Pollution is everywhere – and if it is not adding to greenhouse gas emissions, then it is causing other kinds of environmental damage such as acid rain. However, a researcher at Missouri University of Science and Technology believes that pollution could be useful to us as a building material. Jeffery Volz, assistant professor of civil, architectural and environmental engineering at Missouri S&T, believes that fly ash – the fine particles that rise with fuel gases during combustion – could be used in concrete. If his hypothesis is correct, it could prevent millions of tons of the waste product from reaching landfills in addition to reducing global CO2 emissions.

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Currently, U.S.’ power plants produce 130 million tons of fly ash and bottom ash during the coal combustion process. In order to prevent air pollution, the fly ash is captured through filtration system and then stored at coal power plants or placed in landfills – hardly the most environmentally friendly solution.

While Volz’s idea is not a new concept, as fly ash has been used to build bridges, roads and dams for over 70 years, it is a fact that the ash increases concrete’s durability and as a result, extends the service life of these structures. So what makes Volz’s plan so different?

“Traditional specifications limit the amount of fly ash to 35 or 40 percent cement replacement,” said Volz. “Recent studies have shown that higher cement replacement percentages – even up to 75 percent – can result in excellent concrete in terms of both strength and durability.”

“Concrete typically has three key components: portland cement, water and aggregates like gravel and sand. During the manufacture of cement, limestone and other materials are heated to extreme temperatures, releasing tons of CO2 from both chemical reactions and the heating process. If fly ash could replace cement, it would not only reduce the amount of fly ash that ends up in ponds and landfills but CO2 emissions as well,” says Volz.

The disposal of fly ash is already a source of controversy, especially since one billion gallons of wet concrete spilled into dozens of wells in December 2008 contaminating them with toxic materials, like arsenic and mercury. If this method could reduce such accidents then it is worth consideration. However, there still may be some issues, namely that fly ash has a certain stigma attached to it.

“Construction workers might refuse to work with it,” Volz said. “And there’s also the issue of at what point is it not a hazardous material when used for beneficial reuse. Is it once it is added to the ready mix truck, which means it is a hazardous waste in the silo at the ready mix plant? Or is it once the concrete hardens, which means it’s a hazardous waste up to that point?”

“[However] by nearly doubling the use of reclaimed fly ash in concrete, high-volume fly ash aligns well with MoDOT’s green initiative on recycling,” he added. In fact, you can see a video of Volz’s concept here.

Is this a fantastic example of recycling or a risky proposition? We want to hear your thoughts.

+ Missouri University of Science and Technology

via News Wise