Tons of local steel, ArcelorMittal South Africa’s Chromadek®, were used in the construction of the prestigious Mall of Africa, scheduled to open at the end of April this year.
Local steel from proudly South African company, ArcelorMittal South Africa, was specified for the construction of the high-profile, 130 000m² Mall of Africa, scheduled to open on 28 April 2016.
Roof sheeting manufacturer, Clotan Steel, specified and supplied approximately 600 tons of ArcelorMittal’s 0.58 Z200 Chromadek® White Lion material, profiled into Craft Lock concealed fix, to cover the 80 000m² roof area.
According to Corné Nel, architectural specifier at Clotan Steel, the low-pitched, lateral curved roof design required specific functionality from the roof sheeting to properly channel the flow of water away from the overlaps to prevent leaking, and Craft Lock’s unique design was the perfect fit. Its 41mm-deep through has a water-carrying capacity of approximately 29l/m² on a roof pitch as low as 1 degree.
“It has a very unique way of joining and has excellent resistance to high wind loads. In fact, it has been tested to withstand negative loads of up to 3kN/m². If installed correctly, there is no way it will lift up or tear away from the support structure,” he says.
Clotan Steel rolled the material on site, with some roof sheets spanning lengths of over 112m. At crucial points during construction, the machines were crane-lifted onto the roof to make the handling and installation of these super-long sheets easier.
Reflective colour coating
Emphasising that Chromadek® is ideally suited to the region, Melvin Hickers, product manager for galvanised and colour-coated products at ArcelorMittal South Africa, adds that the choice of the Chromadek® White Lion colour contributes to the building’s energy efficiency through its inherent ability to reflect the sun’s energy. As nature intended, lighter colours are designed to reflect more of the sun’s energy.
“Interestingly, the Chromadek® range also has darker colours that are made to be heat-reflective, although the lighter colours tend to be the first choice in terms of energy efficiency,” he explains. “If a darker colour is a consideration, the Chromadek® heat reflective range also offers the benefit of energy efficiency.
“Another advance is that the chrome has been removed from the paint system, making the product more ecologically friendly. Currently Chromadek® consists of both a chrome-free primer and a chrome-free pre-treatment. The top coat and backing coats applied are also chrome-free,” he says.
Light steel frame
In addition to the expansive roof, Clotan Steel also specified and supplied about 250 tons of ArcelorMittal South Africa’s Z275 commercial quality pre-galvanised steel profiled into lipped channels and approximately 165 tons of Z275 ISQ550 pre-galvanised steel profiled into light steel frame for use in roughly 28 000m² of facades.
“The lipped channels were cut to length on site and the joining holes were precision punched during the roll forming process, with the accuracy of a fraction of a millimetre,” says Nel. “We also hard-stamped relevant drawing numbers onto the lipped channels to indicate which piece of steel goes where, saving the contractors precious time on site. This unique service is especially beneficial on a project with a pressured timeline, such as the Mall of Africa.”
Backing the quality of its steel products, ArcelorMittal South Africa gives a standard ten-year warranty on the colour with the possibility of increasing the colour warranty depending on the choice of colour, and complimentary to this is a 20-year warranty prior to perforation.
Project team members:
• Architect: MDS Architects.
• Main contractors: Group Five and WBHO.
• Developer: Atterbury Properties and Attacq.
• Roofing and LSF profiler: Clotan Steel.