Correlating Chip Seal Performance and Construction Methods

Abstract

A survey of U.S. public highway and road agencies that use chip seals as a part of their roadway maintenance program was developed and conducted as a part of NCHRP Synthesis of Highway Practice 342. Ninety-two individual responses from across the United States, Canada, and overseas were received. This paper seeks to correlate individual chip seal performance ratings with the construction practices reported to achieve those ratings. It finds a number of strong correlations. The most important is that the ambient air temperature specification is generally higher [average of 60°F (15°C)] for those respondents reporting excellent or good chip seal performance. The same trend was observed with the average amount of time before full-speed traffic was allowed to traverse a newly sealed road, with the best performing seals having an average wait period 28 h. Finally, respondents reporting the best performing seals used more preseal preparation measures and more detailed traffic control measures. The same respondents validated the success of their construction procedures by not requiring a fog or scrub seal to be placed on a freshly chip sealed road.