Field observations of the early-age behavior of jointed plain concrete pavements

Newly constructed rigid PCC highway pavements with open graded stabilized base courses have been found to develop non-uniform, transverse saw-cut joint-crack developments and extensive slab movement behaviors, which cause unwanted premature joint failures. Phase I of this study determined the variables associated with the sporadic, large joint opening development by literature review, laboratory tests and some field collected data. The large joints were believed to develop at early-ages of the slabs curing (within the first 48 hours). The early-age stress developments were found controlled by slab temperature history, material property development and frictional resistance. Minimal recommendations for corrects to the behavior were suggested.;The scope of the Phase II investigation was to perform extensive, continuous monitoring of the behaviors of newly constructed slab sections examining concrete temperature behaviors by slab depth and location, joint-crack developments by location, width and growth during the first 72 hours from initial placement. Re-evaluation of the Phase I theoretical pavement analysis and early-age concrete material property developments were also required by additional laboratory testing, slab behavior and actual strain measurement data collection.;The results of the field investigations and re-evaluations were that the analysis required time, location and concrete maturity dependency along the slab lengths. Crack developments were found to consist of primary and secondary formations. The primary cracking was found to be progressive, propagating development behavior dictated by the region of slab end movements determined by the slab to base course interaction, material property developments and slab temperature behaviors. Controlled primary crack development by increasing crack frequencies would reduce the average crack widths and restrict the extensive slab movements. Possible solutions have been examined and will be verified and tested during Phase III of the project