Understanding distresses associated with asphalt pavements
Like most things, asphalt pavements require periodic maintenance in order to maximize the investment. Even the highest quality pavements will be affected by the natural enemies of asphalt (air, sun, and water) or by overloading. This guideline was written to provide a general understanding of why and how pavements deteriorate. Having this basic understanding is can be beneficial for creating a proper pavement maintenance plan.
There are many different methods for identifying and categorizing pavement distresses. In this writing, we’ll identify seven primary distress types observed with asphalt pavements. These distresses are listed below, and depending on the extent and severity, remedies will vary.
- Linear cracks are cracks that tend to appear in random locations. The most common cause of these cracks is due to cold temperatures and are called thermal cracking. Other causes may include: settlement of the aggregate base or subgrade material, frost heave, or reflection cracking. These cracks typically do not affect the pavement structure initially, but if not addressed, they allow water to infiltrate the pavement and eventually cause structural failure. Our recommended solution is to rout, clean, and fill the cracks with a rubberized cracksealer.
- Raveling is the progressive loss of asphalt material from the pavement surface. Minor raveling is the loss of the finer particles, making the pavement look rocky. Rejuvenating sealcoats, emulsion sealcoats, or chipseals can be applied to the pavement surface early in the pavements lifecycle to protect it from premature failure in these areas.
- Block cracking is the interconnection of linear cracks that develop as the pavement ages. For low severity block cracking, we recommend cracksealing, emulsion sealcoats, or chipseals to keep water from infiltrating the pavement structure and slow further deterioration. If the block cracking is more severe, milling and overlaying the pavement with new asphalt can restore the surface and protect the underlying asphalt pavement.
- Deformations and depressions are vertical movements of the asphalt pavement caused by overloading or an unstable foundation. These depressions provide areas for water to pool, which can cause unsafe conditions. Standing water will cause the asphalt to deteriorate more quickly, leading to the development of potholes. Minor rutting or dimpling in parking lots can be repaired by patching.
- Deficient drainage Standing water over time is not only a safety concern, but will erode the asphalt pavement over time and create potholes. For small localized areas, a patch can be performed to correct the drainage issue. If there are large areas of deficient drainage, profile milling and new asphalt overlay, installation of concrete valley gutters, or reconstruction of the pavement are some options to correct the slope of the pavement. As a rule, 1% slope is necessary to ensure adequate drainage.
- Fatigue cracking (also known as Alligator Cracking) is a series of interconnected cracks typically described as resembling an alligator's skin. Fatigue cracking is a structural distress caused by excessive loading or a weak foundation. If the fatigue cracking is localized, the area may be able to be fixed with a full-depth removal and replacement patch. If fatigue cracking is not addressed, it can quickly spread to adjacent areas and grow quite rapidly, requiring reconstruction of the pavement.
- Potholes are the localized loss of pavement material typically caused by structural failures, poor drainage or raveling. Potholes can be simply and inexpensively filled for a temporary repair, or cut out and patched as a more permeant repair. Repairs should never dam up water flow.
BR’s pavement evaluations provide a detailed report including the pavement rating, pictures of each type of distress, and recommendations on what type of corrective action should be performed.
BR strives to be the contractor of choice by providing value added services for our customers and educating our customers with the knowledge to make the right choices for protecting and preserving their pavement asset so it doesn’t become a liability.