Professor Shiho Kawashima, assistant professor of civil engineering and engineering mechanics at Columbia Engineering, has won a National Science Foundation (NSF) CAREER Award to support her work developing concrete systems for use in 3D printing, a technology that could revolutionize the construction and repair of infrastructure.
Kawashima's research specializes in the processing and rheology, or flow properties, of concrete and cement. The five-year, $500,000 CAREER Award will support her project titled "Tailoring Rheological Behavior and Interlayer Properties of 3D Printing Concrete."
"I am very honored to receive an NSF CAREER Award," Kawashima says. "I have been investigating the rheology of cement-based materials, as well as studying nanocomposites, to see how we can improve the construction of infrastructural materials. If we can 3D-print rather than do conventional static formwork casting, we can lower material and labor costs, reduce material waste, cut construction time, and minimize human error."
Over the past few decades, advances in construction techniques have been incremental. Kawashima proposes to develop a new approach in which fresh concrete must be both "printable" and exhibit the desired properties once it sets. 3D concrete printing is an innovative approach that involves incrementally adding fresh concrete through an automated process to build entire structural elements and structures. This would eliminate the use of formwork and vibration typically necessary for consolidation in static casting.
She notes, however, that form-free and vibration-free casting presents significant materials engineering challenges. Among them are achieving sufficient shape stability of the deposited mix, predicting working time, and controlling print speed. Her CAREER project will address these issues by identifying and characterizing fundamental rheological parameters so that she can quantitatively describe the reversible and irreversible stiffening behavior of fresh cement-based materials, and then tie these parameters to the structural response of the material system to the printing process.
3D printing of concrete introduces a new consideration: the interlayer. "This interlayer is unique to our system," she notes. "As a result of the layer-by-layer deposition approach, you are left with these additional interfaces between printed layers that you do not see in concrete elements fabricated using conventional casting methods. It is important for us to study and understand their properties because they will determine the eventual performance and aesthetics of the printed structure. This will be one of the main focuses of the work. My group is really excited about this project, and we think it will be a big advance--truly a disruptive innovation--in how we look at our infrastructure."
Part of the NSF's Faculty Early Career Development (CAREER) Program, the CAREER award is one of its most prestigious honors for faculty at or near the beginning of their careers.