Reliability Analysis of Minnesota’s Unbonded Concrete Overlay Performance

Minnesota Department of Transportation (MnDOT) has studied pavement performance associated with various interventions in the road network. In this study, unbonded overlay, a major concrete pavement intervention known for its long service life, was examined. Curve fitting was performed, including a comparison of the current decay curves with previous patterns toward a default performance curve, stepwise regression to identify performance variables associated with and predictive of remaining service life (RSL), and reliability (Weibull) analysis to examine the reliability and other performance characteristics of unbonded overlay in the Minnesota network. Reliability analysis resulted in a RSL (scale parameter) of 36 years, which was reasonably consistent with the 35.5 year RSL derived from the MnDOT Highway Pavement Management Analysis (HPMA). It also provided evidence that the unbonded overlay displays an end-of-life failure pattern as well as a 7-year threshold time to failure (location parameter). MnDOT’s sigmoidal decay model predicted the same expected service life (35.5 years) as did the Weibull analysis process (35.8 years). Stepwise linear regression showed a positive correlation between the time from the most recent rehabilitation (TTR_MR) and RSL. The other explanatory variables including RQI_Spike and time from original construction to intervention (TTR) were found to be non-significant in the prediction of RSL.