Self-compacting concrete has evolved to a product that offers quality, durability and revolutionary design possibilities.
Self-compacting concrete (SCC) is a relatively new product that sees the addition of super plasticiser and a stabiliser to the concrete mix to significantly increase the ease and rate of flow. By its very nature, SCC does not require vibration. It achieves compaction into every part of the mould or formwork simply by means of its own weight without any segregation of the coarse aggregate.
Concrete is the most widely consumed material in the world, after water. However, conventional concrete technology requires slow, heavy, noisy, expensive, energy-consuming and often dangerous mechanical vibration to compact the concrete and to develop strength and durability.
According to the Cement and Concrete Institute (CCI) in South Africa, SCC is mainly utilised for specialised applications where the use of ordinary concrete is very difficult and often not possible. “The development of SCC in South Africa is still in its infancy and its current use is thus limited,” states the institute’s website.
The first project on which SCC was used in South Africa was the Nelson Mandela Bridge, which was constructed in 2002. Other projects include the deck of Bridge 2235 on the Bakwena Highway in 2002, a spiral staircase at a Pretoria residence in 2003 and a number of relatively small projects in 2004.
SCC needs to be able to easily move under the force of gravity without vibration during mixing, transportation, handling and placement stages. It is so highly flowable that the conventional “slump test” can usually not distinguish between different levels of SCC flow-ability. SCC must also allow the mortar to suspend and carry coarse aggregate, maintaining a homogenous, stable mixture, resistant to segregation, bleeding, excessive air migration or paste separation. It must have dynamic stability during mixing, transportation, handling and placement, and stability during protection and curing.
Benefits of self-compacting concrete
1. Reduced in-place cost
• SCC can increase the speed of construction, improve formed surface finish and reduce repair and patching costs, reduce maintenance costs on equipment, and provide faster form and truck turnaround time.
• Reduced labour costs: SCC reduces labour demands and compensates for a lack of skilled workers to perform the rigorous work required for quality concrete construction.
2. Improved work environment and safety
• SCC eliminates the use of vibrators for concrete placement, thus minimising vibration and noise exposures. It eliminates trip hazards caused by cords. It reduces fall hazards, as workers do not have to stand on forms to consolidate concrete.
3. Improved aesthetics
• SCC provides unequalled formed surfaces.
Although a relatively new and unexplored material, SCC may redeem the image of dirty, polluting concrete and may become the future of sustainable construction.
Full thanks and acknowledgement are given to Hypenica, www.cnci.org.za and Totally Concrete for the information given to write this article.