The Bridge, Vol. 25, No. 2, October 2011
Chip seals can extend pavement life from both ends of the deterioration curve
By Melanie Kueber, P.E., Research Engineer II, and Trevor Kuehl, Assistant Technical Writer
Center for Technology & Training
A chip seal treatment involves spraying a layer of asphalt emulsion over an existing hot mix asphalt (HMA) pavement and then embedding an aggregate cover. It has become a popular road maintenance option for road agencies in Michigan because it requires a low capital investment to get started, a local agency maintenance crew can typically perform the work, and it provides a generous return in pavement service life for the amount of money and time invested to apply it.
In a typical application, a chip seal is performed as a preventive maintenance treatment before a pavement begins to show signs of structural distress. Based on the Pavement Surface Evaluation and Rating (PASER) scale of pavement condition—the statewide standard for rating roads in Michigan—chip sealing is recommended for pavements that have a rating of five or six. Such pavements are in the middle of their cycle of service life; they typically show moderate to severe raveling, some flushing or polishing, and age-related cracks that are no more than ½ inch wide.