Have you thought long-term when it comes to asphalt?
So, you’ve just spent a lot of money to have your roads paved… now what?
That’s the most common question asked by Public Works Directors, Street Engineers and Departments of Transportation.
Hot-mix asphalt is an exceptional material for streets, roads, and interstates. However, the asphalt we purchased, and installed 30 years ago, was a different quality than the asphalt that is manufactured today.
Today’s asphalt has less virgin asphalt oil, and more recycled products added at the plant. These include asphalt millings and asphalt shingles. This new “mix” leads to accelerated oxidation and decreased flexibility. Ultimately, oxidation and loss of flexibility lead to increase cracking and raveling, causing a decrease in the pavement’s life.
What can be done to protect our investment?
One approach is to do nothing. This reactive approach is a “set-it and forget-it” approach to pavement management. Pave. Do nothing. Repave. This approach is extremely costly. A huge inconvenience to the traveling public. A safety risk. And it places an unnecessary tax burden on the public that’s not necessary.
The other approach is a proactive pavement management approach. This approach recognizes there must be routine maintenance to keep the pavement in good condition. Think about changing your oil. You could choose to do nothing and purchase a new engine or spend a little on oil and keep the engine running for a long time. Spending $1.00 on pavement preservation, while your pavements are in good condition, will eliminate or delays you from spending $6.00 to $10.00 on rehabilitation or reconstruction when the pavement is in poor condition.
(Relationship between condition of pavement when treatments are applied and cost of treatment. PCI: pavement condition index; x-axis is in years)
The proactive pavement maintenance approach addresses the pavement from the moment of installation on…
Knowing your new asphalt will become brittle and oxidize once it is installed, applying a rejuvenator during the first year will restore the chemicals needed to keep the asphalt flexible, and aid in retarding the damaging effects from the sun.
As the asphalt/road ages, cracks will form. An effective pavement manager will set aside money for crack sealing. Crack sealing is by far the most cost-effective thing you can do to extend the life of your asphalt. Crack sealing seals out water from entering the subgrade, and from the damaging effects of freeze thaw cycles. Crack sealing is a low-cost high return pavement treatment.
As your pavements age, they will lose friction, they may rut, and they will need to be “resurfaced” to maintain the structure, safety, and rideability of the base below. At this point micro-surfacing should be applied to keep the road base intact.
Micro-surfacing should be applied to pavements that are in good condition. 7 out of 10 on the PCI. It is not designed to be installed on pavements that are in poor condition.
The benefits of micro-surfacing are many: it can be used to fill ruts. It will “seal” the pavement below and stop the damaging effects of the sun and water. It will restore the wearing surface’s friction. It’s fast to apply. There is minimal traffic disruption. It may be applied day or night. It lasts 6-8 years. And it cost a fraction of what a hot-mix overlay does.
In fact, when a composite index score was calculated based on 11 performance criteria, micro-surfacing had the highest score out of thin HMA overlays, slurry seals, and chip seals. (ISRN Civil Engineering, Review Article 30 Years of Micro-surfacing: A Review.)
The ISSA, International Slurry Sealing Association, reports that to address rutted and polished pavement, micro-surfacing costs $17,600 per lane mile, while milling and hot-mix asphalt costs $50,000 per lane mile. Micro-surfacing is consistently more cost-effective than thin hot-mix asphalt overlays.
“Micro-surfacing allows for rapid opening of roadways to traffic, often within 1 hour or less of its application under a range of conditions. Report of great reduction in ride roughness support micro-surfacing’s immediate benefits while additional benefits are seen over time as micro-surfacing effectively addresses rutting, increases ride quality, and has a significant service life. The superiority of micro-surfacing in terms of cost is most evident when treatment life is the measure of effectiveness, and least evident when increased pavement condition is used compared to thin HMA overlays. This further strengthens the fact that the benefits seen with micro-surfacing are appreciated over time when compared to alternative treatments. Micro-surfacing is aesthetically pleasing to people, and it restores a black appearance to roadways. Micro-surfacing requires no adjustment of curb lines, manholes, guide rails, or bridge clearances due to its thin lift height.
Overall, literature appears to demonstrate that micro-surfacing provides the best balance of effectiveness, cost, number of deficiencies for which it addresses, and potential for future development of any preventative maintenance treatment.” (ISRN Civil Engineering)
If you are utilizing all the tools in the pavement preservation toolbox you can keep your pavements in great condition at a minimal cost. By doing so, you’ll have extra money you can apply to major reconstruction projects.