Portland cement concrete (PCC) and asphalt concrete (AC) exposed to aqueous film-forming foam (AFFF) have become an increasing challenge and environmental liability. Of critical importance is the extent to which these AFFF-impacted materials are serving as a source of per- and polyfluoroalkyl substance (PFAS) release to the environment due to PFAS leaching to stormwater runoff and migration to the subsurface. The extent of this leaching for existing in-place materials, removed/stockpiled debris, and recycled materials is unknown.
The overarching goals of this project are to attain insight into PFAS leaching from AFFF-impacted PCC and AC to inform the management of these materials, understand the potential transformation of PFAS during PCC and AC recycling, and develop PFAS transport models that can translate standardized leaching test data to actual field leaching data. These goals will be met by addressing the following objectives for both laboratory-created and field AFFF-impacted concrete materials:
The project team will perform a series of bench-scale experiments with field-exposed and laboratory-exposed PCC and AC to elucidate and quantify the fundamental mechanisms controlling PFAS transport in these materials. The tasks parallel the objectives and include: (i) PFAS characterization and concentration profiling in AFFF-impacted PCC and AC samples obtained from DoD sites; (ii) experimental quantification of the thermodynamics and kinetics of PFAS sorption/desorption in laboratory-created and field (desorption only) samples, using intact, damaged, crushed, and recycled PCC/AC; (iii) experimental measurements of PFAS transport in saturated and unsaturated PCC and AC; (iv) experimental characterization of surface runoff from PFAS-impacted PCC and AC through physical simulation of field surface runoff conditions; and (v) development of practical and implementable models to estimate PFAS transport in intact, damaged, crushed, and recycled PCC and AC materials.
Currently, there are no proven approaches to determine whether PFAS leaching from construction materials under environmentally relevant conditions poses potential risks. Specifically, it is unknown whether PFAS concentrations measured in these materials relate to PFAS leaching or whether existing standardized leaching tests can be used to predict PFAS leaching under various field conditions. Such information is needed so that these materials can be cost-effectively managed and resources are not unnecessarily committed to treatment (e.g., removal/disposal, application of sealants).
Results from this project are expected to provide a fundamental understanding and implementable models to determine PFAS fate based on measured PFAS concentrations in construction materials, and recommendations on the management of AFFF-impacted PCC and AC. The project team expects that data generated in this research will provide mechanistic insights into the leaching behaviors observed in projects evaluating standard leaching-based approaches. With the complementary mechanistic information, it may be possible to identify management strategies to mitigate overall PFAS leaching from PCC/AC. Furthermore, the project team anticipates that the data generated from this research will provide the science-based information needed to make decisions on PFAS mass discharge-based criteria rather than simply selecting concentration-based criteria for PCC/AC management. (Anticipated Project Completion - 2027)