What Is Self Compact Concrete?
Making concrete structures without vibration has been done in the past. For example, the placement of concrete under-water is done by the use of tremie without vibration.
Shaft concrete and mass concrete may be successfully placed without vibration.
But the above examples of concrete are normally of lower strength and difficult to obtain consistent quality.
Modern application of SCC (self-compacting concrete) is focussed on high performance, better and more reliable, and uniform quality.
History of Self Compact Concrete
• Recognizing the lack of complete and uniformity compaction of concrete by vibration, researchers at the University of Tokyo, Japan, started in the late 1980s to develop SCC.
• By early 1990, Japan has used and developed SCC that doesn’t require vibration to achieve full compaction.
• Near abot of the year 2000, the SCC has become popular in Japan for prefabricated products and ready mixed concrete.
• Several European countries recognized the significance and potentials of SCC developed in Japan.
• During 1989, they founded the European federation of natural trade associations representing producers and applicators of specialist building products (EFNARC)
• The utilization of SCC ( Self Compact Concrete) started growing rapidly.
• EFNARC, making use of broad practical experiences of all members of European federation with SCC, has drawn up specifications and guidelines to provide a framework for design and use of high-quality SCC, during 2001.
• Self-compacting concrete has been described as “the most revolutionary evolutionary development at concrete construction for several decades.”
• Originally developed at Japan to offset a growing shortage of skilled labour.
Where Are Used SCC Self Compact Concrete?
as per the below area used Self Compact Concrete.
• Better surface finish
• Easier placing
• Faster construction
• Greater freedom in design
• Improved durability
• Reduced noise level
• Reduction in site human resources
• Safer working environment
• Thinner concrete sections
Advantages of (SCC) Self Compacting Concrete
• Reduces labor costs.
• Improved constructability.
• High durability, strength, and reliability.
• Minimizes voids in highly-reinforced areas.
• Reduces permeability in concrete structures.
• Fast placement without mechanical consolidation.
• The SCC construction is faster than normal concrete.
• SCC enables freedom in designing concrete structures
• Creates smoother and more aesthetic surface finishes.
• Eliminates problems associated with concrete vibration.
• Creates high-quality structures with improved structural integrity.
• Allows for easier pumping, and there are many placement techniques available.
• Allows for innovative architectural features, since it can be used in complex forms.
Disadvantages of (SCC) Self Compacting Concrete.
• Material selection is more strict.
• Construction costs increase, compared with regular concrete.
• Higher precision is required when measuring and monitoring.
• There is no globally accepted test standard to undergo an SCC mix design.
• The cost of construction is costlier than conventional concrete construction.
• Many trial batches and laboratory tests are required to use a designed mixture.
• There is no internationally accepted test standard for self-compacting concrete mix.
Material Use In (SCC) Self Compacting Concrete.
As below material used in (SCC) Self Compacting Concrete.
• Mixing Water
• Chemical Admixtures.
• Mineral Admixtures.
• Fly Ash
• Ground Granulated Blast Furnace Slag Ground Granulated Blast Furnace Slag (GGBFS)
• Silica Fume
• Stone Powder
Ordinary Portland Cement, 43 or 53 grade can be used
Wherever possible size of aggregate higher than 20mm could also be used. Well graded cubical or rounded aggregates are desirable.
Aggregates should be of uniform quality with respect to shape and grading. Fine aggregates can be natural or manufactured.
The grading must be uniform throughout the work. The moisture content or absorption characteristics must be closely monitored as the quality of SCC will be sensitive to such changes.
Particles smaller than 0.125 mm i.e. 125-micron size are considered as FINES which contribute to the powder content
Mixing Water :
Water quality must be established on the same line as that for using reinforced concrete or prestressed concrete.
Chemical Admixtures :
Superplaseizers are an essential component of SCC to provide necessary workability. The new generation superplasticizers termed poly-carboxylated ethers (PCE) is particularly useful for SCC.
Other types may be incorporated as necessary, such as Viscosity Modifying Agents (VMA) for stability, air-entraining agents (AEA) to improve freeze-thaw resistance, and retarders for Control of Setting.
Mineral Admixtures :
Fly Ash :
Fly ash in an appropriate quantity may be added to improve the quality and durability of SCC.
Ground Granulated Blast Furnace Slag Ground Granulated Blast Furnace Slag (GGBFS) :
GGBFS which is both cementitious and pozzolanic material may be added to improve rheological properties.
Silica Fume :
Silica fume may be added to improve the mechanical properties of SCC.
Stone Powder :
Finely crushed limestone, dolomite, or granite may be added to increase the powder content. The fraction should be less than 125 microns.
Fibers may be used to enhance the properties of SCC in the same way as for normal concrete.
List of Test Methods for Workability Properties of Self Compacting Concrete (SCC).
1. Slump flow by Abrams cone.
2. T50 cm Slump flow
5. V-funnel at T5 minutes
9. GTM Screen Stability Test
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