Ultra-Thin Concrete Overlays on Existing Asphalt Pavement

Abstract

In 1991 an experimental project was built on a Louisville, Kentucky landfill access road. The purpose was to evaluate the feasibility of concrete whitetopping overlays less than 4 inches thick for residential streets, parking and other low-volume applications. The landfill site provided accelerated loading conditions and weight-monitored truck traffic data. Two sections with different thicknesses were built, one 2 inches and the other 3.5 inches. The experiment also employed unconventional 6 foot and 2 foot joint patterns. These constituted the major variables of the test project. The landfill traffic conditions necessitated "Fast Track" construction of the thin overlay experiment. The access road was only closed over one weekend and provided just a 4L5 hour window to complete the construction work. This paper includes a description of the ultra-thin overlay performance. As of September 1992, both sections on the project are performing well and have carried over 585,000 Equivalent Single Axle Loads (ESAL's). The designs have out-lived predictions by conventional pavement theory and models. The authors will discuss the influence of the joint spacing and the overlay bonding on the bending stress conditions within the overlay slabs. This paper will also document the design and construction of this project. The cooperation of all parties involved was a major factor and an outstanding tool for innovation. The ultra-thin concrete whitetopping concept could induce major changes to the construction and resurfacing of asphalt roads, streets and parking areas throughout the United States. The promise shown by this initial experiment warrants further experimentation and discussion.