Synthetic version of natural antifreeze used in longer-lasting concrete
As readers who live in cold climates will likely already know, winter is not kind to concrete. That could be about to change, though, thanks to a polymer additive that mimics natural antifreeze.
The problem with concrete and fluctuating temperatures occurs when snow melts into liquid water, which permeates into the porous concrete and then freezes again as temperatures drop. As that water freezes back into ice crystals, it expands, exerting pressure on the concrete from within. Over the course of multiple freeze-thaw cycles, this causes chunks of concrete to pop off of the material's surface.
One method of addressing the problem involves making the concrete even more porous, by introducing tiny air bubbles while it's being mixed. Once the material has hardened, these bubbles give the ice crystals room to form, thus reducing the pressure. Unfortunately, though, such concrete isn't as strong as the regular stuff. Additionally, its increased porosity allows even more potentially harmful water to enter, along with corrosive elements such as road salt.
Instead, scientists at the University of Colorado Boulder looked to the natural antifreeze produced by plants and animals that live in Arctic and Antarctic regions. Led by Asst. Prof. Wil Srubar III, the team proceeded to replicate the effect of these compounds by combining two existing polymers – polyvinyl alcohol and polyethylene glycol.
When linked molecules of these polymers were added to conventional concrete, they reduced the size of ice crystals that formed within the material by 90 percent. As a result, even after 300 freeze-thaw cycles, the treated concrete was found to be highly resistant to ice damage, while also being stronger, less permeable and longer-lasting than concrete containing the air bubbles.
It is now hoped that a commercialized version of the additive could be on the market within five to 10 years. In the meantime, the scientists will further explore its real-world practicality and economic viability.
"We're particularly excited because this represents a departure away from more than 70 years of conventional concrete technology," says Srubar. "In our view, it's a quantum leap in the right direction and opens the door for brand new admixture technologies."
A paper on the research was recently published in the journal Cell Reports Physical Science.