Approach road is an important structure of a bridge. Serviceability of a bridge is affected by the settlement of approach road, especially that on soft soil. One method that is usually applied for minimizing effect of settlement of approach road is to replace soft soil by hill soil. This method however may increase cost of projects in Mekong Delta area with a larger depth of soft soil. In this paper, soft soil strengthened by mixing it to cement and fly ash at different mix proportions was investigated. Test results from unconfined compression test and direct shear test of strengthened soft soil are compared to those of hill soil to determine the optimal mix proportion. Results showed that mixing 25kg cement and 75kg or 100kg fly ash to 1m3 soft soil increased its unconfined compressive strength and shear strength and are higher compared to those of hill soil. Strengthening in situ soft soil by using fly ash, industrial waste from thermal power plant, reduces cost of project and at the same time contributes to solving environmental problems. | Strengthening soft soil for approach road after abutment by cement and fly ash
