Workability is a new or fresh concrete mixture asset. Workability implies, in simple words, the simplicity of installation and workable concrete is the concrete that can be positioned and conveniently compacted without separation.
Workability is a crucial concrete product related to compaction and power. For all concrete forms, the ideal workability is not the same. Instead of a mass concrete structure, more workability is required for a small, unstable portion or heavily reinforced part. For all casting functions, however, we can not set standard workability.
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Reason for Different types of definition
There is a variation of meanings of workability as the technical concept such as actual gravity or weight is not quite accurate. All interpretations are subjective in nature, and instead of scientific accuracy, individual perspective is expressed. There are some other terms used to describe concrete as cohesiveness, consistency, flowability, mobility, pump-ability, etc. Such words are unique to them
Types of Workability of Concrete
Unworkable Concrete: An unworkable concrete that is also known as hard concrete is the cement that has very little heat. This concrete’s hand mixing is challenging. There is a strong separation of aggregates in this form of concrete. And the homogeneity of the concrete mix is very difficult to maintain.
Medium Workable concrete: Many construction works use medium workable cement. Without much separation and homogeneity loss, this concrete is fairly easy to mix, transport, position, and compact.
Highly workable cement: Mixing, packing, placing and compacting this sort of concrete is very easy. It is used where it is not possible to quickly pile concrete. The problem is that in highly workable concrete there are high chances of segregation and loss of homogeneity.
Desirable Workability for Construction
Reinforcement portion width, quantity, and spacing: when a segment is small, difficult, several narrow corners, inaccessible parts; extremely workable concrete is beneficial to achieve full compaction by reasonable effort. When the segment is filled with steel reinforcement and bar width is relatively small, compaction can be problematic and therefore highly workable concrete in such situations is advised. If there are no essential portion constraints or strong strengthening, we will obtain a wide range of concrete casting workability.
Compaction method: When concrete is manually compacted, it is advised to be more workable since hand compaction is not very consistent and reliable.
Strength of Concrete & Workability Relationship
For us, concrete strength is the most important property. It relies on the ratio of density or compaction, and sufficient workability depends on compaction. Fresh concrete must be workable, as maximum density compaction with a reasonable amount of work is possible
Figure: Concrete compressive vs w/c proportion. However compressive strength can be diminished by unnecessary workability. From the diagram above, we see that with a rise in the w/c ratio, the compressive strength of concrete reduces. An increase in the w/c ratio shows an increase in workability. Therefore, it is necessary to avoid the intensity of concrete inversely proportional to the workability and unnecessary workability.
Methods of Improving Workability of Concrete
- Increasing water/cement ratio
- Using larger aggregate
- Using well-rounded and smooth aggregate instead of irregular shape
- Increasing the mixing time and mixing temperature
- Using non-porous and saturated aggregate
- With the addition of air-entraining mixtures
- Adding appropriate admixtures