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24 February 2010
A custom-made concrete paving block, super-tough and never used in South Africa before, is supporting the heavy axle-load of hundreds of buses using the new Rea Vaya bus rapid transport depot at Dobsonville in Soweto. Technicrete engineers developed the Armorflex paver from a block normally specified for flood and erosion control.
Over 15 000m² of Armorflex were used to surface the first-phase development of the depot, which serves as the home base for over 120 BRT buses.
Technicrete experts developed the new paver by taking a standard 115mm-thick Armorflex block and modifying it – first, by eliminating the drainage slots which allow for vegetation to grow through it in its normal erosion and flood-control role; and then strengthening its concrete composition with a special hard-wearing mix to handle continuous, heavy-load bus traffic.
A key feature in Armorflex design is that during the laying process, the blocks are linked together by a tensioned wire restraining system which prevents “rutting” – the creation of track indentation by the repeated procession of heavily laden vehicles along the same route. The entire paved surface is enclosed by barrier kerbing.
“Even on some hard paved surfaces, you eventually get a middle-mannetjie building up when vehicles are continually following the same route,” says Taco Voogt, Technicrete commercial product manager. “This cannot happen with Armorflex, thanks to the steel wire restraining system.”
“First for SA”
An additional cost advantage, he adds, was that less earthwork construction was required than would have been necessary for conventional paving.
It’s the first time that the modified Armorflex has been used in South Africa, but with its success at the Dobsonville BRT project, it could become a stock ultra-heavy duty paving item at Technicrete plants.
“Factors which we had to consider when deciding on the type of paved surface we needed included the extreme axle loads of the articulated buses, their turning movements and possible chemical attack from oils and diesel fuel,” says Kevern Ramborosa, a director of Hlanganani Engineering and Projects Managers, which designed the depot. “We turned to Armorflex, although it had never been utilized for this application before.”
When the client – Johannesburg Development Agency (JDA) – was approached regarding the unusual paving application, Ramborosa says it immediately supported the idea. “And throughout the process, Technicrete experts were on hand to assist with design checks as well as on-site training”.