08-06-2012, 05:18 PM
SELF-COMPACTING CONCRETE
Building conditions for contemporary architectural buildings set new, various requirements regarding construction methods of reinforced concrete buildings. Meeting those criteria led to development of concrete with specifically defined properties in fresh state. An idea of Self-Compacting Concrete (SCC), a material that flows, that is placed into formwork and that is compacted under the influence of self-weight only, without vibration.
Self-Compacting Concrete(SCC) is a fluid mixture suitable for placing in structures with congested reinforcement without vibration. Self-compacting concrete development ensures a good balance between deformability and stability.
History Of SCC:
Self-compacting concrete was first developed in 1988 to achieve durable concrete structures. Since then, various investigations have been carried out and this type of concrete has been used in practical structures in japan, mainly by large construction companies. Invetigations for establishing a rational mix-design method and self-compactability testing have been carried out from the viewpoint of making self-compacting concrete a standard concrete.
Properties of SCC:
Self-compacting concrete produces resistance to segregation by using mineral fillers or fines, and using special admixtures. Self-consolidating concrete is required to flow and fill special forms under its own weight, it shall be flowable enough to pass through highly reinforced areas, and must be able to avoid aggregate segregation. This type of concrete must meet special project requirements in terms of placement and flow.
Self-compacting concrete with a similar water cement or cement binder ratio will usually have a slightly higher strength compared with traditional vibrated concrete, due to the lack of vibration giving an improved interface between the aggregate and hardened paste. The concrete mix of SCC must be placed at a relatively higher velocity than that of regular concrete. Self-compacting concrete has been placed from heights taller than 5 meters without aggregate segregation. It can also be used in areas with normal and congested reinforcement, with aggregates as large as 2 inches.
Advantages Of SCC :
• Faster and more efficient placement of fresh concrete is achieved. Total concreting time is reduced.
• High quality• No vibration of fresh concrete is necessary during placement into forms.
of placed concrete is achieved, regardless the skill of the workers.
• Good bond between concrete and reinforcement is obtained, even in congested reinforcement.
• High quality of concrete surface finish is obtained with no need for subsequent repair.
• With a better final appearance of concrete surface, smooth wall surfaces and flat floor surfaces that need no further finishing are obtained.
• Improved durability of structures is achieved and Maintenance costs are reduced.
Applications Of SCC:
Self-compacting concrete has been used in bridges and even on pre-cast sections. One of the most remarkable projects built using self-compacting concrete is the Akashi-Kaikyo Suspension Bridge. In this project the SCC was mixed on-site and pumped through a piping system to the specified point, located 200 meters away. On this particular project the construction time was reduced from 2.5 years to 2 years.
This project presents an experimental procedure for the design of self-compacting concrete mixes. The test results for acceptance characteristics of self-compacting concrete such as slump flow; J-ring, V-funnel and L-Box will be presented. Further, compressive strength at the ages of 7, 14, and 28 days will also be determined and results will be included.
