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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 asphalt. 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. [ABSTRACT FROM AUTHOR]

The AASHTO mechanistic-empirical pavement design guide ( MEPDG) pavement performance models and the associated AASHTOWare pavement ME design software are nationally calibrated using design inputs and distress data largely from the national long-term pavement performance (LTPP). Further calibration and validation studies are necessary for local highway agencies' implementation by taking into account local materials, traffic information, and environmental conditions. This study aims to improve the accuracy of MEPDG/pavement ME design pavement performance predictions for Iowa pavement systems through local calibration of MEPDG prediction models. A total of 70 sites from Iowa representing both jointed plain concrete pavements (JPCPs) and hot mix asphalt (HMA) pavements were selected. The accuracy of the nationally calibrated MEPDG prediction models for Iowa conditions was evaluated. The local calibration factors of MEPDG performance prediction models were identified using both linear and nonlinear optimization approaches. Local calibration of the MEPDG performance prediction models seems to have improved the accuracy of JPCP performance predictions and HMA rutting predictions. A comparison of MEPDG predictions was also performed between two software programs to assess if the local calibration coefficients determined from one software program is acceptable with the use of another software program, which has not been addressed before. Few differences are observed between one software program and MEPDG predictions with nationally and locally calibrated models for: (1) faulting and transverse cracking predictions for JPCP; and (2) rutting, alligator cracking, and smoothness predictions for HMA. With the use of locally calibrated JPCP smoothness (IRI) prediction model for Iowa conditions, the prediction differences between the two software programs are reduced. Finally, recommendations are presented on the use of identified local calibration coefficients with the two software programs for Iowa pavement systems. [ABSTRACT FROM AUTHOR]

• Converting laboratory dynamic modulus tests to Prony Series as inputs to Abaqus. • Time-depending mechanical behavior by finite element viscoelastic simulations. • Empirical evaluation of simulations to predict long term performance of asphalt. • Extensive field measurements for validating simulation methodologies. Research implementing new pavement technologies often focuses on material characterization; however, expanding the research to study and validate how new technologies influence pavement design is needed for continual improvement. Numerical analysis approaches use laboratory mixture data to predict field performance. This study compares predicted rutting by MEPDG design, estimated rutting from Finite Element (FE) simulations, and actual rutting performance in the field. Ten years ago, warm mix asphalt research was underway to measure the effect of warm mix asphalt (WMA) additives and lower production temperatures on performance. WMA benefits include reduced mixing/compaction temperatures, reduced fuel consumption, and improved compatibility. In 2009, three asphalt overlay projects were constructed in Iowa using both hot mix asphalt (HMA), and WMA mixes to compare their performance. A series of dynamic modulus tests were conducted to determine dynamic modulus and phase angles of HMA and WMA mixtures. The dynamic modulus results were used to develop FE viscoelastic simulations to predict the rutting of HMA/WMA pavement sections. Iowa's pavement management system provided field rutting of WMA/HMA sections. Also, pavement sections were evaluated using mixture input parameters in the Mechanistic-Empirical Pavement Design Guide (MEPDG). The results showed MEPDG based on linear elastic theories might overestimate the rutting of asphalt pavements, especially overlays placed on Jointed Plain Concrete Pavement (JPCP). In contrast, the FEM based on viscoelastic theories more accurately predicted the rutting of pavements. Calibration coefficients are proposed by this study, which may be useful for design engineers and industrial applications to correct and modify MEPDG overlay design thicknesses for HMA/WMA mixes placed on HMA and JPCP surfaces. [ABSTRACT FROM AUTHOR]