Stanford researchers lead efforts to cut carbon in concrete production

Jade Benjamin-Chung has spent the past 12 years working to improve sanitation practices from the ground up.

The assistant professor of epidemiology and population health is working to discover a sustainable solution to a sanitation issue that transcends the surface level, in tandem with Sarah Billington, professor of civil and environmental engineering, and a team of researchers.

While studying the disease-carrying pathogens that often reside in the soil floors of rural dwellings, Benjamin-Chung determined that the installation of concrete flooring would be conducive to improving sanitation. In order to find an eco-friendly means to implement this new infrastructure, she teamed up with Billington, an expert in concrete, to create a low-carbon alternative.

Benjamin-Chung first became interested in the benefits of concrete floors while testing sanitation solutions in Bangladesh and Kenya as part of her doctoral research in epidemiology at UC Berkeley. Through randomized trials, her research tested the effectiveness of “low-cost household improvements,” such as covers and ventilation pipes for latrines, handwashing stations with soap and water and sealed water containers to decrease exposure to pathogens. The results of these projects were “surprisingly modest,” she said.

She and her colleagues returned to the drawing board to entertain new discussions of potential pathogen exposure points. They found the answer in the dirt flooring of many rural residences, which poses public health concerns for young children who play on the floor and ingest harmful germs in the process.

Through “detailed environmental assessments” and video recordings, Benjamin-Chung and her team found these children’s “exposure to soil was really high.”

She cites a study performed in Mexico throughout the early 2000s entitled “Piso Firme” or “hard floor” which found that adults in homes with solid concrete floors “experienced lower rates of depression and stress” as a motivator for her own research. Children in such homes experienced a 13% reduction in diarrhea and a 20% reduction in anemia. 

The team first conducted an observational study in Bangladesh, during which they found that children who grew up in homes with concrete floors did, in fact, have a significantly fewer amount of parasite infections than children who did not. To further test the hypothesis, the researchers did a randomized trial to eliminate socioeconomic factors that could have skewed the results of their initial study.

“We wondered if the homes with concrete floors were just better off [financially] and that’s why they’re healthier,” Benjamin-Chung said. “To really rigorously answer this question, we decided to do a randomized trial. Then, we were able to remove other potential variables.”

While researching the effects of concrete floors in Bangladesh, Stephen Luby, a professor of infectious diseases and the director of the Human and Planetary Health Initiative at Stanford’s Woods Institute for the Environment, suggested that the team bring in an expert on cement to conceptualize the practical implications of Benjamin-Chung’s proposed initiative. 

Billington’s initial concern with Benjamin-Chung’s project was its impact on the environment, as concrete is responsible for 6% of the world’s carbon emissions. She “had not thought about concrete as being such a positive thing, but was really curious about it” after Benjamin-Chung approached her about the project, Billington said in an interview with the Stanford Woods Institute. According to Billington, that led her to begin considering so-called “green” alternatives to traditional concrete.

In order to achieve a concrete both resistant to pathogens and environmentally sustainable, Benjamin-Chung and Billington brought on other collaborators, including Alexandria Boehm and Michael Lepech, both professors of environmental and civil engineering at Stanford, and Jason Hernandez, a Ph.D. student from Lepech’s lab. Lepech, who specializes in concrete and cementitious materials, cites the Woods Institute’s Environmental Ventures Projects (EVPs) as the driving force behind the amalgamation of Benjamin-Chung’s epidemiological research and Billington, Lepech and Boehm’s expertise in sustainable engineering.

The project aims to “bring together very different kinds of researchers to solve really complex problems, like this one,” Lepech said.

In the lab, Hernandez mixed and hardened various concrete solutions, adding a different finish to each one. Then, in Boehm’s environmental engineering lab, Hernandez and other researchers tested the persistence of E. coli and other pathogens. They produced a range of different concrete mixtures and surface finishes that apply to populations in a wide array of climates and living conditions.

Many of the concrete mixtures created in the lab include fly ash, a byproduct of coal fired power plants. Fly ash replaces some of the cement — a component of concrete whose production emits greenhouse gases — and makes use of a waste product that would otherwise end up in a landfill.

“Rather than sending [fly ash] to a landfill or doing something else with it, we can actually use it for a productive application,” Lepech said.

Now, after several months of experimentation, Benjamin-Chung and her team are performing randomized trials of the new concrete mixtures in rural areas of Bangladesh. In order to facilitate the implementation of the concrete, Benjamin-Chung has partnered with the government of Bangladesh and other stakeholders, such as the International Centre for Diarrheal Disease Research, Bangladesh in order to come up with a feasible plan for executing the transition to concrete flooring in civilian homes.

“I’ve been working with [the center] for 13 years,” said Benjamin-Chung. “They’re really close, wonderful collaborators, and we design the study together. We sought the funding together. We make decisions jointly. It’s a very fruitful collaboration, and they really have deep knowledge of the local context.”

The long-term effects of concrete flooring in rural homes could be profound. The comfort and convenience of a hard floor in homes “may lead to lower depression, less stress and more time to spend on leisure, child care and preventative health measures,” she said.

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