By Nicki Loo

Lindsey Conlan ’18 spent the summer working with Claire White, assistant professor of civil and environmental engineering and the Andlinger Center for Energy and the Environment, to study the feasibility of using acidic wastewater to liberate aggregate from used concrete. Video by Greta Shum.

Lindsey Conlan ’18 is a senior concentrating in civil and environmental engineering who spent her summer as an intern at the Andlinger Center for Energy and the Environment at Princeton University researching ways to recycle the gravel used in concrete. In the United States, the largest end use of gravel, known in the industry as natural aggregate, is for concrete production. Mining for aggregate has environmental impacts on a local and regional scale through mud and rock slides, changes in the water table, biodiversity, and carbon sink loss due to clearing vegetation. Conlan worked with Claire White, assistant professor of civil and environmental engineering and the Andlinger Center for Energy and the Environment.

Concrete’s life cycle is linear, according to Conlan, who has long been interested in environmental issues. When buildings are torn down, concrete is usually crushed for use in constructing roads. Conlan’s research sought to recycle concrete for use again in buildings by subjecting crushed concrete aggregate to acid derived from drainage from coal mining. This method removes residual older Portland cement paste on the concrete that is preventing strong bonds from forming between new cement paste and the concrete aggregate. Moreover, the treatment also recycles the acid, combating one of the negative environmental effects associated with acid mine drainage. The acid does not linger in the landscape and pollute water sources.

Conlan said her involvement with the program helped expand her experience with lab equipment and further piqued her interest in environmental issues and life cycle analysis of materials.

“I want this project to open the conversation about better concrete recycling and dually beneficial recycling processes,” Conlan said.

“Being in the civil and environmental engineering department here and learning about the Andlinger Center has really helped me develop my interest even more and exposed me to a whole bunch of issues that I never thought I’d be interested in. I didn’t realize that concrete would be such a draw as I was graduating from high school,” said Conlan.

More on the summer internship program:

Over the summer, six undergraduates embarked on energy and environmental research that ranged from charging devices wirelessly with solar energy to developing biofuels from yeast at the Andlinger Center for Energy and Environment at Princeton University.

The Peter B. Lewis Fund for Student Innovation in Energy and the Environment and the Dede T. Bartlett P03 Fund for Student Research in Energy and the Environment, which are administered by the Andlinger Center, funded five summer internship projects by theses six students.

This past summer’s students were selected for their excellent academic record and the promising potential of their research in helping secure the world’s energy and environmental future. The selected students received a $4,000 stipend for the summer research and up to an additional $4,000 for research-related expenses. Information on students and projects from past years can be found here.

Greta Shum contributed to this article.