A Fracture Energy Approach to Model the Thermal Cracking Performance of Asphalt Rubber Mixtures

Authors: Aleksander Zborowski, Kamil E. Kaloush



During the Asphalt Rubber 2006 conference in Palms Springs – California, the authors reported on the development of predictive equations to evaluate thermal fracture of Asphalt Rubber mixtures. The paper concluded by recommending a fracture energy modeling approach to truly capture the thermal cracking performance of asphalt rubber mixtures in the field. This paper is a follow up effort on the AR2006 study and recommendation. A major
accomplishment of this new study is the development of a new Crack Depth Fracture Model that is based on utilizing fracture energy.
The paper discusses how the existing Thermal Cracking Model (TCMODEL) TCMODEL, which is an integral part of the Mechanistic Empirical Pavement Design Guide (MEPDG), falls short in properly predicting the observed thermal cracking resistance of Asphalt Rubber mixtures in the field. Necessary revisions and refinements of the existing IDT test protocol were made, and an IDT test results database was created and used in the development of
a new Crack Depth Fracture Model that was based on utilizing fracture energy. The new fracture energy model is presented and validated with laboratory test results and field observations. Recommendations on changes to the existing TCMODEL in the MEPDG are made.

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