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First carbon-friendly pour for Khobab wind farm foundations

6th July 2016

By: Natasha Odendaal

Creamer Media Senior Deputy Editor

  

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The first of 61 low-carbon foundations for the turbines at the new Khobab wind farm, in the Northern Cape, has been poured, using a 89% cement-replacement formula that would reduce the wind farm’s carbon footprint to 90.7 kg/m3 of carbon dioxide (CO2).

The formula for the emerging wind farm’s foundations, all of which were expected to be completed by December, comprised 35 kg/m3 of high-grade Portland cement  – 90% less than a standard concrete mix – and an iron industry by-product, Ground Granulated Corex Slag, leveraging the same formula used on its sister farm, Loeriesfontein, in the Hantam municipality.

The achieved strength of 55 MPa on a 28-day compressive strength test – and an expected ultimate strength of 100 MPa within a 56-day period – surpassed that of the standard rated 30 MPa concrete supplied by the ready-mix industry, while significantly reducing the carbon footprint of the 300 kg/m3 to 350 kg/m3 of CO2 output of traditional concrete.

“Traditionally, 30 MPa concrete requires between 300 kg/m3 and 350 kg/m3 of ordinary cement. But now scientists working for Murray & Roberts have developed a technology that meets the 30 MPa standard using just 25 kg of cement, or even less,” explained Khobab wind farm project manager Kevin Foster.

“The strength of concrete is measured in megapascals; theoretically a cubic metre of concrete that is rated 30 MPa, is able to withstand the weight of six bull elephants, whereas these foundations are able to withstand the approximate mass of 20 bull elephants standing on a square centimetre of concrete – a phenomenal feat,” added Murray & Roberts Construction group concrete and research manager Cyril Attwell.

The 3 200 ha wind farm, which would comprise sixty-one 140 MW wind turbines, generating about 563 500 MWh/year of clean, renewable energy to the national grid, was expected to avoid around 550 000 t of carbon emissions each year.

The Khobab consortium, led by Lekela Power, was in the process of testing a higher cement replacement formula, Foster concluded.

Edited by Creamer Media Reporter

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