by John Gagnon
Making Concrete Greener
Concrete is the number one building material in the world and ranks second only to water as the most consumed substance on Earth. Cement, a key ingredient in concrete, has a large carbon footprint. PhD student Melanie Kueber is part of a team that wants to reduce the use of cement by replacing more of it with coal fly ash. The process would use what was once a discarded material as a useful one that would mitigate stress on the environment.
Fly ash is a by-product of coal combustion to produce electricity. "Power plants," Kueber says, "are focused on the efficient production of electricity. When they can sell a by-product like fly ash, then they've won twice." In 2007, 72 million tons of fly ash were produced in the US. About 44 percent was beneficially used, with about half of that amount in concrete.
Fly ash has been used in concrete since the 1930s. Currently, when used in highway concrete, it makes up about 5 to 15 percent of the total cementitious material used. Kueber envisions increasing that to 25 percent shortly, with government and industry targeting 50 percent by 2010. "We want to come up with an inexpensive way to use fly ash just like it is," Kueber says.
Several problems face researchers working on this initiative: carbon in coal fly ash causes adsorption of air-entraining chemicals, which compromises the concrete air-void system and makes the concrete susceptible to damage from freezing and thawing; in different power plants, different coal fuels, and burning conditions produce inconsistencies in the makeup of fly ash, which makes higher replacement rates "risky," with regards to achieving the necessary concrete strength.
Kueber earned a bachelor's degree in civil engineering from Michigan Tech, a master's in project management from Northwestern University, and is now back at Tech as a doctoral student in civil engineering. She has been supported by the University Transportation Center for Materials in Sustainable Transportation Infrastructure (UTC-MiSTI) at Michigan Tech, has received the UTC Student of the Year Award, and has been named a trainee in the NSF-sponsored Integrative Graduate Education and Research Traineeship (IGERT) program that focuses on sustainability.
Before returning for doctoral studies, she spent eight years in industry, including five years with the Illinois Department of Transportation. That work gave her insight into the scope of making and maintaining roads.
"It takes so much money and time and human effort," she says. "The process is surprisingly complex." So she returned to Tech to work with researchers on finding a better, simpler, and more-sustainable way to build roads and other structures.
Kueber is on a research team that includes two other students; Professor Lawrence Sutter, director of the Michigan Tech Transportation Institute; and Professor David Hand of the Department of Civil and Environmental Engineering. Sutter is an expert on concrete chemistry; Hand is an expert on carbon applications.
Kueber takes a multidisciplinary approach to her work. "Concrete is a complex mix of chemicals," she says. Therefore, she is studying organic and physical chemistry to learn how ingredients in concrete interact.
She never envisioned studying chemistry. "I chose the tough road because it's the path to solve the problem. Tech professors always challenge students. I expect nothing less."
The implications of this inquiry are huge. It is estimated that the production of concrete will total two billion tons by 2010. Using fly ash as a component, then, has significant economic and environmental benefits.
The goal: to develop new tests and specifications. The hope: that the industry adopts and implements the findings.
Kueber says the team anticipates success and adds, "The faculty leaders and student researchers have the expertise and the perfect resources needed to make this work."
Volcanoes' Dangerous Reach
Rüdiger Escobar-Wolf is a native of Guatemala who grew up in the shadow of volcanoes. Thus, he says, it was "a natural" that he would end up studying these fiery mountains.
Escobar-Wolf is working on a PhD in Geology, and he made the trek to Tech after he met Professor Bill Rose, who does extensive work in Guatemala. Escobar-Wolf had been working for a Guatemalan government agency that deals with disasters.
Now his research involves assessing the risk of active volcanoes that might harm populations.
Guatemala is part of the volatile Pacific "Ring of Fire" that stretches from Alaska to southern Chile. The agitation results from plate tectonics—in this case, the Pacific Cocos Plate moving east and being pushed under the continental Caribbean Plate, causing magma to rise from the depths and form volcanoes at the surface.
"As we speak," Escobar-Wolf says, "there are three volcanoes erupting in Guatemala." He is studying one in particular, Fuego: Spanish for "fire."
There are three major hazardous phenomena that volcanoes discharge: lava flows that ooze out of a volcano slowly; gas and ash that rise and form huge clouds; and the deadly pyroclastic flows—a heavy mixture of dust, gas, and rock that "tumbles down the mountainside like a hot rock avalanche."
Pyroclastic flows can suddenly reach populated areas, and several towns and villages with about 25,000 people are within the reach of Fuego. As recently as 2003, a pyroclastic flow extended almost five miles. "That was a close call for people of one village," he says.
Escobar-Wolf's work is to assess the possibility of such an eruption so people can flee from harm's way, much the way hurricane warnings function.
He says that Fuego erupts almost constantly. "There's hot ash and rock on the perimeter of the mountain all the time. We're worried about when activity intensifies."
The surface area at the foot of Fuego abounds in volcanic deposits that are hundreds of years old. As part of their investigation, Escobar-Wolf and colleagues study historic deposits, and if they contain charcoal or charred wood, they can date them and reconstruct a history that might inform their inquiry. As well, these scientists measure seismic activity, gas, temperature, gravity, deformation, and noise—all "to infer something about magma rising."
The idea: try to come up with correlations that might indicate the onset of out-of-the-ordinary volcanic activity and forewarn people of imminent danger.
"You can't say for sure what will happen," he says. "Volcanoes are way too complex to do that. So we do a forecast rather than a prediction. We are trying to give a probability, a likelihood."
The work is not without its dangers, and there have been catastrophes. "We do a good job of not exposing ourselves to danger unnecessarily," Escobar-Wolf says. "Some people take much larger risks than what I would consider necessary. You don't have to get that close to get good data."