Sidewalk Research

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The Search for Eco-Friendly Concrete

civil engineering students
Current students Ryan Dagger (left) and Scot Larson (right) pour the concrete mixture for testing.

UMD is committed to being a sustainable campus. As U.S. society continues to demand more eco-friendly practices, UMD continues to supply innovations in sustainability areas.

In fall 2014, former UMD student Robert Larsen and civil engineering Assistant Professor Mary Christiansen, took sustainability efforts to the next level. They researched and tested various ways to make concrete mixtures more eco-friendly. Now, in summer 2015, additional civil engineering students have joined the project.

Concrete’s flaw
Today's concrete works well for many applications, but it has an environmental flaw. “One of the key ingredients in concrete, portland cement, releases harmful carbon dioxide into our atmosphere during production," said Christiansen. Even though it’s a minimal amount per cubic yard, when you consider all of the concrete used around the world, it adds up.

Larsen explained, “Concrete is one of the most frequently-used man-made materials, about five to seven percent of global carbon dioxide emissions comes from the production of portland cement.”

One solution is to use less portland cement in the concrete composition. Christiansen said, “When water is added to portland cement, a paste is formed, which acts as the glue that holds all of the other ingredients, namely sand and gravel, together. In order to create a strong and durable concrete, a reliable alternative to portland cement must be included. There are many industrial byproducts, such as fly ash, blast furnace slag or silica fume that serve that purpose as well. Finding just the right mixture of these materials is the key."

The research opportunity
Larsen received two Undergraduate Research Opportunities Program (UROP) grants to help fund the project. He said, “The UROP's really challenged me because I wasn’t prepared for the amount of time a real research project would take.” Larsen's task was to proportion concrete mixtures that would not only be eco-friendly, but also last for a long period of time.

Larsen explained, “It was hard because you have to keep in mind that the concrete needs to be able to sustain harsh environments of freezing and thawing, otherwise it will require intensive maintenance work."

Topping off his senior year at UMD, Larsen had the opportunity to present his research at the American Concrete Institute (ACI) spring convention in Kansas City, Mo., and the National Conference of Undergraduate Research (NCUR) in Spokane, Wash. He said, “I enjoyed being able to showcase what we’ve been working so hard on, and I’m grateful to have gained that type of professional presentation experience.”

Taking research to the next level

Since Robert Larsen graduated from UMD and has landed in Fargo, N.D. at an engineering firm, UMD graduate student Scot Larson has taken over the research project. 

In July 2015, Larson and recent graduate Ryan Dagger, in conjunction with UMD's Facilities Management Department and a local concrete contractor, placed three different sections of concrete sidewalk on campus, each containing a different test mix. They are using a traditional formula containing 100% portland cement, a Minnesota Department defined mixture, and a special sustainable mix using a reduced amount of portland cement including fly ash and silica fume. Larson and Dagger prepared a large number of sample specimens of each of the three mixtures to test in the civil engineering lab.  The plan is to evaluate the laboratory concrete mixtures over the next two months, and the actual in place sidewalks over the next five years.

Turning a vision into reality

What began as mixture formulas on original creator Robert Larsen's computer, eventually evolved into a sidewalk that hundreds will walk on while at the UMD campus. Christiansen plans to continue the Sustainable Sidewalks program into the future, with the hopes of installing student-developed eco-friendly concrete mixtures every summer. Although the project still requires hard work and further research, the goal of reaching a more sustainable campus is on the horizon.

Robert Larsen presenting project. concrete testing concrete testing
Former student & project creator, Robert Larsen, presenting the project at the American Concrete Institute conference.   Scot Larson (left) and Ryan Dagger (right) move some of the concrete mix to the civil engineering building.     The second poured concrete mixture sets up. The third test section is ready for pouring.    
concrete testing concrete testing concrete testing
Larson(left) and Dagger (right) analyze the fresh properties of the concrete mixtures. Larson preparing a concrete beam specimen for laboratory testing. Dagger (left) and Larson (right) pouring concrete.


Does civil engineering sound like your kind of career? See the UMD Civil Engineering Department.

Written by Elise Viger, August 2015.

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