Self Compacting Concrete

Abstract

The essential qualities of concrete in a construction project are its strength, durability and serviceability. All these qualities can only be obtained through a proper mix design and good compaction. Compaction of concrete is very important in multistory buildings and long span bridges where the steel reinforcement is very congested. Column of high rise buildings and piers of cable stayed bridges have heavily congested steel. In addition in tall building and deep foundation, the concrete need to be placed at large distances and hence requiring concrete pumps. For such operation, the concrete need to be extremely workable requiring a slump of 7”-9”. Optimum compaction of concrete requires a lot of hard work, labor and close supervision by the field staff. In spite of the best effort, this aspect of construction may be compromised resulting in one or more problems. The problem of Compacting concrete can be overcome if it can be made self compacting which can be accomplished by using modern admixtures. These admixtures temporarily increase the workability making it free flowing concrete. Self compacting concrete, as the name implies, is the concrete requiring a very little or no vibration to fill the form homogeneously. Self Compacting Concrete (SCC) is defined by two primary properties. Ability to flow or deform under its own weight (with or without obstruction) and the ability to remain homogeneous while doing so. Flow ability is achieved by utilizing high range water reducing admixtures and segregation resistance is ensured by introducing a chemical viscosity modifying admixture (VMA) or increasing the amount of fines in the concrete.