Road rehab fix

Posted On Friday, 04 February 2011 02:00 Published by eProp Commercial Property News
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Recent disruptions to the supply of bitumen may encourage road builders to try an alternative technology developed by the Council for Scientific & Industrial Research.

Road InfrastructureRecent disruptions to the supply of bitumen, a key ingredient in the production of asphalt, may encourage road builders to try an alternative technology developed by the Council for Scientific & Industrial Research (CSIR).

Bitumen, a crude oil derivative used for road surfacing, is produced by local oil refineries. But a lack of co-ordination between the oil companies on maintenance shutdowns has resulted in a supply shortage.

This has hampered the progress of the SA National Roads Agency’s (Sanral) Gauteng Freeway Improvement Project.

Sanral has spoken out about the shortage, saying it will organise a meeting with the department of energy on the matter.

It wants to ensure better co-ordination by the refineries and prevent overlapping maintenance shutdowns.

As a last resort, Sanral says it might ask the minister of energy to declare bitumen a “strategic mineral”. This would force refineries to maintain a minimum reserve — by importing, if necessary. Its price would also be regulated by government.

Meanwhile, road builders are considering a new technology developed by the CSIR’s built environment unit which could be an alternative to bitumen.

It has developed an ultra-thin concrete technology, 50mm thick and reinforced with a steel mesh.

The concrete costs about the same as asphalt, says CSIR engineer Rafeek Louw, though location and the prices of bitumen, steel and concrete are variable factors needing consideration.

It also requires less maintenance, which means fewer disruptions to road users.

Louw says there are other advantages. It requires more labour, thus contributing to job creation. About 14 times more jobs are created than by surfacing roads with asphalt.

In urban, low-traffic environments, the duration of construction could be shorter and more cost-effective, he says.

The technology has been piloted in Soshanguve, Atteridgeville and Mamelodi in Gauteng. In Mthatha in the Eastern Cape, it was used to construct a section of an access road to a stone quarry.

There are proposals to construct demonstration sections in the Northern Cape, Western Cape and KwaZulu Natal.

Sanral has also used a slightly different form of the technology in its rehabilitation projects.

It applies a 50mm layer of highstrength, flexible concrete, which is used as a durable topping on an existing road in need of rehabilitation.

This technique was first used in Paarl, in the Western Cape, on a 4,3km steep downhill lane used by heavy vehicles on the N1 freeway between the Klip River toll plaza and the Huguenot Tunnel.

It has also been used on a section of the N12 near the Gillooly’s interchange, as well as on an apron at OR Tambo International.

The concrete is reinforced using seven times more steel and the concrete itself has a high concentration of steel fibres. Its compression strength, or the capacity of a material to withstand forces from different angles, is up to five times higher than normal concrete paste.

Rising oil prices, coupled with bitumen shortages, could make this option more attractive.

For now, however, the utility appears to favour the technology as a cost-effective option to rehabilitate roads, rather than in the construction of new roads.


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