Utilization of Mine Tailings as an Alternative Material for the Upper Foundation Layer (UFL) of Road Pavement

Tailings waste is a by-product of gold ore processing activities that is generated in large quantities and has the potential to cause environmental problems if not utilized. This study aims to evaluate the technical feasibility of tailings as an alternative material for the Upper Foundation Layer (UFL) of road pavement and to determine the percentage of tailings that can be added to the mixture to meet the technical specifications of the Upper Foundation Layer (UFL). The research was conducted experimentally in a laboratory using aggregates obtained from PT. Passokorang and tailings waste from PT. Citra Palu Minerals. Tailings contents of 0%, 25%, 50%, 75%, and 100% were used as substitutes for conventional filler. The tests conducted included sieve analysis, specific gravity and absorption, abrasion, clay content, plasticity index, modified compaction, California Bearing Ratio (CBR), Scanning Electron Microscopy (SEM), and X-Ray Fluorescence (XRF). The results showed that the tailings met the filler requirement based on the percentage passing the No. 200 sieve of 81.92%; however, they did not satisfy the requirements for clay content and the ratio of the percentage passing the No. 200 sieve to the No. 40 sieve. The compaction test results indicated that the optimum mixture occurred at a tailings content of 50%, with an optimum moisture content of 5.38% and a maximum dry density of 2.766 g/cm³. The highest CBR values were also obtained at a tailings content of 50%, reaching 75.939% in the oaked condition and 75.376% in the soaked condition. SEM analysis showed that the mixture containing 50% tailings had the highest particle density and the smallest pore area, while XRF results indicated that silicon (Si) was the dominant element at 41.356%. Although the 50% tailings mixture exhibited relatively better characteristics, none of the tailings variations tested met the minimum CBR requirement of 90% for UFL. Therefore, technically, tailings are not yet suitable for use as an alternative filler material in the Upper Foundation Layer of road pavement.