workability of concrete

Workability of Concrete | Factors Affecting Workability of Concrete7 min read

What Is Workability Of Concrete?

Workability of concrete is the ease, with which concrete mixes can be mixed, transported, placed in formwork, and compacted completely as possible while using the lowest possible water/cement ratio.

workability of concrete
Workability of Concrete

In the workable concrete mix, the function of water is to lubricate the concrete so that the concrete can be compacted with minimum effort at the site of work.

The care should be taken that the concrete may not experience segregation, loss of homogeneity, compaction with a minimum amount of effort and finish easily; the presence of a certain quantity of water is of vital importance. 

Workability of concrete is also the ability of fresh concrete to fill formwork properly with a sufficient amount of vibration and without reducing the concrete’s quality.

The fresh concrete workability mainly depends on water content, cement content, aggregate particle size distribution and amount of hydration and can be modified by adding chemical admixtures, like superplasticizer


Types of Workability of Concrete

The workability of concrete can be classified into three types as follows,

  1. Unworkable Concrete
  2. Medium Workable Concrete
  3. Highly Workable Concrete

1. Unworkable Concrete

Unworkable concrete is a type of workability of concrete, in which the concrete has a very little amount of water. It is also known as Harsh Concrete, in which the hand mixing of concrete is likely very difficult.

Segregation of Aggregates is high in such concretes, leading to a difficulty to maintain the homogeneity of such concrete mix.

2. Medium Workable Concrete

Medium workable concrete is considered good in the sense of all properties a concrete should possess. The same is the reason it is used in most construction works. It can be easily mixed, transport, place, and compacted without much segregation and loss of homogeneity.

3. Highly Workable Concrete

As the name suggests Highly workable concrete will be very easy to mix, transport, place, and compact. In th circunstances where effective compaction of concrete is not possible, this type of concrete is well suited one.

With high workability, the problem is such that there are high chances of segregation of concrete and loss of homogeneity.


Desirable Workability for Construction

Desirable workability depends on two factors which are as mentioned below,

Workability Depending on Section size, amount and spacing of Reinforcement

For a narrow, complicated section with several narrow corners and inaccessible parts, highly workable concrete is recommended to obtain full compaction of concrete with sufficient effort.

The section crowded with steel reinforcement and if the spacing between the bars is relatively small, then compaction is difficult. For such cases also highly workable concrete is recommended by engineers.

With no limitations of the critical section or heavily reinforcement concrete, we can get a wide range of workability for concrete casting in construction.

Method of Compaction

The second factor responsible for selecting the type of workability is the method of compaction. Manual compaction of concrete requires more workability because the hand compaction method is not much uniform and effective one.

Vibrators or machines provide high workability rang because of the efficiency and effectiveness offered by such machines.


Relationship Between Strength And Workability Of Concrete

The Strength of Concrete defines the nature of concrete hence it is the most important property for us. However, its dependency on other properties of concrete forces us to relate them with the strength.

Strength is affected by density ratio or compaction and in turn, compaction depends on sufficient workability. Fresh concrete should have have a specific workability in order to obtain maximum density with a reasonable amount of work.

However excessive workability can affect compressive strength or even lessen it. The compressive strength of concrete can decrease with an increase in the w/c ratio, which in turn increases workability.

Hence we could conclude that strength of concrete inversely proportional to the workability. So in order to obtain specific strength of concrete too much workability should be avoided.


Factors Affecting Workability of Concrete

The following are the factors affecting concrete workability,

1. Water content or Water Cement Ratio

As we increase the water-cement ratio workability increases simultaneously. But, the excessive water content may also result in the bleeding of concrete mix.

Moreover, high water content provides loose cement slurry which is capable of escape through the formwork joint.

 As we increase water content, the strength of concrete gets reduced. To avoid this and to keep the water-cement ratio constant add a sufficient amount of cement also while increasing water content in the concrete mix so that the strength remains the same.

Sometimes when concrete becomes too loose or high workability. Cement can be added to it to make concrete of good workability.


2. Mix Proportions

When concrete mix contents a higher amount of aggregate or aggregate/cement ratio is greater, less cement slurry is available to make concrete lubricant or workable.

On another side, if the concrete is having a lower aggregate/cement ratio, more paste is available to make the mix cohesive and fatty to give better workability


3. Size of Aggregate & Surface Texture

Size of Aggregate & Surface Texture- workability of concrete
Size of Aggregate & Surface Texture

The smaller the size of aggregate particle higher will the surface area of aggregate and which requires a greater amount of cement paste to lubricate them.

So, a smaller size aggregate needs a more water-cement ratio to get good workability.

On other hand, bigger size aggregate requires less surface area, and hence less amount of water is required for wetting the surface and less amount of cement paste require for reducing internal friction between them. 

As the aggregate size is high low water requires lubricating it, hence the extra water is available for workability.

In the case of porous aggregate more water is required to lubricate them compare to nonporous aggregate for achieving the same degree of workability.


4. Shape of Aggregates

It is a fact that concrete mix with rounded aggregate has greater workability with less water-cement ratio compare to angular, elongated, or flaky aggregate. This shape of aggregate makes concrete harsh and difficult to handle.

The rounded aggregate offers better workability due to the fact that for the given volume or weight it has less surface area and fewer voids than the angular or flaky aggregate.

Moreover, because of their rounded shape, the frictional resistance is also greatly reduced.

This is a major reason for river sand and gravel cost more than crushed.


5. Grading of Aggregates:

Graded aggregates are those aggregate which has least amount voids in a given volume and that offers higher workability to concrete.

As the number of voids reduced, the excess paste is available to lubricant the particles. With this excess amount of paste concrete mix becomes cohesive and fatty which prevents segregation of particles.


6. Use of Admixtures:

The workability of concrete can be increased by adding chemical admixture. As a chemical admixture air-entraining agent is used, which acts as ball-bearing between particles and increases workability, mobility and decreases bleeding, segregation.

For a better lubricating effect and more workability, pozzolanic materials can be used.


7. Weather Conditions:

The weather condition has a significant effect on the workability of concrete. As the temperature increase, the evaporation process becomes rapid, and concrete loose water content quickly.

As the water content in concrete reduces, workability also gets reduced.  In an area, if the velocity of wind is high water in the concrete evaporates quickly and that results in lower workability of concrete.


Workability Test of Concrete

workability of concrete is measured by


FAQs:

What Is Workability

Workability of concrete is the ease, with which concrete mixes can be mixed, transported, placed in formwork, and compacted completely as possible while using the lowest possible water/cement ratio.

Workability of Cement

The Cement Concrete Workability is defined as the ease with which a freshly concrete mix can be properly compacted and also that it can be transported, placed, and finished

You May Also Like:

Share This Post

2 thoughts on “Workability of Concrete | Factors Affecting Workability of Concrete”

  1. Pingback: Civiconcepts - Make Your House Perfect With us

Leave a Reply

Visit BlogAdda.com to discover Indian blogs

x

Related Posts

Setting Time of Cement | Initial and Final Setting Time of Cement Test | Initial Setting Time of Cement | Final Setting Time of Cement
What Is Setting Time of Cement? Initial setting time gives an idea about how fast cement can start losing its plasticity and the final settin...
Foundation Materials List | House Foundation Materials | Materials Used In Foundation Construction
There are different types of Building Foundation Materials used to the foundation of the house. House foundation materials have prime importance...
Water Cement Ratio | Watercement Ratio | Water Cement Ratio Calculation Example | W/C Ratio Formula
What Is Water Cement Ratio? It Is the ratio of the mass of water to the mass of cement added to concrete. The Watercement Ratio directly affe...
powered by RelatedPosts
Scroll to Top
DMCA.com Protection Status