Sealants and Other Management Strategies for PFAS-Contaminated Concrete and Asphalt

Abstract

Purpose of Review The unique properties of per- and polyfluoroalkyl substances (PFASs) have seen their widespread adoption, subsequent accumulation in the environment and concern regarding potential environmental effects. Globally, airfields and paved firefighting training surfaces are hotspots for accumulation of PFAS due to extensive use of aqueous film-forming foams (AFFF). Evidence from contaminated concrete and asphalt airfield and training pavements suggests they may serve as an enduring PFAS source. This review investigates sealants as remediation technologies to minimise PFAS mobilisation from pavements drawing on current knowledge of remediation options for soils, sediments, surface and groundwaters. Recent Findings The review did not identify any published sealant information specific to PFAS. Our analysis showed that surface and penetrative sealants may offer an immediate solution via encapsulation of PFAS residues in concrete and asphalt. The most promising surface sealants likely to minimise water ingress and PFAS leaching are selected polymers and (modified) bitumen, owing to the relatively low cost, good adhesion, trafficability and chemical, heat and UV resistance. Potential also exists to enhance PFAS immobilisation using additives to absorb or otherwise chemically bind PFAS. Prospective penetrative sealants include silicates or siloxanes that bind to internal mineral surfaces and/or fill pores to restrict PFAS mobility. It is likely that combinations of surface and penetrative sealants will be required to meet functional, operational and management requirements with respect to new or existing contamination in concrete or asphalt pavements. Summary At present, few if any sealants have been evaluated for their ability to bind or mitigate PFAS mobility. This review serves as a starting point for further studies to evaluate their short or long-term effectiveness in immobilisation of PFAS residues in in situ or ex situ concrete and asphalt. Several knowledge gaps along with suggestions for future research have been made.