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CMA NEWS AND MEMBER ARTICLES

CMA News & Articles - The CMA is the precast concrete industry association of South Africa. Find our members on our website to source quality precast concrete products, professional built environment service(engineers, architects, contractors and more).

V&A Waterfront 'Silo District' Project

Various examples of precast concrete usage are in evidence in Phase 2 of the V&A Waterfront’s Silo district, currently under construction and due for completion in 2017.

Precast concrete products that have been used so far include sheet piles deployed in a new 2 750 m2 parking-bay basement and culverts used to construct a sea water service corridor under Fish Quay Road.

The Silo district, situated at Cape Town harbour’s old grain silos, is already home to the 18 000m² six star green-rated No.1 Silo, which made extensive use of aesthetically pleasing concrete cladding, and No. 2 Silo, a luxury residential apartment complex.

The new development involves the construction of Nos. 3 – 5 Silos and will feature environmentally sustainable building techniques, as applied with Silos 1 and 2.

No. 3 Silo will comprise a structure with 80 one-to-four bedroom luxury apartments and No. 4 Silo will house a 4 000 m² Virgin Active gym. When completed, No. 5 Silo, a 15 500 m² office building, will be the South African head office for PricewaterhouseCoopers.

The old grain silos are being converted into the architecturally innovative Seitz Mocca art museum. Some of the silo tubes will be cut away and others will be retained to form viewing galleries. There is also the potential for a new hotel on the Silo site, which when constructed, would become No.6 Silo.

David de Villiers, Associate Director of Mace Ltd, the Silo district’s Phase 2 project managers, said precast concrete is to be used wherever possible.

“In addition to the sheet piling and the Fish Quay Road corridor elements, we are looking at using precast concrete stairs on Nos. 3 and 5 Silos. They will speed up construction and give us a better quality finish,” he explained.

”We are also investigating the installation of precast concrete cladding on some of the facades and we will be using precast concrete stormwater piping for the drainage of the precinct.”

One of the more challenging applications was in the design and implementation of geotechnical solutions for the construction of lateral support for the new parking basement. This was handled by Franki Africa and involved the use of precast concrete sheet piles and post tensioned anchors.

Anton Stoll, Senior Contracts Manager for Franki Africa, said the sheet piling operation entailed the delivery of a wide variety of products and services on a site which was hampered by strong tidal flows, varying rock profiles and restricted access.

“The site’s geology comprised imported fine silty and clayey sands together with rock fill overlying highly fractured greywacke residual rock. Areas of beach zones or sand and shelly fragments were also encountered in areas above the residual rock, which varied in depth from ground level to 13 m,” he said.

The piling took place on the northern and eastern ends of the basement where driven concrete sheet piles with grout socks and anchors were installed to provide the necessary lateral support.

CMA Member Concrete Units of Cape Town supplied 228 precast concrete sheet piles, ranging from 9 m to 13 m in length, which were installed to create a 206 m wall. Grout socks were installed between the concrete sheets to prevent water seepage. Temporary anchors will be installed to support the sheet piles once excavation of the basement begins.

“The choice of the concrete sheet pile solution over other forms of lateral support, such as steel sheet piles or diaphragm walls, was simple when one considers the constraints under which the operation took place. Consequently the concrete sheet piles be cast off site at Concrete Units’ factory premises in Airport Industria,” said Stoll.

Among the more serious constraints were limited access for piling and equipment, varying rock profiles, restricted material availability and the frequent changing of traffic access points, together with the short lead-in times and fast-track nature of the programme.

Concrete Units cast up to six piles a day in specially-prepared precast beds. It also provided storage space for the piles during the installation programme, delivering them to site as and when required.



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