A review of the use of recycled solid waste materials in asphalt pavements

The construction and maintenance of UK roads consume large amounts of quarried aggregates. The use of secondary (recycled), instead of primary (virgin), materials helps easing landfill pressures and reducing demand of extraction. However, concerns over inferior road performance and additional costs have hindered the widespread use of secondary aggregates in such applications. This is especially the case in surface layers of asphalt pavements that may represent a value application for recycled solid waste materials (SWM). Waste glass, steel slag, tyres and plastics are selected for this study, which reviews standards and literature for technical requirements, as well as the performance of asphalt pavements constructed using such recycled materials. Waste arising and management indicates that although there is a large potential for supplying secondary materials, a few factors have effectively depressed such recycling activities. Such barriers are described here and may also apply to the secondary use of other SWM. After identifying and quantifying such barriers a brief discussion suggests ways of their removal.