Nanotechnology, as defined by the National Nanotechnology Initiative is "the study and application of extremely small things and can be used across all the other science fields, such as chemistry, biology, physics, materials science, and engineering." It's becoming an increasingly important area for scientific development, especially for the concrete industry. The latest findings? Researchers at Purdue University in Indiana, and in the UK are exploring new findings at the molecular level that could lead to both self-healing and more durable concrete.
According to a press release:
Researchers at Purdue University have demonstrated that the cellulose nanocrystals can increase the tensile strength of concrete by 30 percent.
"This is an abundant, renewable material that can be harvested from low-quality cellulose feedstocks already being produced in various industrial processes," said Pablo Zavattieri, an associate professor in the Lyles School of Civil Engineering.
The cellulose nanocrystals might be used to create a new class of biomaterials with wide-ranging applications, such as strengthening construction materials and automotive components.
... One factor limiting the strength and durability of today's concrete is that not all of the cement particles are hydrated after being mixed, leaving pores and defects that hamper strength and durability ... However, the researchers have discovered that the cellulose nanocrystals increase the hydration of the concrete mixture, allowing more of it to cure and potentially altering the structure of concrete and strengthening it. As a result, less concrete needs to be used.
Findings were published in the journal Cement and Concrete Composites.
Researchers in the UK are looking at a different angle. According to a news release from the University of Cambridge, researchers there, along with partners at the University of Cardiff and in Bath, are taking inspiration from human skin to develop a kind of self-healing concrete.
The team in Cambridge is addressing damage at the nano/microscale by developing innovative microcapsules containing a cargo of mineral-based healing agent. It’s like having a first-aid kit in a bubble: the idea is that physical and chemical triggers will cause the capsules to break open, releasing their healing and sealing agents to repair the lesion.
In parallel, the team in Bath is investigating healing at the mid-range micro/mesoscale with spore-forming bacteria that act as tiny mineral-producing factories, feeding on nutrients added to the cement and facilitating calcite precipitation to plug the cracks in the concrete. Different techniques for housing and protecting the bacteria and nutrients within the cement matrix are being investigated, including the capsules that are being developed at Cambridge.
The University of Cardiff researchers are engineering ‘shape memory’ plastic tendons into the cement matrix to close large cracks at the larger meso/macroscale through triggering of the shrinkage of the tendons by heat.