Earlier this month, engineering students from Ohio Northern University comprised one of 42 college and university research teams competing at the Environmental Protection Agency’s 2015 National Sustainable Design Expo in Alexandria, Va.
The annual event showcases new sustainability research by college students and faculty advisors from across the nation, while bringing together government agencies, nonprofit organizations and businesses that are working to create a sustainable future.
The ONU team presented new research looking at a method to lower the carbon dioxide footprint of concrete. The carbon dioxide footprint of a material is the amount of carbon dioxide directly and indirectly released during the production of the material. Specifically, the team looked at adding limestone to concrete mixtures. Limestone has a lower carbon dioxide footprint than cement and offers the additional benefit of absorbing carbon dioxide from the air as it cures. Their hope was for some evidence that this new take on an old technology could help reduce carbon dioxide in the Earth’s atmosphere.
While the terms concrete and cement are often used interchangeably, they are different materials. Concrete is a mixture of various components, which are combined to form the product that we see every day in the form of sidewalks, roads and bridges. There are many ingredients that can be used in concrete, but the three primary are water, aggregate (sand or gravel) and Portland cement.
“When Portland cement is manufactured, some limestone is used, but only up to five percent of the overall composition. Our students are looking at the environmental benefits of using much more limestone—up to 40 percent of the overall composition—in concrete,” says Dr. Ahmed Abdel-Mohti, associate professor of civil engineering and principal investigator of the research project.
This research looked to see if more limestone equaled more carbon dioxide absorption. Concrete trails only water as the most commonly used substance on Earth by humans, so proving that using more limestone in concrete could have even modest effects on carbon dioxide uptake is significant.
There is a reason concrete is so commonly used by humans. It is inexpensive, easy to make, adaptable to many applications and, most importantly, strong. Regardless of any new material’s potential environmental benefits, it would still need to maintain the structural integrity of concrete.
“With this research, we were trying to see proof of concept,” says Dr. Bryan Boulanger, associate professor of civil engineering. “We want to see if there is any difference between [percent] limestone compositions and uptake of carbon dioxide. And, is there any difference structurally between limestone and traditional cement?”
To test their hypothesis, the students first augmented concrete formulas with greater proportions of limestone. They tested formulas with 5 percent, 15 percent and 35 percent added limestone to get a data across a manageable range. Then the formulas were mixed up as concrete and cast into cylinders. Some of the cylinders were cured in a carbon dioxide-rich environment, while others were left to cure in a normal environment. Curing time ranged between seven, 14 and 30 days. Finally, the cured cylinders were sliced to expose the cross section and tested for surface pH with the chemical indicator dye phenolphthalein.
Measuring pH change in carbon dioxide exposed concrete is a practical way to test for carbon dioxide uptake because exposure to carbon dioxide makes concrete more acidic. The surface pH of common cement is basic (pH < 10). Phenolphthalein turns pink at a pH above 10 but is colorless at a pH below 8.3. By using the cross section, the hope was that there would be a corollary to carbon dioxide penetration (as observed by a shift in color across the sliced sample) and either the percentage of added limestone, the duration of the concrete’s exposure to carbon dioxide, or both.
It was an ambitious and fascinating project to be sure, but that is what’s expected of projects that are awarded EPA research grants.
Abdel-Mohti and Boulanger applied for, and were awarded, a $15,000 EPA People, Prosperity and Planet (P3) grant to fund this research. The aims of the P3 program are to promote and encourage projects that benefit people, promote prosperity and protect the planet in order to advance a sustainable future. Innovation and goals are part of it, but so too is teaching good, hard science.
“We had laboratory components where we made samples. We had the laboratory component where we exposed them to high carbon dioxide. We had the analysis side where we cut samples and tested them for both structural integrity and also chemical composition. And then we also had the analytic side to interpret data and tell us what it all means. So our students got to do bench-top lab work, chemical analysis and statistics,” says Boulanger. “And then they got to go to our nation’s capital to share what we learned.”
What they learned—beyond how to actually conduct research—is that big ideas are complicated and, well, hard.
“Basically, the results [of enhanced carbon dioxide uptake] were inconclusive. This was true for all amounts of limestone as well as the duration of time exposed to carbon dioxide,” says senior civil engineering major Allan McDaniel, of Portage, Ohio.
But that isn’t to say their research was insignificant. They did learn other important findings including that there is a definite limit to how much limestone can be used before concrete stops being concrete. With 35 percent added limestone, the material failed the structural tests. And the students did detect evidence of lower pH levels in concrete with more limestone. It’s just that the research didn’t generate a tidy one-to-one measurement to tell them how much limestone addition equals how much carbon dioxide uptake.
Two conclusive takeaways for the students involved with this project are the experience and the confidence they gained along the way.
“Although we didn't win any of the awards at the Expo, I feel as if this experience was very beneficial to us students as we continue to prepare for our professional lives. This project helped blossom our technical skills as well as our communication skills. And it was nice to see that people were actually interested in our work. The audiences we spoke to seemed very engaged in what we had to say,” says senior civil engineering major Addison Wolf, of Wapakoneta, Ohio.
For Rafael Ferreira Alves, a Brazilian Scientific Mobility Program (BSMP) student at ONU, the chance to do research and present at the Expo was akin to an international research project. Alves was one of two students on the project from the BSMP. He and Julia Rossini Lupinacci took part in the project as they pursue training in STEM fields at ONU this year.
“The opportunity I had to participate and compete with brilliant teams from all over the United States was unique! I'm sure the experience I got from the research and presenting at the Expo is going to help me in my career, and even more in my personal life,” he says. “I am glad I had the chance to work with such nice teammates and professors. I still believe that our project has a promising future and will be beneficial for the environment after the right adjustments.”
The College of Engineering at ONU has never shied away from trying new things even when success isn’t guaranteed. This project is the epitome of that ambitious spirit. This undergraduate research project looked at an infrastructure challenge that governments and industry are spending millions of dollars on finding answers to. Abdel-Mohti and Boulanger deserve credit for pushing their students to the fore of their future career field, so that they might better understand the kinds of professional challenges their generation is likely to face.
“We could teach these classes the same way we have taught them forever. But that doesn’t push the concepts further, and it doesn’t fully explain the research process,” says Boulanger. “Sure, our students would be in the lab testing materials, but they would be doing so just to see the way they perform. There wouldn’t be a bigger scope to the project for them to realize. With this, it’s more than just a class that they’ve taken. It’s a real-world experience that they’ve participated in.”
Civil engineering is a field that demands real-world experience. So much of what civil engineers do is for the rest of us. They build the roads to keep our economy moving. They develop the water and sewer systems to keep our bodies healthy. And in the future we might well look to them for solutions to the challenges that face us all. Because the real world just might be in real trouble if more students at more universities don’t become interested in doing the kinds of things that ONU students just did for their EPA P3 project.