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Together with a number of leading contractors, Nynas has been working since the late 1990s to develop emulsions for the production of cold mix asphalt. Despite very good test results, the technology has found it difficult to gain acceptance across a broad front. But the time now seems to be ripe.
Cold mix asphalt is manufactured using either an emulsion – a mixture of bitumen and water – or foamed bitumen. As the aggregate doesn’t need to be heated, thus the mixing and application temperatures are much lower, both energy consumption and carbon dioxide emissions are a fraction compared with traditional asphalt. The working environment is also improved, as both heat and fumes are avoided.
Another benefit is that cold mix technology is ideal for recycling old asphalt. It’s possible in principle to manufacture a cold mix asphalt that consists solely of recycled asphalt. The corresponding figure for conventional mix is approximately 20-30%. This, of course, can significantly reduce environmental impact.
A cold mix is not necessarily cheaper than a hot one. However, surfacing work can proceed more quickly if you use an emulsion, which combined with the possibility of maximising recycling means significant savings. This flexibility is also evident in the fact that cold mix asphalt can in some cases be stored overnight and used the next day if there’s some left over.
When cold mix technology was introduced, it was used exclusively on the less heavily used parts of the road network, but in recent years, thanks to successful development work, cold surfaces have been used on trunk roads in the UK, motorways in the Baltic region and container terminals in Sweden.