With the highly anticipated arrival of Spring 2015 almost upon us, most of the U.S. east of the Rocky Mountains will welcome warmer temperatures, grass instead of snow, and streets filled with potholes.
Well, perhaps the potholes will not be welcome. But as sure as the sun will shine, there will be many, many potholes wherever there has been precipitation, freezing temperatures and vehicular traffic.
Because those things are precisely what crater the pavement. Every time water gets into a crack and then freezes, the crack will expand by almost 10 percent. The repeated freeze-thaw nature of winter and spring all but guarantees that potholes will form on roads, streets and highways.
A second bewildering fact of winter and potholes is that it’s technically not likely that the road can be repaired during the winter itself. That’s due to several factors: asphalt plants close for the winter in northern latitudes because hot asphalt cools too quickly to be applied. So departments of transportation in most places make do with a temporary cold patch that may not hold up for more than a few weeks. In Boston, where record snowfall and altogether nasty weather has crippled the city since mid-January, street crews have set up orange cones in the worst of the road craters as they simply lack the resources to repair them now (typically, snow removal workers and trucks are redeployed in the spring and summer as pothole repair crews).
But the realm of potholes lacks not for creativity and invention. Several alternative methods of pothole repair are being tested:
- A silly putty-like material: Contained in a Kevlar bag, the pliable material is placed in the potholes to ensure temporary safety. The bag is removed when a permanent repair can be done.
- A two-step process: Muncie, Indiana’s Street Department is attacking potholes in a two-wave approach. One crew clears the hole with a propane torch (to melt ice in the hole) and a high-power leaf blower (to clear out water and loose debris). The second crew follows with cold mix asphalt and a roller.
- A four-step process: Madison Heights, Michigan (near Detroit) contracts with a pothole specialist company for a couple of weeks in later winter to repair streets with a four-part plan. First, blow the area dry. Next, apply a tacking material, followed by the asphalt and a loose-stone layer on top. The fourth step, a steamroller to flatten the fill, costs extra and therefore is sometimes not used (allowing traffic itself to compress the material).
- Infrared technology: From a heavy-duty truck, a heating unit lowers onto the street to heat the hole to make the surrounding pavement more likely to bond with the replacement asphalt. Reportedly, it saves money by reducing the number of people required to fill a pothole and because the fix is longer lasting.
Most of these innovations are in years two, three or more of testing. There are additional methods and materials as well, including polymer-modified cold-mix that has been available for more than a decade. Still, the majority of states and municipalities continue the two-season process of temporary fixes in winter and more permanent pothole repairs in the warmer, drier months.