Composite cements lead in sustainability drive

AfriSam has become a trailblazer in cutting carbon emissions in one of the economy’s most energy-intensive sectors.

Hannes Meyer, cementitious executive at AfriSam, highlights that the energy consumed in producing ordinary Portland cement can be 20% to 25% higher than a composite cement of the same strength class.

“This results from the added cost of producing a higher-percentage clinker at high temperatures used per tonne of composite cement manufactured,” says Meyer.

“Extenders like fly ash or ground granulated blast furnace slag can be blended into the mix, reducing the amount of clinker milling required per tonne of cement.”

This has more recently become a focus for other players in the market – even those who had previously not embraced the concept of composite cement, he notes. AfriSam has in the meantime become the benchmark for these cement innovations, along with a range of sustainability initiatives to monitor and reduce carbon emissions.

“A vital aspect of our use of extenders has been our ability to activate these materials for greater reactivity,” he says. “Through evolving our chemical and mechanical activation methods, we achieve a more reactive product – allowing us to progressively replace more and more clinker while retaining high cementitious quality and strength performance.”

Meyer points out that cement blending companies have already recognised the high reactivity of AfriSam cement, with many of them preferring AfriSam’s products as they ‘go further’ in a blending application.

Grinding aids “We have also had great success in the use of grinding aids in our milling processes, collaborating closely with specialist firms to address our exacting requirements,” says Meyer.

“These grinding aids are specific to the extenders we use, helping to improve reactivity and, in some instances, adding 10% to 15% early strength enhancement,” he continues. The result is that less clinker needs to be produced per tonne of final product, leading to less carbon dioxide being generated.

Energy gains AfriSam has also become more efficient in the use of thermal and electrical energy in its processes.

While electricity used to be a minor cost in cement plants, it is now a major factor in cement manufacture. In this context, AfriSam has explored alternative fuels, which has also become a major focus for many cement producers globally.

“We have made progress with responsibly disposing of waste products in our energy generation strategies, and we hope that government will take the necessary steps to allow us to expand these initiatives,” Meyer continues.

These include the combustion of waste tyres and industrial carbon sludge, using high-efficiency multichannel burners that reduce hazardous emissions.

“The employment of increasingly sophisticated process control technology is also part of the ‘AfriSam Way’ towards a sustainable planet,” Meyer concludes.