A group of researchers is turning to waste to make concrete more sustainable.
The cornerstone of many building projects, concrete is also one of the leading contributors to the warming of our planet because it is partly made up of cement, which creates 8% of the world's human-caused carbon dioxide pollution annually, according to The Economist.
So the Idaho State University Department of Civil and Environmental Engineering and many other teams worldwide are testing a concrete mix made with precipitated calcium carbonate, the waste produced when sugar beets are turned into refined sugar.
"Conventional concrete production generates substantial amounts of carbon emissions and consumes a significant quantity of raw materials on a global scale," graduate student Kabiraj Phuyal told ISU News in November. "Exploring greener and more sustainable options for concrete production is important in addressing environmental concerns. Additionally, the concrete we tested may offer a lower cost alternative for builders because it uses upcycled and recycled materials."
In addition to cement, concrete consists of air, water, sand, and gravel. In a study published in August, the researchers found that they could replace up to 30% of the cement with precipitated calcium carbonate and 100% of the sand and gravel with upcycled concrete aggregate, or pieces of previously used concrete, which is another way to make the substance more sustainable.
ISU News cited a 2020 report by the Environmental Protection Agency that showed construction and demolition debris accounted for 600.3 million tons of waste in 2018. Of that, concrete made up 405.2 million tons, and 71.2 million tons of the stuff went to landfills.
"PCC is chemically identical to its natural version, limestone, and to make cement currently, manufacturers heat limestone, clay, and other materials and then grind them into a powder," ISU News reported.
But it turns out you can make concrete with just about anything, including the byproducts of things we drink and eat. Similar developments have been made with used coffee grounds, bagasse (sugarcane waste), and food waste, and other iterations include green concrete, low-carbon concrete, and ECOncrete.
Now, we can add PCC concrete to the list.
"Working on this project was an exciting and rewarding experience for me," Phuyal, the study's lead author, said. "It was an excellent opportunity to apply what I've learned and my skills on eco-friendly construction."
The researchers plan to test the concrete's freeze-thaw performance, shrinkage, surface hardness, and rebound rate to "comprehensively evaluate the suitability of PCC and UCA in concrete applications," according to the study.
"We have plans to build on our research and explore other aspects of this eco-friendly concrete using recycled and by-products that we have developed at ISU," associate professor Mustafa Mashal said. "We are also collaborating with our industry partners to identify applications for these concrete mixes."
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