WHO'S WHO IN CONCRETE
Updated specifications are needed to meet cement innovation
Roelof Jacobs, manager: Integrated Solutions & Innovation, Lafarge South Africa
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South Africa cannot afford to rebuild concrete structures every few years because they were not constructed correctly the first time. By Kirsten Kelly
oelof Jacobs, head: Technical Sales and Innovation at Lafarge Southern Africa, believes that greater thought needs to be given when specifying cement and concrete products. “Outdated cement and concrete specifications are still used. We still see tenders/specifications requesting outdated cements like PC15, which was produced in the 1980s.” He adds that if the specifications for cement are correct, there is often a request for as little extension as possible. “The reality is that there needs to be a fair amount of fly ash or slag to improve the durability of structures. Furthermore, there is a significant environmental advantage to using SCMs (supplementar y cementitious materials). Updated cement and concrete specifications will likely lead to more durable structures that leave a smaller environmental impact.” Ten to twenty years ago, slag and fly were used to make cement cheaper, but presently this is not always the case due to transport costs. It often costs more to produce cement with a high fly ash content than to produce cement without it. But even with the increased cost, the durability and environmental benefits of using SCMs are significant. “Fly ash par ticles, for example, are smaller than cement particles, plugging any gaps. Once cement starts to hydrate,
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fly ash starts to hydrate and creates a gel, producing a denser paste matrix. Therefore, fewer harmful chemicals can penetrate the concrete. Like fly ash, slag can also be used to create a denser matrix, but it is usually not as fine or as readily available as fly ash,” says Jacobs.
Sulf8CEM Sulf8CEM also assists with the durability of concrete structures. As the only registered sulfate-resistant cement in South Africa, Sulf8CEM is an ideal solution in aggressive environments (like sewage plants). Sulfates are said to ‘attack’ concrete because they can permeate the sur face layers in solution with water, and react with calcium hydroxide and tricalcium aluminate in the cement paste – making it weak and brittle. The cement paste starts to fall away, exposing aggregates As the only registered sulfatethat then also star t to fall away resistant cement in the country, and the concrete structure begins Sulf8CEM is an ideal solution in to deteriorate. aggressive environments like sewage plants Sulf8CEM is a low-heat (LH), Sustainability sulfate-resistant (SR) cement that On the environmental side, Lafarge is is formulated from Portland clinker that launching a new range of eco-cements. meets the C3A requirement and over 36% selected quality siliceous fly ash, as well Lafarge is the first global building as per formance-enhancing additives. It materials company to sign the Unite Nations has been certified to conform to the latest Global Compact’s Business Ambition for applicable South African and European 1.5°C initiative, with a 2030 SBTi-verified standards (SANS 50197-1 and EN 197-1) (Science Based Targets initiative) action for a CEM IV/B-V 42,5N LH SR. plan. Lafarge plans to reach 475 kg net
