During the late 1980s and 1990s, the Pennsylvania Department of Transportation constructed numerous miles of its new drained jointed plain concrete pavement (JPCP) design. Portions of the JPCP were built in reconstruction efforts, and some of the JPCP was placed as an overlay on rubblized sections of old jointed reinforced concrete pavement. The performance of the new JPCP has been quite variable; in some instances, it has performed very well, and in others some slab cracking and joint-related concerns have occurred. Two different base types were used beneath the JPCP: an untreated open-graded granular material (OGS) and an asphalt-treated permeable base. In general, the cracking has occurred only in the sections with the untreated OGS base layer. The cracking was top-down, transverse cracking that is generally located near midslab. A comprehensive study of the cracking was performed to identify its probable cause and to develop a repair (or preventive repair) technique. The results of this study showed that the top-down cracking was caused by a combination of excessive upward slab curling, loss of slab support (slab lift-off), and repeated heavy-truck loadings. The built-in slab curling was also found to be a major contributor to the observed top-down cracking. One of the keys to the analysis effort was quantifying the amount of built-in curling in the slabs; the techniques are described that the research team used to determine the amount of built-in curling in the in-place JPCP slabs.
Abstract