Microstructure Analysis and Mechanical Properties of Backfill Material Using Stone Sludge

In this study, the optimum mixing ratio for backfill was determined by analyzing the mechanical properties and microstructure of controlled low-strength material (CLSM)―the backfill material for road excavation and restoration―using the total amount of stone sludge generated during aggregate production, including analysis of the flow and material separation resistance by compounding factors. A small-scale field evaluation was conducted using the derived optimal mixing ratio. A comprehensive analysis of the mechanical properties was based on the relevant standards and specifications, and a microstructure analysis indicated that the optimal mixing ratio of CLSM containing stone sludge was 350% W/B. A field applicability evaluation indicated that the flow was 230 mm, and the initial and re-excavation properties were 0.75 and 1.15 MPa, respectively, which met ASTM standards. Monitoring for approximately 5 months revealed that there was no ground subsidence caused by traffic, and it was confirmed that re-excavation with equipment was possible. After re-excavation, the filling properties of CLSM using stone sludge and the pipe periphery were checked, and it was found that no significant filling and pipe damage had occurred.