You may have heard engineers, manufacturers and construction workers referring to the properties of concrete in different ways. You may hear them refer to the compressive strength of concrete, its tensile strength, and you may also hear them refer to the workability of concrete. However, what is meant by the workability of concrete? And, what are the main factors affecting it? Let’s find out.
Concrete Workability Definition
The workability of concrete refers to how easily freshly mixed concrete can be placed, consolidated and finished with minimal loss of homogeneity. In other words, it refers to how ‘workable’ the concrete is, how easily it can be manipulated without its strength being compromised. In general, workability is determined by how fluid the mix is (i.e. the cement to water ratio). However this isn’t the only factor affecting concrete workability.
Factors Affecting Concrete Workability
Now that we’ve determined what is meant by workability of concrete, let’s take a look at the main factors influencing it. These are:
Water To Cement Ratio
Ensuring that concrete has the correct balance of water to cement is important for ensuring that the concrete is the right strength and delivers the correct finish. Generally speaking, concrete that has a higher proportion of cement to water makes a stronger concrete. If too much water is used, the concrete mix can segregate and lose strength. That’s why a good balance is required to achieve workable concrete.
The size and shape of the aggregates that are present in the concrete mix will also have an impact on how workable it is. The surface area of the aggregates affects the amount of cement paste that is needed to cover them, and this affects the water to cement ratio and consequently the workability. In general, crushed aggregate bonds best with cement, creating a workable concrete.
Concrete mixes often include additional components such as plasticisers and chemical admixtures. These may be added in order to improve the workability of concrete.
Types Of Workability Of Concrete
When discussing what is meant by workability of concrete, it’s important to emphasise that there are different types of workability. These are:
Unworkable concrete is concrete with a very low ratio of water. This type of concrete has high segregation making it difficult to maintain the homogeneity.
This concrete is relatively easy to mix, transport, place and compact without the homogeneity being compromised and the mix segregating.
This type of concrete is very easy to mix, transport, place and compact. This is because it is a more fluid mix. It is usually used where effective compaction of concrete is not possible.
When discussing what is meant by workability of concrete, it’s important to note that this can be improved by certain factors. It is possible to improve the workability of concrete through factors such as increasing the water/ cement ratio, using different aggregates and adding the appropriate admixtures.
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