Feature: Cement & Concrete
road performance with block paving Block-paved Roman roads are justifiably famous for their longevity and low maintenance requirement. In South Africa, concrete block paving (CBP) is vis-
blocks, manufactured by Technicrete (formerly Concor Technicrete),
ible proof that the Romans knew what they were
build the road.
doing when it came to building reliable roads.
were laid over an area of 113 000m² during the 13 months it took to The road was built entirely by local people. This not only created 70 000 man-days of employment but also entailed on-site training in skills such as pipe-laying, brickwork for manholes, stone-pitching,
ne of the most successful examples of CBP as a road surface
the construction of gabions, and, of course, concrete work and block
material is a 9,5 km stretch of road in the eastern Free State,
paving. These skills have been subsequently used in other construc-
linking the Harrismith Golden Gate main road and several villages to Phuthaditjhaba. Completed over 11 years ago, the road has performed extremely
tion-related projects by members of the construction team. CMA director Hamish Laing says that, although CBP is sometimes more expensive to lay than asphalt, it generally has double the lifespan.
well under moderately heavy traffic conditions. In fact, since its offi-
Furthermore, CBP roads can be maintained and repaired by the local
cial opening in 1995 by the Free State Minister of Public Works and
community, using skills developed during the construction period.
Roads, Gregory Nthatisi, the road has required no maintenance at all.
“This project proves once again that unskilled people can be
Funded by the Development Bank of South Africa, the R15-million
trained to lay concrete blocks with a high degree of workmanship.
road was built by Basil Read using local labour (a Development Bank
The fact that after eight years of use the road has not needed any
requirement). Five-and-a-half million Double Zig-Zag interlocking
maintenance bears this out. This type of CBP road should have a lifespan of at least 30 years.
A section of the 9,5km concrete block paved road in the eastern
“Besides its labour-intensive and job-creation attributes, CBP
Free State which has required no maintenance since its comple-
is proving to be a very durable and aesthetically appealing road
tion over eight years ago.
surfacing material. This is particularly so in areas where the traffic density is high or where CBP enhances visual appeal, such as in townships, shopping centres, office car parks and residential driveways,” he says. FLOORS says that the latest edition of the Interpave on-line magazine e-Pave.com (to which acknowledgement and thanks are given), has an interesting take on the pothole problem. “When the road surface is new, the bitumen binder is flexible and sticky so that the layer can move under the vehicle tyres and the binder can stretch to cope with the stresses imposed. From the moment it is laid the bitumen is getting harder and more brittle, particularly in cold weather.” So, with older surfaces in winter the thin bitumen film between the stones can crack open, exacerbated by frost penetration and water being forced through the material by tyre pressure. Engineer Ian Walsh says, “It is the use of block paving on heavily trafficked trunk roads that is particularly impressive – we have three village high streets and a busy section of the A2 that have been in place now for 25 years, without any maintenance necessary by the County Council. The blocks look as good as new and there is no rea-
son why they should not last another 25 years,” he says.
F LO O R S S e p t e m b e r 2 0 1 0
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