Release of PAHs from reclaimed asphalt mixtures into the water environment after passivation by cold in-place recycling technology

The paper deals with an analysis of the amount of 16 polycyclic aromatic hydrocarbons (PAHs (Polycyclic aromatic hydrocarbons—16 defined by US EPA.)) released from reclaimed asphalt mixtures used in base layers of road surfaces and in binder layers in road construction using cold in-place recycling. For the ten samples tested, the sum of 16 PAHs was determined directly for the crushed asphalt mixture and for its 24-h leachate. The crushed asphalt samples were used to make cylindrical asphalt specimens of the cold recycling mixture. The asphalt specimens were prepared to simulate as realistically as possible the use of the mixtures in road reconstructions implementing the cold in-place recycling technology, which should ensure the passivation of PAHs. The asphalt specimens were subjected to a dynamic leaching test under laboratory conditions with regular replacement of the leaching liquid. The results showed that the concentration of PAHs released into the water environment from the test specimens (passivated material) was approximately 40–50% lower than the amount of PAHs released from the asphalt mixtures in the 24-h leaching test. When compared to the input PAH concentrations in the asphalt mixtures (36–1323 mg.kg⁻¹), on average, only 0.15% of PAHs is released from the passivated material. Dynamic leaching test has shown that the wrapping of the original asphalt mixture with a new binder and its subsequent compaction leads to the preservation of PAHs in the original material at such a level that their total concentrations are reduced by two orders of magnitude.