ECO-RAP

With an annual production of 37 million tons, reclaimed asphalt pavement (RAP) from road milling in France is a valuable resource for road construction. RAP recycling is part of a circular economy approach, helping to preserve natural resources (bitumen and aggregates) and reduce landfill disposal. However, the incorporation rate of RAP in road pavements remains low (19.9%), even though studies suggest that rates of 30–50% are technically feasible. This is mainly due to the poor chemical quality of RAP and its potential toxicity. Indeed, older road materials may contain tar, significantly increasing the concentration of toxic organic compounds in pavements incorporating recycled materials. To mitigate health risks, hot RAP recycling is subject to a maximum threshold of 50 mg/kg of dry RAP for the 16 priority polycyclic aromatic hydrocarbons (PAHs) listed by the US EPA. However, this regulation only applies to the solid fraction, without considering the fumes generated during the manufacturing and application of asphalt, even though they are inhalable and easily dispersed into the environment. Moreover, only PAHs are regulated, whereas recent studies have shown the presence of methylated, nitrated, oxygenated, nitrogenated, and sulfur-containing PAH derivatives (referred to here as PAH+), which can be even more toxic than their parent compounds. The ECO-RAP project aims to develop a methodology to increase the recycling rate of RAP in new asphalt while effectively managing health and environmental risks. The project will study the influence of RAP incorporation rates, binder types, and asphalt manufacturing temperatures (110–160°C) on fume toxicity as well as the physical and rheological properties of the resulting pavements (cracking resistance, compactibility, and water sensitivity). The objective is to anticipate the health risks associated with fumes based on the chemical composition and physical properties of the raw materials used. A predictive model will be developed from the project’s experimental results to define (i) the optimal mix ratio between virgin materials and RAP and (ii) the best manufacturing methods (hot, cold, or intermediate temperature mixing) to ensure high pavement quality, minimal toxic fume emissions, and maximum RAP recycling. This transdisciplinary project brings together air chemistry specialists, toxicologists, statistical modelers, road engineering experts, and an industrial partner to facilitate the transfer of findings to practical applications. The teams will leverage advanced tools and methods such as proton transfer reaction mass spectrometry (PTR-ToF-MS) and high-resolution mass spectrometry (HRMS) for chemical analysis, a laboratory-scale pilot to simulate industrial asphalt production, effect-directed analysis (EDA) for identifying toxic chemical species, and deep learning approaches for predictive modeling (PLS, neural networks). This work will optimize recycling processes while reducing health risks for workers and nearby residents of construction sites and asphalt plants. The project’s results will contribute to improving the sustainable management of road infrastructure while addressing health and environmental concerns related to RAP recycling.