Verification of Curling In PCC Slabs At FAA National Airport Pavement Test Facility

During the testing period from the summer to winter of 1999, heavy weight deflectometer (HWD) tests were routinely conducted on the three Portland Cement Concrete (PCC) test items in the FAA's National Airport Pavement Testing Facility (NAPTF). The analysis of the HWD data indicates that the measured deflections at the center of slabs remain almost the same but at the joints and corners, the measurements vary significantly. In wintertime, the deflections at the joints and corners are significantly larger than those measured in the summer. In addition, the joint load transfer capability, defined by the ratio between unloaded and loaded side deflections (LTD), was lower in winter. Also, the dummy joints received lower values than the doweled joints. A stronger nonlinear relationship between corner deflections and loads was also observed in the wintertime. The analysis indicates that the slab shapes varied all the time but were always curled up and more significant for slabs resting on a stronger subgrade in wintertime. It has been found from the HWD data that the calculated LTDs could be very different when the HWD loading is applied on both sides of the joints, indicating that LTD may be sensitive to traffic direction. However, the sum of the above two deflections (SDs) still remain almost the same for both traffic directions. The SDs varied significantly from the summer to the winter, or it is sensitive to curling state of the slab. Therefore, the parameter SD that has not been used often in engineering practice may be a good indicator for investigating the slab curling.

Authors: Edward H. Guo, Wayne Marsey