Keep out of the Pits – How Potholes are Repaired

This time of year, many of us across the Northwest are discovering some bumpier roads due to an increased number of potholes. The rising number of usual potholes is common and rather routine as we exit the winter temperatures and road conditions that create them. You may also find yourself avoiding potholes on your usual routes as they’ve widened, deepened, and presented a real nuisance for your travels. Ruts and depressions are another common problem on the road despite warmer conditions, making maintenance a necessary investment to prevent reconstruction and renovation. So what exactly triggers the formation of potholes, ruts, and depressions during the cold, dark months of the year? 

In short: 
The freeze cycle

Potholes originate mostly from water infiltrating the subgrade (the surface of rock on the road). Combined with the cold, water that infiltrates the paved surface expands upon freezing. The pressure applied as a result of freezing causes the asphalt to crack and break apart. As ice melts and refreezes, the pothole expands which in turn, allows more water to enter and corrode the asphalt. The cycle continues. 

What can be done? 

Potholes can be reported and requested for repair by citizens through several avenues. One of those most leveraged by city governments is social media. Many cities across the U.S. are utilizing social media as a useful source for combating these public “pitfalls” around our roadways. Social platforms such as Facebook and Twitter accounts for your city provide an opportunity for citizens and city officials to work together for the cause of keeping our communities safe through reducing transportation hazards. You can visit your local city government social media platforms and websites to accurately report potholes to the proper authorities.

State highway agencies and local governments are largely responsible for maintaining and improving roadways in the U.S. Their infrastructure budgets provide the means for asphalt repairs, which when made known by reporting, can deploy crews for repair.

A Simple Fix?

Patch material consists of binder and aggregate which come in hot and cold mix forms. During the winter months (typically November-April), cold mix is the option necessary to make emergency patch repairs which unfortunately, isn’t very durable and often fails. Patches provide a temporary measure until hot mix asphalt plants are available to make longer lasting repairs during the warmer seasons.

  • The most basic form of repair is called the throw-and-roll method, which is quite self explanatory. It is the most cost effective, but also the most volatile and short-lived; commonly employed for cold weather emergency repairs. This is how its’ done: place the asphalt patch material in the hole and run it over, compacting it densely with a heavy vehicle. Typically a tractor, large truck, or a compacting machine. 
  • The most common method you will see in the spring-summer months includes semi-permanent patching. While not permanent, it is longer lasting and stands next best to full-depth roadway reconstruction. Water and debri is removed from the pothole, then the corroded edges are trimmed back to in-tact asphalt. Patch material is placed and compacted with a vibrating roller or plate. 
  • Spray injection repair is similar to the former method but does require more specific equipment. It does not, however, require compaction. Similarly, water and debris is removed. Then, a tacky substance that acts as a binder is sprayed into the hole. Following, asphalt and aggregate is blown into the pothole and finally covered with a layer or aggregate.
  • Edge Seal Pothole Repair is a method which first employs the throw-and-roll method. Next, asphaltic tack is placed along the edge of the patch, overlapping the pavement around it. Once this is done, sand is placed on the tacy material so vehicle tires don’t track it along the road. 
  • The Final method we’ll discuss is full reconstruction; eliminating potholes completely and replacing with new pavement. It is the most efficient and long-lasting option for repair, but does involve much time, expense, traffic detours, and larger crews to complete. Essentially, old asphalt is used to replace worn asphalt via pulverizing it with water and cement, then compacted to create a base for a new asphalt surface. 

With over 2.68 million miles of paved roads in the U.S., and counting… along with the high cost of ongoing maintenance, there is bound to be innovation to increase the efficiency and durability of pothole repair. Many methods are currently underway for experimentation. Perhaps the combination of technology and social media will bring innovation to better maintain our roadways and protect our community all around. What will always be necessary is awareness, community involvement, and action plans to keep you traveling smoothly.