CSIRO scientists are converting mine tailings into geopolymer concrete that cuts CO2 emission by up to 90 per cent.
CSIRO scientist Clint McNally said that the team experimented using repeatable forms of clay found in excavation waste, like kaolinite which can be bought from local pottery stores. What they discovered is that the same clay potters that are used to create porcelain is also the basis for geopolymers, a rock-solid concrete formula which the group believes can solve one of the mining industry’s most prevalent issues in mine tailings.
Mine tailings in Australia comprise all the rock, clay, water, and other materials remaining after separating ore from everything that a miner digs up. These waste materials can even be potentially toxic, depending on the source ore.
CSIRO’s Recovering Tailings group within the Sustainable Mining Technologies program are converting mine tailings into geopolymer concrete, which can tackle the mining waste crisis and the construction industry’s carbon waste problem.
“Geopolymers can be substituted for the cement used in most concrete,” McNally said.
“By using an aluminosilicate instead of limestone, we can get a significant amount of our clays from mining waste.”
McNally said that geopolymers are binding agents that replace cement in concrete and can be tailored to different purposes; high-strength blocks for roads, stable forms for safe disposal all dependent on how the ingredients are mixed.
“It’s a bit like making a cake. Change the ratio of eggs, sugar, and flour to get the type of cake you want,” he said.
The team discovered that geopolymers cut CO2 emission by 80 to 90 per cent compared with Portland cement, which contributes about eight per cent of global carbon emissions.
“Mine sties normally handle tailings using a fines circuit, where waste goes to a large dewatering pong,” McNally said.
“After the solids drop out, the underflow of about 30 per cent solids gets pumped to a tailings dam.”
McNally said that the geopolymer discovery is vital to tackle mine waste tailings and cutting carbon emissions in Australia.
“We have to either work out something to do with mining waste, or work out some better way to store it,” he said.
“Geopolymers are a way to do both; our process is able, not just to make tailings strong enough so it holds together more safely, but to also make it into something with value.”