Consideration of Finite Slab Size in Backcalculation Analysis of Jointed Concrete Pavements

The effects of finite slab size and load transfer across joints usually are ignored in the backcalculation analysis of jointed concrete pavements when the test load is applied on an interior point of the slab concerned. Although correction factors have been proposed to take these effects into consideration, the benefits of doing so have yet to be established, and their use has not been accepted in routine backcalculation tests. A study was conducted to assess whether significant improvements in the accuracy of backcalculation analysis could be achieved by considering finite slab size and load transfer at joints in the backcalculation analysis of jointed concrete pavement systems. Five backcalculation methods were evaluated with measured deflection data extracted from the Long-Term Pavement Performance database, and comparisons were made with the measured pavement properties. The analysis based on the measured field data offered affirmative evidence of the theoretical lower- and upper-bound estimates provided by backcalculation solutions based on the infinite slab model and one-slab model, respectively. An error analysis was presented to show that the infinite slab model gave superior solutions as compared with the one-slab model. A nine-slab model that considered finite slab size and joint load transfer effects resulted in only marginal improvements in the backcalculation results. Two finite slab size models that applied correction factors to infinite-slab solutions were found to produce the largest errors among the five backcalculation models studied.