Road Specifications

US System (SuperPave)
US European Specifications

Specifications are essential to describe the requirements of the customer in relationship with the supplier. Road owners have traditionally had a detailed involvement in the technology applied and consequently with the composition of the asphalt mix and the binder.

The type of specifications depends on the split of responsibilities between supplier and customer:

• Composition specifications
• Performance specifications of binder or asphalt mix
• Performance specifications of the road
• Performance specifications related to aspects such as maintenance delays and safety.

In most cases specifications are still made on the binder composition or its performance in tests. These tests have traditionally been based on the Newtonian behaviour of unmodified bitumen allowing the use of simple tests such as Penetration (PEN) and Ring and Ball (R&B). However, these measurements are not always suitable for polymer-modified bitumen.

With the important benefits inherent with polymer-modified bitumen, it was recognised that the specifications should be adapted to represent the added value of polymer-modified bituminous binders and to distinguish the high performing from the low performing binders. Performance based specifications are now used to enable a fair comparison between unmodified and modified and between different modified binders. These specifications are based on fundamental properties, which have been linked to road failure modes.

Contracts between authorities and consortia of companies to design build operate and maintain have resulted in very different performance criteria, focusing on economics, safety and environmental performance. In this case the consortia road owner will produce internal specifications typically to design the most economical road. This usually leads to a wider use of modifiers.