Thickness Tolerance for Portland Cement Concrete Pavements

The thickness tolerance limit currently used by the Texas Department of Transportation for portland cement concrete pavements was developed about 50 years ago, when the pavement thickness was normally less than 10 in., and no additional study on the tolerance limit has been conducted since its development. Because the current thickness tolerances are independent of the design pavement thickness, they are very tight, especially for thicker pavements. These tight tolerances give difficulties in construction and in the use of nondestructive testing (NDT) methods for slab thickness determination because errors of NDT methods depend on the thickness. In this study, the sensitivity analysis of the slab thickness has been conducted to investigate whether the current thickness tolerance can be loosened and to propose acceptable thickness tolerance limits. The concepts to find the thickness tolerance have been developed on the basis of various methods, including the AASHTO pavement life prediction equation, the mechanistic distress prediction model, and fatigue failure models. The sensitivity of slab thickness to pavement performance has been investigated with those methods. The analysis results clearly show that the thickness tolerance should be dependent on pavement thickness. On the basis of the analysis results, reasonable approaches for thickness tolerance determination have been proposed.