In the 1980s, the construction industry in Japan experienced a decline in the availability of skilled labor. This situation aroused a need for concrete that could overcome the problems of defective workmanship.
This led to the development of self-compacting concrete (SCC). It was primarily started through the work of Prof. Dr. Hajime Okamura (Father of SCC Technology). A committee was formed to study the properties of self-compacting concrete, including a fundamental investigation on the workability of concrete. This was carried out by Ozawa et al. at the University of Tokyo. The usable version of self-compacting concrete was completed in 1988. It was named “High-Performance Concrete”. Later it was proposed as “Self Compacting High-Performance Concrete”.
High-performance concrete is used basically for two reasons.
- Higher Compressive Strength.
- Workability and Compactibility.
In large and complex construction projects, congestion of bars is a very common phenomenon. It becomes very tough to compact concrete with vibrators. Also, segregation takes place during placing the concrete in the formwork. This situation can be tackled with highly workable concrete. Highly workable concrete has a slump of over 650 mm-800 mm. Their testing (Slump flow test instead of normal slump test) and quality assurance procedure is different from normal concrete.
Self-Competing Concrete is also known as self-consolidating concrete. In this article, we will discuss the definition of self-compacting concrete along with the practical application field of it.
What is Self-Consolidating or Self-Competing Concrete?
Self Consolidating or Self Compacting Concrete (SCC) is a highly flowable, deformable, non-segregating concrete that spreads and fills in the formwork under its own weight. Flowability is maintained by using a high range of water-reducing admixtures.
Stability (avoiding segregation) is increased by using admixtures or increasing the number of fine aggregates in the plastic concrete. This also changes the viscosity of the mixture.
SCC has a more improved interface between aggregate and cement paste. It increases the strength of concrete.
Self Compactibility = High Deformability + High Segregation-resistance
Self-compacting concrete can also be defined as a mix balancing the fluidity and resistance to segregation where those two properties are conflicting with each other. A balanced equilibrium should be maintained between them.
Application of Self-Competing or Self-Consolidating Concrete
The followings are the applications of self-consolidating/compacting concrete.
- Areas of congested reinforcements.
- Bridges and precast sections.
- Drilled shaft columns, earth retaining structures.
- High concentration rebars where normal tempering or vibrating is difficult.
- Manufacturers of concrete pipes.
- Flow in closed spaces-pipes (during pumping).