Aggregate particles can be coated with relatively small additions of bitumen by mixing cold moist aggregate with bitumen foam produced by injection of saturated steam. This process, known as the foamed bitumen process, has been widely adopted as an accepted method of treating recycled and reclaimed materials for road construction and maintenance. The quality of this material can be improved by the addition of small amounts of hydraulic or pozzolanic binder, and this is now fairly standard practice. The process can be used to treat materials in situ, or the pavement can be broken up and removed from its location and treated off site or `ex situ'. This study examined several ex situ produced foamed bitumen materials laid in experimental pavements with the objective of determining their performance characteristics and comparing the relative properties of the ex situ produced materials with those of in situ produced materials. This information was used to develop guidance on pavement design using ex situ materials and provide recommendations for material source approval. The research indicated that the thickness of a pavement can be reduced by up to 20mm if ex situ replaces in situ mixed material. This study will help with the implementation of recycled materials and lead to more sustainable pavement construction. (Author/publisher)
Abstract