It can take weeks, months or years to build a road. It requires machinery, manpower and considerable amounts of capital.
We look at how tar and concrete roads are currently built in South Africa.
Planning the road
Before any construction takes place, the road’s design and route must be precisely planned by design consultants, civil engineers and surveyors.
This initial phase can cost as much as 15% of the budget. It requires expertise to calculate the more complex aspects of the road, such as gradient, radius and bank angle, as well as environmental impact and area-specific topography.
Preparing the surface
Once the route has been mapped out, heavy-duty earth-moving equipment is transported to the site. This includes motor graders, bulldozers and dump trucks. Their job is to clear vegetation, smooth bumps and cut through raised areas.
Constructing the road
Aggregate and other materials are delivered to locations along the route. The road is constructed in layers of varying thickness containing different materials – gravel, cement-stabilised gravel, crushed stone and tar or concrete.
Each layer is compressed using rollers and other specialised compactor equipment. The surface is graded. Drains and culverts are cut.
Once the road is structurally sound and water has been directed away from the surface, the paving begins.
Although South Africa’s road construction process is heavily reliant on labour, more than 100 heavy-duty vehicles are required to build 30 km of single-carriageway road.
Paving the road surface using tar
Most provincial and national roads in South Africa have tarred surfaces. Tar is a mixture of aggregate and bitumen that’s heated to around 150°C. The hot tar is spread on the surface and compressed into the crushed stone foundation.
Due to the elasticity of the material, blacktops are flexible. Compared to concrete, they’re quieter, provide a smooth ride and have better traction and skid resistance.
Tar roads can handle heavy traffic flows and loads. However, an average lifespan of just 10 years means tar roads have to be re-laid, repaired or reconditioned frequently.
The pros and cons of concrete as a road surface
Concrete is another popular road-surfacing material that’s made from a mixture of cement, sand and rocks. It’s much stronger than tar, requires less maintenance and lasts up to four times longer.
However, pouring the concrete is time consuming and expensive. The surface is prone to cracking. As a result, the slabs have to be cut to allow for expansion and contraction. This can make the surface uneven and noisy.
Apart from being used to surface a few roads with steep inclines and declines, concrete has not taken off in South Africa.
What does it cost to build a tar road in South Africa?
According to recent estimates, it costs R40 million to construct just one kilometre of single-carriageway road. It takes around 45 days.
Even resurfacing an existing thoroughfare has a hefty price tag of around R2 million per kilometre. It takes more than 400 workers to build 30 km of highway.
KH Plant
It would be impossible to build a road in South Africa without using motor graders.
At KH Plant, we specialise in restoring Caterpillar 140G, 140H and 140K motor graders and components to as-new condition – so you can get the benefits of a new motor grader at a fraction of the cost of a new machine. Contact us for more information or to discuss your needs.
