Micro Surfacing – Not Just For Rural Roads!
I find it interesting as I chat with State DOT and City / County engineers from around the United States, that many believe that micro surfacing is a great product for slow speed, low volume roads, but hesitate to use it on their high volume, high speed routes.
In fact, Micro surfacing was designed by its inventors for high volume/ high speed German Autobahn routes. Micro surfacing, with its 100% crushed single source aggregate combined with 8% highly polymer modified asphalt, is engineered to be as resistant to heavy/ fast traffic as many HMA Thin Overlay mixes.
The 2015 International Slurry Surfacing Associations President’s Award was given to a Micro Surface that was placed by a Bergkamp Inc. customer, Strawser Construction, on a high volume/ high speed I-670 in Columbus, Ohio. This project was a 3.88 mile long section of urban interstate with an ADT count of 191,663 vehicles per day.
Other Bergkamp customers are placing high quality micro surfacing on urban routes that handle well over 220,000 AADT. These are not one-off projects. One agency in the northeast has placed micro surfacing for four straight years on separate sections of a major interstate loop near a major international airport. The micro surfacing is performing well and the agency continues to let similar work with great success.
Micro surfacing works well on high speed sections as well. Multiple projects have been completed in the western portions of the Unite States on Interstate highways that boast speed limits at or above 75 mph. The micro and macro texture of micro surfacing makes an excellent skid resistant surface which makes traveling at this high rate of speed as safe as possible.
Here are some steps that an agency should take to help insure success when micro surfacing a high traffic roadway:
- Place Micro surfacing in two lifts. The first lift will be a leveling course and should be applied at a slightly heavier rate than the surface course. 55% leveling course and 45% surface is a good place to start.
- Pay items for the micro surfacing should be by the ton of aggregate and gallon of asphalt emulsion.
- Paying by the ton and gallon allows the agency and contractor to easily shift quantities around the project as needed.
- Paying by the ton and gallon insures that the contractor will apply the desired application rate.
- Paying for asphalt emulsion directly allows the contractor and agency to increase or decrease the Job Mix Formula as conditions dictate.
- Preparation of the existing surface is critical.
- Seal the cracks prior to micro surfacing.
- Remove all thermos-plastic and/or heavy paint markings prior to surfacing
- Apply a light fog or tack coat ahead of the level up coarse if existing pavement is dry or raveled.
- Require the contractor to place a test strip to prove that materials, equipment, and crew are capable of producing quality work that meets specifications.
- A night test strip should be completed it the work is to be completed at night.
Micro surfacing is designed to handle high traffic roadways and contractors all over the world prove this on a yearly basis. Make sure you add this tool to your pavement preservation toolbox for every road in your network. Have more questions? Contact me or firstname.lastname@example.org today and we will give you many examples of micro surfacing on high traffic/high speed roadways.
Author: Rex Eberly, Global Sales Director