Fibre reinforced asphalt

Fibre reinforced asphalt is asphalt to which small, very strong fibres — usually aramid — are added during production to slow down cracking, ravelling and rutting. It is an alternative to polymer modified bitumen (PMB) and reinforcement mesh, with comparable or better field performance against generally a lower environmental impact. On this page we bring the knowledge together: what fibre reinforced asphalt is and how it works in mixes such as porous asphalt (ZOAB), how it compares to PMB, what it means for rutting and asphalt maintenance, and what the costs, environmental performance and field evidence are. The in-depth articles below each work out one part in more detail.

How fibre reinforcement in asphalt works

Asphalt consists of aggregate, sand, filler and bitumen as a binder. Under the influence of traffic loading, temperature fluctuations and ageing of the binder, cracking, ravelling (loosening of aggregate) and rutting (permanent indentation from tyre loads) eventually develop. Open-graded mixes such as porous asphalt (ZOAB) are particularly susceptible to this, because the stone skeleton has less mutual contact than in dense mixes. The article on ZOAB asphalt explains how this Dutch porous asphalt, with around 20% air voids, drains rainwater and dampens tyre noise, and where it is vulnerable.

Fibres are added dry to the aggregate, well before the bitumen, and once distributed through the mix work at microscale as three-dimensional reinforcement: they bridge microcracks (crack bridging), distribute the traffic load better across the mix and hold the mortar bridge between the stones more firmly against ravelling. Aramid fibres — aromatic polyamide — combine very high tensile strength with heat resistance, chemical inertness and low elongation: precisely the properties needed to keep asphalt intact for longer. Even in heat, when the binder softens, the fibres retain their strength and so reduce the likelihood of permanent rutting. The explainer what is fibre reinforced asphalt sets out which paving fibres are used, at which dosage and with which results on the A73 and the N337.

Fibres versus PMB: production and temperature

Traditionally, asphalt is reinforced with polymer modified bitumen or with reinforcement mesh. PMB is harder to recycle and requires a higher production temperature; reinforcement mesh requires a separate, time-consuming operation. Fibre reinforcement combines the best of both: a standard penetration-grade bitumen suffices, and no separate reinforcement layer is needed.

Because penetration-grade bitumen is naturally less viscous than PMB, the mix can be produced at a lower asphalt temperature — in field trials on the A73, around 15 to 20°C lower. That means less energy use at the asphalt plant, fewer fume emissions during laying and a better working environment for road crews, without compromising on compactability or mix quality.

Rutting, maintenance and damage

For road managers, the business case starts with the damage fibres prevent. Rutting makes a road unsafe long before it is technically written off, and well-timed asphalt maintenance — from preservation to replacing the surface course — ultimately determines the annual cost of a road section. Fibre reinforcement acts on both: the mix withstands higher pavement temperatures and heavier loading, and the longer service life pushes back the maintenance cycle. Rutting, permanent deformation in the wheel paths, comes in three types, with severity classes by rut depth that indicate when repair should be planned. Heat plays a large part in it: asphalt has no fixed melting point, and the article at what temperature does asphalt melt shows that bitumen already softens from around 45 to 55 °C on a hot road surface. The guide to asphalt maintenance then lists every measure from crack sealing to mill and inlay, with indicative costs per m² and the service life per surface course. The articles in the Maintenance & damage section explain how rutting develops, which maintenance measures exist and where fibres make the difference.

Environment, standards and certification

The sustainability advantage is now also measurable. The life-cycle assessment carried out within the European FIBRA project found that the PMB mix had the highest environmental impact at cradle-to-gate level — more than a 10% difference on the Environmental Cost Indicator (MKI) compared with the aramid variant. Since 1 July 2026, the PCR Asphalt 2026 determines how the environmental performance of asphalt mixes is calculated uniformly, with a revised energy model that more clearly credits the lower production temperature of fibre mixes.

The environmental-hygiene side is equally regulated. Additives must appear on the OPWA list to be dosed without additional leaching research under an NL BSB® certificate (BRL 9320). AsphaltX® is on that list, with a maximum applicable percentage of 0.1% — well above the recommended dosage of 500 grams per tonne (0.05%).

Costs, tendering and field evidence

The direct premium of fibre reinforcement on the asphalt price per m2 is limited: the cost sits mainly in the fibre itself, not in an extra work step. Research within FIBRA shows that fibre reinforcement can work out cost-neutral compared with PMB in the Dutch situation, provided a comparable service life is achieved — and viewed over the service life, the potentially longer lifespan of the road surface counts in its favour. Anyone wanting to capture those benefits includes fibre reinforcement explicitly in the tender, preferably specified functionally on environmental performance, service life and production experience.

The evidence comes from the field. Within the European FIBRA research project, BAM and Rijkswaterstaat built a trial section on the A73 near Roermond with four variants of the same porous-asphalt surface course, where the fibre variants performed comparably to the PMB reference mix — at a 15 to 20°C lower production temperature and a lower environmental impact. These test sections are monitored over the long term. The articles in the Applications & field cases section cover the project, the measurement results and the use on heavy-duty construction roads.