Self Compacting Concrete (SCC) is a concrete that is capable to compact under its own load.
Also in past, making concrete structures without compaction and vibration has also been done. For examples, placing of concrete under water is done without vibration.
Mass concrete and shaft concrete can be well placed without compaction.
But the examples of these concretes are generally of lower strength, and it is difficult to obtain uniform quality.
Recognizing the need of uniformity and complete compaction of concrete, the Scientists at University of Tokyo, Japan; started to develop self-compacting concrete.
By the early 1990’s Japan has developed and adopted self-compacting concrete that didn’t require vibration to attain full compaction.
Self-compacting concrete has been described as ‘The most Revolutionary development in concrete construction for several decades.’
Originally developed in Japan to offset a growing shortage of skilled labor, it has provided to be beneficial in the following ways: Faster Construction.
Reduction in site manpower.Better surface finish.Easier Placing.Improved durability.Greater freedom in design.Thinner Concrete sections.
Reduced Noise Level.Safer working Situation.
Ingredients of Self Compacting Concrete:
1.Cement: Ordinary Portland cement, 43 or 53 grade can be used.
2. Aggregates: The maximum size of coarse aggregate is usually restricted to 20 mm.Well graded cubical or rounded aggregates are desirable.
Aggregates should be of uniform quality regarding shape and grading.Fine aggregates may be natural or manufactured. The grading should be uniform throughout the work.
3. Water: Water quality should be established on the similar line as that for using RCC or Prestressed concrete.
4. Chemical Admixtures: Superplaseizers are an important part of Self Compacting Concrete to provide the necessary workability. The new generation superplasticizers termed Poly-carboxylated ethers (PCE), is particularly helpful for Self Compacting Concrete.
5. Mineral Admixtures: Fly ash, Blast furnace slag, Stone Powder, Silica Fumes, and fibers may be used to improve the properties of Self Compacting Concrete.
Self Compacting Concrete Mixes:
There are three ways in which Self concrete can be made: Powder Type VMA Type Combined Type.
How Economical is Self Compacting Concrete?
There is a feeling that cost of Self Compacting Concrete is much higher than that of the corresponding ordinary or High strength concrete.
It is seen that the cost of materials of Self Compacting Concrete is about 10-15% higher. If one takes the other components of costs such as cost of compaction, finishing etc.
Then one would realize that Self Compacting Concrete is certainly not a costly concrete for comparable strength.