THERE is a great deal of discussion around the use of extenders in concrete.
However, in order to ensure a blend that is uncompromised in strength and integrity, extensive experience and knowledge are needed. AfriSam is able to leverage a multitude of applications in various market sectors, in the successful application of chemical admixture technologies.
According to AfriSam’s Furio Di Nardo, one needs to be aware of the challenges associated with increasing the extender content. “Some structures, such as concrete bases, allow for increases to the extender blend of up to 50% replacement proportions. However, we caution that with more intricate structures like floors, surface beds or pavements, one should reduce the extender blend to minimise the potential for the concrete to crack and curl. In these instances, one requires an advanced knowledge of curing.”
As pressure increases for the construction industry to reduce the carbon footprint of new buildings, it is critical that the limitations of concrete with added extenders are carefully reviewed. “AfriSam has invested a substantial amount of time and money into this issue and we are now in a strong position to offer concrete products with the same properties and performance as a product that has less extender in it,” says Di Nardo.
Cement extenders are finding increasing favour from an environmental perspective. Primarily, the use of extenders results in a large reduction in the equivalent carbon dioxide per ton of cement. “AfriSam’s ‘green cement’ utilises extenders such as AfriSam slagment, fly ash and limestone to reduce the amount of clinker needed in the cement. The use of these extender materials is a classic example of recycling at its best, since most of the material would end up in landfills,” says Di Nardo.
The Green Building Council of South Africa (GBCSA) recently refined its requirements to qualify for each of the three points focused on the use of concrete to lessen a building’s environmental impact. In order to support the construction industry in meeting the criteria for all three points AfriSam has closely reviewed the content of concrete used in various building projects.
“An example of this collaboration includes AfriSam assisting Standard Bank to qualify for two GBCSA points in the concrete category, for its new customer service office in Rosebank. We also designed custom mixes for Nedbank’s new Lakeview development in Roodepoort that will also attract two points,” comments Di Nardo.
In addition to its environmental benefits, cement produced with green extenders has no negative effect on concrete quality or workability, durability and density. “In fact, it promotes workability of fresh concrete and results in a more durable and impermeable concrete. AfriSam will continue to drive research into the use of secondary products in green cement mixtures as a catalyst for environmental stewardship,” Di Nardo concludes.