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.
