Optimal overlay thickness to ensure design life of pavements based on empirical deterioration characteristics

Abstract

Road agencies conduct pavement maintenance work to serve a satisfactory level of road service. Among the numerous maintenance designs for asphalt pavement, the overlay would be the most general method at rehabilitation level. However, the overlay thickness has often been uniformly decided for all networks without consideration of the deterioration characteristics of each section. Accordingly, the uncertainty of life spans is very large, and it is not possible to guarantee the reliability of the design life, a critical issue in asset management. Thus, this study aims to suggest a method to draw the optimal overlay thickness to ensure user-defined design life, based on empirical deterioration characteristics. The first step is estimating life expectancies in network and project (section) level, considering Structural Number (SN) and traffic loads (ESAL) by employing the hierarchical Bayesian Markov mixed hazard model. Based on the result, the optimization technique finds the optimal hazard rate satisfying the design life. An empirical study was carried out with 5 years of time-series inspection data from 150 special monitoring sections in the Korean highway network. The result shows that the current overlay design which applies uniform thickness to all road sections is not suitable to ensure design life. This study would be meaningful in developing an overlay design procedure which could prolong life expectancy or save budget. Above all, it can contribute to building a reliable long-term asset management plan, as well as performance-based contract.