CANBERRA, Nov. 5 (Xinhua) -- Australian scientists are pioneering a solution that transforms vast volumes of mine waste into a low-carbon building material that could address both mining's waste crisis and construction's carbon problem.
Researchers at the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia's national science agency, said they can convert mine tailings into geopolymer concrete, a cement alternative, cutting carbon dioxide emissions by 80 to 90 percent compared with commonly-used Portland cement, a CSIRO statement said on Wednesday.
Tailings, stored in dams all over the country, comprise all the rock, clay, water and other materials remaining after separating ore from everything miners dig up, often forming a wet slurry making up around 80 percent of the volume extracted.
Australia generates an estimated 620 million tonnes of mine waste annually, stored in 250 active tailings dams. The University of Queensland's Sustainable Minerals Institute estimates 13 billion tonnes of mine tailings are generated globally each year.
Geopolymers, binding agents that replace cement in concrete, use aluminosilicates, which are clays rich in aluminium and silicon compounds, instead of using limestone heated to 1400 degrees.
"Geopolymers can be substituted for the cement used in most concrete," said CSIRO scientist Clint McNally. "By using an aluminosilicate instead of limestone, we can get a significant amount of our clays from mining waste."
However, previous research found geopolymer concrete costs about twice as much as Portland cement, mainly due to alkaline activator production. CSIRO's approach, using waste tailings rather than purchased materials, could solve this economic hurdle while addressing the waste crisis, researchers said.
"By switching waste, whether from mining or construction, from a problem, into something that can earn revenue, there's potential for a big, disruptive change to the way we do things," he said. ■
