1533Self Consolidation Concrete

Self-consolidation concrete (SCC) or self-compaction concrete means a concrete that has a high fluidity and can be easily placed by itself in formwork (even highly congested ones, without external consolidation by vibration). It is characterized by its high filling capacity caused by high viscoplastic deformability and resistance to segregation.

The mix proportion of SCC has some characteristics comparable to conventional concrete. The unit paste is much more elevated, supplemented by a decrease in the volume of the coarse aggregate, and the water powder ratio of the paste is lowered to assure the required viscosity. Hence, the powder content is elevated up to, in some cases, 600 kg/m3 or more, and the water content is restrained to an adequately low level. Various mineral admixtures are utilized to increase the powder content. High fluidity is produced by a high-performance superplasticizer, and a viscosity modifying agent may be added to restrain segregation.

Thus, the characteristics of mix proportions of SCC are somewhat near to those of high-strength concrete. Hence, high-strength concrete can be easily transformed to SCC, and vice versa.

Despite reports on self-levelling concrete that appeared in Europe in the 1970s, the concept of "self-compacting" was first systematized by Prof. Okamura [17] in 1988 and he named it "high-performance concrete.'' This SCC/HPC was initially conceived with the aim of assuring the durability of structures by eliminating consolidation defects. However, its major purposes have shifted toward the simplification of placing and improvement of efficiency. The effects of self-compaction, however, are not limited to these advantages. It enables concrete to be placed into structures that would otherwise be impossible to be constructed with concrete, and to have dramatic improvements in construction efficiency of extra large scale structures.

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