A Methodology for Identifying Zero-Stress Time for Jointed Plain Concrete Pavements

摘要

This study focuses on identifying the zero-stress time (TZ) in Jointed Plain Concrete Pavements(JPCP)s. TZ is the time when the concrete slab is sufficiently strong to deform (thermallyexpand/contract and hence curl) despite the existing external restraints, including the friction atthe base/slab interface. It is critical to be able to identify TZ so that the temperature gradientpresent in the slab at TZ, known as the built-in temperature gradient, can be characterized.In this study, TZ was established through the instrumentation of thirty-six concrete slabsin four different JPCP construction projects. Strain-temperature behavior in each slab was usedto identify TZ. The slabs in each project were paved at different times of the day: morning, noon,early afternoon and late afternoon to investigate the effects of the ambient curing conditions onTZ. The degree of hydration corresponding to TZ (α_(TZ)) was established for each slab.The field data was used in the development of a model for predicting α_(TZ) as a function ofthe concrete water-to-cement ratio, unit weight, early-age elastic modulus and slab thickness.