Accounting for temperature susceptibility of asphalt stiffness when designing bonded concrete overlays of asphalt pavements

A bonded concrete overlay of asphalt (BCOA), also known as whitetopping, is a thin concrete overlay placed upon a distressed asphalt pavement. The asphalt-resilient modulus is kept constant in current BCOA design procedures. This practice results in an underestimation of the damage as compared to when the hourly temperature variation of the asphalt is considered. The framework to establish an equivalent asphalt modulus involves generating a database of hourly middepth asphalt temperatures. This database should include hourly temperatures for different BCOA structures and a large range of geographical locations representing different climatic conditions. The hourly middepth asphalt temperatures are then used to generate hourly asphalt moduli using master curves. Through fatigue equivalency, the equivalent asphalt moduli are calculated for each month. In order to establish the relationship between the asphalt modulus and middepth temperature, the United States was divided into seven different zones according to their annual mean ambient temperatures. For each zone, models for predicting adjustment factors were developed for the asphalt modulus. Designers can calculate the monthly asphalt stiffness over the design life using the adjustment factor and reference month stiffness regression models. This asphalt stiffness is then corrected for aging and fatigue using the models incorporated into the AASHTO Pavement ME program. The methodology presented here has been incorporated into the recently developed BCOA mechanistic-empirical design and analysis procedure.