Self Compacting Concrete
Self compacting concrete (SCC) was developed in Japan during the late 1980s by Professor Okamura and has attracted world-wide interest. SCC is a highly flowable yet stable concrete, it easily fills formwork without segregation and (depending on the mix design) without the need for vibration. This segregation resistance along with the high fluidity means consolidation is achieved due to the concrete’s own weight. Standard concrete batching and truck mixing equipment is used to produce SCC, but the mixture proportions are based on the creation of a high degree of fluidity whilst maintaining a low water/cementitious material ratio (w/c<0.40). This can be achieved by using new high-range water reducing admixtures (HRWR) along with stabilizing agents or fine-fillers to ensure homogeneity of the mixture.
The advantages of SCC are numerous. Most notable are faster placement with less labour, good density when reinforcement is very congested, and increased pour heights as a vibrator’s reach is no longer a limitation. Another major advantage is in the excellent surface finish which is virtually risk-free in its application. Improved finish also reduces remedial costs in filling bug holes while reduced wear and tear on forms from the absence of vibration can be a significant cost saving in all types of concrete construction. A quieter construction site, or pre-casting factory, is an added bonus while SCC can eliminate many of the health and safety issues associated with concrete vibration. The successful, even dramatic, use of SCC is best seen in projects where the confines of the available space would have made conventionally vibrated concrete virtually impossible to place and where the surface finish quality was paramount.
Case study examples of SCC use in New Zealand can be found at:
www.concretesociety.org.nz
Recommended further information:
www.baustoffchemie.de
www.wisegeek.com
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