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Many agencies place hot-mix asphalt overlays on deteriorating jointed or cracked portland cement concrete pavements to improve the ride, protect the pavement structure, and reduce noise. Reflection cracking of the joints and preexisting cracks through the overlay is a persistent problem. In climates such as that in Wisconsin, the initial reflective cracks often appear within a year or two. The Wisconsin Department of Transportation and the City of Milwaukee tried a fine-aggregate, asphalt-rich, polymer-modified asphalt mix interlayer to absorb joint movements, delay reflective cracking, and protect the existing pavement. Four Wisconsin projects are discussed. In the first project, constructed in 1996, the interlayer showed no effect on delaying reflection cracking within the first 3 years. Later projects, however, included specifications for performance-related design tests for flexural beam fatigue and Hveem stability and were overlaid with improved mixtures to complement the flexible interlayer. The later projects showed an average 42% improvement in the time to the appearance of surface cracks compared with the control sections. Furthermore, cores taken from the projects showed that even when the overlay cracked, some of the interlayer samples did not, even under severe conditions, thus further protecting the underlying pavement structure. Other major factors contributing to the cracking delay included the type of concrete pavement, concrete patches, and climate.

The design and performance of concrete pavement test sections constructed in Wisconsin in the summer of 1997 to validate the constructability and potential cost-effectiveness of alternative concrete pavement designs incorporating variable dowel strategies and slab thicknesses are described. To reduce the number of dowel bars across the transverse joints and remain consistent with dowel bar installation equipment currently used within the state, four alternative dowel patterns were examined. Test sections were constructed with alternative dowel materials including fiber-reinforced polymer (FRP) composite dowels, solid stainless steel dowels, and hollow core mortar-filled stainless steel dowels as well as a variable slab thickness. Postconstruction monitoring including deflection testing, joint distress surveys, and ride quality surveys have been done. Observed joint distress including minor spalling, chipping, and fraying is mainly due to joint saw cut operations. No transverse joint faulting or slab cracking has been observed. Deflection testing to date indicated general uniformity of foundation support in all test sections. Deflection testing has also been done across transverse joints to quantify deflection load transfer efficiency. Joint tests in the fall of 1997 and 1998 indicated reduced load transfer efficiencies in all test sections compared with control sections, most notably in the FRP composite dowel test sections and the placement alternative with three dowels in each wheelpath. Ride quality surveys indicated general uniformity among sections.