Modern civilisation relies heavily on concrete, as it is the world’s most used construction material, says South African cement producer PPC architec- tural concrete specialist Daniel van der Merwe.
Cement, which makes up about 11% of concrete, is a vital and strategic commodity, with about 2.9-billion tons of concrete pro-duced each year, he said at media and events company Alive2green’s Green Building Conference, held at the Sandton Convention Centre, in July.
“This is a significant amount of concrete, so every step taken to reduce the levels of carbon dioxide (CO2) emissions produced as a result of the concrete production process, by improving the efficiency of the process, is an important step towards creating a more sustainable future [for the building industry],” said Van der Merwe during his presentation, entitled Concrete and Sustainable Strategies.
He added that concrete accounted for about 5% of worldwide CO2 emissions.
Van der Merwe explained that the South African building industry was concerned about CO2 emissions resulting from building operations and construction.
A building’s operating energy consumption over its lifetime was 87% to 97% of the total energy requirement for the building process, while the embodied energy consumption of construction only accounted for 3% to 13% of a building’s total energy requirement, he noted.
Van der Merwe acknowledged that cement production was energy intensive, but highlighted that, owing to technological advances in the cement manufacturing process, energy consumption had dropped by 40% from 1962 to 2005. In 1962, cement production required 7.5 GJ/t to manufacture, but this had dropped to 4.2 GJ/t by 2005.
“Further, by using cement extenders and industrial by-products, such as fly ash, limestone and slag, CO2 emissions for every ton of cement are dramatically reduced,” he noted, adding that all CEM II cement products were already mixed with cement extenders, comprising several million tons of construction material by-products that would otherwise have ended up in landfills.
He also highlighted that admixture technology was assisting in improving the control properties of concrete, such as workability/pumpability, durability, aesthetics and cost-effectiveness.
“Admixture technologies have a major positive effect on improving the levels of building sustainability and could reduce cement con-tent requirements by as much as 15%,” he emphasised.