Performance of Louisiana's chip seal and microsurfacing program, 2002

A 5-year field performance study was conducted of the 1995-1996 Chip Seal and Microsurfacing projects with a summary of data generated by the Louisiana Department of Transportation and Development's pavement management group. The pavement management data set includes performance indicators such as the international roughness index, crack analysis, rut depth, and ground-penetrating radar thickness. A subjective survey designed for maintenance surfacing was developed and used on this same set of projects. The pavement condition rating was examined from the point of pretreatment and annually until spring of 2001. The survey suggests that treatments will improve a pavement's initial condition, but no conclusion can be drawn on the effect on pavement condition index (PCI) over time compared with untreated pavements, as all pavements' PCI curves are similar and are independent of PCI before treatment. General observations for chip seal projects are as follows: the median PCI was 75 after 52 months with a significant reduction in cracking; 20% of the projects showed moderate to heavy bleeding; rutting was not evident; and measurement for skid resistance was very good. For a life expectancy of 5 years, the equivalent annual cost (EAC) of a chip seal is approximately 27 cents a year. For microsurfacing projects, the median PCI of microsurface sections is approximately 85 after 60 months of service with significantly fewer cracks detected after treatment. Projects with 0.5-in. initial rut showed substantial reduction after treatment. The friction numbers (FN) for smooth tire are in the low teens to low thirties on 50% of the projects. The lower numbers are attributed to a combination of the use of limestone and high asphalt content. Sandstone sections exhibited FNs in the 50s. For a life expectancy of 6 years, the EAC is about 49 cents a year.