Maintenance 101

Maintenance 101

To better understand authorities' road maintenance choices and what pavement preservation treatments are good for (and not good for), it helps to understand what’s beneath that top layer and how it can affect the overall state of the road. Below is a basic diagram of how most roads are constructed, a look at how they age, and the options available for common road conditions.

1  Wearing Course

This is the top layer that’s designed to provide a smooth riding and driving surface with enough abrasion to provide friction to our vehicle’s wheels for good traction, steering, and braking ability. As the name suggests, this top layer is expected to wear and can be restored many times over the lifetime of the road.

Base Course

This is a layer of asphalt that gives the top layer a firm base and takes most of the stresses given to the road by the traffic above. This layer’s thickness varies depending on the location and purpose of the road and the stresses it’s been designed to take. Some road failures begin here when anticipated traffic and loads are higher than those predicted.

3  Base

This is a layer of granular material, usually compacted gravel, that divides the softer subgrade from the rigid base course. It serves several functions including acting as a drainage layer and general water manager, as well as a shock-absorber for the continuous stresses on the asphalt layers above. Serious road surface problems begin when cracks in the top layers allow too much water to get to this layer. 

4  Subgrade

The first layer of a road that sits on raw earth and allows for some movement to help keep the layers solid above. This is the most important layer to the long-term success of the road. If it fails, the entire road will need to be rebuilt at substantial cost to taxpayers. 

Sun, rain, traffic, utility work and the movement of the earth itself all take their toll on an asphalt road. Below are the main stages of the average asphalt road's 15-year lifetime without regular maintenance. (Click here to see how pavement preservation treatments extend the road's life and save tax dollars).

With tens of thousands of miles of road to maintain, state and local officials are constantly monitoring roads and applying what they learn to determine how best to keep them maintained. With ever-increasing demands and tight budgets, officials are also continuously looking for the best mix of paving products and techniques to help them achieve their goals. To accomplish this, they typically use a scale to grade roads and determine how best to maintain the system in their care (within the budgets they're required to do it in.) These are some of the most common road conditions we drive over every day and the various treatment choices to fix them.

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