Self compacting concrete
Compaction of concrete is often seen as the Achilles´ heel of traditional concrete, poor compaction affecting concrete´s physical appearance, its strength and durability. Although poor compaction is not prevalent in the majority of concrete cast today, any development that reduces the risks must be considered as beneficial. Therefore, there is much interest in self-compacting concrete (SCC), a form of concrete that needs no mechanical vibration after placing as it flows into formwork under its own weight, displacing the air. SCC allows high-quality, durable finishes to be achieved simply and effectively.
Although SCC often has a higher than usual cementitious and admixture content, the reduced noise (vibration equipment noise is eliminated), simpler formwork and access staging and improved construction process benefit the construction site and surroundings. The material can also be of great benefit to the manufacturers of precast concrete products, with improved working conditions in their factories.
Because the fresh properties of self compacting concrete are very different from those of ´normal´ concrete, a number of test methods have been developed. BS EN 12359 Testing fresh concrete, parts 8 to 12 (August 2010) cover these test methods.
Concrete production and testing was covered in BS EN 206-9 (April 2010) Concrete: Additional rules for self-compacting concrete. This part has now been rationalised with BS EN 206-1 (2000) and published as a single Standard BS EN 206 (2013) including corigendum May 2014.
Information on aspects of SCC is summarised in two Concrete Society Current Practice Sheets, No. 123, Self-compacting concrete: the material and its properties (published in Concrete, July/August 2001) and Self-compacting concrete: production and use (published in Concrete in October 2005). Copies of Current Practice Sheets may be downloaded from the Members´ area of the Concrete Society web site.