Low-temperature thermal treatment of Portland cement concrete contaminated with per- and polyfluoroalkyl substances

AFFF-impacted concrete pavements represent a large and persistent reservoir of per- and polyfluoroalkyl substances (PFAS) with limited disposal options. This study demonstrates that the naturally high calcium-to-fluorine molar ratio (>50:1) in Portland cement concrete (PCC) enables near-complete PFAS mineralization at 500 °C, well below the > 1000 °C required for conventional incineration. Mineralization onset varied by PFAS structure (350-450 °C), and at 500 °C, PCC converted 95 to > 99% of PFAS-derived fluorine to stable inorganic products within 1 min. This rapid conversion reflects the higher thermal conductivity of PCC relative to granular activated carbon (GAC) and the reactivity of calcium phases with fluorinated intermediates formed after headgroup cleavage. Destruction and removal efficiency (DRE) exceeded 99.99% across all matrices tested, including GAC, sand, and gravel, yet only the cement-based materials achieved high mineralization. GAC mineralization remained below 40% even after 15 min, demonstrating that DRE alone is an insufficient metric for evaluating PFAS thermal treatment. FTIR off-gas analysis confirmed that fluorinated products of incomplete destruction (PIDs) accounted for less than 2% of the initial fluorine mass during PCC treatment. Demonstration using two field-collected AFFF-impacted concrete cores spanning nearly three orders of magnitude in PFAS concentration (0.1 and 48 μg/g total PFAS) confirmed average DREs exceeding 99.9%, with greater than 95% of fluorine recovered as mineralized products in the solid. These results establish low-temperature thermal treatment as a viable, scalable approach for PFAS-contaminated concrete and highlight the need for total fluorine measurements alongside targeted PFAS analysis to verify true mineralization.