Microsurfacing best practices in North America

Microsurfacing is an important tool for both pavement preservation and preventative maintenance. It is generally considered to be a highly specialized process and public highway agencies often depend on the experience of the microsurfacing contractor and its emulsion supplier for both design and construction. This paper reports a study of microsurfacing best practices found in a survey that included 44 US state and 12 Canadian provincial transportation agencies and reports the major findings from the survey, a specification content analysis, and several case studies in both countries. The study found that microsurfacing is best suited to correct rutting, oxidation, bleeding, and aggregate loss and does not perform well on structurally deficient pavements, which makes project selection the most important step in the microsurfacing design process with respect to long-term performance. It also found that most agencies assign the contractor the responsibility to develop the mix design and this practice yielded satisfactory performance and did not degrade final quality. The paper also reports individual best practices found in microsurfacing procurement, design, and construction. Finally, it concludes that microsurfacing is a pavement preservation and maintenance tool with very few technical or operational limitations and recommends that its usage be increased.