Long life pavements with recycled concrete in unbound granular layers

Abstract

The construction of unbound granular layers (UGLs) in pavement construction is mainly based on empiric knowledge of the behaviour of natural aggregates. Is it possible to transfer this behaviour to the performance of recycled materials in UGLs? In an in-situ test-section, divided into 12 sub-sections, BASt has evaluated the performance of UGL made from recycled concrete and different percentages of recycled bricks in comparison to an UGL of natural aggregates for ten years. The data analysis of regularly executed Falling Weight Deflectometer measurements show a sufficient bearing capacity according to the requirements for all different sub-sections. There are nevertheless significant differences due to the composition of the UGLs in the different sub-sections. Regardless of a sufficient bearing capacity other damage has become noticeable. Transversal cracks appeared after a first severe winter and during the next years in the sub-sections with a high percentage of recycled concrete in the UGL. The observed number of cracks correlates strongly with the composition of the UGLs. For a long service life of such pavements, however, an adopted structure and a better determination of their performance in laboratory trials have then been taken into account with regard to the post-hardening behaviour of recycled materials to avoid early damage.