What a waste — or is it?
1. Along with asphadur, Iowa Department of Transportation created crumb rubber in the 1990s, which added ground up tires to asphalt. While it was an improvement, Iowa DOT eventually moved away from crumb rubber to seek improvements through other experiments. (Photo provided)
Not all plastic is equal
The biggest challenge Iowa DOT has encountered is finding the right quantity of the plastic quality needed.
The incoming stream is unpredictable, and manufacturers are having to adjust their mixes to ensure the quality of the finished products meets necessary requirements.
“There are a couple of different directions this could go in the future, and we could go in both at the same time,” elaborated Reis. “One is utilizing recycled plastics within our roadways in areas we don’t need to worry so much about for longevity and durability. Currently, we’re looking at a 30-40 year lifespan. When we make a mistake, we’re stuck with it for a long time. We can’t afford to throw something in there without knowing the outcome.
“Then we look at bridges, which are double that lifespan. We have to do our due diligence in the materials that go into construction. We have to assure taxpayers that they’re getting the products they expect.”
Bar chairs are another product that could be made from recycled plastic as their only purpose is to offer reinforcement for steel on bridges until the concrete hardens. Then the bar chairs simply sit there until it’s time to work on the bridge again.
So long as it isn’t detrimental to the concrete, commented Reis, there aren’t strict requirements as to what the bar chair should be made of.
For short-term uses where durability isn’t a priority, a variety of recycled plastics can be used in a silt fences for runoff during the construction of a roadway, which slows down water and prevents erosion.
