Asphalt Chemistry and Maltene Replacement Technology
In our efforts to manage an asset like a road, it's easy to overlook something important like asphalt cement. You can think of it as the glue that holds your road together. A typical asphalt surface contains only 5% of this asphalt cement glue. It's the only thing holding the asphalt together, and interestingly, it's the only part of the asphalt we can make improvements to.
With proper maintenance, it's also one of the only things in your road that can create a significant financial benefit over the long term. There is no question that improving the quality of the asphalt cement in your roads will decrease their lifetime maintenance costs.
That's the general rule of thumb for asphalt mixes. Most asphalt mix designs call for about 5% asphalt cement to 95% aggregate.
100% of your road's future depends on 5% of it's mix!
Maintaining that 5% is already a priority many Ontario Municipalities.
Are you prioritizing and maintaining your 5%?
There's nothing quite like a freshly paved road to put a smile on the face of one of your tax-payers, or the kids shooting hoops in the neighbourhood. New roads have a nice uniform black appearance that appeals to motorists, bikers and walkers alike.
Unfortunately, that smile frequently turns to a grimace far too soon.
What makes roads age so quickly?
Asphalt aging starts before your road is even paved, and occurs at the asphalt plant where the asphalt is mixed. Temperatures in excess of 300 degrees fahrenheit are used to melt the asphalt cement and heat the aggregate to ensure everything is coated with an even film of asphalt cement.
Unfortunately this heating process destroys some of the Maltene in the Asphalt Cement. Maltene is the part of the glue that provides flexibility to asphalt, so even though your freshly paved road looks fantastic, it has already aged an equivalent of 2 years, just by being mixed at the plant! That's like buying a brand new car with 40,000 kms on the odometer when it comes out of the factory!
Asphalt labs have a test that simulates this damage called a Rolling Thin Film Oven Test or RTFO. RTFO tests are used to determine how a road's asphalt cement will perform after paving is complete.
Components of Asphalt Cement.
Oxidation of Asphalt Cement.
What is it, what role does it play in your asphalt, and how does it's behavior affect your pavement?
The main underlying cause of road failures is damage to the maltene components of asphalt cement that occurs as a result of exposure to oxygen and sunlight.
Oxidation is a complex process, and can affect many different elements and compounds. Rust is a good example of oxygen "stealing" electrons from iron during a redox reaction, and turning it into rust (iron-oxide). In a similar fashion, oxidation damages the components of asphalt cement that are responsible for flexibility. Photons from sunlight cause photo-oxidation as well, which causes similar damage. The compounds in asphalt cement that are constantly and slowly decaying are collectively called Maltene, or the maltene fractions of asphalt cement.
When maltene oxidizes, the Asphalt Cement becomes less flexible, and begins to crack when under stress. It's important to think about cracks in a road like this... The cracks in the road are a result of the asphalt cement glue cracking, not the aggregate.
Every crack in every road is a crack in the glue! We can stop this glue from cracking by helping it maintain it's flexibility by replacing the maltene lost through the oxidative process. Reclamite is a very effective Maltene Replacement Technology that can return flexibility to aged roads.