Asphalt is composed of many different components (see the Asphalt Chemistry blog in a few weeks), but generally, the main components are light oils and heavy oils. The heavy oils provide the strength and bonding to the asphalt, and the light oils keep the asphalt flexible and rubbery. Asphalt ages due to a process called oxidation. Aging of asphalt pavements (oxidation) occurs:
- Briefly during production of the asphalt mixture, due to the high temperatures.
- Slowly during the lifetime of the pavement, due to the UV radiation from the sun.
Oxidation occurs when the light oils are lost (high temperatures) or when the light oils are combined to form more heavy oils. This makes the asphalt more brittle and more likely to crack or ravel.
What Can You Do to Protect Your Asphalt Pavement?
Bituminous Roadways, Inc. (BR) now provides a preventative maintenance option to help reduce pavement aging, called BIORESTOR®. BIORESTOR® is a clear soy-based liquid designed to protect your investment in asphalt pavement from the effects of aging. BIORESTOR® is sprayed onto the surface of asphalt pavements and cures within 20 to 30 minutes depending on environmental conditions. Asphalt paving maintenance practices like BIORESTOR® are called rejuvenating seal coats. As the BIORESTOR® is absorbed into the asphalt, it is replenishing light oils that are lost due to aging of the asphalt. This “rejuvenation” of the asphalt makes it more flexible and less likely to crack or ravel due to aging. Also, unlike other seal coats, BIORESTOR® is clear and does not require the asphalt pavement to be restriped after application.
When Should You Use BIORESTOR®?
As mentioned above, oxidation occurs during the production and construction of asphalt pavements. Therefore, it is recommended that BIORESTOR® be applied immediately or up to two years after construction.
“Using a rejuvenator on new construction does not seem to be logical at first glance. However, it has been established that the greatest change in composition of an asphalt binder takes place during the manufacture of the hot mix asphalt (HMA). Applying a rejuvenator to a new surface a few weeks after it has been laid does several things to the pavement. Besides restoring the original asphalt properties that were lost in the HMA manufacture, the chemical assists in sealing the pavement as well as in improving the durability of the surface course.”
-Robert E. Boyer, Ph.D., P.E., Senior District Engineer of the Asphalt Institute (2002)
In addition to oxidation occurring during construction, oxidation also occurs continually due to UV radiation from the sun. Because aging continues to occur, it is also recommended that BIORESTOR® be reapplied every one to two years after the first application, until significant cracking or other deterioration occurs. BIORESTOR® is a preventative maintenance; therefore, it should only be applied to asphalt pavements in good condition. Once your pavement has begun to deteriorate (cracking, raveling, potholes), it is too late for preventative maintenance (see BR’s other Maintenance Practices).
Does BIORESTOR® Work?
In 2004, a roadway was paved in Ohio and then half of the roadway was treated with BIORESTOR® and the second half was not. In 2011 and 2014, JG2 Consulting performed pavement evaluations on both sections. Both pavement evaluations showed that the BIORESTOR® section had less cracking and less raveling.
“Based on my experience with asphalt based surface types, rates of deterioration and the ASTM inspection methodology, it is clearly evident that the product BIORESTOR® inhibits the oxidation process while providing for increased flexibility and a longer lifespan of pavements treated after paving” – James Golden, President of JG3 Consulting
For more information on BIORESTOR®, contact your local asphalt pavement expert at Bituminous Roadways (651) 686-7001.