Twenty-four existing concrete pavement sections covering a wide range of performance levels, ages and types of subbase, surface layers and joints were selected for evaluation in order to determine the causes of the problems in the pavements with poor performance. Each section was evaluated by a condition survey, falling weight deflectometer (FWD) tests, laboratory tests on core samples, and a structural analysis. FWD tests were preformed at both midday and midnight. Loads were applied at four different positions on the slab, namely, slab center, slab corner, edge center and joint center. The measured FWD deflections at various locations were then used along with the results of the laboratory tests on the Cored samples and a finite element program, FEACONS IV, to estimate the pavement parameters. With the pavement modeled by the estimated pavement parameters, the maximum stresses caused by critical temperature-loading conditions were computed using the FEACONS IV program. The computed maximum stresses were then compared with the flexural strength of the concrete to evaluate the structural adequacy of each test section.
The critical stress analysis method, which was used in this study, was shown to give good prediction of the structural performance of the test sections. The use of a very stiff subbase is not beneficial to the performance of a concrete pavement, as indicated by the results of the critical stress analyses as well as field surveys. High elastic modulus of the concrete and long slab length were also shown to produce adverse effects to concrete pavement performance.