Researchers at the University of Colorado Boulder (CU Boulder) (Boulder, Colorado, USA) have discovered a synthetic molecule that minimizes freeze-thaw damage and increases the strength of durability of concrete.
This new biomimetic molecule, which mimics the antifreeze properties of flora and fauna in Arctic and Antarctic regions, could be added to concrete in order to prevent ice crystal growth and subsequent damage. Not only does this new method challenge decades of conventional wisdom regarding frost damage mitigation in concrete, it could also improve the longevity of new infrastructure that uses concrete and decrease carbon emissions over its lifetime.
“No one thinks about concrete as a high-tech material,” says Wil Srubar III, an assistant professor of civil, environmental and architectural engineering at CU Boulder. “But it’s a lot more high-tech than one might think. In the face of climate change, it is critical to pay attention to not only how we manufacture concrete and other construction materials that emit a lot of carbon dioxide in their production, but also how we ensure the long-term resilience of those materials.”
Since the 1930s, concrete manufacturers have put small air bubbles into concrete in order to prevent water and ice crystal damage. However, this comes at the cost of decreased strength and increased permeability, which ultimately leads to degradation and corrosion. By contrast, concrete made with the new biomimetic molecule was shown to have equivalent performance to conventional concrete, along with higher strength, lower permeability, and a longer lifespan.
Srubar is author of a new study in Cell Reports Physical Science that details the team’s new method. They observed that many plants, fish, insects, and bacteria in extremely cold conditions contained antifreeze proteins that bind to the surface of ice crystals, thereby keeping them small and unable to do damage. “We thought that was quite clever,” says Srubar. “Nature had already found a way to solve this problem.”
With that principle in mind, Srubar’s team went about gathering these natural antifreeze proteins and putting them in concrete in order to prevent ice crystal formulation. However, they found that natural proteins did not interact well with concrete, so they used a synthetic molecule, polyvinyl alcohol (PVA), that behaves like those proteins but is more stable at a high pH. They combined it with polyethylene glycol, a non-toxic, robust molecule often used in the pharmaceutical industry to prolong the circulation time of drugs in the body.
These two polymers combined to make a material that remained stable at a high pH and inhibited ice crystal growth. According to Srubar, the hope is that this new, patent pending method of concrete production will enter the commercial market in the next 5 to 10 years. In an ideal scenario, this will help meet the global demand for concrete while reducing the carbon footprint of manufacturing.
“The infrastructure which is designed today will be facing different climatic conditions in the future. In the coming decades, materials will be tested in a way they’ve never been before,” says Srubar. “So the concrete that we do make needs to last.”
Source: University of Colorado Boulder, www.colorado.edu.