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Warm Mix HRA – they said it Couldn’t be Done!


Some said it couldn’t be done, that was incentive enough for us to do it!

As our industry rapidly evolves to address the need to reduce the carbon footprint in construction, Leiths contributes by continuing to research and develop more sustainable road surfacing materials.

Wanting to add to our list of lower carbon and lower energy consumption products, Leiths partnered with Aberdeen City Council in trialling an industry leading Hot-Rolled Asphalt mix (HRA) using Warm Mix technology. This technology allowed us to manufacture the material at temperatures of 30-400C less than conventional HRA.

One of the risks associated with producing HRA at lower temperatures is having the Pre-Coated Chippings (PCC) not properly embedded into the surface and adequately bonding to the HRA.  Leiths addressed this risk by properly designing the mix; planning to work; holding briefings with the operational staff and placement crews; and by close monitoring at every stage. 

As a result, Leiths was able to produce a high quality pavement that will perform as designed with the added benefits of:

- Energy and resource savings due to the lower mixing temperatures

- Improved working conditions due to lower emissions of fumes, aerosols and odour at both plant and work sites

- Quicker public reopening of new traffic surfaces, and

- Improved sustainability due to the reduced thermal aging of the bitumen

In addition to the product innovations, the carbon savings on this project by using warm mix technology are equivalent to taking 20,000 plastic bags out of production.