By Emmanuelle Brière
Large scale testing of underground mine backfill material
Some underground mine shafts extend for dozens of kilometres. Unfortunately, if these shafts are not shored up on a regular basis with backfill, the walls crumble and collapse. However, the backfill used to shore up the rock face contains Portland cement, the production of one tonne of which produces one tonne of CO2. That’s why Natural Resources Canada (NRCan) is launching a new green recipe of its own: slag binder.
What is a Binder?
As its name implies, a binder is a product that binds the molecules of one element to those of another element. Thus in cooking, for example, eggs serve as the binder that holds cake batter together. In mining, backfill contains a binder that acts as a glue and helps to stabilize pillars and prevent roof collapses in mine sites.
A New Green Recipe
Casting cylindrical samples of the alternative binder material
Portland cement typically serves as the binder used in backfill. But slag binder is an environmentally friendly alternative due to its composition of slag, waste rock from mining operations and calcium hydroxide (from gypsum), materials that are usually discarded and stored at mine sites. As these leftover materials are already found nearby at certain mines, they can thus be put to good use.
In addition, replacing Portland cement with this new slag binder significantly reduces CO2 emissions. “Thanks to solutions like this one, mining companies can continue to improve their operating practices and contribute to more environmentally friendly mining in Canada,” says Louise Laverdure, director of Green Mining Research at NRCan.
Saving Time and Money
Conditioning stage of the alternative slag binder material
This binder, for which NRCan’s Mineral and Mining Science Laboratories (MMSL) holds an international patent, has a clear advantage over Portland cement as it can be produced locally. In fact, the formula can be made at the mining site, whereas Portland cement comes from cement plants that are sometimes very far away. Slag binder is therefore very attractive for mining sites in the North and other remote areas that face very high transportation costs for their cement needs.
The goals of this research project are the reduction of our environmental footprint and innovation in tailings management, two of the four research pillars of the Green Mining Initiative. For more information on this topic, you can watch the video and read the article “Green Mining Initiative to Reduce Mining's Environmental Footprint” from our May 2010 issue.
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