| Popis: |
Proper management of mine tailings containing high amount of sulfide is a crucial issue in order to reduce their environmental hazards including generation of acid mine drainage and release of heavy metals. This study was conducted targeting to understand the effects of using lead-zinc sulfide tailings (LZSTs) as cement substitution on the hydration properties of concrete samples. Mechanochemical activation of the LZSTs containing 19.9% sulfide content in mixtures of 20%, 40%, 60%, 80% and 100% was performed to cement-replacement in concrete production. Analyzes were performed on the produced concrete samples. X-ray diffraction, compressive strength, toxicity characteristic leaching procedure (TCLP), mercury intrusion porosimetry, X-ray spectroscopy, scanning electron microscopy, energy-dispersive fourier-transform infrared spectroscopy, thermogravimetric analysis and differential thermal analysis were performed on the constructed concrete samples. The results of XRD analysis confirmed that introduction of activated tailings in the concrete construction led to form hatrurite (Ca3SiO5) phase. According to the TCLP, with increseasing curing days, leached amount of studied toxic metals decreased and was lower than the allowable limit. The results of the mercury intrusion porosimetry (MIP) indicated that as the curing time prolonged, the critical pore size was reduced from 150 to 50 nm in the constructed sample containing 20% activated tailings. Therefore, by activating the tailings, the specific surface area was enlarged and more cohesion took place in the concrete samples. The compressive strength results indicated that the compressive strength after 90 curing days in the constructed sample containing 20% activated tailings was 40.85 MPa, while it was 38.15 MPa in the control sample. In general, the results indicated that the mechanochemical activated of LZSTs with calcium carbonate can be a suitable alternative for cement (up to 40%) in the production of concrete samples. |
