Alcoa, Nova Pb and St. Lawrence Cement have pooled their expertise and developed a way to turn the aluminum company’s hazardous waste into a non-toxic product that improves cement.
Pot-liner, the residue produced during the smelting of primary aluminum, is dangerous stuff, containing cyanide and fluoride. It has been banned from most landfill sites for years.
Alcoa has been removing the residue, neutralizing it and storing it, said company spokesperson Pierre Despres, but a new process will allow all the waste to be recycled.
Brian McIver, vice-president of Nova Pb, located in Ste. Catherine on the South Shore, said the company worked with the Universite de Sherbrooke to devise a method of adding other materials to the residue to render it non-toxic and create a new product called CALSiFrit.
CALSiFrit strengthens cement and also makes it more porous, he said, reducing the moisture infiltration that causes deterioration.
The product has gone through three years of development and commercial trials, he said, and has received the blessing of Quebec’s Ministry of the Environment. Tests have indicated “beyond a shadow of a doubt” that nothing toxic leaches from the cement, he said.
The companies have signed a three-year deal that will see Nova recycle 50,000 tonnes of Alcoa’s industrial waste.
St. Lawrence Cement said it has secured contracts to consume 100,000 tonnes of CALSiFrit producing a blended cement for mining industries.