Monday, May 25, 2020

Self-Compacting Concrete - Easy explanation ( Minerals, Admixtures, Adv/Disadvantage)

Self-Compacting Concrete

Introduction - Self Compacting Concrete

Self-Compacting Concrete (SCC) is also known as Super-workable concrete/self-consolidating concrete, the concrete got its name due to the characteristics it possesses of highly flowing nature which does not require any type of vibrator for compaction. The development of the concrete was started at the late 1980’s and was started been used in the early 90’s by University of Japan.

It is a highly flowable concrete in which if you pour the concrete from one side, it will readily move to the other side and get self compacted. The concrete will not show any kind of segregation behavior and and the compaction of the self - compaction concrete is achieved with its own self weight.

When we consider the case of dense or a very heavy reinforcement where the compaction is hard to achieve with the help of mechanical vibration, there with the help of SCC we can easily achieve the desired strength and the durability without compromising anything.

How is workability achieved without any segregation?

Self compaction concrete is a uniform mix of minerals & fines such as Ground Granular blast furnace Slag or Fly Ash with combination of special admixtures improving the workability of the concrete.

Materials Used - Self Compacting Concrete




Grade or Size

1) Cement



43 & 53

2) Coarse Aggregate


Well Graded cubical or rounded

10mm-12mm are desirable.

Maximum limited to 20mm.

3) Fine Aggregate

Natural or Manufactured

Grading - Uniform

0.125mm which is 125 micron

4) Water

Suitable for RCC & Prestressed concrete.



Chemical Admixtures

Admixtures are used to improve the characteristics of the concrete with decreasing the water to cement ratio. Different types of admixtures are used based on the desired characteristics we require for the work.

Now, we will see different admixtures and there roles.




1) Poly-carboxylated ether .

Improves Workability.

(i) New generation superplasticizer.

(ii) They only work with Calcium Aluminate cement, resulting in improving workability.

2) Viscosity Modifying Agent (VMA).

Decrease viscosity.

(i) As the viscosity decreases, the workability improves.

3) High range water reducing agent ( HRWRA).

Decrease in water to cement Ratio.

(i) Maintaining the workability by reducing the water content in the concrete.


Mineral Admixtures.

SCC always tends to show high strength when they are compared with normal concrete or the conventional concrete we use. This is achieved due to the mineral admixtures we use to enhance the characteristics of Self compacting concrete.

Following table will show you the different mineral admixtures and the properties they show, resulting in improving of concrete.


Mineral Admixtures

Properties Improved


Fly Ash

Quality and durability.


Ground Granular Blast Furnace Slag

Property of flow and deformation, i.e rheological properties.


Silica Fume

Mechanical properties


Stone Powder

Increase power content should be < 0.125mm



Flexural tension stress capacity.


Different Self compacting concrete(SCC) Mix

The mix is generally categorized and is prepared in three methods. They are carried out based on the required site conditions and the demand of the mix type of concrete. These three mix are

(i) Powder Mix

In this type of mix, the powder content are increased while preparation Self Compacting concrete which results in increase in compressive strength and the durability of self compacting concrete.

(ii) VMA type

In the preparation of VMA type self compacting concrete, there is a increase in percentage of viscosity modifying admixture. The result of increase in VMA is the decrease of the viscosity of the concrete which helps in maintain the workability.

(iii) Combined Type

In this type of mix, it contains both the mix of increase in powder content with the mix of VMA. 

Why use of SCC - The Requirement

As self compacting concrete shows the characteristics of self compacting due to its own weight, the mix is classified into three types broadly for which they are used.

(i) Resistance to segregation

Due to the uniformly mixed fines, the concrete does-not show segregation even after dropping from a height of 4m-5m.

The tests which are done to test the Segregation resistance are

V- funnel at T5

GTM screen stability Test

(ii) Ability to fill

SCC have characteristics of high workability which makes the concrete flow with its own weight, having this property lead to fill up all the congested areas having high density of reinforcement or area where it is hard to reach and do mechanical vibration. Those area self compacting concrete is used to maintain the strength. The following are the tests which are used to check the workability/Ability to fill.

Slump flow by Abrams cone.

T50cm Slump flow.

V- funnel ability.


(iii) Passing ability

Maintain the homogeneous and uniform behavior of concrete. Further the tests used to check the characteristics are  




Fill box

Self compacting concrete- Advantages

(i) Self Compacting concrete possess - High compressive strength and durability because of low w/c ratio, Better quality because of the homogeneous mix of mineral admixtures, and rapid strength develpoment of concrete.

(ii) Less man-power - Less no of labours are required since the workability is high making it easier to spread the concrete and no team required for manual compaction.

(iii) Good Finish - Because of good workability of concrete.

(iv) It is cost efficient and is preferred widely for pre-fabrication, for the pour of thin layer on top of them.

Self compacting concrete- Disadvantages

(i) It is expensive compared to conventional concrete.

(ii) The formwork should be tighten up properly, since the concrete will possess high outward pressure on the shuttering board due to the workability.

(iii) It is hard to maintain the concrete consistency for as verylong period of time.

(iv) As the high pressure is generated to the formwork, the rate of casting should be maintained and must be done at slow rate.

Related Topics

1 comment: