Cold asphalt recycling with 100% reclaimed asphalt pavement and vegetable oil-based rejuvenators

Abstract

Cold in-place recycling methods are used to different extents but are often not very suitable for small construction sites. Therefore, a new process was developed using vegetable oil-based rejuvenators to reactivate the old binder of the reclaimed asphalt pavement (RAP) material. Briefly summarised, RAP is produced on-site from the old pavement, then sprayed with water and rejuvenator before it is mixed thoroughly and immediately compacted. Process parameters have been optimised in laboratory tests with gyratory compacted specimens. It turned out that rejuvenators with used cooking oil did give comparable results to virgin rapeseed and linseed oil. Only the outcome of the water sensitivity tests was not satisfactory, as the wet specimens showed a considerable loss of tensile strength. However, the damage was only temporary and the stability recovered to the original value after drying of the water-saturated specimens. In a second step, four cold mixtures with different rejuvenator compositions were compared in a trial field section with conventional hot mix asphalt concrete. In situ testing with the mobile load simulator MMLS3 showed good performance for three of four cold mixture pavements, which was comparable to the rutting behaviour of hot mix asphalt. Several wearing courses but also surface layers for small secondary roads have been constructed during the last three years. No significant damage has been reported for these cold mixture pavements so far. Particularly, the use of used cooking oil as a rejuvenator is promising due to its low price. Since only recycling products are used and no transport of the cold mixture is necessary for in situ recycling, this new cold recycling system is highly ecological as well.

Keywords:

• cold recycling
• rejuvenator
• vegetable oil
• curing
• laboratory tests
• field trials

Acknowledgements

The project was funded by the Swiss Commission for Technology and Innovation CTI. The authors would like to express their special thanks to the staff of the Empa laboratory road engineering/sealing components and Morant AG.