Fracture Characterization of Polymer Modified Mixes for Applications in Diverse Climatic Region

Challenges of Quantifying Cracking Resistance for Arizona Mixes

Although cracking resistance research has been carried out extensively in other states, a large amount of the work is not immediately applicable to Arizona, where the climate is substantially more extreme both in heat and in cold than many other parts of the country.

A wide range of mixes, including fine-dense-graded Marshall mixes and Superpave dense-graded and asphalt-rubber-modified gap-graded mixes, are currently used by various agencies. Binder grades used in these projects also show great variability.

In addition, polymer-modified binders are increasingly used in various resurfacing applications in Arizona and elsewhere. All of these factors result in mixes with substantially different cracking resistance characteristics.

The main goal of this study is to develop a balanced mix design framework applicable across diverse climatic regions and to better understand the fracture behavior of polymer-modified mixes. 

Combining Advanced and Practical Fracture Testing Methods for Plant and Laboratory-Produced Mixes

Laboratory-produced mixes with a range of binder grades, from PG70-10 to PG76-34, were combined with plant-produced mixes commonly used by state and local agencies.

The mixes were subjected to advanced and index fracture tests over a wide range of temperatures. The tests included SCB, DCT, Ideal-CT, I-FIT, and Complex Modulus.

A Fracture Energy-Based Approach for Diverse Climatic Regions

The effectiveness of SBS polymer modification was highlighted using dense-graded mixes and stone-matrix asphalt (SMA).

The concept of critical thermal cracking temperature was introduced, at which the fracture energy threshold was reached. The applicability of the critical cracking temperature concept was demonstrated to develop a preliminary performance-based mixture and binder selection protocol in diverse climates.