Finite element viscoelastic simulations of rutting behavior of hot mix and warm mix asphalt overlay on flexible pavements

The implementation of warm mix asphalt and chemical compaction aids is becoming more widespread. A growing number of contractors are using warm mix asphalt technologies to reduce mixing and compaction temperatures, reduce fuel consumption, improve compatibility, and increase economic and environmental value. In 2009, three pavement overlay projects were constructed in the state of Iowa using both hot mix aphalt and warm mix asphalt mixes to compare their performance. A series of dynamic modulus tests were conducted using field and laboratory mixtures of hot mix asphalt and warm mix asphalt. For each project, twelve specimens, including six hot mix asphalt specimens and six warm mix asphalt specimens, were tested to determine dynamic modulus and phase angles. These results were used as input parameters for designing each pavement in the mechanistic-empirical pavement design guide (MEPDG) and in finite element viscoelastic simulations to predict the performance behavior of warm mix asphalt and hot mix as phalt. A step-by-step framework to convert dynamic modulus results to Prony series to use in finite element simulation models was developed and is detailed for one mixture. This research compared predicted rutting damage by MEPDG design, estimated rutting from finite element simulations, and measured rutting in the field. The results show that MEPDG based on linear elastic theories may overestimate the rutting of pavements while the finite element based on viscoelastic theory accurately predicted the rutting of pavements. Therefore, a series of proposed calibration coefficients from this research can be useful for industrial applications and design engineers to modify and correct MEPDG overlay design thicknesses on top of hot mix asphalt, and jointed plain concrete pavement surfaces with either hot mix asphalt and warm mix asphalt mixtures.