Mayadah W. Falah
Building and Construction Techniques Engineering Department, College of Engineering and Engineering Techniques, Al-Mustaqbal University, 51001, Babylon, Iraq
1.1General for Self-Compacting Concrete (SCC)
Self-Compacting Concrete (SCC) is considered as one of the most significant developments in concrete technology. It is a new type of high performance concrete with the ability of flowing under its own weight and without the need of vibrations. Recently, a great native interest had been derived
towards self-compacting concrete (1).
SCC is a relatively new type of concrete that is highly flowable and non- segregating. It does not require vibration when cast, is capable of flowing through narrow opening or extremely congested reinforcement, and provides a void-free surface. It is known as self-consolidating concrete, self-leveling
concrete and high fluidity concrete (2).
SCC flows like ''honey'' and has nearly a horizontal concrete level after placing. When SCC is placed in a form, its motion may be a creeping movement or a rapid flow. Because of this style of flow, the surface finish between the form and the concrete can be exceptionally smooth, creating a much-improved
from finish over conventional concrete (3),(4).
SCC has been proved beneficial economically because of a number of factors, including (5, 6, 7 and 8):
1. Fill all voids, no segregation and reduced permeability.
2. Easier placing, easy to deliver and excellent pumpability.
3. High performance.
4. Better surface finishes (without blow-holes or other surface defects) Because of more fines and better fluidity.
5. No consolidation needed and reduction in site manpower.
Greater freedom in design of structures therefore, thinner concrete Sections can be obtained.
6. Increased early strength.
7. Reduced wear on mixers due to reduced shearing action.
8. Reduced energy consumption from vibration equipment (although the energy required for longer mix times will offset this somewhat).
9. SCC proves successful in repairing and strengthening members.
The main mechanisms controlled the balance between higher flowability and stability were related to surface chemistry, the development of SCC has thus been strongly dependent on surface active admixtures as well as on the increased specific surface area obtained through the used fillers (9).
Since the development of the prototype of self-compacting concrete in 1988, the use of self-compacting concrete in actual structures has gradually increased. In general some areas of use of self-compacting concrete:
1. Bridges and structural application.
2. Pumped concrete and repair applications.
3. Utility application and hard to reach areas.
4. Pre-cast and pre-stressed concrete and areas with congested reinforcement.
5. Prefabricated and ready-mixed concrete.
6. Floors, walls, beams and columns.
7. Detailed formworks.
8. Reinforced concrete structures with narrow cross-sections.