During the production and laying of Hot Mix Asphalt (HMA) for the construction and maintenance of road pavements, high process temperatures cause the release of emissions into the atmosphere.

Despite measures like higher stacks, filters, and scrubbers, these odour emissions remain a nuisance, often representing a cause of unquestionable and persistent annoyance for the city dwellers. The HMA odorous flows can severely limit the usability of the territory, becoming the object of numerous legal disputes between citizens and industry, above all when the plants are located near to the urban and already settled areas of a city.

The asphalt emissions consist of hydrocarbon aerosols, vapours, and gases, including volatile organic compounds and polycyclic aromatic hydrocarbons. Odor perception varies due to factors like source characteristics, atmospheric dispersion, and receptor sensitivity, making objective measurement challenging.

In addition, the sustainability of the entire process of HMA production suggests the opportunity to recycle polyurethane materials, often structured as foams, by inserting them as additives in the mixtures. The link between these two aspects becomes clear considering that these additives can trap some of the substances responsible for odour emission.

The present project has two main objectives:

• to ascertain the behaviour of road paving mixtures with polyurethane foam residues as additives, to guarantee the circularity of materials through reuse;
• to reduce odour emissions during preparation and after paving of the mixture.

The first objective requires to ascertain the mechanical and structural behaviour of the mixtures to achieve optimization in terms of technical properties and economy.

The second objective requires the installation of a newly conceived sensor chain, which has been adopted for the first time for measures of this nature. This installation must also be planned in a way that ensures reliability, safety, and continuity.

The proposed approach is mainly experimental, with numerical modelling of some aspects, and includes:

• laboratory activities in a wind tunnel
• field measurements in a pilot mix production plant

The reduction in the perception of odorous substances is achieved by verifying:

• the effectiveness of wind turbulence in accelerating the decay processes
• the effectiveness of additives in the mixture for trapping these substances

To achieve the objectives, the research group brings together:

• the National Research Council (CNR) in Naples, with documented experience in formulating mixtures containing the additives
• the University of Parma, with expertise in sensor technology and physical modelling in wind tunnels

The technology has already a TRL 5, hence the framework of the project is sufficient to increase the overall performances to TRL 7.

The objectives of the proposal are SMART. In fact:

• Specific: clearly defined and related to environmental and production problems that have been clearly delineated
• Measurable: in terms of reducing the environmental impact of recycling polyurethane foam and in terms of reducing odour emissions
• Achievable: the technology adopted is part of the proponents' know-how and requires specialization that can be acquired through the research project
• Realistic: fitting into known problems and widely used technological processes
• Time-bound: correctly embedded in the logic of Design of Experiments (DOE)