Public defence in Civil Engineering, Soili Solismaa, M.Sc.

Title of the thesis: Classification and utilization of different types of mine tailings: An environmental perspective

Thesis defender: Soili Solismaa
Opponent: Dr., Senior Researcher, Annika Parviainen, Andalusian Institute of Earth Sciences, Spanish National Council of Research (IACT-CSIC), Spain
Custos: Prof. Jussi Leveinen, Aalto University School of Engineering, Department of Civil Engineering

Dissertation: Soili Solismaa ‒ Classification and utilization of different types of mine tailings: An environmental perspective

Management of extractive waste, such as mine tailings, requires significant financial resources and land areas. Additionally, depending on their composition, tailings may pose environmental risks. More efficient utilization of these materials could reduce both the volume of the waste and the need for primary raw material extraction. However, the utilization outside mining areas has remained limited, as profitability and the productization process present challenges.

The doctoral research by Soili Solismaa provides a preliminary classification for Finnish mine tailings, aiming to improve understanding of their potential for utilization. Tailings containing harmful substances may be utilized as cemented paste backfill (CPB) material to fill empty mine cavities. The production of cement, which is traditionally used in CPB preparation, generates carbon dioxide emissions, making the use of more environmentally friendly binders relevant.

The study examined the partial replacement of cement with blast furnace slag in CPB materials. This partial replacement improved the compressive strength of the test specimens, but when exposed to mine water, it increased the dissolution of calcium-rich phases from the CPB. This reduced the concentrations of As, Sb and Ni in the water but simultaneously degraded the mechanical properties of the material.

By characterizing and classifying mine tailings, and examining the properties of materials made from them, the potential for their use in various applications can be identified. This reduces dependency on primary raw materials and helps to mitigate the environmental impact of the mining industry.

Keywords: Mine tailings, circular economy, environmental geochemistry

Thesis available for public display 10 days prior to the defence at Aaltodoc. 

Contact information: soili.solismaa@aalto.fi