Tensar Pavement Optimisation System
Location of work/project:
Bloemfontein, South Africa
Tensar International Limited
Tensar Mechanically Stabilised Layer (MSL) comprising bitumen emulsion stabilised materials paved over TriAx® geogrid.
Bloemfontein is the capital city of the Free State Province of South Africa and one of South Africa's three national capitals – the other two being Cape Town and Pretoria.
Conventional rehabilitation methods would have involved full depth reconstruction by excavating at least 300 mm of the highway and rebuilding with well-graded material. Unfortunately, the consultants discovered that the subterranean municipal services in Harvey Road and Hanger Street were located at a depth of just over 200 mm. Due to the importance of these roads and the situation they had on-site with the services, the engineers realised that conventional methods would not be sufficient.
The shallow services and utilities included electric cables, telecommunication cables and water pipes under the existing pavement. In particular, a very old lead-based water pipeline was located on some of the sections and disturbing this service would be detrimental to the project as fittings and couplings for the old service are no longer obtainable. The cost to replace these services would in fact outweigh the cost of the whole project.
Tensar Technology was exploited to provide a proven, practical solution to the customer’s site-specific requirements. Recycling the existing pavement material reduced disruption and environmental concerns. To reduce the required pavement thickness the whole pavement structure was optimised by utilising a Tensar MSL™ (Mechanically Stabilised Layer) incorporating TriAx® geogrid below the recycled materials. This allowed the existing kerbs levels to be retained and avoided disturbance of underlying services. A key additional benefit included an accelerated contractor’s programme which enabled traffic to be diverted back onto the reconstructed highway 3 hours after pavement construction.