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Causes of Asphalt Pavement Deterioration
Reclamite In-Depth Preservative Seal replaces Maltene, returning flexibility to your road.
Some background detail on asphalt cement in Ontario.
We pave roads with the best of intentions and have an underlying hope that the road will last 15-20 years with minimal maintenance. Unfortunately, a typical road lifespan has been getting shorter since the mid 1990’s, and as time goes on, the situation is getting worse. There has been much discussion within the industry about asphalt cement quality, led by OMPHA and its industry partners.
At a PPRA symposium in Niagara Falls in October of 2015, Becca Lane P.Eng. Head, Pavements and Foundations Section MTO, told the audience composed primarily of industry suppliers the following. “The Provincial Highway Network is in jeopardy, and if allowed to decay at the current rate the entire transportation industry will be affected. Within 25 years we may have a disaster on our hands. We need your help to solve the problem with early failure of our roads.”
Even more frightening was a statement made by Stephen Lee, Pavement Engineering Section MTO. “Financially, we are at the fiscal cliff, and we’re in free-fall!”
When challenged by engineers, the paving industry states that here is nothing wrong with A/C, and that it’s the same today as it was 30 years ago. They claim that “another factor must be affecting roads and causing them to fail, because their A/C is just as good as it has always been.”
This is simply not the case. Asphalt Cement is essentially the left-over after you extract a long list of products from Crude Oil. These include gasoline, distillates such as diesel fuel and heating oil, jet fuel, petrochemical feedstocks, waxes, and lubricating oils. (All the good stuff!) Not surprisingly, as refining technology has improved over time, refineries have become more efficient at the refining process. This means they are extracting more products from the crude than ever before. They are squeezing as much juice out of the “proverbial” orange as possible!
Although A/C is a residual of the refining process, it is still a highly complex product that can accomplish amazing things when mixed with aggregate. A quality un-adulterated A/C containing the correct ratios of Asphaltene and Maltene has excellent viscoelastic performance characteristics. Asphaltene and Maltene can be thought of as two opposing sides of the chemical make-up of A/C. Asphaltene gives A/C its strength, and Maltene gives A/C its flexibility. Together they create a compound that remains stiff under load in hot conditions but remains flexible and ductile enough in cold conditions to avoid cracking.
Maltenes are CRITICAL to A/C performance. Unfortunately, they are the ONLY compound in your road that can decay through oxidation. If we want to fix our A/C we need to start looking at the Maltenes. Reclamite is Maltene!
We need to dig a little deeper into the chemistry involved to really answer that question.
The five major components of A/C shown above are all important to the performance of the A/C in your road. In concert, they combine to create this amazing “glue’ that holds all of the aggregate in place in the matrix of an asphalt road, but 4 of the 5 components are volatile and susceptible to damage through oxidation.
The first and second accidifins are light aromatic oils, which, combined with the saturated hydrocarbons and polar compounds, are responsible for keeping A/C flexible. We call these the Maltene Fractions of asphalt cement, or Maltene for short. It’s this Maltene that is being damaged by oxidation. This oxidation process is unstoppable, and starts right at the asphalt plant when the asphalt is mixed.
There is nothing that can be done to stop the oxidation process, but because it is isolated to the surface of the road once the pavement is laid, we can combat oxidation through increasing the amount of Maltene in the surface of a road.
Reclamite does just that. Reclamite is simply composed of Maltene the only components of A/C that are susceptible to oxidation. Reclamite (Maltene) boosts the available amount of Maltene in the top ¼ inch of the road, giving the oxidation process extra material to oxidize so that the original levels of Maltene are maintained. Essentially Reclamite keeps the Maltene levels above the danger zone!
Often we think of a road as a whole, and we use common descriptions of aging roads such as…
The road is cracking.
The road is losing fines.
The road is decaying.
The road is falling apart.
What we really need to do is describe aging roads like this…
Lack of Maltene is causing my road to crack.
The A/C isn’t performing properly.
The A/C is destroying my road.
The Maltene levels have dropped to the danger zone.
This change in the way we describe road decay helps us narrow down the cause, and makes the solution easily understood.
What happens if the Maltene in the surface of your road oxidizes to the danger zone?
Again, we have to dig a little deeper.
Not only does Maltene keep your road flexible, it works in tandem with the
Asphaltene. If you were to extract Asphaltene from A/C you would see a black crystal that looks like sand, but when it’s combined with enough Maltene it becomes part of the solution of A/C. It is believed that the hardening of A/C is caused in part by Asphaltene coming “out of solution” and returning to a solid. This is the chemical description for hardening A/C. When the Maltene levels reach the danger zone, asphaltene starts coming out of solution.
Because we can’t see this microscopic change, we need another way of measuring and identifying it. That’s where asphalt testing labs and engineers come into the picture. The chemical changes contributed to by oxidation manifest themselves in physical changes to the A/C. Testing methods such as Bending Beam Rheometry, Dynamic Shear Rheometry, Rotational Viscosity and Penetration index testing can describe the chemical changes in a physical way.
We can measure the viscoelastic properties of A/C using these test methods to determine the Maltene levels of an existing road, by analyzing A/C recovered from cores. When we apply Reclamite (Maltene) to a road we can measure the changes to the viscoelastic properties by taking post- treatment cores and testing the recovered A/C.
These PGAC characterization results give us a clear picture of the performance of the A/C before and after Reclamite treatment.
Everyone at Superior Road Products is trying to help Road Managers make informed decisions regarding the performance of their roads, and this type of engineering gives us the evidence and clarity we all need to feel confident we’ve used the correct treatment. Please reach out to us today.