PRESTRESSED SLABS USED TO BUILD SECURITY WALLS IN PORT ELIZABETH:

The first wall is three metres high and 1.5km long, and was built around the Dora Nginza Hospital in Port Elizabeth.

It was designed by Ninham Shand/Hix Architects and built by SBT Construction for the Department of Public Works. A total of 756 prestressed slabs were used on the project, each slab measuring 6m x 1.2m x 120mm and cast to a strength rating of 50MPa.

The slabs were laid horizontally in stacks of three and were installed between in-situ cast reinforced columns, erected by SBT Construction. Only the bottom half of the lowest panel in each  section is situated below ground level, a factor which facilitated the creation of a high security wall.

The second wall was erected around the Greenbushes Business Estate which was developed by Sweet Equity. In this instance the wall was 2.75km long and 2,4m high. A total of 916 panels measuring 6m x 1.2m x 120mm were used and supporting columns were constructed using Shukuma column blocks on reinforced foundations laid by SBT Construction.

CMA director, John Cairns says increasing use is being made of prestressed hollow-core paneling for security walling.

“There are several advantages to this type of walling, speed of erection being one of the major considerations and a superior strength-to-weight ratio being another.

“The current cost of building a precast security wall, say 3,0m high, is approximately half that of a wall offering the same properties using in-situ casting. Furthermore, it would take two to three times as long to build such a wall using in-situ casting, with no advantage in strength or durability.

“In fact walls built with prestressed hollow-core slabs are exceptionally strong, far more so than walls of the same dimensions built with conventional masonry. The latter can be broken with a heavy-duty hammer and chisel unlike prestressed slab walls which require much greater, not to mention, noisy destructive force to break them.

“Another advantage is that being factory manufactured, precast concrete slabs are produced to a quality that is consistently high,” concludes Cairns.

The security wall (above two photographs) at the Dora Nginza Hospital in Port Elizabeth which was built with precast hollow-core panels supplied by Shukuma Flooring Systems.

This security wall (above three photographs) at Greenbushes Business Estate in Port Elizabeth is 2.75km long and 2.4m high. It was built with Shukuma Flooring System’s precast slabs and column blocks.

DATE:  May, 2009
ISSUED BY:  David Beer Communication Consultants
FOR:  Concrete Manufacturers Association 
ENQUIRIES:  John Cairns (011) 805 6742
David Beer (011) 478 0239 or 082 880 6726.  Email: bigsky@ibi.co.za