Cement leader champions slag TO REDUCE CLINKER FACTOR

Over the years, AfriSam has accelerated its efforts to substitute clinker through the development of composite (extended) cements and in 2000 launched Project Green Cement to increase the use of extenders to promote more sustainable products.

Examples include the use of pulverised fly ash from coal-fired power stations and ground granulated blast furnace slag – a by-product of the steel industry. The use of the latter remains central to the company’s efforts to substitute clinker in its products.

“The use of extenders has resulted in a substantial 20% reduction in the company’s clinker factor since 1990,” explains Hannes Meyer, cementitious executive, AfriSam.

Ground granulated blast furnace slag has been used in the manufacture of cement since the second half of the 19th century. Back then, the practice was to intergrind it with clinker. However, in the 1950s, AfriSam’s slagment operation pioneered the use of separately ground slag for the construction industry.

A more reactive product

By evolving its chemical and mechanical activation methods, AfriSam has achieved a more reactive product, allowing the company to progressively replace more and more clinker while retaining high cementitious quality and strength performance.

“Reusing waste products from other industries reduces the amount of limestone that we have to mine and clinker that we have to produce, thus reducing carbon emissions from those processes, as well as minimising waste to landfill,” says Meyer.

“We are therefore constantly searching for new extenders and additives to further reduce our carbon footprint and our impact on the environment at large. The end result is less clinker produced per tonne of each final product, resulting in less CO₂ generated from our operations,” Meyer concludes.

According

Hannes

Meyer, cementitious executive, AfriSam the Association of Cementitious Material

12%

1990 to 23% in 2000, and a substantial 41% in 2009. The industry is pressing for a 60% rise by 2030