Study on Subsidence and Shrinkage of Super-Workable Concrete

Recently, application of super-workable concrete with high flowability, has been increasing in the construction of steel-concrete composite structures of sandwich systems, concrete-filled steel tubes, and structures with congested reinforcing bar arrangements, since compacting of concrete is difficult in those kinds of structures. In such cases, it is necessary to avoid impairing integrities of the structures as a result of gaps formed between steel and concrete due to subsidence and shrinkage of concrete and cracks formed due to restraint by steel. In this study, the influences of the kinds of cement and admixtures, and differences of addition rates on autogenous shrinkage, drying shrinkage, and subsidence of super-workable concrete are examined, as are the influences on gaps formed under disphragms in concrete as well. As a result, it is found that shrinkage and subsidence behaviors differ considerably depending on the kinds of concrete and admixtures.