Sixty degrees on Thursday and snowing by the weekend, this seems to be the M.O. of our erratic winter this year. It’s a recipe for the sniffles, slush and poorly chosen outerwear, but it’s also chipping away at our already deteriorated and aging roads in the Northeast.
Yaghoob Farnam, PhD, an assistant professor in Drexel’s College of Engineering whose lab researches sustainable materials and designs for infrastructure, took some time to explain just why the whacky weather in the Northeast is a challenge for infrastructure design and maintenance, and how roads could be made more resilient.
As the weather gets colder, what sorts of treatments do state and local municipalities use to prevent roads from icing? How do they work?
They do several things to secure safety: pre-salting of pavement surface before a snow event helps to prevent icing on the road and give them some time after snow to plow. Sometimes they also add sand to the salt. In pre-salting, normally they use high concentrated salt solutions. They use mainly sodium chloride and sometimes, in some states, calcium or magnesium chloride. After the snow, they normally use dry salt with sand and they spray it on the road. They also do a lot of snow plowing.
What are some unintended side effects of these treatments? Are there better options?
Use of an enormous amount of salt is not good, first, to the environment and, second, to the pavement or road. It can make the surrounding soil salty and harm the vegetation. In terms of pavement, salts can deteriorate concrete or asphalt and increase freeze-thaw damage and road scaling problems. Local departments of transportation spend a lot of money each year to repair or rebuild pavements and most of the damage in cold states is coming from water freezing, along with using large amount of salts.
Why do roads seem to degrade faster in the winter? It always seems like there are more potholes by the time it comes to spring. Is that accurate?
Yes, this is right.
In cold states like Pennsylvania, we have a very harsh environment. Cold weather, freezing and thawing cycles and use of a large amount of deicers can be very destructive. In cold temperatures, materials behave more brittle and can be broken or damaged easily. Imagine, if you add freezing and thawing of water/ice to this and it will be more problematic.
When water freezes and becomes ice, it expands its volume by 9 percent. So if the water seeps into the pavement and then freezes, the expansion in volume can cause internal pressure and damage the pavement. We also use an enormous amount of salt that can chemically react with pavement materials and cause degradation. We have done quite a bit of work to show how salts can be destructive to concrete pavement.
Without funding for massive infrastructure improvements, are “quick patches” the best way to deal with deteriorating infrastructure, or are there other intermediary steps that could be taken?
Well, this is a hard question. I would say no, if patches are needed we have distresses anyway. We could use high quality patches and they sometimes work. But the problem here is that, when we need to repair a road that is open to traffic, the repair and patch happen very quickly since we need to stop that traffic. Often, the only time that roads can be repaired is for a few hours over night, when they can be closed. This is a problem because the patch is not allowed to properly settle and bond. This is why you see damage in the same location year after year.
There is a research on improving the quality of accelerated concrete pavement and people try to improve the quality. Doing things fast may be good for traffic and the department of transportation — since they face more blame the longer roads are closed — but it will not provide the long-term right solution.
What, if any, developments have there been in mitigation procedures (snow, ice removal/prevention) and the infrastructure design itself to improve its resiliency?
One of the things that my research group has been looking for is better options for deicing. We are designing special types of phase change material — like paraffin wax or vegetable oil — that can be used to expedite the snow/ice melting process. Right now we have lab-scale work that is very promising. We have proven that these materials can melt about two inches of snow and they will stay in the pavement for longer periods of time, which saves the labor of reapplying it before every snow/ice event. Imagine how much salt and snow plowing could be avoided! By keeping the snow and ice from sitting on the road surface, the phase change materials could also reduce damage from freeze-thaw cycles.
We are reaching out to local departments of transportation, as well as the Federal Aviation Administration, as possible research partners who could help support full-scale outdoor testing — and benefit from the findings.
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