Self compacted Concrete

Self compacted Concrete

Making concrete structures without vibration have been done in the past but are generally of lower strength and were of un-consistent quality. Recognizing the lack of uniformity and complete compaction of concrete by vibration, researchers at the University of Tokyo, Japan, started in late 1980’s to develop self compacting concrete (SCC). SCC is a highly flowable, yet stable concrete that can spread readily into place and fill the formwork without any vibration even when access is hindered by narrow gaps between reinforcement bars and without undergoing any significant segregation.

SCC is recognized by two of its primary properties: Ability to flow or deform under its own weight and the ability to remain homogeneous while doing so. Flowability is achieved by utilizing high range water reducing (HRWR) admixtures and segregation resistance is ensured by introducing a chemical viscosity modifying admixture (VMA) or increasing the amount of fines in the concrete. Increased fines contents can be achieved by increasing the content of cementitious materials or by adding mineral fines. A well distributed aggregate grading helps achieve SCC at reduced cementitious materials content and/or reduced admixture dosage. Self-compacting concrete development must ensure a good balance between deformability and stability. Compactibility of SCC is greatly affected by the characteristics of materials and the mix proportions. As there is no standard method for SCC mix design therefore it becomes necessary to evolve a procedure for mix design of SCC. Another problem regarding SCC is that the tests carried out for ordinary concrete are not applicable for SCC because of its high fluidity, therefore separate testing should be done for testing the properties of SCC. The paper presents an experimental procedure for the design of self compacting concrete mixes. The test results for characteristics of SCC such as slump flow, J-ring, V-funnel and L-Box are also presented.