The varying stiffness of materials surrounding a railway bridge abutment section has caused concern for rapid deterioration. Particularly on the transition toward the bridge approach, a significant contributing factor to the bad experience is the consolidation of the backfill material used. The objective of this study is to conduct experimental research utilizing locally available soil in a lightweight foamed concrete mixture as an alternative sustainable solution. The new technique combines the merits of the self-leveling air foam and the early strength attainment of portland cement concatenate into a flowable soil mixture. To attain this objective, the properties of the flowable soil mixture are tested by using various laboratory experiments. Furthermore, a numerical simulation was utilized to evaluate the performance of the backfill material under cyclic train loads compared with the conventional cement-treated base. The test results suggested that air foam content noticeably improves the self-leveling of backfill material, however, it should be controlled at lower than 20 % to ensure sufficient strength gain. Adding more cement content and lowering the usage of air foam not only shortens the setting time to less than 12 h and enhances the compressive strength up to 1.45 MPa, but it also reinforces the frost resistance of the lightweight foamed soil mixture. In addition to the numerical simulation, the test results reveal that the new material provides great settlement resistance and can withstand vibration load for a railway track system. The elastic displacement can be reduced up to 21 % (2 mm), and the plastic settlement can be lower to more than 60 % (6 mm) under 10,000 cyclic loads. In general, the application of lightweight foamed soil mixture as a backfill material for railway bridge approach poses a green and sustainable alternative solution.
