ROADS & BRIDGES | MAINTENANCE & MANAGEMENT
For slipform paving technology, the pouring and levelling of concrete are done simultaneously
CONCRETE PAVEMENTS
have come a long way
C
oncrete pavements generally last for over 30 years. In addition, they require relatively little maintenance and repair, resulting in long-term savings in raw materials, transpor t 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 cer tain 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
Bryan Perrie, CEO of Cement & Concrete South Africa
22
IMIESA April 2022
When it comes to riding comfor t, Perrie believes that the situation is now totally different to early concrete pavements. The latter did not offer top-quality riding comfor t because of the length of slabs and width of joints, faulting at the joints, or damage to suppor ting 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: • shor ter slabs with 4.5 m maximum length to make concrete pavements
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. less susceptible to cracking, curling and faulting • narrow sealed construction joints to overcome the problems previously encountered with joint per formance • 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 primar y 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 comfor t,” says Perrie.
Smooth pavements Fur thermore, smooth concrete pavements can now be built thanks to: • optimised concrete mixes offering constant workability and prepared in modern, computer-controlled
