Concrete 3D printing is a new, innovative technology for the construction industry with the potential to save cost on labor and material. An optimal mixture design for printable concrete was determined by experimenting with two viscosity modifying admixtures (VMAs): Acti-Gel and polyacrylamide (PAM). PAM was found to enhance the rheology and cohesiveness of concrete. This project investigated improvements to the interfacial bond between layers of concrete. Test results indicated that geometric interlocking enhanced shear strength while a liquid adhesive enhanced tensile strength. Scanning electron microscopy revealed the PAM microstructure bridging across the interface and anchoring to the hydrated C-S-H structure. It is concluded that PAM is the most suitable VMA for printable concrete.
Worcester Polytechnic Institute
Major Qualifying Project
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Civil and Environmental Engineering