Collaborative Research: Engineering Fracture Response and Transport Behavior in Additively Manufactured, Layered Concrete Materials

This research focuses on the development of a new generation of 3D-printed cementitious materials with enhanced performance. Layered, 3D-printed concrete components are being developed in infrastructure and housing construction. However, broad adoption of these components by the construction industry is impeded by less-than-satisfactory mechanical properties and durability.

As such, there is an urgency to better understand and improve performance of 3D-printed concrete materials. This research will gain fundamental understanding of the internal arrangements of 3D-printed concrete at the micron scale and explore layer deposition to tailor the internal structure of these novel materials and enhance mechanical and fracture properties, as well as the long-term durability and safety.

This research will push forward the boundaries of knowledge, leading to transformative engineering solutions, broad implications, and recommendations transferable to large-scale applications where concrete is used, such as homes, buildings, roads, and bridges. Findings from this research has the potential to improve conventional concrete infrastructures, such as advancing curing and slip-form construction.

The educational and outreach activities will provide opportunities for students (including graduate, undergraduate, and K-12 students) to learn about new directions and career prospects in civil engineering.

The research will achieve a foundational understanding of the physics of 3D-printed concrete in several temporal and spatial scales. Material characterization will be conducted during extrusion, 3D-printing, and hardening stages using neutron radiography, micro-computed tomography, X-ray diffraction, and elemental mapping of interfacial zones and filaments.

The research will answer fundamental questions about the mechanisms involved in the extrusion process, such as the formation of a so-called “lubrication layer”. The research will examine the hypothesized ways in which this water-rich layer can de-homogenize and control the spatial water distribution within the tube/barrel prior to deposition, after deposition (during the knitting/bonding), and the spatial morphology and connectivity of the pore network and hydrated compounds surrounding the interfaces.

The knowledge will then be used to inform designs of the internal architecture of the material with the goal of tailoring fracture response and transport behavior. By engineering the weak attributes of the interfaces with internal helical architectures, this research will enhance mixed-mode fracture toughness in 3D-printed cementitious materials based on linear elastic fracture mechanics principles.

By engineering intentional flaws and tailoring the morphology of the pore network, the fluid-transport behavior in these materials will be controlled.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.