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Mine tailings as partial raw materials substitutes in restoration and modern mortars: converting a "waste" to a "product"

Avgerou Nefeli

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Summary

During the restoration and reuse of monuments and monumental structures, it is crucial to research historic construction materials and formulate new ones to ensure the structural and historical integrity of monuments. A study of using mine tailings for construction materials is the subject of this thesis.Mine tailings are normally considered waste, which is expensive to store in mine facilities and may impair environment and society.However, the shortage and late price increases in some construction materials, together with the increasingly more restrictive environmental regulations, making this “ground dust”, a by-product of mining activities, an attractive alternative for construction materials.Many studies have been carried out on the use of mine tailings as construction material in the past, but a comprehensive study including tailings originating from different ore ore-forming processes and therefore having varied mineralogical and chemical compositions has not yet been carried out. Moreover, to date, there have been no known instances of mortars specifically designed for use in the restoration of historical buildings or modern structures.In this work, mine tailings from different deposits have been studied (Zinkgruvan, Kiruna and Vale). The experiments involve the analytical characterization of the tailings (mineralogical, chemical), formulation in mortars, testing (mechanical, physical) and optimization of the mix designs over the whole process to obtain the best-fitting solution for the tailings from the deposit studied.Concrete monuments and buildings, that already use cement as a construction material, can be restored with these products. The tailings used as substitute are used as a partial replacement of cement, and/or aggregates, where in grout when cement is substituted by Zinkgruvan or Kiruna tailings, in the presence of an activator, the 1d compressive strengths increased from 24.5MPa to 40MPa and from 21.4MPa to 39MPa respectively in comparison with the reference 1d strength 50MPa. Whereas, when they were used as an aggregate’s replacement the 28d strengths reached 96MPa (Zinkgruvan) and 93.7MPa (Kiruna).When Vale tailings are used as cement and/or aggregate’s replacement for repair mortars the values obtained are comparable with the reference, and no cracks are observed when applied on a concrete substrate.

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