Date of Award

12-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Civil Engineering

Advisor

Ravichandran, Nadarajah

Committee Member

Juang , Hsein

Committee Member

Putman , Bradley

Abstract

Rubberized half-warm mix asphalt (HWMA) is being considered as one of the promising and sustainable solutions to the current environmental and economic crisis of asphalt industry. A fully mechanistic characterization and performance analysis of this mixture subjected to realistic loading and temperature conditions is necessary before its application in a practical pavement structure. The objective of this research is to characterize the viscoelastic properties of rubberized HWMA at different temperatures and to develop and validate a finite element model of a tire-pavement structure. In this research, a generalized Maxwell model is chosen to represent the time dependent stress-strain behavior of rubberized HWMA. The dynamic modulus test results are used to calculate the viscoelastic model parameters and the resilient modulus test results are used to calculate the elastic modulus of the mixture. A finite element model is developed to conduct numerical experiment of dynamic modulus test. The model parameters are fine-tuned by comparing the finite element simulation results and the laboratory dynamic modulus experimental results. Results show that the viscoelstic model represents the actual rubberized HWMA behavior well in the high loading frequency range and shows deviation in low frequency range indicating that another model or a modification to the existing model is required to represent the behavior of rubberized HWMA for a wide range of loading frequency. The same procedure is followed to calibrate model parameters for neat hot mix asphalt (HMA), warm mix asphalt (WMA) and HWMA mixtures to compare the differences in model predictions and to use in full scale modeling. In addition to the material model, the mechanistic behavior of flexible pavement under realistic loading and boundary condition requires accurate representation of the vehicular load on the pavement. The load from the tire in this study is modeled using both a moving distributed load and rolling tire in contact with pavement in 2- and 3-dimensional simulation domains to understand the relative accuracy of various combinations of simplified and complex modeling techniques and their central processing unit (CPU) cost. The contact pressure and length, which are critical for accurately predicting the pavement performance, are calibrated by matching the pressure distribution exerted at the top of the pavement, especially for 2D simulations. Temperature dependency of pavement materials is considered by incorporating model parameters from low to high range temperatures. The computed longitudinal strain and vertical stress are compared with the measured field data found in the literature. The results show that the values computed with the viscoelastic material model in 3D simulation domain agree well with the measured data. Fatigue and rutting performance of rubberized and neat HWMA pavements is evaluated using the 3D rolling tire-pavement model. Results of neat binder mix have better fatigue resistance compared to the rubberized mixture. Similarly, the effect of layer thickness, pavement temperature and traffic speed are also computed to gain further insights into the applicability of various asphalt mixtures. Finally, the 3D pavement-rolling tire model seems to be a promising tool for obtaining valuable information about mechanistic behavior of various geometric and material combinations for economical design.

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