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Self Compacting Concrete

This video visually explains Self Compacting Concrete. Self-compacting concrete (SCC) is a special type of concrete which can be placed and consolidated under its own weight without any vibration effort due to its excellent deformability, and which at the same time is cohesive enough to be handled without segregation or bleeding. Self-compacting concrete (SCC) has many benefits in terms of production and placement compared to traditional concrete namely, elimination of external or internal vibration for compaction, better flowability, workability and pumpability, as well as increased bonding with congested reinforcement. Moreover, the placement of SCC is faster and requires less labour. The appearance (surface finish), mechanical performance and durability of SCC can be considerably better than traditional concrete. However, the methods of production, placement, quality control and finishing are essential for SCC. Constructability issues may arise for specifiers and contractors if related standards, guidelines or practices are not appropriately followed for production and placement. Self-compacting concrete is less tolerant to abrupt changes in aggregate moisture content, chemical admixtures and water content. The type of concrete mixer, transport time and the methods of concrete placement and finishing can affect the properties of SCC. Therefore, robust quality control measures must be in place during the production and placement of SCC. The excellent flowability of SCC compared to traditional concrete makes pumping the best method of placement. However, there is a high chance of air entrainment due to a higher flow rate, which can result in bugholes and segregation. Normally SCC has less surface imperfections compared to traditional concrete, but it would be susceptible to bugholes, honeycombing and cracking if guidelines of production and placement were not followed appropriately. This chapter explains how the admixtures, aggregate moisture content and water to solids ratio should be controlled for the reliable production of SCC. Also, the effect of concrete mixers on the properties of SCC, and the methods of quality control at batching plants and during placement are explained.