Analysis of Emulsion and Hot Asphalt Cement Chip Seal Performance

Abstract

The study collected both design and performance data on 342 chip seal projects worth nearly $30 million that had been completed in the Texas Department of Transportation’s Atlanta District since 1996. One hundred sixty five of these projects were emulsion projects utilizing CRS-2P as the binder and 177 were asphalt cement projects using AC15-5TR binders. The external variables were minimized as Atlanta District had used the same seal coat contractor, Area Office, construction season, asphalt suppliers, and aggregate on all its districts chip seal projects for the past 12 years. The one difference in the aggregate was that the AC15-5TR used a lightweight aggregate that was precoated unlike the emulsion seals’ lightweight aggregate that was not precoated. Thus, the comparison of the two binders can be made in a very direct manner, and the results can be viewed as specific to the engineering properties of the binders themselves without the need to qualify the conclusions based on independent parameters that could not be mathematically removed from the data. The study found that the emulsion chip seals performed as well as the hot asphalt cement seals and were the more cost effective of the two alternatives. Emulsion chip seals also furnished a better long-term friction course as measured by the skid number.