A suburban city street in Kansas was rehabilitated with a 50 mm (2 in.) Portland Cement Concrete (PCC) thin overlay, commonly known as ultra-thin whitetopping (UTW). The construction and performance of this UTW project have been described in this report. The project, constructed in the Spring of 1995, incorporated the following design features: 0.9 m x 0.9 m (3 ft x 3 ft) panels versus 1.2 m x 1.2 m (4 ft x 4 ft) panels, plain versus fiber reinforced concrete, and sealed versus unsealed joints. The project has performed fairly well to date although some test sections needed periodic maintenance and all of the test sections except two have been overlaid as of October 2001. Experience on this project shows that the UTW overlay can be easily built with conventional equipment and locally available materials. UTW also permits a skid-resistant finish to be applied. Excellent smoothness can also be obtained although the slab thickness is very small. Corner cracking appears to be the most dominant distress type, though it was observed that bond existed between the concrete and the asphalt layers even for the cracked panels. The bond appeared to degrade with time. Joint spacing has a significant effect on performance. The sections with smaller joint spacing appeared to perform better. The performance of the sections with fibers in concrete was inconclusive. Also, joint sealing did not appear to affect the performance.

TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 338: Thin and Ultra-Thin Whitetopping summarizes available information to document how state departments of transportation and others are currently using thin and ultra-thin whitetopping overlays among various pavement rehabilitation alternatives. The report covers all stages of the proper application of whitetopping overlays, including project selection, design, materials selection, construction, maintenance, and eventual rehabilitation or replacement.

This report presents the latest information on the design, construction and performance of portland cement concrete (PCC) overlays. It describes the four types of PCC overlays that are commonly used in highway pavement applications: bonded PCC overlays, unbonded PCC overlays, conventional whitetopping and ultra-thin whitetopping. Recommended applications, critical design elements, current overlay design methodologies, recommended construction practices, and performance highlights are described for each overlay type. Information is also provided on the selection of PCC overlays as possible rehabilitation alternatives for existing pavements. Taken together, this document addresses the current "state of the technology" of PCC overlays placed on both existing PCC pavements and on existing hot-mix asphalt pavements.

Pack: Book and CDInternationally, full-scale accelerated pavement testing, either on test roads or linear/circular test tracks, has proven to be a valuable tool that fills the gap between models and laboratory tests and long-term experiments on in-service pavements. Accelerated pavement testing is used to improve understanding of pavement behavior,