We remain enthused with the Pavement Preservation & Recycling Alliance (PPRA) Treatment Toolbox, a free, online resource for your pavement preservation planning and in their Treatment Resource Center is a deep-dive on microsurfacing.
Pavements in good condition don’t stay in good condition by themselves and the best way to extend their service lives is regular maintenance and preservation techniques that can add years of good performance for a fraction of the cost of mill and overlay. The key is to use the right technology for the right road at the right time.
For pavements still in good condition, microsurfacing is a surface treatment that can restrict moisture intrusion, reduce oxidation and raveling, and provide some skid resistance to a roadway that may have become a bit polished. It often follows a best practice of crack sealing and/or filling (see our exciting e-newsletter from January for that topic) by a few months to a year.
Microsurfacing is a mixture of polymer-modified asphalt emulsion, mineral aggregate, water and additives. It is carefully proportioned, mixed and uniformly spread over a properly prepared surface. This last piece, “properly prepared surface,” cannot be overstressed, as is the case with just about any treatment of your roadways, including milling and paving. A littlecare with the surface in the beginning goes a long way towards successful outcome.
Pioneered in Germany in the 1960s or so and introduced in the United States in 1980, microsurfacing is a homogenous mat that adheres firmly to the prepared surface and forms a uniform, black appearance upon curing. It allows traffic to return quickly (often less than one hour, depending upon local conditions) after placement. When applied well to a road that has not yet experienced severe or widespread distresses (but no structural distresses), the service life extension can be 6-8 years and many agencies have seen even better results.
With smaller runs and more complicated streets, a special truck mounted paver is used, but for longer runs, a continuous paving train can add efficiency and improve the consistency of the application. In addition, the mat is sometimes treated with a rubber-tired roller where there is lower traffic loading, to better seat the material.
Because the mix is an emulsion, the material is placed as a chocolate brown mat, but when it “breaks” (as the water is released from the emulsion through some kind of magical ionic/cationic wizardry of chemistry), the mat turns to a black surface.
Of course, these are just the highlights of microsurfacing and the PPRA Resource Center, as well as the experience of a qualified contractor, can be very helpful, whether you are totally new to microsurfacing or are looking to improve upon past performance and understand best practices better.
The PPRA Resource Center is worth a little time to better understand a whole array of pavement preservation approaches. The Delaware T2/LTAP Center’s Municipal Engineering Circuit Rider is intended to provide technical assistance and training to local agencies and so if you have pavement management questions or other transportation issues, contact Matt Carter at matheu@udel.edu or (302) 831-7236.
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