Title:

Temperature dependent plastic response in the design and analysis of pavement structures with cold in-place recycled layer

Cold In-Place Recycling (CIR) allows the existing asphalt pavement layer to be recycled directly on site. The mixture that is generated through this rehabilitation process usually includes approximately 2% new added asphalt binder (added as emulsified or foamed asphalt); for this reason, these mixtures are often considered as partially bonded materials. The objectives of this research were to demonstrate the importance of incorporating plasticity behavior and the effects of temperature on mechanical properties of CIR in the design of pavements with CIR layers. A 2D axisymmetric finite element model was designed using ABAQUS software. The model was verified for elastic and elastoplastic responses using layered elastic software JULEA and finite element pavement analysis software ILLIPAVE, respectively. Different temperature distributions and three pavement structures were subjected to the same loading applications and their responses were compared to determine the regions and pavement types where plasticity behavior of CIR layers is most critical. In addition to traditional asphalt pavement design responses (tensile strain in HMA layer and vertical strains on subgrade), this study adopted the Deviator Stress Ratio for CIR layers as a critical rutting potential response. Comparisons of critical pavement responses from the ABAQUS elastoplastic model and corresponding design lives demonstrate that plasticity plays a major role in the pavement structural response to traffic loading, primarily at high temperatures and for thinner pavement structures. The pavement designs that do not include the plasticity response in subsurface layers may overestimate design lives by more than 50%.

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