Pavement preservation is an important tool departments of transportation (DOTs) use to maintain and enhance the conditions of their highways. Pavement preservation treatments do not improve the structural capacity of a pavement; rather they delay pavement deterioration by sealing cracks, preventing pavement oxidation, and, in the case of surface fog seals, rejuvenating the existing pavement surface layers. Rejuvenating fog seals consist of a rejuvenator, which is delivered as an emulsion; however, recently non-emulsion based seals have also been introduced to the industry. Traditionally petroleum-based rejuvenators have been used in such applications, though in recent years bio-based rejuvenators have also been increasingly utilized. Preservation treatments utilizing asphalt emulsions as the binder have generally been considered secondary to hot mix asphalt (HMA) technologies. As such, these treatments have not been researched to the same extent as HMA technologies. Over the past 5 years, however, the AASHTO 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, twelve standards have been approved.
Rejuvenating fog seals are believed to have the ability to modify the surface binder of aged, cracked pavement surfaces. If they can rejuvenate the surface, they may be able to restore functionality to old pavements and allow them to function for longer without total reconstruction. This is an area that has not received adequate investigation. There are new materials on the market that warrant a review of those materials and the efficacy of rejuvenating seals.
The objectives of this project are to (1) determine the extent that rejuvenating fog seals penetrate and rejuvenate the asphalt pavement; (2) determine how the different rejuvenating compounds impact the underlying pavement; (3) determine how the impact and the desired performance for rejuvenating seal are measured and quantified in the laboratory and in the field; and (4) determine the optimum dose of rejuvenator required to provide the desired performance and friction properties.
The ETF recently prioritized its efforts to reestablish rejuvenator seals as standard preservation practice and views this research project as critical to both DOT materials (emulsion purchase specifications) and maintenance (application performance specifications) and to divisions wishing to safely extend pavement life at minimal cost.
Direction from the AASHTO Special Committee on Research & Innovation: Consider coordination with NCHRP project 09-63, “A Calibrated and Validated National Performance-Related Specification for Emulsified Asphalt Binder.”