In some countries recycling of bituminous road materials is a standard alternative for both construction and maintenance. In the UK there is not much need for recycling, but owing to environmental and resource conservation considerations it is gaining ground. Hot mix recycling in UK is carried out either in-situ or at central plants. In-situ mixes are used for wearing course and plant mixes for roadbase, basecourse and wearing course. Trials have been carried out. Material produced complies with specifications. Resistance to permanent deformation has been assessed in laboratory tests. Performance of recycled roadbase is generally as good as of conventional roadbase. Stiffness modulus is not significantly different, and fatigue life is unaffected. Measurements of longitudinal profile for in-situ mixes show that profile variance is better than on control surfacings, probably due to longer wheelbase of Remix machine. Rutting is the same. Skid resistance is not influenced, and macrotexture is similar. Performance of plant mixes was assessed by measuring longitudinal profile, rutting, deflection and cracking; all these are similar to conventional surfacings. DOT specifications have been revised to permit use of recycled materials for roadbase, basecourse and wearing course on motorways and trunk roads. Maximum permitted admixture is 10% for wearing course, 30% for roadbase and basecourse.
Samenvatting