Lessons Learned from the Construction and Initial Performance of a Double Chip Seal over a Paving Mat Pilot Project

Single chip seals are used by many agencies to maintain or preserve their roadways. While the construction and performance of single chip seals can be easily found from literature, the construction of double chip seals with and without paving fabric or paving mats is still not common. This paper investigates four double chip seal strategies used in a pilot project constructed on US 395 in Inyo County, California, by Caltrans. Within the double chip seal project limits, eight Performance Evaluation Sections (PESs) using four treatment strategies were established for detailed performance monitoring and evaluation: 1—a 3/8-inch asphalt rubber chip seal followed by a 1/4-inch PME chip seal without pavement-reinforcing fabric (PRF) or a paving mat as a control section; 2—a 3/8-inch PME chip seal over PRF, followed by a 1/4-inch PME chip seal; 3—a 3/8-inch PME chip seal over a paving mat, followed by a 1/4-inch PME chip seal; and 4—an asphalt rubber 3/8-inch chip seal over a paving mat, followed by a 1/4-inch PME chip seal. This pilot project was monitored during construction and evaluated 1 year later to help identify any construction issues and was used to improve the specifications and performance of Caltrans’ chip seals. This paper presents the initial findings following construction, and the one-year performance of the pilot project and lessons learned. The findings presented were accomplished by using these four treatment strategies on a highway with a very adverse high desert climate type and high traffic volumes. Project reviews are also planned for up to seven years to determine the long-term project performance.

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