'Growing Impact' Examines Sustainable Cement Replacements

The January episode of “Growing Impact” discusses the search for cement replacements that are more environmentally friendly. Cement is one of the most energy-intensive products to produce, and the need for it continues to grow as infrastructure in many developing regions is expanding quickly. The primary concern in the cement manufacturing process is carbon dioxide emissions, which add up to 8% of all human CO2 emissions. These are generated by both the fossil fuels used to heat the kilns and the chemical reaction when the cement mixture is heated. To address this challenge, two researchers at Penn State — Juan Pablo Gevaudan, assistant professor of architectural engineering, and Kaitlyn Spangler, assistant professor of community development and engagement — are exploring how leftover agricultural materials could be used as a cement replacement to create concrete that is sustainable. 

“In the U.S., upwards of 70% of all of our harvested cropland is corn, soy or wheat,” Spangler said. “If we're looking for byproducts from agriculture, whether stover from corn or straw from wheat, it makes a lot of sense to start with crops that we have a ton of.” 

However, the team discovered that many farmers were hesitant to get rid of their stover or straw. This inspired the team to explore other options that could provide environmental solutions and assist farmers. One of these options was to utilize a piece of technology developed by Gevaudan and his colleagues that locks captured carbon dioxide in the inorganic components of plants, keeping it out of the atmosphere. 

“Corn stover actually has a lot of potassium, silica, some sodium, and calcium in it,” Gevaudan said. “These are usually found in the soil, and over time, corn will accumulate a lot of these in its biomass.” 

By putting the biomass through Gevaudan’s technology, two things happen. First, the inorganic material of the biomass is infused with carbon dioxide to create mineral nutrients that a farmer can use to fertilize the soil. Second, some lignin, the durable fibers of plant cells, is removed, preparing the treated biomass to be used for bio-refineries that create aviation fuel, for example. 

“Additionally, the inorganic material is what's being looked at by our project for its potential to be a component for these alternative cementitious materials,” Gevaudan said. “These are interesting because we can take an industrial biproduct, let's say slag from the steel manufacturing process, and we can add some potassium carbonate from our process and this mixture can be a complete replacement to Portland cement that we use today to create conventional concrete.” 

Alternative cementitious materials have two major benefits. First, its manufacturing process can use waste or other byproducts, which lends to the circular economy. Second, manufacturing alternative cement generates up to 90% less CO2 than conventional form cement concrete, Gevaudan said. 

“We're offering a potentially more efficient and better way for farmers to manage their post-harvest byproducts, one that explicitly considers what farmers go through in deciding whether or not they want to take off their stover,” Spangler said. “We’re asking farmers what they're doing with their crop residues, what they see as feasible, and what are the gaps and benefits that could be filled by finding a way to prepare the mineral nutrients that they need for their field in another way.” 

“Growing Impact” is a podcast by the Institute of Energy and the Environment. It features Penn State researchers who have been awarded IEE seed grants and discusses their foundational work as they further their projects. The podcast is available on multiple platforms, including YouTube, Apple, Amazon and Spotify.