Self Compacting Concrete

Self Compacting Concrete is highly flowable concrete mixture which is able to consolidate under its own weight. It also known as Self Consolidating and Flowing concrete. These type of concrete does not require the mechanical vibrator for compaction. It can reach all the possible corner of shutter without any effort. 

Self Compacting Concrete does not have large amount of water. Rather it contains less amount of water than normal mix. The higher flowability can be achieved by higher proportion of fine aggregate (sand) 

and use of superplasticizers and viscosity modifier agent. Polycarboxylate,Glenium C303SCC are common example of superplasticizers.

In addition to basic element used in concrete, superplasticizers and viscosity modifier agent (VMA) helps to reduce bleeding and segregation. SCC have all the necessary and desire properties and characteristics strength of normal concrete.

A well mix SCC has higher deformabitly and stability. 

In comparison with normal concrete having same water-cement ratio and compacted with vibrators, SCC have slightly higher strength as no vibration gives well and improved interface with cement water paste. 

Advantage

• Improved labour work
• Proper bond with reinforcement 
• Lesser requirement of skilled labour
• Improved Constructablity
• Superior surface finish
• Improved Strength and Durability
• Accelerate production and lesser the required time
• Easy Pumping and Placing of Concrete
• Allow the designing more complex and innovative structure
• Lesser numbers of voids in concrete

But these Self compacting Concrete is littler costlier than ordinary concrete. The formwork should be such that it can withstand under the weight of liquid concrete. 

Testing on Self Compacting Concrete:

1.Slump Flow and T500 test: The test is require for finding the flow ability and flow rate of concrete in absence of any obstruction. It is rapid and on-site test.

The time (in seconds) required for taking outer edge of the flowing concrete to reach an average diameter of 500 mm is noted.

If there is serious segregation, then major aggregate collect in middle spot. If there is minor segregation,  then the circle the surrounded by little water-cement paste. 

2. Fill box Test: The test is used to measure filling ability of self compacting concrete with aggregate of maximum nomial size of 20mm. The difference between height of concrete level gives measure. It is also called as 'Kajima Test'.

3. L Box test: L Box test is widely used for measuring the passing ability of SCC and also possibility of segregation. 

The ratio of H2/H1 is called blocking ratio.

The maximum value of ratio is 1. Higher the value, higher the passing ability.

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