Reuse of paint sludge in road pavements: Technological and environmental issues

This paper presents some of the results obtained in a research project focused on the use of paint sludge (PS) as a modifying agent in the production of bituminous binders for paving applications. The scope of the project was to provide an innovative, sustainable and profitable solution to waste management problems which automotive industries have to face worldwide as a result of the production of PS. The authors applied for a patent which defines the industrial process for the production of PS modified binders (PSMBs). Measurements and analyses which were considered relevant for the assessment of technological feasibility included evaluation of: PS physical characteristics, PSMB high-temperature viscosity and PSMB storage stability. Environmental issues were addressed by considering PS chemical composition, gaseous emissions during PSMB production, and leaching behavior of bituminous mixtures containing PSMBs. Obtained results show that with a proper adaptation of the PSMB production process (i.e., PS drying at a higher temperature than 105°C) it is possible to comply with technological and environmental requirements such as those related to storage stability and to gaseous emissions during PSMB production and laying of bituminous mixtures. Leaching tests, aimed to evaluate runoff water quality, show no substantial difference in the release of substances in water between standard bituminous mixtures and bituminous mixtures prepared with PSMBs.