The biggest of the eight PCBP projects completed to date is the 13 000 square metres car park on the West Campus of the University of the Witwatersrand. Abutting one of Johannesburg’s major thoroughfares, Empire Road, the parking ground comprises a lower section about 6 000 m square metres in area and an upper section of some 7 000 m square metres.
Designed by consulting engineers, Arup, the car park was paved with PCBP to provide on-site stormwater infiltration and attenuation and to avoid additional run-off to the Empire Road stormwater system.
Emannuel Prinsloo, director of the property and infrastructure management division at Wits, says the university opted for PCBP in view of its environmental and stormwater management attributes.
CMA director, John Cairns, says besides the prevention of flooding, PCBP offers environmental benefits such as filtering out of pollutants and the storage of water for reuse.
“The threat of flooding on Empire Road has been avoided and the water that infiltrates beneath the paved surface will replenish the underground water table,” Cairns states.
The sub-base of the PCBP installation at Wits comprises several layers, including re-compacted in-situ soil, a geotextile membrane, quarried stone, a second geotextile membrane, and another layer of smaller stone.
The 60 mm thick concrete paving blocks, with a strength rating of 30 MPa, were supplied by Concor Technicrete. The pavers incorporate vertical slots – 40 mm wide and 3 mm deep – at each end, to allow water to filter through to the sub-base.
Taco Voogt, product manager at Concor Technicrete, says the paving blocks were laid in a herring bone pattern as this is the simplest and most effective system for heavy traffic areas like the car park. Weko Civils was the main contractor, responsible for the earthworks and laying of the sub-base. The paving contractor was Mondo Meccano, a CMA contractor member.