Abstract
This paper includes a study of curling and warping in jointed Portland Cement Concrete (PCC) pavements based on the temperature and moisture conditions at the time of paving and immediately following construction. Field data collected from fully instrumented sections at two locations, Phoenix, Arizona and Mankato, Minnesota, were used in this study. These sections were paved at nighttime and daytime respectively. Temperature data were collected through the slab thickness at different times of the day and profile measurements were recorded along the longitudinal edge, transverse edge and the diagonal of the slab. As the data at Mankato were collected for three days immediately following construction and later at the end of 15 days, 40 days and two years, this section provided data suitable for the study of early age and longterm behavior of PCC slabs. On the other hand, the test sections at Arizona with data collected at 3 days and 40 days provided a comparison of the effects of slab length and restraint conditions on the curling and warping of PCC slabs. Material properties determined from lab tests were used in modeling using the Finite Element Method (FEM) program, ISLAB2000. Based on theoretical analysis, an “equivalent temperature gradient” was determined at different ages to account for the combined effects of built- in curl, shrinkage and creep. It was observed that paving during daytime induced high negative gradients that further increased as the pavement underwent drying shrinkage and creep. At the end of two years, as a result of creep in concrete, the pavement appeared to relax its upward curling and warping. Furthermore, the equivalent temperature gradient increased with larger slab length and decreased with the presence of load transfer mechanisms. Finally, it was concluded that in addition to actual temperature gradients, the effects of not only built- in curl but also shrinkage and creep have to be considered in pavement analysis and design.
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