Resin-bound recycled-tyre roads for extreme traffic noise reduction

Traffic noise abatement can be drastically improved by incorporating elasticity into a road's top layer to suppress tyre vibrations.

The EU-funded ‘Poroelastic road surface: An innovation to avoid damages to the environment' (PERSUADE) project aims to develop such an ultranoise-abating material using recycled tyre shreds.

Poroelastic road surfacing (PERS) consists of tyre-shred–derived rubber granules, mixed in varying proportions with stone aggregates and bound with synthetic resin (in place of bitumen) and some other ingredients with specific functions. PERSUADE researchers developed two different laboratory-derived mixes that they first tested in small-scale tracks in Denmark, Belgium, Sweden and Slovenia.

To test their surfaces further, the team built full-scale tracks with different stone/rubber/binder mixes, of varying length and on roads carrying different traffic loads in Denmark, Sweden, Poland, Belgium and Slovenia. While noise reduction was achieved (8 up to 10 dBA compared with conventional asphalt), they experienced technical problems with surface construction and durability: the first Danish test track e.g. had to be replaced due to a too liquid binder causing premature failure. This problem has been solved and apart from the Polish section, where one had a problem with the tack layer, all test tracks are doing fine.

Despite these setbacks, PERS shows enormous promise in extreme noise reduction, offering an interesting (and cheaper) alternative for noise screens, requiring less energy to construct than bituminous top layers, and reducing used-tyre waste. The PERSUADE consortium is monitoring the full-scale test tracks for a variety of parameters, including skid resistance, winter behaviour, noise reduction and durability.