Construction season is starting to ramp up quickly and whether I am talking to agencies in person or through Zoom, one common theme I am starting to find is that preventive maintenance is becoming top-of-mind for agency officials. 
 
Many of the conversations I’m having include questions regarding the different pavement surface treatments and their uses within municipality or county maintenance programs. These applications are important because they can have many benefits to a pavement, such as protecting it from weathering, delaying and minimizing cracking, and correcting pavement distresses like raveling or rutting. For the purposes of this article, I thought I would address three of the more common questions I receive regarding these different surface applications. 

What are the most cost-effective surface treatments available to an agency? 

Road surface treatments within a preventive maintenance program are looked at as a cost-effective strategy to increase pavement life. However, some are more affordable than others. 
 
Each agency needs to understand their community’s pavement condition rating to determine the most effective strategy. However, for the purposes of this article, I think it is important to discuss two applications that I believe every agency should start to incorporate: asphalt rejuvenation and crack seal. Both applications have been studied for decades and have proven to greatly extend pavement life. 

Rejuvenation and crack seal are best used within the first three to seven years of a pavement’s life cycle; generally, these treatments are less than $1.00/sy applied. Typical pavement life extension is from three to five years with either of these approaches, and since these two treatment options can be used in conjunction with one another, even greater life expectancy can be expected.  

The biggest concern I see with crack seal is candidate selection. The purpose of this surface treatment is not to obliterate the roadway with material. You want to get to the pavement relatively early and address the main construction joint and early transverse cracking. Below is a great example of proper crack sealing job that was done early on. 

How effective are maltene-based rejuvenators at sealing pavements? 

Maltene-based rejuvenators are field- proven in nearly 50 years of pavement application to improve the binder chemistry of the asphalt while delaying and minimizing cracking and raveling. One of the other benefits of maltene-based rejuvenators is the ability to keep moisture from getting into the asphalt. There is no better example than to see a treated section of pavement after a rainfall, vs. an untreated pavement. Below is a roadway that had a maltene-based rejuvenator applied two years ago. The photo was taken just 30 minutes after a rain, and the difference between the treated and untreated pavement is dramatic.  

What is the difference between a black surface seal (like a fog coat) and a rejuvenator? 

I get this question a lot throughout the industry, and with good reason. Many black surface applications contain the verbiage “rejuvenate.” Let me first state that I believe black surface treatments and rejuvenators are both good applications that should be looked at as effective tools to maintain agency roadways. Nevertheless, lumping both applications into a single category can be misleading.   

Fog coats are highly diluted, slow-setting asphalt emulsions that are black in color. Most often, they are placed on top of a chip seal to help lock in the aggregate and give a nice dark appearance for the residents. Some are even placed on top of asphalt pavements as way to help protect the pavement from weathering. However, I see contractors and vendors use the term rejuvenation loosely with these applications.   

Remember, a true rejuvenator will penetrate the asphalt and improve the binder chemistry in the pavement. It will also help to make the asphalt more ductile and to seal the pavement from within. Rejuvenators are most often recommended for application earlier in a pavement’s life cycle.   

Black surface treatments such as fogs or mastic surface emulsions do not penetrate the asphalt nor alter the chemistry. They are a topical seal and are usually used later in a pavement’s life cycle, in comparison with a rejuvenator.     

Look at the picture below. This agency placed a black surface treatment on their road back in 2014. However, prior to using the surface seal, they sprayed the right side of their pavement with a maltene-based rejuvenator, which they did not apply on the left, so they could compare results.  

This picture was taken in the spring of 2021 (seven years later). You can tell the side with the rejuvenator is in considerably better shape than the untreated side. The rejuvenator was also half the cost of the black surface treatment.   

If this agency could go back and do it again, a better approach would be to use the rejuvenator on the entire roadway, and then postpone using the topical black pavement sealer until later in the pavement’s life cycle. Unfortunately, sometimes our public works officials receive pressure from legislative bodies to give their roads an attractive, shiny black appearance. While this is of some curb-appeal benefit for residents, we must also look at functionality prior to making pavement preservation decisions. 

Conclusion 

Road surface treatments play an important role for public works professionals with tight budgets looking for ways to extend pavement life. Before trying to implement various surface treatments, the first line of business is to understand the condition of your overall network. From there you can start to develop a plan and run various scenarios to see which application will benefit your agency the most.   

Also, do not be afraid to question individual pavement solution providers about the cost-to-benefit value of the options they provide. It’s tempting to look at these individuals as pure “product salesmen.” Though it’s certainly true that product distributors want your business, they don’t get much benefit from a one-year contract. Long-term relationships only develop when pavement preservation partners achieve your goals by applying the right products with a high level of customer service.

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To most of us, this is just routine pavement maintenance and preservation. But caring for roads takes many shapes and forms.  It could mean improving the striping on the road, patching pot holes, crack sealing, or drainage improvement.  All these activities are vital to maintaining our infrastructure, but it is the timing of these various operations that will reveal their real-world impact on pavement conditions and ultimately, on the cost-efficiency of the dollars invested. 

Reactive Maintenance 

I was out driving roadways a couple of years ago when I came across this pavement that had been recently crack sealed.  

Typically when I display this picture I hear several chuckles from the crowd, while the motorcyclists among us cringe at the thought of having to drive on this. The “shock value” is high, but this practice is far more common than you might think. 

I am a person who likes to give the benefit of the doubt, and I’m sure the agency responsible meant well; after all, see crack, seal crack. However, think about the costs involved in this type of reactive maintenance. The material alone would send your invoice through the roof, not to mention the time spent and headaches experienced in performing this operation. I suspect the agency received a couple of citizen complaints as well.   

Clearly, this is not routine pavement maintenance, but rather, maintenance that is essentially reactive in nature. The idea of waiting to try to fix a problem only when it becomes a problem is a waste of agency dollars.  

Preventive Maintenance and Preservation 

Now let’s look at another pavement that received maintenance, but with an entirely different approach. Six years ago, this agency decided to try a maltene-based rejuvenator on several roadways. On one of the streets, the agency treated only one side of the pavement with the penetrating sealer, leaving the other side untreated so the township could evaluate the results over time.  

The treatment was applied while the asphalt was still relatively new, and some may have wondered why any maintenance was being performed so early in this road’s service life. But after six years, you can see how the treated pavement remained in great condition with minimal cracking, while the same degree of exposure to weather, UV and traffic did significant damage to the untreated roadway.

The treated side of the pavement contained far less cracking and raveling, which is evident from the significant amount of crack seal applied to the untreated side. As the Public Works Director commented at the time, “Which side would you rather maintain?” He readily understood that the time and money spent on the untreated side would far outpace that spent on the side treated with the maltene-based rejuvenator.

This is an example of an agency treating the roadway prior to, and in anticipation of, the inevitable wear on aging pavements. Clearly this type of preventive maintenance is a better use of taxpayer funding.

Conclusion  

As previously noted, pavement maintenance and preservation is vital to any community. But the timing of each operation will determine how successful an agency’s program is.   

The dentist is usually not my favorite place to go, but the trip is much more enjoyable when I am just getting a cleaning rather than having a cavity filled. Our family’s monthly budget also is far less impacted. If we can start shifting our focus away from reactive to preventive, not only will our pavement conditions improve, but our dollars will go a lot farther. 

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What’s the difference?

Buildipedia refers to asphalt surface treatments as the “reconditioning of the wearing (surface) course of older existing asphalt pavements.”¹ Such treatments are topical and are typically used on older, structurally sound surfaces to prevent water intrusion and delay further pavement oxidation. You may see an increase in the use of surface treatments during election years, due to their aesthetic appeal to the public and their relatively low cost.

Below is a good example of a highly oxidized pavement that was recently crack sealed and then had an asphalt surface treatment placed. It is easy for a manufacturer to call an application like this a “rejuvenator,” but it is simply a protective coating for the asphalt. Surface treatments do nothing to improve the chemical composition of the asphalt binder within the pavement; they are, as the name implies, only “skin deep.”

In contrast, genuine asphalt rejuvenation is the process of restoring to the asphalt the actual chemical components that the high temperatures of production and subsequent oxidation have removed. These components, known as maltenes, are the sticky resin compounds in the binder that give the pavement its flexibility.

Both surface treatments and asphalt rejuvenation can be effective in addressing your pavement network; however, it is imperative to use them at the appropriate time in a pavement’s life cycle. When using a genuine rejuvenator with Maltene Replacement Technology (MRT), it is critical it be applied within the first three to five years of a pavement’s life. In fact, many agencies are noticing extremely beneficial results by placing the rejuvenator down the same year as the new asphalt. The cost of such rejuvenation adds only around eight to 10 percent to the original re-surfacing program budget, with studies demonstrating a resulting 30 to 40 percent increase in pavement life. Those of us who contribute to annual retirement plans would take those returns all day!

What You Can Expect

The photo below shows a newly paved sub-division, which was completed in 2019 in central Tennessee. A couple of weeks later, this community’s roads engineer specified a maltene-based asphalt rejuvenation product for the entire project. To help the agency determine the outcome, the applicator left untreated a 200-foot control section. Just six months later, the results were already evident. Notice the pitting and openings on the untreated (left) side, while the remaining treated (right) side is notably smoother with hardly any voids in the pavement.

The effects of MRT treatment remain visible far beyond a single year. Take a look at the below photo of an agency that used the same MRT rejuvenation product on the left side of the pavement in 1996, and then compare its surface 24 years later with that of the untreated (right) side.   

Which one should I use? 

My profession has allowed me the opportunity to work with asphalt surface treatments and rejuvenators.  As stated, both should be implemented in a pavement preservation program; however, timing will greatly determine the success of your efforts. A maltene-based rejuvenator literally restores the asphalt to something close to its original chemical structure while imparting an in-depth seal to the pavement.  MRT solutions should be placed within that three to five-year window before the pavement has become highly oxidized.  Asphalt surface treatments, as protective coatings, are best used later in a pavement’s life cycle, once the asphalt has become more seriously oxidized with surface cracking apparent.   

The Final Challenge

It is understandable why public works officials involved in infrastructure decisions are tempted to put something down on their roadways because it gives them a “pretty appearance.” I once had an official tell me “as long as residents have green grass and black roads,” complaints are minimal.

On the surface, this may seem true. But think about it: don’t most of your roadway complaints reference those nasty potholes we all are too accustomed to seeing? Doesn’t extending the service life of your roadways make more sense than investing in short-term, skin-deep improvements? As your pavements continue to age, there will likely come a time when surface treatments make sense; but if putting that time off for as long as possible is your goal, then genuine MRT rejuvenation is your solution.

The black shiny appearance of a roadway does not prove its durability. What road engineers need, and community members want, are sustained results – drive-worthy performance over time. MRT rejuvenators may not provide that like-new appearance that residents will notice; but it will provide them with roads that remain drivable longer and the assurance their tax dollars have been well spent.

¹ http://buildipedia.com/knowledgebase/division-32-exterior-improvements/32-01-00-operations-and-maintenance-of-exterior-improvements/32-01-1362-asphalt-surface-treatment/32-01 

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According to the National Asphalt Pavement Association, the United States has more than 2.7 million miles of pavement, 94 percent of which use asphalt either as full-depth roadways or as overlays to restore aging concrete pavements. Roadway preservation typically consists of a programmatic approach to restoring a pavement’s original performance characteristics.

What factors influence the success or failure of pavement preservation programs?

The primary factors influencing road preservation outcomes include:

• The types of chemistries used and, more specifically, how those chemistries achieve their results
• Treatment application methods, i.e., whether the treatments used were applied precisely in accordance with its manufacturer’s recommendations
• The batch quality of the materials used
• The expertise of the service crews applying the treatment
• Traffic and weather exposure

What is the difference between preservation and rejuvenation?

As previously stated, the intent of preservation is to restore a pavement’s original performance characteristics. Rejuvenation is a sub-category of pavement preservation. It too restores a pavement’s original performance characteristics, but it does so in a specific manner, i.e., by returning to the pavement the precise chemistries that have been depleted from it due to the high temperatures of manufacturing and exposure-related oxidation. Only asphalt pavements are capable of genuine rejuvenation that literally rebuilds the molecular structure of the asphalt binder.

What benefits can I expect from adopting a pavement preservation program?

• Proactive preservation will sustain pavement performance, extending intervals between rebuilds and conserving both budgetary and natural resources.
• The correct preservation treatments will improve skid resistance and provide a smoother safer surface for optimum driver safety.

How do I determine the “Right Treatment for the Right Pavement at the Right Time”?

Many state-based DOTs (Departments of Transportation) have developed specification documents and recommended application procedures for a variety of available preservation treatments. Your local DOT is your best resource for best practice recommendations for any particular type of roadway and condition.

For a checklist of potential treatments to get you started, visit FP²’s Preservation Toolbox.

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Rejuvenators using Maltene Replacement Technology (MRT) deeply penetrate aging asphalt pavements with the same, molecularly compatible chemistries that oxidation has removed. MRT application benefits include:

Extending roadway service life by as much as two-fold by reversing the effects of oxidation related to the high temperatures used during the manufacturing of asphalt and prolonged UV exposure

Reversing the Heat Island Effect generated by modifications to the natural environment

Dramatically reducing carbon footprint by prolonging the intervals between rebuilds

Asphalt is a petroleum-based organic material that naturally deteriorates throughout its service life, first from the high temperatures of the manufacturing process, and later through continued exposure to sunlight, weather and traffic. Proactive preventative maintenance deployed at the top of the maintenance curve stretches the maintenance budgets of municipalities, counties, private communities, and state governments while conserving our natural resources.

Asphalt Rejuvenation

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