Promoting innovation in road pavements through the use of cold processes and recycled materials: an example of cold recycling with 90 percent of recycled materials

This paper describes a study on cold bituminous mixes containing fire extinguisher powders (REP) and Reclaimed Asphalt Pavements (RAP). It is well known that fire extinguishers should be maintained (REP disposal) at regular intervals and therefore many issues can arise in terms of waste management. Furthermore, cold mixes use less energy and produce fewer emissions than hot mixes, but more efforts are still needed to develop a generally acceptable laboratory design method for asphalt emulsion cold mixes. Therefore, in order to pursue the objectives of the feasibility study on cold recycling of RAP and REP, the following main tasks were carried out: analysis of process; REP and RAP characterization with emphasis on thermogravimetry analyses; cold recycling and mix testing. A reduction in energy consumption and in green house gas emissions compared to conventional practices was obtained. A more sustainable design and construction practices that incorporate high percentages of recycled material content was proposed. As for mix design and mechanical performance, studies and experiments allowed to address the following key-issues: allocation of REP powders with respect to the aggregate skeleton; potential for the use of REP-RAP recycled mixes in order to optimize the resulting fire performance. The results indicate that the application of fire extinguisher powders into cold mixes can result quite satisfactory both on a mechanical and environmental standpoint. This information could help decision makers to prioritize rehabilitation candidates and to select more sustainable rehabilitation strategies and procedures in order to achieve the best overall condition.