A research team from the University of Virginia School of Engineering and Applied Science is pioneering the use of cellulose nanofibrils (CNF) to improve 3D-printed concrete. This plant-based material offers significant potential for enhancing the printability and mechanical properties of concrete used in construction.
“The improvements we saw on both printability and mechanical measures suggest that incorporating cellulose nanofibrils in commercial printable materials could lead to more resilient and eco-friendly construction practices sooner rather than later,” said Osman E. Ozbulut, a professor in the Department of Civil and Environmental Engineering.
These findings will be detailed in the September 2024 issue of Cement and Concrete Composites.
3D-printed concrete structures are revolutionizing the housing industry, offering rapid and precise construction with reduced labor costs and waste, and the potential use of recycled materials. This technology employs a specialized printer that layers a cement-like mixture, guided by computer-aided design software. However, the sustainability and durability of the current printable materials remain under scrutiny.
“We’re dealing with contradictory objectives,” Ozbulut said. “The mixture has to flow well for smooth fabrication, but harden into a stable material with critical properties, such as good mechanical strength, interlayer bonding and low thermal conductivity.”
Cellulose nanofibrils, derived from wood pulp, are renewable and have a low environmental impact. CNF has shown promise in enhancing the flow properties and mechanical strength of composites. Yet, until the UVA team’s detailed investigation in Ozbulut’s Resilient and Advanced Infrastructure Lab, the specific effects of CNF on 3D-printed concrete were not well understood.
“Today, a lot of trial and error goes into designing mixtures,” he said. “We’re addressing the need for more good science to better understand the effects of different additives to improve the performance of 3D-printed structures.”
By experimenting with various CNF concentrations, the team, led by Ozbulut and Ugur Kilic, a Ph.D. alumnus of UVA, discovered that a minimum of 0.3% CNF significantly enhances flow performance. Microscopic examination of the hardened samples showed improved material bonding and structural integrity.
Further testing in Ozbulut’s lab revealed that CNF-enhanced 3D-printed components also exhibited improved resistance to pulling, bending, and compression.
Research Report: Effects of cellulose nanofibrils on rheological and mechanical properties of 3D printable cement composites.