With the Paste 2012 conference on mine tailings just a few weeks away in Sun City, I’ve pinched this title from a question posed at the 2008 conference in the paper Surface disposal of paste and thickened tailings – A brief history and current confronting issues. So thank you to the authors (M. Williams, K. Seddon, and T. Fitton) for putting that insightful paper together.
For those less familiar with the terms paste or thickened tailings, an impressive visual summary of these materials can be found here with a focus on pipeline design. I am always impressed by photos of slumping tailings. The fact that they retain some statuesque form due to their increased strength is an achievement in itself – a long way from sculpture, but an achievement of materials engineering nonetheless.
Another very illustrative piece of work can be found here, where the authors focus on innovative ways to measure the geometry of paste and thickened tailings deposits. Yes, you too could use personal hover craft or Light Detention and Ranging (LIDAR) to learn more about deposits of paste and thickened tailings.
These last two pieces, however, masterfully avoid the subject of distinguishing between the two supposedly distinct materials – paste tailings and thickened tailings.
The paste and thickened tailings expert will rightly tell you that these materials are but elements of a continuum that starts all the way back at watery, segregating tailings, transitions to non-segregating, thickened tailings, then to paste tailings, and finally arrives at solid cakes of filtered tailings. While there is some distinction based on density and rheology (yield stress, namely), each process engineer, rheologist, and tailings person will have their own “thresholds” on which they base decisions for pump selection, pipeline design, deposition planning, etc.
Most will agree that there is an overlap between the two flavours of tailings, and that the name adopted will likely depend on the continent you’re visiting and the person you’re speaking with. A safe bet might be to stick with thickened tailings, as much as addressing a square as a rectangle is acceptable to some, but we should be aware that paste tailings have the potential to have uniquely strange and wonderful behaviours. To learn more about these materials and their applications, pick up a copy of the Paste conference proceedings, or get yourself to Sun City in April.
Let me know if you have come across better definitions, or if you’ve coined your own terms. There’s room for creating new vocabulary when we create new materials – just don’t expect Merriam, Webster, or Oxford to jump on your band-wagon right away.