Strength Characteristics of Subgrade Stabilized With Lime, Fly Ash and Fibre

India is experiencing tremendous growth in infrastructure including road network and highways. Roads are to be designed with good reliability to fulfill the long term performance during the design period. Long term performance of flexible pavement depends on the soundness of the underlying subgrade soil. Unstable, poor or weak soil can create significant problems for the pavement. Weak soil has low California bearing ratio (CBR) which will lead to more layer thicknesses of the pavement section. Considering an escalating cost of the aggregates, utilization of weak soil by imparting additional strength by way of stabilization technique is a need of time. Present research study insights on the evaluation of benefits of stabilization of subgrade soil. Two types of soil (Soil A and Soil B) having CBR of 1.45 and 4.67 and three types of stabilizers namely hydrated lime, class F fly ash and polypropylene fibre (aspect ratio of 100) were selected for the laboratory investigation. Experimental program consisting of Atterberg limit, compaction, california bearing ratio and unconfined compressive strength tests were carried out. These tests were performed on unstabilized as well as stabilized subgrade soil at different percentages of stabilizers by dry weight of soil. Percentage of lime varied from 1.5, 3.0, 4.5 and 6 %, for fly ash stabilization it was 5, 10, 15 and 20 % whereas percentage of fibre varied from 0.25, 0.50, 0.75 and 1 %. Results of laboratory investigation revealed that 4.5 % lime, 10 % fly ash and 0.5 % of fibre were optimum for the improvement of strength characteristics of subgrade soil stabilization.