Construction World June 2019

PRODUCTS & SERVICE

Benefits of slagment grow WITH RISING CARBON CONCERNS

As a leading producer of high quality cementitious material, AfriSam is ideally positioned to support customers seeking to reduce their carbon footprint while insisting on superior building material.

especially in applications like wastewater treatment plants, or where there is seawater or sulphate-rich soil. “However, there is now an added consideration in business today, as companies anticipate the impact of the new carbon tax,” he says. “Slagment assumes a significance here too, as it reduces the amount of clinker in concrete, and cutting the energy consumed and carbon emitted in its manufacture. The use of slagment therefore presents not just a technical solution but an opportunity to achieve higher environmental standards.” AfriSam’s dedicated slagment plant in Vanderbijlpark has the capacity to produce over 800 000 tons of slagment a year, along with over 200 000 tons of blended cementitious products. The slag is a by-product of the steel and iron industry, and the plant mills this to a fine consistency before blending. “As part of AfriSam’s sustainability journey, we have implemented various strategies in response to the energy-intensity of the cement manufacturing process,” says Meyer. “Slagment remains a vital part of this journey, and we continue to develop innovative ways of extending its benefits to customers.” Another important capability of slagment is to reduce the thermal heat gradient generated when pouring concrete. This reduces the likelihood of micro-cracking, which may weaken the structure’s strength. Slagment can also alter the colour of concrete to near-white by replacing 50 to 70% of the concrete, giving the concrete a better appearance. In addition, it produces a smoother, more defect-free surface. 

By focusing on the beneficial use of slagment, AfriSam significantly reduces its CO 2 footprint.

F or over half a century, AfriSam has produced its trade-named ‘slagment’ from ground granulated blast furnace slag (GGBFS), according to AfriSam cementitious executive Hannes Meyer. “We have used this latent hydraulic binder in an extensive range of concrete applications, including major structures such as dams, bridges and roads,” says Meyer. “Indeed, it is only very specific and limited applications that today demand our cement without added slag.” He highlights the self-cementing properties of slag, which can double the lifespan of buildings. Among its key benefits, however, is to prevent sulphate attack and alkali-silica reaction in concrete,

CONCRETE FLOORS CALL FOR KEEPING TO THE RULES

The construction of industrial floors, such as warehousing and factory floors calls for concrete with characteristics entirely different from that required for vertical structures, says Bryan Perrie, managing director of The Concrete Institute which monthly receives huge volumes of appeals for advice regarding faulty flooring.

P errie says that the properties required of the concrete for flooring are governed largely by using correct materials and in correct proportions. Material specifications for all the ingredients of the concrete exist – and should be adhered to – as well as South African Codes of Practice for the actual placement of concrete and the finishing of floor slabs. “A thorough understanding of all the characteristics of concrete, the influence of material selection, environmental inconsistencies, as well as handling and finishing, are essential to produce a quality floor. A disregard for any of these factors can result in problems which are normally observed too late in the process to be corrected” he states. Perrie stresses that consistency is crucial during all the stages of the construction process: receiving the concrete, discharging, placing, consolidating and finishing. The importance of protecting the concrete while it is being placed, and curing thereafter, are also vital factors. "An incomplete brief from the client; lack of attention to correct proportioning, handling and finishing; inexperienced contractors and operators; could all contribute to a floor with poor durability, strength

and aesthetics. The flooring process relies on the successful completion of successive phases; understanding what is being done in each phase, using the right concrete and equipment, by the right person at the right time," he adds. 

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CONSTRUCTION WORLD JUNE 2019