Abstract
The Illinois Department of Transportation (IDOT) has been constructing concrete overlays of existing concrete pavements on the Interstate system for nearly 50 years. The construction of two bonded concrete overlays and eight unbonded concrete overlays have been documented to date. IDOT has also constructed one thin unbonded concrete overlay. An evaluation of performance history of the eleven pavement sections was undertaken. The following conclusions can be drawn from the evaluation of the concrete overlays in Illinois: 1) bonded concrete overlay performance on the Interstate system varied widely, and should only be used in the future judiciously, with engineering judgment; 2) unbonded concrete overlays performed consistently well, with all observed pavements exceeding or expected to exceed their design lives and design traffic factors; and 3) the thin unbonded overlay was too new to conduct a meaningful analysis of performance.
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