BUILT TO LAST

Hannes Meyer, cementitious executive, AfriSam

Q: How big is SA’s cement market?
A: We use between 13 million and 14 million tons of cement per year – 70% in residential and commercial buildings and 30% in civil construction and infrastructure.

Q: How has the strength of concrete evolved?
A: The compressive strength of concrete has increased significantly over the years, due mainly to engineering requirements. These days, concrete mixes are designed to achieve higher and earlier strengths to meet the requirements for high-rise buildings and fast-track construction programmes. Ten years ago, for example, an 80 MPa concrete mix was unheard of; today it is a common request, due to the nature of modern construction projects.

Q: What is concrete’s life cycle? And how does it integrate with other construction processes and materials?
A: There is a reason why, after water, concrete is the globe’s most widely used substance. It is an extremely durable material that, when used correctly, will last for hundreds of years. We don’t always notice it but virtually everything around us has been built using concrete. Concrete is also an extremely versatile product and integrates well with other construction materials such as steel, glass, wood and more, and it delivers a number of benefits to construction and society. With the development of greener cements, it has great potential to contribute significantly to the sustainability of our planet.

Q: What are the new technologies/innovations that bring about greener cements?
A: Internationally, research into new technologies, such as the use of nanotechnology in the cement-manufacturing process, is gaining momentum and could provide wide-reaching benefits to the industry, specifically from a sustainability perspective. However, this technology is still some way from reaching SA’s cement industry.

New technologies and innovations available to us in Africa apply largely to the hardware, in other words, the equipment we use. Be it in equipment or in the manufacturing process, the biggest impact of new technologies in terms of transforming our industry is in the manner that they enable cement manufacturers to significantly reduce the impact of their operations and products on the environment, and to produce far more environmentally responsible cementitious products than in the past.

Q: The industry is known for its high carbon emissions created in the manufacturing process. What are AfriSam’s counter measures?
A: We have always been concerned with our C02 emissions and have played a pioneering role in the industry, introducing for example the use of alternative fuels and resources (AFRs), such as the burning of old tyres rather than coal in cement kilns, and applying more expensive extenders such as slagment – which has better cementitious properties than traditional use of fly ash – in our concrete. These have reduced our C02 emissions by 35% over the past two decades. We welcome the introduction of carbon tax to incentivise energy-saving innovation, provided there are positive spin-offs, with revenue constructively ploughed back into the sector to promote changes in technology and behaviour.

Q: What waste products are used in the production of cement and how does this enhance SA’s environmental directives?
A: The cement-manufacturing process provides significant opportunities to use waste materials from other industries that would otherwise end up on landfill sites. Most commonly used waste materials include fly ash and ground granulated blast furnace slag (GGBFS). AfriSam has invested significantly in the research, development and use of GGBFS as an extender in its cement products.

Due to its cementitious properties, GGBFS can replace up to 70% of the mass of the total cementitious material and, in so doing, significantly reduce the COfootprint of its cement products. Other benefits of using waste products to extend cement are reduced limestone mining (and the subsequent reduced mining footprint); reduced limestone transportation, crushing and raw meal milling; and less fuel and energy consumed per ton of cement produced.

Other AFRs that can be effectively used in the cement-manufacturing process include paper and plastics, tyres, biomass and lower-grade coal that would otherwise have been stockpiled and, in the process, emit large quantities of greenhouse gases.

Q: What are the water-saving techniques adopted by the industry?
A: We have long been implementing measures to reduce AfriSam’s water consumption, including reusing and recycling water, and minimising any wastage. Most of the water consumption goes into cooling air as it moves between different equipment components and before being released into the atmosphere. Progress in technology in the cement-manufacturing process – such as dry kilns with five-stage preheaters, as well as waste heat recovery technology – has enabled the industry to significantly reduce water consumption and, actually, minimal water is used during the cement-manufacturing process.

Most of the opportunities for a reduction in water consumption are during end-consumer mixing. As such, AfriSam specifically manufactures cement that demands as little water as possible to reach the required strength and consistency for concrete work. The less ‘thirsty’ the cement is, the less water is required during end-user mixing, which is better for our environment.

By Kerry Dimmer
Image: Janine Petzer

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