Potholes, potholes everywhere: What’s the best approach to asphalt pavement repair?

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It’s that time of year when asphalt really shows its wear—sand, salt, snow, and ice take their toll, and plows encourage the development of potholes and cracks everywhere we look. As a civil engineer, I’m frequently approached by clients who want a set of engineering plans to remedy asphalt pavement that’s in disrepair. The nature of these projects can range from municipal roadways to small parking lots. As with every project, the owner is looking for a cost-effective solution. However, with paving projects, the least expensive alternative is not necessarily the most cost-effective in the long run. In order to select the appropriate method of repair, one must first understand the capabilities of each method. While there are many alternatives available to repair and rehabilitate asphalt pavement, there are a few common methods that are typically considered: 1. Asphalt Sealcoat An asphalt sealcoat is a surface treatment intended to prolong the life of a properly constructed pavement surface that is experiencing minor deterioration due to aging. It is generally the least expensive alternative when compared to other methods described below. It is applied in a liquid form to the surface of the asphalt pavement and acts as a sealant to prevent water from penetrating the asphalt and causing damage. Although most of us are probably familiar with a sealcoat being used to repair asphalt driveways, a sealcoat can also be utilized for commercial and municipal applications. A pavement sealcoat will provide protection for asphalt pavement that has not yet failed. Cracks or other visible defects that have already formed will not benefit from a sealcoat and will need to be repaired by other means to prevent water intrusion. Pavement that has begun to exhibit more advanced deterioration should probably be repaired by other means.

The picture on the left is an example of cracked asphalt pavement that can be repaired and successfully treated with a sealcoat; the picture on the right is an example of pavement that is too damaged to benefit from a sealcoat and will need to be replaced: 2. Resurfacing When pavement starts to exhibit moderate deterioration, the use of an asphalt overlay (resurfacing) can be an appropriate option. Resurfacing provides structural improvements to an existing pavement system. Typically, a minimum of 1.5 inches of asphalt is placed over the existing pavement. To be effective, existing defects such as “alligatored” pavement, large cracks, and potholes need to be repaired before the new asphalt is placed. One thing to keep in mind when considering an asphalt overlay is that cracks and other pavement failures that are caused by movement of the underlying base or soil will need to be addressed to prevent further movement.

Otherwise, this movement will continue and cause the new overlay to crack as well. 3. In-place recycling For pavement with more advanced deterioration, resurfacing is still an option. However, the cost for larger quantities of the preparatory work such as patching and crack repairs may render that option cost-prohibitive. Under such circumstances the use of in-place recycling may prove to be more cost-effective. In-place recycling of asphalt pavement is a procedure that involves grinding and pulverizing existing asphalt pavement and mixing it with the underlying base material and an asphalt emulsion to create a dense graded aggregate base material. New pavement is then placed over this recycled material, essentially creating a “new” pavement section. The beauty of this procedure is that it works independent of the current condition of the pavement—but it does require a properly constructed aggregate base material beneath the pavement. Pavement cores and/or soil borings are typically needed to confirm the presence of an aggregate base and the suitability of this method.

The in-place recycling process underway The completed process, ready for new asphalt paving 4. Complete replacement Of course, when other options are not viable, complete replacement is always an option. It is typically the most expensive, due to the need to remove and dispose of pavement and underlying soil. However, the end result is a brand new road or parking lot that should last 15 years or more before major repairs are required. While this is not intended to be an exhaustive list of all options, these represent the most common methods. Each method of repairing and rehabilitating asphalt pavement should be evaluated on a case-by-case basis by a professional, but hopefully this will provide some guidance when considering your next pavement repair project. Matt Mohlin, P.E., manages H2M’s Municipal Engineering group. He can be reached at mmohlin@h2m.com.