Fibre asphalt production temperature explained
Fibre reinforced asphalt can be produced at a lower temperature than asphalt with PMB. Why that is, and what it means for energy and the environment.
One of the most frequently cited advantages of fibre-reinforced asphalt is its lower production temperature compared with asphalt containing polymer modified bitumen (PMB). But why is that, and what does it mean in concrete terms for production and environmental impact? This article explains.
Why does PMB need a higher temperature?
Polymer modified bitumen contains added polymers (often SBS) that make the binder more flexible and tougher, but also more viscous. To mix this more viscous bitumen properly with the aggregate and distribute it evenly, a higher temperature is needed — in practice quickly around 180-185°C.
Why can fibre-reinforced asphalt be produced at a lower temperature?
Fibre-reinforced asphalt combines fibres with a standard penetration bitumen (for example 70/100), which is naturally less viscous than PMB and therefore mixes well at a lower temperature. The fibres themselves do not need a high temperature to do their job — they are added dry to the aggregate, well before the binder is added, and are heat-resistant enough to comfortably withstand the standard production temperatures of penetration bitumen.
Concrete figures from practice
Practical research on the A73 (FIBRA project) shows the following temperature difference between the tested mixes:
• Reference with PMB: ~181°C.
• Reference with pen bitumen + cellulose fibre: ~160°C.
• Aramid fibre (Twaron 1080) + pen bitumen: ~165°C.
The difference between the PMB reference and the fibre-reinforced mixes is therefore around 15-20°C.
What does this mean for energy consumption?
A lower production temperature directly means lower energy consumption at the asphalt plant, where the aggregate and binder must be heated. At large-scale production (asphalt plants typically produce hundreds of tonnes per day), a difference of 15-20°C adds up to a substantial saving in fuel consumption and associated CO₂ emissions.
What does this mean for the working environment?
A lower processing temperature also means fewer fumes and aerosols released during laying of the asphalt — relevant for the health of road workers who work with the material daily. In addition, practical tests showed that fibre-reinforced mixes at a lower temperature are easier to work by hand than the hotter PMB mix.
Does the lower temperature affect quality?
Practical tests showed no negative effect of the lower production temperature on the compactability or laboratory production of the fibre-reinforced mixes. This is because the properties of the penetration bitumen (which is naturally already workable at a lower temperature) are matched to the temperature difference — in other words: the combination of binder type and temperature is internally consistent.
In conclusion
The lower production temperature of fibre-reinforced asphalt is no coincidence, but a direct consequence of choosing a standard penetration bitumen instead of PMB. The result: lower energy consumption, fewer emissions during processing, and a better working environment for road workers — without compromising on quality.