The term asphalt surface treatments is used to cover a vast range of materials that are typically surface coatings made up of materials using asphalt emulsions and often-times a combination of asphalt emulsions and aggregates. 

Typically, these materials are placed in a thin layer on the surface of roadways that have been previously constructed with hot mix asphalt and Portland cement concrete. As a topical treatment, asphalt surface treatments do not change the molecular composition of pavements; but they can serve a variety of useful functions. For a review of such treatments, please see Dave Helm’s blog on that subject.

In contrast to providing a surface covering for pavements, Maltene Replacement Technology (MRT) deeply penetrates into asphalt, reintroducing to it the maltene fractions of asphalt cement. A concrete sealer would be a similar preservation material for Portland cement concrete, but for the remainder of this article we will stick with asphaltic cement pavements.

Properly formulated and constructed surface treatments are expected to add value and life to the pavement by being both economical and long lasting. Such materials have a rapid construction time and are expected to add years to a road pavement’s useful life.

Unlike topical sealers, MRT extends the service life of the pavement by modifying the asphalt binder’s rheology, increasing penetration values while decreasing viscosity and corresponding DSR (Dynamic Shear Rheometer) values. By improving the molecular structure of the asphalt binder, MRT-treated roadways remain as flexible and adhesive as they were originally designed to be for a longer time. In contrast, surface coating treatments are typically designed to seal, and in many cases, operate as a sacrificial layer from wear and tear.

It might be helpful to consider road surface treatments thrifty maintenance techniques. The primary question to ask yourself is what are you trying to achieve?  

Here are some possible answers to that question:

1. To resist abrasion possibly due to winter conditions
2. To provide a new wearing surface
3. To seal and protect from the elements
4. To provide an attractive black appearance
5. To provide a short-term stop-gap strategy for deteriorated pavements

Once your goal has been identified, the appropriate asphalt surface treatment tool becomes more apparent. In general, it can be said that the thinner the layer, the shorter the life of the product. By taking the cost of a particular surface treatment and dividing it by the life of the material you can determine the annual cost of using that maintenance tool. Be aware: some surface treatments cost as much as the hot mix asphalt per year of service.

An MRT surface treatment extends the life of the hot mix asphalt from the inside out. It also provides a sealing effect, keeping water and the elements out. Keep in mind that to achieve a penetrating rejuvenation of the asphalt binder there can be no asphaltene content in the emulsion you are using. When asphaltenes are present, the maltenes will bond with them rather than penetrating the surface to replace the depleted maltenes.

Since alternative asphalt surface treatments reside on the surface of the pavement, eventually weathering or abrasion will remove them. Some coatings last only a few months to a year while other surface treatment are able to last several years.

Make sure to do your cost analysis and understand clearly the reasons for doing any asphalt surface treatment. Do your homework and you will be able to find long-term programs with proven results. Wisdom comes from following guidance from other pavement owners with years of experience. So shorten your learning curve, do the research and move forward with confidence that you’ve chosen the right surface treatment for your road maintenance objectives and your budget.

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Charleston County, SC, recently launched a pilot program using PTI’s A.R.A.‑1 Ti^® asphalt rejuvenator sealer to treat Lowcountry roadways.  This pollution-reducing pavement preservation solution combines Maltene replacement and photo catalytic technologies to reduce airborne pollutants and mitigate heat island effect related to vehicular traffic.

Click here for a recent video report from Live 5 WCSC news.

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• What is my goal in managing the pavement asset I am responsible for?
• Am I merely attempting to prolong (at any cost) the time interval between resurfacing cycles?
• Am I attempting to satisfy a political agenda?
• Am I being pressured to implement maintenance activities that I believe will cause complaints from those I serve?

As an engineering professional, when I seek tools from the pavement management toolbox, I look for products and materials that will add value and lower operating costs – solutions with a track record for long-term success in a wide variety of applications. In my former role as a City Engineer, I took this responsibility extremely seriously and found counsel in other professionals in the industry. I knew an effective, full-scale implementation of any maintenance activity would rely not only on my own personal experience, but also on researching and spring-boarding off the success of others who have faced similar challenges.

Early on, I recognized that once a road was resurfaced, it would soon show the initial signs of aging. How could I slow this down? I did not want to resurface this road again in my career if at all possible. So I went on the offense against the cause of asphalt deterioration.

What I discovered was that if a road was structurally sound, I only had to slow the effects of the environment and oxidation. I found that asphalt cement keeps its ductility and flexibility by maintaining the proper maltene/asphaltene balance.¹ Reintroducing the natural maltene component of asphalt would slow the effects of the environment on my roads. As I surveyed the roads over time, I witnessed service life extension by several years each time the maltenes were re-introduced to the pavement. I was encouraged to learn, when I spoke with fellow road maintenance professionals, that others were making similar observations.

The 2016 research performed by Joe Vitale and Khalid M. Siddiqi, Ph.D., “The Feasibility of Asphalt Pavement Rejuvenator Applications,” confirmed my own experiences: roadways were aging more slowly when treated with maltene rejuvenation of the asphalt binder. The slower deterioration added eight years of service life! Further, they demonstrated that the longer service life divided by the cost of all maintenance over the longer life provided a 29 percent lower annualized operating cost. This study definitively demonstrated that asphalt pavement rejuvenation saves money!

In effect, replenishing the maltenes holds the roads together from the inside out. The introduction of maltenes makes the asphalt binder more resilient to environmental stresses, binding the entire matrix of aggregates together with better cohesion. This keeps the road surface tight so it actually sheds water faster. All the other environmental factors (UV rays, snow, de-icing treatments, etc.) are similarly kept at bay. The result is a longer lasting, better performing asphalt pavement.

So ponder no longer and do the research yourself: it is possible to have high-performing pavements that last longer while lowering your annualized maintenance costs.

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What does it take to manage them?

Since all of us who use them daily tend to overlook the value of our roads, I guess it’s no surprise that what it takes to manage our pavements is often underestimated as well. To manage this valuable asset requires commitment and some type of plan. In many cases, software is used to help model pavement performance. This type of forecasting helps local and state agencies have the necessary funding in place to keep our roads in acceptable condition.

Everyone wants what’s “best” for our pavements, right?

Because most of us don’t consciously think about how long a pavement should last, or at what point roads start to deteriorate once we start using them, we don’t really consider their condition until we hit that darn pot hole. You know the one…where someone just threw a little asphalt in it and all seemed great until it rained.

Unfortunately, this type of “corrective” maintenance is frequently the norm: we wait until a problem occurs, and then we “fix it.” Unfortunately, by the time an issue becomes apparent on our roads, it is an indication that the pavement is already aging – regardless of its actual age. Distresses, such as cracks and roughness, are inevitable when new roads go untreated. Asphalt is an organic material that starts a natural degeneration process even before it becomes a pavement, due to the high temperatures required in the manufacturing process. The stresses of traffic and weather only accelerate the process. The best way to slow these negative effects is to develop a good preservation program.

Two approaches to solving pavement problems

The National Center for Pavement Preservation focuses on helping agencies promote the pavement preservation process through an open, educational forum. They explain that pavement preservation is intended to “extend pavement life and improve motorist safety and satisfaction while saving public tax dollars.” That’s right, preservation actually saves money.

Basically, agencies have two options when attempting to extend pavement life:

1. Just keep correcting damage as it occurs, and then repave when repairs are no longer practical
2. Prevent distress by applying a restorative chemistry that actually returns to the asphalt the maltene fractions that have been depleted 

Correcting damage

Repairing damage is typically the easiest way to get funding. It kind of makes sense – see a problem, repair the problem. Once pavement distress becomes apparent, there is a compelling argument to perform corrective maintenance. Some of our typical corrective maintenance strategies include crack seal, slurry seal, chip seal and patching. These are all very effective tools, and when done correctly will provide useful life extension to our pavements.

Preventing damage

Preventing damage is the most sustainable type of pavement preservation. We know pavements begin to age during the production process. We can actually see the light maltene oils, which keep asphalt flexible and adhesive, escaping as a light smoke. It is not possible to completely stop this process, but early reintroduction of the maltene oils using Maltene Replacement Technology (MRT) genuinely restores the molecular structure of asphalt. 

Some might even call this rejuvenation process a form of “corrective maintenance” since it does correct the damage caused during asphalt processing. Early reintroduction helps reestablish the expected adhesion and flexibility properties of the pavement. Additionally, it has been shown to defer corrective maintenance for several years.

So what works best?

For as long as I can remember, I have heard that “An ounce of prevention is worth a pound of cure.” This holds true in all areas and definitely is true when performing maintenance on a needed infrastructure. Keeping a pavement in excellent condition just makes sense. The asphalt surface intended for public use maintains its intended integrity. The people that use the roads experience less disruption. Vehicle wear and tear is reduced. The prevention approach is a win on all levels.

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