The crossover temperature: significance and application towards engineering balanced recycled binder blends

Abstract

Increased quantities of asphalt-based recycled materials can be incorporated in asphalt paving mixtures by using recycling agents. Previous studies demonstrated that restoring the required performance grade (PG) by the inclusion of recycling agents may not be sufficient to guarantee long-term durability. In this study the crossover temperature was used to characterise the viscoelastic properties of asphalt binders at the intermediate service temperature range for asphalt pavements. Durability thresholds for crossover temperature with aging were proposed on a trial basis from a correlation to the Glover–Rowe parameter. In combination with high PG, crossover temperature was used to evaluate rheological balance: resistance to early rutting and long-term embrittlement. Practical recommendations are provided in terms of appropriate materials selection (base binder, recycled, binders, and recycling agents) towards engineering long-lasting rejuvenated binder blends with increased quantities of recycled materials. Limitations and additional considerations for extending the rheological balance approach to evaluate polymer-modified materials are also summarised.

Keywords:

• crossover temperature
• compatibility
• recycling agents
• binder aging

Acknowledgements

The Qatar National Research Foundation (QNRF), Dr. Dallas Little, and Dr. Eyad Masad contributed to Figure 6 with supporting data from project QNRF NPRP 5-506-2-203. The authors are thankful to Dr. Charles Glover, Dr. Gayle King, and Dr. Geoffrey Rowe for valuable technical discussions. Appreciation is extended to Akash Bajaj, Thomas Henz and Mengge Yuan of the Texas A&M Transportation Institute for their efforts and contributions in the laboratory.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Lorena Garcia Cucalon http://orcid.org/0000-0003-3139-1457

Fawaz Kaseer http://orcid.org/0000-0002-9443-4429

Edith Arámbula-Mercado http://orcid.org/0000-0002-1435-3662

Amy Epps Martin http://orcid.org/0000-0001-7207-5368

Nathan Morian http://orcid.org/0000-0001-8231-6786

Elie Hajj http://orcid.org/0000-0001-8568-6360

Additional information

Funding

This work was made possible by the financial support provided by the National Cooperative Highway Research Program (NCHRP) through project NCHRP 9-58: “The Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios”.