Evaluation of the use of high silica mining tailings as a partial cement substitute in concrete mixtures

Abstract

This study evaluates the technical potential of using silica-rich mine tailings (MTs) as a partial substitute for Portland cement in concrete. The MT was characterized using particle size analysis, inductively coupled plasma optical emission spectrometry, X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy, and sequential extraction. The material contained 25.01% silicon, 1.89% iron, and 0.21% calcium, with approximately 40% of particles smaller than 0.074 mm. XRD identified primarily quartz and moganite, two polymorphs of SiO ₂ , and nearly the unique source of Si. Mixtures were prepared with 0, 2.5, 5, 10, 15, and 20% replacement. At 60 days, the mixture with 2.5% substitution reached 37.17 MPa, compared with 30.06 MPa for the reference concrete, representing a 23.7% increase; the mixture with 5% substitution reached 35.88 MPa. In contrast, the 15% and 20% substitutions reduced the strength to 25.42 and 22.14 MPa, respectively. Chloride transport exceeded 4,000 C in all mixtures, classifying them as highly permeable. The mixture with 2.5% had a value of 8,616 C, compared to 8,350 C for the control, whereas the maximum value (10,645 C) was observed at 10% substitution. The 2.5% mixture exhibited the best overall performance under the conditions studied.