Fracture Characterization of Polymer Modified Mixes for Applications in Diverse Climatic Region
Contact: Hasan Ozer ([email protected])
Researchers: Samuel Castro Brockman and Ashraf Alrajhi
Sponsor: Southwest Pavement Technology
Timeline: July 2021 – July 2022
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.
Main goal of this is to develop a balanced mix design framework that can be used in diverse climatic regions and develop a better understanding of 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 starting 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 experiments conducted over a wide spectrum of temperatures. The tests included SCB, DCT, Ideal-CT, I-FIT, and Complex Modulus.
A Fracture Energy Based Approach for Diverse Climatic Regions
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 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.
Figure 1: Exemples of the diverse fracture testing of the mixes a) SCB Test with CMOD controll, b) DCT test.
Figure 2: Preliminary proposed thermal cracking test temperature and binder selection chart