Pavement Preservation Journal, Spring 2016
Mark Ishee, Vice-President
Ergon Asphalt & Emulsions, Inc.
Micro surfacing has served the traveling public well for decades as an efficient solution for restoring friction, filling ruts, halting raveling, and leveling distressed pavements. It also extends service life of roadways, adding over seven years in many instances, more cost-effectively than traditional mill and fill options.
The versatility exhibited by this thin surface treatment is remarkable, but one thing micro surfacing has never been intended to do is address roadways where cracking is the predominant distress.
While micro surfacing does offer a significant reduction in the size of surface cracks and impedes the overall damaging effects of water flow into the pavement, it is not designed as a crack solution. In fact, experienced industry users and countless studies have long suggested the use of crack sealing treatments to specifically address cracks that are wider than a quarter of an inch prior to placing micro surfacing.
With that said, the search for the “Holy Grail” – a micro surfacing system engineered with the added proficiency of impeding sizeable cracking – is part of the evolution of this important pavement preservation tool.
Looking at the current categories of micro surfacing available today, we see meaningful advancements:
• Conventional micro surfacing now is commonplace. Expectations of a successful project are generally met as long as site selection, design, material supply and placement practices are thoughtfully considered and properly carried out. The educational pieces available to assure a successful project are in place and well vetted. The sciences of asphalt emulsification and polymer modification continue to progress. Manufacturers of equipment used by material suppliers and applicators improve their offerings at a steady pace and the future is indeed bright for a treatment that was once considered a “magic act.”
•Fiberized micro surfacing has been used in Europe and the U.S. for a number of years. There are variations found in this treatment related to the fiber type and configuration, as well as the method of introduction into the mix. There are multiple nationally recognized research projects underway intended to prove the effectiveness of this treatment as related to durability and crack mitigation. This research will eventually determine if this category should be considered “flexible.”
• Highly modified micro surfacing is a more recent attempt to take micro surfacing to a new level. An increase in durability realized in successfully addressing distresses such as raveling, power steering burns, and damage from snowplows and utility vehicles on freshly applied projects, continues to be confirmed in roadway projects across the United States. Properties that would warrant the product being classified as “flexible,” however, have not been consistent. Independent research is also underway with this category to provide understanding as to the type and extent of improvements that can be expected.
• Flexible micro surfacing is a relatively new category that’s in the development stage. “Flexibility” in terms of a micro surfacing system must eventually be defined so that the system can be specified. We can measure with certainty how much fiber is added to a system and how much additional polymer modification is provided, but how do we measure flexibility? There is at least one product currently in the research and development stage that is showing some promise in initiating the discussion.
