Structural evaluation is perhaps more difficult for asphalt-overlaid concrete (AC/PCC) pavement than for any other pavement type. This is partly due to the inadequacies of available tools to analyze the complex behavior of composite pavement structures, and partly due to the lack of guidance available for interpretation of structural analysis results. Guidelines for deflection data analysis and interpretation of backcalculation results for AC/PCC pavement are presented in this paper.

In recent research, a procedure has been developed for backcalculation of concrete slab and foundation moduli from deflections measured on asphalt-overlaid concrete (AC/PCC) pavement. This backcalculation method quickly and repeatably produces results consistent with other backcalculation methods and consistent with observed distress and the condition of cores, with efficiency and repeatability unmatched by iterative or database search methods.

Guidelines were also developed for practical interpretation of the backcalculation results, by this or any other reliable method. These guidelines were developed for evaluation of AC/PCC pavement but are also relevant to PCC pavement evaluation. Backcalculation can yield many useful results, including mean PCC slab and foundation moduli, variability in moduli, percentage of backcalculated moduli below a selected critical level, identification of specific areas with unusually high or low moduli, and the relationship of slab and foundation moduli to type, quantity, and severity of distress.