The inherent properties of iron and steel slag make it an ideal aggregate for base and surfacing asphalt products (bitumen bound application of slag aggregates). However, as they all exhibit different characteristics the properties have to be matched to the requirements of the specific material type.

The properties are assessed in accordance with the requirements of the European standard EN 13043 (Aggregates for bituminous mixtures and surface treatments for roads, airfields and other trafficked areas), and the relevant national guidance documents.

In addition to the environmental benefits of reducing the need to quarry and the avoidance of unnecessary landfill (disposal), the use of slag aggregates can produce asphalt materials exhibiting superior properties to those manufactured with natural aggregate. 

For instance, steel slag produces an aggregate that: 

  • Is cubical in shape, providing excellent resistance to the formation of ruts in surface course asphalt
  • Is alkaline, providing a strong affinity to the bitumen binder, ensuring long life of road surfaces
  • Is hard – providing a durable material that will not wear away
  • Resists polishing, providing a safe riding surfaces for the whole life of the road 

Steel slag asphalt can be used for surfacing domestic driveways as well as heavy industrial areas and the heaviest trafficked roads.

Porous asphalt roads – safe and quiet

Close up of porous asphalt

Steel slag has proved to be an excellent material for porous asphalt surfaces. Porous asphalt is a bituminous bound mixture with carefully selected, homogenous aggregate grains with a fixed grain size distribution. It has over 20 % interconnecting voids. These voids absorb noise from the traffic and allow water to drain, reducing water “backspray” form the vehicles and risk of aquaplaning.  In addition, less water on the road means better tyre/road grip and less spray effects improve the driver’s visibility. Roads built with porous asphalt using steel slag are quiet, safe and long-lasting.