The N3 National Route between Durban and Johannesburg is a route of considerable strategic importance in South Africa, carrying heavy long distance freight traffic as well as light vehicles. It was let as a toll concession to the N3 Toll Concession Company (N3TC) in 1999 for a 30-year period.
As technical advisor to the N3 Toll Concession Company, WSP adopts a practical and innovative approach incorporating strict quality control and experienced site supervision of all works. This is generating cost savings whilst delivering consistently high standards and safe conditions for road users.
Solution for mountainous terrain
One of the greatest technical challenges for the team has been the rehabilitation of the mountainous Van Reenens Pass section of the route. Here the road is prone to become badly rutted and deformed due to the volume of heavily laden and slow moving freight vehicles sinking into the surface in the intense heat of summer. WSP
specified the use of steel slag aggregate to stop the deterioration of the road surface.
Steel slag asphalt has unique properties that make it a safe and durable alternative to natural aggregates. The technology is widely used in Europe and in applying it for the first time on a major road in South Africa, WSP is providing a cost-effective, sustainable solution to a previously insoluble problem.
Innovative and practical techniques for maintaining and improving the route include:
- Optimised cost efficient pavement and rehabilitation strategy, resulting in substantial cost savings
- Use of new materials and approaches, particularly steel slag asphalt to combat heavy pavement loading
- Use of new technology to find optimal alternative route alignments in difficult mountainous terrain
Client: N3 Toll Concession Company (Pty) Ltd (N3TC)
Size: 416 km of inter-urban freeway
value: approximately £13M per annum
Status: ongoing, started 2003