A review of in-place cold recycling/reclamation in Canada

The current concept of in-place cold reclamation/recycling of bituminous pavement was introduced in Canada in 1983. It is estimated that more than 40 million square metres of pavement have been rehabilitated using an in-place cold reclamation/recycling method over the last twenty years in Canada. The driving engine of in-place reclamation/recycling is associated with the concept that the existing pavement is the source of primary materials to create a new pavement material. The existing pavement materials are reclaimed and transformed into a sized material, which is then mixed with a bituminous binder and laid down in-place. The reclamation/recycling of the pavement is performed without heat and depending on the existing pavement conditions, the operation is performed using the Cold In-place Recycling process (CIR) or the Full Depth Reclamation/Stabilization process (FDR). The bituminous binder is either an emulsified bitumen or a foamed bitumen. The environmental benefits associated with in-place cold reclamation/recycling are significant. There is nearly no transportation of pavement materials and the processes are performed without heat. The energy consumption for the production of in-place cold recycled material is approximately 20 % of the energy necessary to produce new hot bituminous materials for an equivalent quantity. As a result the emission of greenhouse gas is also greatly reduced. The recycled mixtures have mechanical properties that differ significantly from those of standard hot bituminous mixtures. The voids in the mixture are high and as a result the stiffness of the recycled mixtures is typically lower than that of standard hot bituminous mixtures. The high void content of recycled mixtures offers an improved mitigation of reflective cracking, which before the introduction of in-place reclamation/recycling was one of the primary causes of pavement failure in Canada. This paper outlines the concepts associated with in-place cold reclamation/recycling of bituminous pavements with a particular focus on project selection and design practices. The binder selection is discussed in detail as well as the equipment, construction procedures and performance of recycled mixtures.