Pavement preservation treatments delay pavement deterioration by sealing cracks, preventing pavement oxidation, and, in the case of surface fog seals, rejuvenating the existing pavement surface layers. Rejuvenating seals are believed to have the ability to modify the surface binder of aged pavement surfaces. If these seals can rejuvenate the surface, they may be able to restore functionality to old pavements allowing them to function for longer without total reconstruction. Traditionally petroleum-based rejuvenators have been used in such applications, however bio-based rejuvenators also have been increasingly utilized.
Preservation treatments utilizing asphalt emulsions as the binder generally have been considered secondary to hot mix asphalt (HMA) technologies and therefore have not been researched to the same extent. Over the last 5 years, the AASHTO Technical Services Program (TSP2) Emulsion Task Force (ETF) has made a concerted effort to improve the state of the science in emulsion technology and to create consistent, performance-based standards (specifications, test methods, design practices, etc.) that are sponsored by AASHTO and are not vendor specific. To date, 12 standards have been approved. The emergence of new materials on the market warrant further study of rejuvenating seals to determine the extent the new materials penetrate and rejuvenate the asphalt pavement.
The objectives of this project are to (1) provide the characteristics of the rejuvenator based on chemistry and rheology; (2) determine how different rejuvenating compounds are penetrating and rejuvenating the underlying pavement; (3) determine how the desired performance for a rejuvenating seal is measured and quantified in the laboratory and field; (4) determine the life extending benefit and impact on friction properties of a rejuvenating seal measured and quantified in the laboratory and field; (5) determine how practitioners may design an optimum dose and/or application rate for a rejuvenator required to provide the desired performance and friction properties; and (6) document suggested practice prepared in conformance with AASHTO standard format.
Accomplishment of the project objective(s) will require at least the following tasks.
Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objectives. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objectives.
Task 1. Conduct a literature review related to rejuvenating seals. Include a discussion related to but not limited to the following: (1) the characteristics of the rejuvenator based on chemistry and rheology; and (2) distinction between softening and rejuvenating the bituminous materials.
Task 2. Review previous work related to similar preservation treatments (both national and international), and current types of rejuvenating technology used for rejuvenating fog seals, and, where available, the history of application and performance.
Task 3. Collect a representative selection of samples of current technologies. It is anticipated that this will include both petroleum-based and bio-based rejuvenators.
Task 4. Prepare an interim report that documents the work completed in Tasks 1 through 3. Include a detailed work plan for the work anticipated in Phase II. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the project panel. Work on Phase II of the project will not begin until the interim report is approved and the Phase II work plan is authorized by the NCHRP.
Task 5. Determine best method, including innovative analytical means, for determining the efficacy of rejuvenating additives in rejuvenating seals in terms of penetration and effect on the underlying pavement. It is anticipated that analysis of the surface tension of the rejuvenating compositions, permeability of pavements, and the interrelationship of these parameters will play a role in this analysis.
Task 6. Develop a method to determine the life extending benefit of a rejuvenating seal measured and quantified in the laboratory and field.
Task 7. Develop a method to determine the effect of rejuvenating agents on pavement friction and their impact on macrotexture and microtexture properties before application, upon curing, and during the pavement life-cycle.
Task 8. Determine best practical means of determining the correct dosage for different types of rejuvenators in the rejuvenating seals application.
Task 9. Using the findings from Tasks 5 through 8, provide draft language—regarding the recommended actions and practices to implement performance-based evaluation of rejuvenating seals—for consideration by AASHTO in a future publication or update in a format used by the TSP2 ETF. This will henceforth be referred to as the “AASHTO Deliverable”.
Task 10. Prepare final deliverables which should include, at a minimum (1) a Conduct of Research Report documenting the entire research effort; (2) the AASHTO Deliverable as a standalone document; (3) prioritized recommendations for future research; (4) a PowerPoint-style presentation describing the background, objectives, research approach, findings, and conclusions; (5) a stand-alone technical memorandum titled “Implementation of Research Findings and Products” (see Special Note E for additional information); (6) a presentation of findings to two AASHTO committees or councils concerned with pavement; and (7) a draft article suitable for publication in TR News (Information regarding TR News publication may be found on the TRB webpage https://onlinepubs.trb.org/onlinepubs/trnews/info4contributors.pdf.
STATUS: Research in progress.