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.
2 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.
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.
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).
Several years into the road's life, the sun and elements begin to take their toll though at this stage it's mostly cosmetic.
Simple shrinking and swelling of the earth and the asphalt itself will cause minor cracks to appear. If left untreated, they will allow more severe problems to develop.
Untreated cracks have become more severe. The road can still be fixed but is in danger of losing integrity below the surface.
Age and an ill-advised treatment over the initial alligatoring has led to more severe problems and this road will have to be rebuilt. Fortunately, there are modern technologies and practices that are greener and more cost-effective than those available in the past.
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.
Sound But Slick
This surface is doing well but the rock that gives the road texture and skid-resistance has become polished. Here, the most cost-effective treatment would be some type of preservation treatment depending on the budget, traffic, etc.
Cracks caused by the settling of the road running across the surface can be addressed with crack-sealing and a pavement preservation treatment.
Even if the friction rating is good on a road, bleaching can speed up its deterioration. An appropriate preservation treatment will not only make it look better, but will also protect it from further damage.
Minor Cracking and Delamination
This road may be able to be fixed with crack-sealing, patching and a pavement preservation treatment. It may also be time for milling and a thin asphalt overlay to fully restore the road.
Multiple asphalt overlays without milling on this road has led to a loss of correct surface geometry and created raised humps along the road's edges. Full depth reclamation, milling and new asphalt will fix this road.
Bad Utility Patching
This road has multiple, serious issues caused by age and improper patching by utility contractors. This area should be rebuilt with Full Depth Reclamation and a new asphalt surface.
Patches and Potholes and Cracks, oh my!
When a road starts to look like a patchwork quilt, it's time to mill it and put down some fresh asphalt. Just pave it!
Freshen Up The Old
Multiple years of treatments at this intersection are showing their age. But they're doing their job as evidenced by the lack of cracks. Time for fresh coat of latex micro, chip seal or slurry!
Slurry Pavers, Inc. 3617 Nine Mile Road, Richmond, VA 23223