Unlocking the potential of iron ore tailings in controlled low-strength material: Feasibility, performance, and evaluation

Iron ore tailings (IOT), the predominant solid by-products of iron ore mining and refining, present significant environmental challenges due to their sheer volume. This paper endeavors to scrutinize the prospective deployment of IOT as an alternative to soft soil in the fabrication of controlled low strength materials (CLSM) for backfill applications. The flowability of the CLSM is evaluated by adjusting the IOT, soft soil, and water contents and subsequent appraisal of mechanical properties of the cured CLSM samples is performed via unconfined compressive tests, dry-wet cycles, and direct shear tests at the flowability of 20 cm. Furthermore, scanning electron microscopy and mercury intrusion porosimetry tests are deployed to investigate the impact of IOT on the microstructure of the cured CLSM. Experimental results demonstrate that an increase in IOT content considerably reduces the requisite water content to achieve a flowability of 20 cm for CLSM. Both unconfined compressive strength (UCS) and direct shear tests signal that the infusion of IOT into CLSM substantially enhances the UCS (e. g., from 200 to 440 kPa) along with improving the cohesion (e.g., from 65.9 to 103 kPa) and friction angle (e.g., from 11.5 degrees to 16.3 degrees) of the cured CLSM samples. The mass loss of CLSM, post dry-wet cycles, is notably mitigated, and the corresponding UCS is also bolstered by increasing the IOT content. Microstructural observations in conjunction with pore size characterizations corroborate that the strength augmentation of the CLSM mixture can be attributed to the densification of the microstructure and the proliferation of cement hydration products with increased IOT content. Consequently, this investigation sheds light on the promising potential of employing IOT as a central ingredient in CLSM production.