of demolition concrete waste. Soaked California Bearing Ratio (CBR) tests were conducted for optimum percentage of bamboo and polypropylene fibres with demolition concrete waste, where it increased the CBR values to a smaller extent.