The workability requirements for various concrete placement is explained below:
The prerequisites of concrete workability changes along with range of assortments of construction. Workability of concrete is determined by highly skilled design engineers depending on the concrete strength necessities, the requirements of durability and the for the easiness of the construction at site.
For the constructions with the utilization of greater percentage of reinforcement, where the space amongst the reinforcement is minimum and additionally, compaction could not be carried out effectively, highly workable concrete like the self-compacting concrete is suggested.
Because the workability of concrete is attained by higher proportion of water, it diminishes the power of concrete. That is why, it is better recommended to make utilization of workability augmenting blends like the air-entraining agents. But the utilization of admixtures might also have impact on the strength of concrete. So, for vital materials of building like the slab, columns and beams, and for structures where the relative strength of concrete is very critical, the extent of workability suggested is not very high. For mass concrete and lightly reinforced concrete structures, lower extent of workability can be utilized.
The extent or the degree of the workability is assessed with the process of slump test of the concrete while mixing. The slump value suggested for each degree or extent of workability for various positioning conditions of concrete is shown in table below:
Degree of workability for various placing conditions
|Placing Condition||Degree of concrete workability||Slump (mm)|
Pavement using pavers
|Very low||Use compacting factor test as per IS: 1199|
Lightly reinforced sections in slabs, beams, walls, columns, foors, hand placed pavements, canal linings, strip footings
|Heavily Reinforced sections in slabs, columns, walls, slip form work, pumped concrete||Medium||50 – 100, 75 – 100|
|Trench fill, in-situ piling||High||100 – 150|
|Tensile concrete||Very high||Use determination of flow test as per IS: 9103|