Early Age Response of Jointed Plain Concrete Pavements to Environmental Loads

The behavior of jointed plain concrete pavements during the initial time period following paving provides vital information concerning how the pavement structure will perform throughout its intended life. A primary contributor to the development of stresses in pavements following paving comes from environmental conditions, particularly from differential thermal and moisture gradients throughout the pavement depth.The following study analyzes the response of a jointed plain concrete pavement structure during the period of initial concrete strength gain (first 72 hours after paving) and throughout a full cycle of seasonal conditions (first ten months after paving). The response of the pavement structure is characterized through the analysis of on-site climatic conditions, analysis of embedded strain, temperature, and moisture gages, as well as through manual field data collection.The field data collection effort conducted for this study is described in terms of an overview of the site conditions, construction parameters, instrumentation utilized and data acquisition employed. The climatic response of the pavement structure was analyzed, with particular emphasis on curling and warping.This study investigated the strain response of the pavement structure with respect to the parameters influencing strain location and magnitude. Both the early-age (the first 72-hours after paving) and the seasonal strain response with respect to spatial characteristics and level of restraint were analyzed.Based on the results from this study, the built-in construction gradient was found to be 0.7 °F/in. at the edge of the slab and negligible at midpanel. In general, the measured curvature tended to be 7 percent larger for unrestrained slabs when compared to restrained slabs. The tie and dowel bars produced a reduction in strain with changes in temperature of approximately 0.34 to 0.41 microstrain/°F at locations near the joints. The strains measured in the restrained slabs also tended to be more uniform than for the unrestrained slabs. A couple of seasonal observations were also made. The average strain at midslab was -450 microstrain in the fall and -600 microstrain in the winter with diurnal strain fluctuations being the lowest in the winter. This study also evaluated the drying shrinkage that occurred in the slab. Drying shrinkage increased drastically during the first 50 days after construction and continued through the winter but began to decrease during the spring when rain events occur more frequently