Engineers add cellulose nanofibrils to printable cement composites to augment their rheological and mechanical properties.
A research team led by engineers at the University of Virginia School of Engineering and Applied Science is exploring how an emerging plant-based material, cellulose nanofibrils, could amplify the benefits of 3D printed concrete.
“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.
Buildings made of 3D-printed concrete offer a slew of potential benefits: quick, precise construction, the possibility of using recycled materials, reduced labor costs and less waste, all while enabling intricate designs that traditional methods would struggle to deliver. Unfortunately, printable material options are limited and questions about their sustainability and durability remain unanswered.
“We’re dealing with contradictory objectives,” Ozbulut said in a press release. “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 (CNF) are made from wood pulp and, like other plant-fiber derivatives, it shows strong potential as an additive to improve the rheological and mechanical properties of additive cement composites.
However, the influence of CNF on conventional 3D printed cement composites wasn’t clear prior to the research by Ozbulut and his team. “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.”
Experimenting with varying amounts of CNF additive, the team found that adding at least 0.3% CNF significantly improved flow performance. Microscopic analysis of the hardened samples also revealed better material bonding and structural integrity. In further testing in Ozbulut’s lab, CNF-enhanced 3D printed components also stood up to pulling, bending and compression.
These findings will be published in the September 2024 issue of Cement and Concrete Composites.
