choosing road surfaces

The type of surface material used in road construction is largely dependent on traffic volume, weight load and weather conditions. As extreme temperatures are not a factor in South Arica, the roads network features three types of road construction surfaces, with a fourth only sporadically used.

Let's take a look at the different road surfaces, the pros and cons of each, and when a particular material is considered the best all-weather road construction solution.

Gravel

Gravel is a practical, affordable, low maintenance surface for rural roads that have a low traffic volume, particularly of load-bearing trucks. Gravel can be brought in and applied to a freshly cut road and compacted, or the existing surface is graded to create a crown, sloped shoulders and run-off ditches.

Drains are typically added at intervals to remove rainwater, so as to preserve the integrity of the road.

  • Pros
  • Low cost
  • Easy to maintain
  • Preserves the rural ambience
  • Cons
  • Requires frequent maintenance
  • Generates dust and stones
  • Can become impassable in wet weather

Bituminous seals and slurries

Bituminous seals and slurries are effective surface solutions for low traffic roads with minimal weight loads. A bitumen rubber chip emulsion is sprayed onto pre-compacted aggregate and rolled into the base layer to create a hardy, sealed road surface.

It's a durable and comparatively inexpensive solution for secondary roads, and is widely used in villages, towns and suburban areas of the cities.

  • Pros
  • Waterproof, skid-resistant and dust free
  • Cheaper than asphalt
  • 5-year maintenance cycle
  • More durable than gravel
  • Cons
  • Not as long-lasting as asphalt
  • Can crack in hot weather
  • Rough surface increases road noise
  • Costs more than gravel

Asphalt

In South Africa, almost all newly-constructed highways and arterial roads are surfaced with asphalt, or tar, as it's locally known. These roads are built to handle high traffic volumes and heavy loads.

They consist of several base layers of aggregate that are compacted and stabilised before a final layer of tar is laid over the surface. The application method and temperature can range from cold mix to hot mix, and is dependent on the average traffic load.

Hot mix consists of free floating screed, and is the surface of choice for highways with high traffic volumes. Conversely, cold mix is predominantly used on quiet secondary roads.

  • Pros
  • Quick to apply, fast drying
  • Relatively low road noise
  • Costs less than concrete
  • Easy to repair
  • Recyclable
  • Can last over 40 years
  • Flexible load distribution
  • Cons
  • Heavy traffic can cause rutting
  • Toxic to the environment
  • Wet conditions can damage surface

Concrete

Concrete road surfaces are composed from cement and other materials, such as aggregate, fly ash and chemical admixtures. The concrete is laid on a prepared surface in jointed blocks, or in a continuous layer reinforced by mesh or steel.

This type of road surface has only occasionally been used in South Africa. In 2012, a section of the N12 between Tom Jones and Rietfontein was constructed using continuously reinforced concrete.

As a trial, part of the N2 near Cape Town International Airport was surfaced using a method known as jointed reinforced concrete, but has since been re-tarred.

The 'bridal path' road running up the back of Table Mountain near Constantia Nek is constructed from concrete blocks reinforced with steel bars, and there are several rural roads with steep inclines that are finished in rough concrete to avoid slippage.

In other parts of the world, concrete road surfaces are as popular as asphalt. 

  • Pros
  • Long service life
  • Consumes 20% less fuel than asphalt
  • More eco-friendly construction process
  • Cons
  • Rigid surface and uniform load distribution can cause cracks
  • Costs more than asphalt
  • Slippery in wet conditions
  • Higher maintenance costs

To construct roads that are safe, durable and easy to maintain, you need the proper equipment – including a reliable motor grader.

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.

Contact us for more information