Concrete pavements have come a long way

There are several misconceptions about concrete pavements, even though they often offer the most favourable solution when whole-life roadbuilding costs are considered, according to Bryan Perrie, CEO of Cement & Concrete South Africa (CCSA). Additional advantages include speed of construction and riding comfort.

Concrete pavements generally last for over 30 years. In addition, they require relatively little maintenance and repair, resulting in long-term savings in raw materials, transport and energy.

The reduction in traffic disruption and delays caused by roadworks also cuts fuel consumption and exhaust gas emissions.

“When it comes to speed of construction, the curing time of concrete is far from the 28-day period that is sometimes incorrectly suggested,” Perrie explains, adding that a new concrete pavement, made from conventional concrete, can be opened to traffic after only four to seven days of curing.

“High early strength concrete mixes make it possible to reduce the curing time to just three days and, in certain cases, to only 24 hours. This technique is used in several countries on busy traffic routes and has been used on a number of projects in South Africa as well,” Perrie continues.

Advances in jointed pavements

When it comes to riding comfort, Perrie believes that the situation is now totally different to early concrete pavements. The latter did not offer top-quality riding comfort because of the length of slabs and width of joints, faulting at the joints, or damage to supporting erosionprone layers.

He says that, for over 40 years now, these problems have been dealt with by using designs that implement new and superior measures in jointed pavements.

These include:

• shorter slabs with 4.5 m maximum length to make concrete pavements less susceptible to cracking, curling and faulting

• narrow sealed construction joints to overcome the problems previously encountered with joint performance

• dowels in the transverse joints and cement-bound bases to ensure excellent load transfer and the prevention of faulting at the joints.

“Continuously reinforced concrete pavements – which have no transverse joints – are often chosen for freeways and primary roads. The shrinkage of the concrete is absorbed by a pattern of fine microcracks that has no impact whatsoever on the pavements’ evenness or ride comfort,” says Perrie.

Smooth pavements

Furthermore, smooth concrete pavements can now be built thanks to:

• optimised concrete mixes offering constant workability and prepared in modern, computer-controlled batching and mixing plants often established on-site

• new generations of slipform pavers equipped with automatic vibrator control systems and a longitudinal levelling beam behind the finishing machine or so-called super-smoother

• properly installed guide wires for controlling the machine or the use of modern wireless guidance

• new types of evenness measurement set up immediately behind the paver to allow correct construction.

“It should be remembered that an important property of concrete pavements is that the longitudinal evenness obtained after construction is retained for many years,” Perrie explains.

Conclusion

“There is no doubt that concrete pavements are the logical and sustainable solution for South Africa. One only has to look at the thousands of potholes on our road networks at the moment to see how concrete could have prevented such a costly and dangerous situation. Concrete pavements are the natural choice for projects where performance, value, longevity, social responsibility and concern for the environment are paramount,” Perrie concludes.