Catalyst Regeneration of RAP-Binder in Asphalt

Roads play a significant role in the quality of our lives, and asphalt is one of the key substances used to create roads. As the cost of asphalt materials increase, federal and state agencies, design engineers, road contractors, and asphalt suppliers search for methods to decrease material costs without compromising the pavement performance. One such sustainable method is the use of recycled materials to compensate for part of the virgin materials. The use of recycled asphalt pavement (RAP), generated from milling of old pavements, can potentially protect the environment and conserve resources; however, incorporation of RAP in virgin asphalt may be a challenging task. The aged asphalt binder extracted from RAP (hereinafter referred to as RAP-binder) generally cannot be used as a direct substitute for virgin asphalt binder due to its aging during service life and the resulting changes in its chemical composition and properties. Asphalt binder’s chemical composition has a very delicate balance of polar to non-polar molecules, small to large molecules, and aromatic to paraffinic compounds. When there is an imbalance in this composition, incompatibility between the components may occur, resulting in poor engineering performance. Such an imbalance can originate from the aging of asphalt binder. The blending process of RAP-binder with virgin asphalt binder is not well understood yet, and the chemical complexity of the RAP-binder is difficult to work with. RAP has been used with virgin asphalt binder in Louisiana and other states for a significant period of time; however, many state agencies are becoming more concerned with the use of high percentages of RAP (> 25%) with virgin materials. This is a potential issue because the increasing percentage may adversely affect the performance of asphalt pavements, eventually resulting in higher pavement maintenance and rehabilitation costs. RAP-binders are difficult to reuse because they often contain associated molecules with very high molecular weights. Due to the polarity gained during oxidative aging, the asphaltene-type molecules form associated structures. These high molecular weight components are responsible for RAP-binder’s increased viscosity and certain deteriorated rheological properties. As a remedy, rejuvenators, softening agents, softer binders, and antioxidants can be added to asphalt that contains high amounts of RAP-binder to rebalance their rheological properties. Another approach to increase the amount of RAP-binder would be to modify the binder’s chemical composition with the help of a reagent or catalyst. Catalysts have been already positively impacting our lives with clean energy and green chemistry. This proposal will study effective ways to incorporate a high amount (> 25%) of RAP content in asphalt mixtures using a novel approach of introducing a catalyst that can disrupt the associated molecules formed during aging. The use of a catalyst such as a Lewis acid to break the associated molecules in the RAP-binder is a new promising approach. The project will investigate the effect of a Lewis acid catalyst such as Iron (III) chloride and Zinc chloride on the chemical composition of RAP-binder. These catalysts are known to catalyze the conversion of coal to liquid product, but the mechanism of action is not well understood. A detailed study of the chemical changes that occur to the RAP-binder before and after the modification will be carried out. The various virgin binder and RAP-binder blends with catalyst will be subjected to extensive chemical characterizations. This research is anticipated to facilitate the use of higher RAP contents in road construction. The outcomes of this study reduce the cost of highway construction and develop more environmentally friendly practices.

• Record URL:
  https://transet.lsu.edu/research-in-progress/
• Supplemental Notes:
  • 20BLSU19

Language

• English

Project

• Status: Completed
• Funding: $ 74998
• Contract Numbers:

  69A3551747106

• Sponsor Organizations:

  Office of the Assistant Secretary for Research and Technology

  University Transportation Centers Program
  Department of Transportation
  Washington, DC  United States  20590
• Managing Organizations:

  Transportation Consortium of South-Central States (Tran-SET)

  Louisiana State University
  Baton Rouge, LA  United States  70803
• Project Managers:

  Mousa, Momen

• Performing Organizations:

  Louisiana State University

  3660G Patrick F. Taylor Hall
  Civil and Environmental Engineering
  Baton Rouge, LA  United States  70803
• Principal Investigators:

  Spivak, David

• Start Date: 20200801
• Expected Completion Date: 20220201
• Actual Completion Date: 0
• USDOT Program: University Transportation Centers Program

Subject/Index Terms

• TRT Terms: Asphalt; Binders; Catalysts; Chemical analysis; Chlorides; Iron compounds; Mix design; Reclaimed asphalt pavements; Zinc
• Subject Areas: Highways; Materials; Pavements;

Filing Info

• Accession Number: 01757514
• Record Type: Research project
• Source Agency: Transportation Consortium of South-Central States (Tran-SET)
• Contract Numbers: 69A3551747106
• Files: UTC, RIP
• Created Date: Nov 10 2020 4:26PM