Two-component Robotic Extrusion Additive Manufacturing of Concrete Structures: Silicone-solution Phases and Fiber Distributions for Functionally Graded Materials

Princeton University, Princeton NJ

Investigators

Abstract

Additive manufacturing using concrete materials has a potential to revolutionize the future of building infrastructure constructions. Current additive manufacturing techniques, however, are limited in their ability to produce more structurally robust concrete, mainly because of employing a single material in the process and complex process physics in concrete-mixture extrusion. This award supports fundamental research to advance two-component robotic additive manufacturing (with concrete and adjustable chemical liquid phase) that provides an innovative method to create cutting-edge designs and manufacturing of concrete components. The project brings together work on the science of an extrusion-based process with materials and chemistry research, achieving concrete materials with properties that can be engineered and tuned across fabricated layers, namely, to produce functional gradient. The two-component extrusion additive manufacturing investigated can be applied to develop highly engineered infrastructure components and will benefit the construction additive manufacturing industry to better exploit the growing global market. The study will support the U.S. industry in maintaining its competitiveness in a rapidly growing technological field of concrete additive manufacturing, as it continues to spread in the construction and housing sectors. The project will also stimulate manufacturing innovations and broaden diversity through educational and outreach activities including workshop and research opportunities to high-school, undergraduate and graduate students from underrepresented groups. This research aims at a foundational understanding of the two-component extrusion process in layer-wise robotic additive manufacturing and the physical and chemical characteristics of fiber-reinforced concrete with silicone-containing hydrophilic or hydrophobic compounds to develop tunable functionally graded concrete. The primary scientific barriers in two-component extrusion reside in the need for fundamental knowledge about the physics of intermixing with two materials. This research is motivated to understand how the two-component process, together with the chemistry of the silicone-containing concrete compounds at the layered interfaces, be leveraged to tune the local gradient properties of materials and improve their load-bearing capacities. The project will elucidate (i) the underlying physical relationship between the materials' rheological properties and the processing parameters (flow rates, pressures, in-line intermixing in an extrusion nozzle) combining an experimental method and analytical model, (ii) the novel engineering of the interfacial bonding mechanisms through hydrophilic and hydrophobic chemistry, and (iii) new manufacturing of stronger and tougher functionally graded concrete materials by incorporating fiber reinforcements of various configurations investigated by an experimental-analytical-modeling approach including fracture mechanics. The enhanced materials processing knowledge gained through this project will help harness opportunities for effective designs and manufacturing of stronger engineering materials. 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.