Red Sand in a trial as a road base in the Perth to Bunbury road network in Australia.
Australia - 2010
Alcoa-Developed Process Converts Bauxite Residue Component into Commercially Viable Product
An Alcoa-developed process to convert a component of bauxite residue into a commercially viable product called Red Sand™ could potentially reduce the company’s global residue volume by one-fifth while providing an environmentally sound solution to Australia’s declining sand supplies.
A byproduct of the alumina refining industry, bauxite residue is made up of two components of roughly equal quantity—sand and mud. This byproduct of the refining process, which also carries with it some residual caustic soda, is stored in impoundments that are capped and revegetated when full.
Efforts to reduce the volume of stored bauxite residue historically focused on the mud component. In 2006, scientists at Alcoa’s Technology Delivery Group in Australia began investigating the sand portion and subsequently developed a dewatering, washing, and carbonation system to process the material.
The system neutralizes any remaining caustic soda in the sand and removes most of the remaining carbonate salts, making the end product, known as Red Sand, environmentally benign. If integrated at all of Alcoa’s nine refineries worldwide, the process could reduce the amount of bauxite residue the company stores by 20%.
Red Sand is essentially crushed rock that is red in color. Testing shows that it can be used for general fill, construction backfill, or road-base construction. It is a potential cost-effective alternative to limestone, and it could be a high-quality construction sand due to its excellent drainage and strength characteristics.
“In Australia, there is quite a shortage of sand for cement making and lowland filling,” said Chris Oughton, director of the Kwinana Industries Council. “As demand for new sand sources increases, quarry companies will be pressured to open new quarries, which generally requires clearing bushland ecosystems. If Red Sand can alleviate the need to mine bush areas, that is a big environmental plus.”
Using Red Sand created at a pilot washing plant, Alcoa has conducted demonstration projects with external groups to prove the viability of the material. In 2009, the company established a project team to drive the product’s commercialization. The goal is to work with a co-developer that specializes in the production and marketing of sand products.